Do you have to heat them while curing? Can you just stick them in the oven after curing? Edit: 5 seconds after I posted this comment, I got to the answer in the video.
I was guessing you were going to cure with heat and an oxygen inhibiter (water). Siraya Tech actually suggests using water to cure Blu resin (in their TDS). I believe the idea is to inhibit oxygenation, which is determental to the curing process. Siraya Tech mentions its more efficient as well, generally speeding up the curing process.
Evidently I need to make a resin-version youtube channel of CNC kitchen. When you devote 2 years to making graphene additives for photopolymer, the testing methods to get there paint a different story. Water-curing after an ultrasonic bath for specific formulas is also quite effective.
One of the most important things for me in 3D prints for functional parts is creep. Rarely do I need higher than 60ºc temperature resistance, but often I do need parts to stay in shape while loaded for long times. This kills PLA for several of my projects, despite it's many advantages. The same is true for the Formlabs Black resin, we also got the wash and cure station at work and we use the machine whenever we need to show pretty stuff to the costumers, but when it's time to make some functional prototypes to last field use, no no. It creeps way too much. Creep tests is one thing I would like to see being explored more thoroughly, there's much more to part strength than short loads after all. One thing I've often done with larger resin prints with heat is straightening warped walls. Large parts will sometimes get warped during printing or curing (specially that 60°c 1h curre that we go with the Formlabs station), a friendly Ender 3 with it's flat glass bed at 60°c for some minutes with correctly placed weights, then let it cool naturally until about room temperature, and we're good to go. Same with PLA actually.
There are no non-creeping resins. They are all amourphous polymers based on acrylates or epoxy -for obvious reasons. The glass filled ones like Formlabs 4k are somewhat better, but it's always just a quantitative difference. If you want non creeping stuff you need to use ASA with CF or annealed PET with CF.
@@testboga5991 Nice addition, didn't know that far into the resins, kind of a bummer. I was wondering most about FDM as that's what I've got on reach for my own stuff (home printer), on which I use ABS when the parts are small enough and PETG for larger stuff as an in-between compromise material. At work we got the Rigid 4K too, used mostly or almost entirely for injection molding prototype molds. That thing is a heck of an annoyance to work with tho, don't use it for a few months and you'll have a viscous paste at the vat, that also has way shorter lifespan when used with that resin.
We post-cure our Siraya Tech and 3DMaterials resins immersed in a rotating hot water bath for at least 1 hour. The first 15 minutes are exposed to UV. The water will be heated to 60-80 Celsius depending on the resin used. Most of the time, the resin will be directly immersed in water, except those that are meant to be used at high temperatures or contain filles, such as ST Sculpt and Sculpt Ultra White. These will be put in a bag with light vacuum seal. Most of the parts we make are meant for end-of-arm tools for industrial robots, manufacturing aid elements and injection molding tool components
What do you mean rotating? A submersed pump circulating water in the bath, that you change the water between post cures, or the whole bath is physically turned around during the process?
@@imperatormegatron2014 agreed. I've only ever water cured my parts. I dont have any kind of rotation setup yet tho. And make sure you clean the parts well, and wait for the IPA to dry
I own a FDM printer not resin, but I use epoxy resin for projects and put them in the oven after it has had its minimum cure time. I have always wondered why people never used heat for their resin prints and just presumed the resin used for 3D prints isn't possible, glad someone (you) have shown resin printer users this trick. Good work.
Another tip also, when I use epoxy resin, if say 60c is the highest you want to cure, start at 40, then to 50 then 60, when time is up, do not remove the part, leave the part inside until the inside of the oven has gone back to ambient temp.
I print a lot of resin dental prosthetics we use temps anywhere from 20-60c for up to an hour depending on your curing unit. Some units use nitrogen filled chambers to cure while others finish cures in a 60c water bath .
I worked back and forth with siraya tech over a cunfusion with their blu mecha formula. One incredible technique the engineer told me to cure the resin 3D print submerged in water. I noticed a big difference in hardness and strength when doing this
Hi Stefan! We print from BASF and Loctite resins at work (automotive prototyping) - and it is actually required to "bake" the finished prints for a while before UV curing. Not so high temperatures - around 40-50C for 30-60 minutes. So if manufacturers like these companies recommend it, there is actually some science behind :) And with Siraya Blu You can even go higher - i did several tests up to 250 C - for 60 minutes. Interestingly - part remains in its original shape, but starts to crack at temperatures above 125 C. Resin prints dont melt into blobs as FDM prints - there are a lot of "undiscovered" areas of resin printing ...
@@tomthebard42 absolutely correct, stuff will stick inside of there and it off-gasses a ton. also, since working with resin (irresponsibly, i will add) I've developed 2 or 3 skin tags particularly where i've handled the resin with bare hands. don't be like me- wear your PPE!
Important addition: beside monomers, oligomers and photoactivator there is also up to 50% filler. Filler made of some organic molecules wich didn't parcicipate in polymerisation. They made part less brittle but also less strong. And may result in developing cracks in a part over time. Cheaper resins usually have higher % of filler.
Not long ago I aquired a new resin printer and immediatly made a curing station with a 20 dollar used microwave that I salvaged (because I wanted something with a rotating plate and a timer) replacing the magnetron with a 405nm UV lamp like yours. There's still two 220v terminals that were originally connected to both the normal microwave bulb and ventilation fan that I now could connect to a heater and have a fully automatic Curing and Heating station with a rotating plate and timer! I could also add a thermostat for safety
I've been curing my abs-like resin in a very large glass container filled with water that I preheat with a old sous vide heater. Works fantastic. The water inhibits oxygen thus boosting curing rate, and it helps get far more even uv exposure!
@@MoonWind32690 Both, but the concept of "cure time reduction" is a deception - a resin needs a certain dose and duration of UV (and heat) until it competes the polymerization (aka "curing") process properly. Undercuring resin is always bad, and will not prevent the inevitable embrittlement, warpage, shrinkage, etc., of using a defective (improperly formulated) resin when it reaches "full cure", whether in a curing chamber or after 6 months on your shelf, for example. Proper cure duration is usually 30-60 minutes at least at 30-80 deg C depending on the resin (in a curing chamber with proper UV power and wavelength(s)). Glycerol is completely water soluble and it's very easy to clean and work with cleanly with the slightest forethought.
What you mentioned about curing PLA vs resin is a usual behaviour of thermoplastics (everything on a FDM printer) vs. cross-linked materials (everything on a resin printer) and explained absolutely correctly. About your thermal curing experiment: nicely done. Many photoinitiators are also unstable towards thermal initiation, so I am not very surprised by your result without UV light, and any crosslinking reaction will be quicker due to heat (our old friend Arrhenius), but it's nice to see the data. I still admire your DIY tensile and impact testers. edit: it might be interesting to do the same with non-transparent resin to see if the effect of thermal treatment is even higher compared to using UV light which would be expected since UV will not reach the interior of the part then or to vary the length of the curing to see if it is just an Arrhenius effect or you are actually starting new initiation reactions with the heat treatment.
Another banger Stefan. I always recommend your channel to newcomers to printing. Your scientific approach is such a breath of fresh air compared to so many other sources.
Great stuff. Kudos to Stefan, I generally don't look for new videos in my TH-cam subscriptions, but on weekends I always hope CNC Kitchen has a new video to watch while I workout.
I actually discovered this by accident thanks to a messy house finch couple. Putting prints outside had been part of my post curing process already. I assumed it was more UV from the sun making the prints stronger but the finches knocked a part into the shade and it was still as strong as the rest. Turned out it was the heat.
That "use your heated bed as your oven" trick is a game-changer. We only have one climate chamber at work and it's always in use, so I could only borrow it for enough time to prove that annealing works, but not long enough to anneal every part we print. That and I can't afford a climate chamber at home!
Super interesting results! A natural progression from this topic will be how to keep the prints strong as many report the parts become brittle after a few months. So what is the difference after 3 months vs painting them vs coating with UV clear coat. Great video!!!!!
i usually post cure with the parts submerged in water - this quickly removes all stickiness from the surface (oxygen contact seems to inhibit the curing of the resin!) eg. if you didnt clean them 100%. And using hot water may double in adding strength while keeping the parts from deforming - Thanks for the tip!
More SLA videos please! :) At the moment the resin printing community is sadly still at the stage "do I *really* need to buy a curing station?" as well as "do I *really* have to clean and cure my hollow prints from the inside?". But there are at least fewer people asking "but is resin *really* toxic?" and "do I *really* have to wear PPE?", which is nice.
I do a post-wash cure in a glass jar filled with hot water. I'm able to cure prints faster in water so I don't worry much about the water cooling before I'm done. It works great!
Hi Stefan, very good video as usual! Always a pleasure to watch your videos. Regarding your test results I think I have an idea, why your last test worked: During heat+UV cure, you split the photo initiators into radicals, which then lead to polymerization. More heat increases the brownian motion and thus increases the cure speed. If you now do the UV cure first and the heat treatment afterwards, I think the following happens: First you create radicals of the photo initiators with the UV light, which mostly find a monomer or oligomer due to their sheer number. Some of those radicals however end up not finding a partner to react with and thus stay in their radicak form. If you now increase the temperature without UV light, you don't create new radicals, but you increase the mobility of the remaining radicals through brownian motion and thus increase the likelyhood for those to find a matching monomer, oligomer of polymer. Repetition of the cycle might lead to less scatter in the results, I think.
@@austenite239 Not necessarily, BUT it's well known and observed that the resin continues to "shrink" and "cure" for quite some time (days, weeks) after _conventionally_ curing. Longer cures [60 to 90 minutes in general] in Glycerol with proper UV power with temp. reaching 60 - 80 deg. C will lead to the resin properly curing to its final properties and strength. Most people improperly under-cure the resin prints in air, which either hides the resins' deficiencies or prevents the resins from reaching their full and best properties.
@@joeljonker990 Copy and paste this into your favorite search engine: "Evaluating oxygen shielding effect using glycerin or vacuum with varying temperature on 3D printed photopolymer in post-polymerization"
THANKS SO MUCH! I print a lot of rather technical stuff in resin. This for I mostly take water washable black ABS-like resin from Sunlu. Making the parts even stronger is a great thingtp look fwd to… 😃
I had read that the main purpose of the UV in acting on the photoinitiator is not very different from how resin polymer initiators are activated, it essentially is adding energy to the system. The photoinitiators have been found to be more sensitive to that style of energy instead of say, heat but it makes sense that heat would also do it.
Being able to throw a print into an oven post-curing is a lot more hobby friendly than trying to make a setup to cure and heat at the same time. That's exciting to hear and I hope there is more research done with it.
Stefan, excellent video (as always!) I find that curing the parts in very warm water has yielded drastically different results in the quality of my prints.
@@CNCKitchen As someone who primarily resin prints, I'd personally love to see that tested, as it's much more reasonable than buying/making a small heater lol
i just want to point out that i am happy to see how you look like... you look allmost as i would have imagined... but with more curls in your hair... has seen your videos for a long time and actually seeing how you look like is amasing :) i have allways loved your unbiased and sciantific approtch to 3d printing and i have alot of respect for your work... as someone who has a education in plastic injection molding it is amasing to see someone who knows so much about and experiment so much with 3d printing :) keep up the good work :)
Neat! I usually cure my prints using 3 different light sources and I've also notice parts get stronger a few days post cure. Firstly I accidentally cured some resin using a super bright WHITE light. Not sure if the LED in it kicks out some UV but it flash cures the top layer and never really penetrates. I also use 395nm and 365nm. The 395 does most of the curing and penetrates really well with minimum yellowing but the 365nm seems to cure resins extremely well and leaves a harder than normal surface but it does tend to yellow most resisn. Secondly I was printing cupons one day for a simple comparison between different resins, colors, and additives I've been playing with and I found out that if the prints is post-cured and then allowed to rest for a few days the prints generally hardens some more, yield less and get stronger. In my experience all the resins I've been playing with do this, water washable resins, abs-like, abs water washable, traditional resins. Plus the manufacturer 3DMaterial does mention that their resins will harden some more after a few days, and no they haven't been the only brand I've tried.
@@BrunodeSouzaLino Blue light alone doesn't cure resins, plus I have several flashlights that don't cure any of the resins even after hours of exposure and if brightness alone was the factor then it would be impossible to record good quality video of resins in an uncured state. And, no, white LEDs aren't "actually blue light." Although a good white led emits a well-balanced spectrum from red to purple, most LEDs have spikes at specific spectrum and are balanced around the spikes. Which is why Color Rendering ratings and pantone color palates are a thing.
If you haven't been curing in glycerol for at least 60 minutes, that "hardening some more after a few days" is a side-effect of improper under-cure. I cure as above with 300-500nm fluorescent bulbs [LC-3DPrint Box] at up to 80 deg. C, and the results are outstanding even for consumer resins like Sunlu ABS Like...
Absolutely amazing research! I just saw a video with Adam Savage and the team at Carbon who is working with Adidas. They do a combo like this but use the printer to lock in polyurethane chains the. Use heat to fully cure it which gives a durable shoe sole. Very impressive stuff. I hope we start seeing resin manufacturers design in heat cure properties for DIY guys in the near future.
anycubic came out withe Rigid 100 resin, it cures requires 1 hour of UV curing at 80C to get 100% more strength, i threw a chunk of it as hard as i could on concrete and it chipped a stone aggregate in it and resisted shattering with only deep scuffs.
I work in the carbon fiber industry and have some input! You mentioned the “giant ovens” aka “autoclaves”, but you didn’t mention the other huge property of them; they are pressurized! Carbon fiber parts are vacuumed down to get the resin into the fibers, and for high tech applications the autoclaves are also pressurized. It would be interesting to see if pressure would net these resin-only parts any strength. Maybe putting some UV LED strips inside of a pressure cooker would make an interesting video!
Thanks for the interesting study! I look forward to more resin print videos from you! Hopefully, SLS plastic printing will someday be affordable for hobbyist too! I bet you could come up with a lot of cool videos on the topic.
This is really cool! I love the thought and effort that goes into your videos, I appreciate your diligence to find solutions and answers to questions that so many have ignored or considered unknowable. Excellent video :) However, something important to understand about statistical analysis is that if the error bars on the graph overlap, that means there is no statically significant different. In other words, one cannot say that there is a trend upward in the tensile strength of resin as the temperature before curing goes up (for the CW1S test graph). The error bars overlap, therefore the strength cannot be considered different. This is also the same for the graphs about heat during curing, the IZOD impact test, and the additional information about heating after curing. However! I still think you have excellent results! You showed the results clearly and there *is* a difference between temperatures during curing, which means this **does** result in stronger prints from a statistical analysis! As I said, I love your videos! And I think this one is very cool! It’s hard to get statistics right, so I totally understand, I’ve made many mistakes myself! Even though I am criticizing some of the analysis, that doesn’t mean I feel like you are being dishonest! It is a mistake that I feel the vast majority of people make, especially if statistical data analysis isn’t a part of their daily lives (that being said, I don’t know what your daily life looks like, so I apologize if I’ve spoken out of turn in this regard). All that to say, excellent video, as always, and I really look forward to the next one! I am always excited to see what new ideas, experiments, and cool techniques or methods you’ll show us next :)
For many years now, there are a lot of dental curing devices which combine UV and thermal curing. Some models even have programmable temperature ramps like reflow ovens. Another inexpensive option is to use incandescent UV light source, which produces a lot of heat (like 10% efficiency in light conversion - the rest is heat)
I bought a microwave convection oven with turn table and removed the magnetometer and installed a UV lamp in its place. It was a bit of work to invent a new control system, but it was worth it. I created a stand for my parts to insure even heat and UV exposure to prevent warping
I've discovered this effect when I left a resin printed part on my windowsill. It was way stronger than any of the parts I cured with UV light. I wasn't sure what caused it at first, but eventually figured out the the temperature of the sun helped with curing.
You proved an idea I've had ! You mentioned composites earlier, its pretty standard to post cure parts. Most thermosets are the same. Its a heat reaction. Ive long hypothesized that you dont need the uv. Even two part resins will cure with just heat. Even with no heat other than ambient. I used to mix resin that had no catalyst. I had to add the reactants to the resin before we could add mekp to infuse composite parts. But even the un accelerated resin would cure after a long time in summer heat 😂 😂 Awesome 👍
I print a ton of resin prints. The way I do it is I use a heated ultra sonic to clean my parts which heats them up and cleans them, then I put the prints on top of my radiator heated to 60c for a hour ish(i often forget and do like 4 hours no biggie lol). Move them to cure chamber while still hot or best yet put them in a small transparent container filled with warm water and UV cure to retain heat and maximize the cure process. Fun fact, heat cure is required for Blu resins to be properly biocompatible.
I have a strong background in resin casting. Using chemical hardeners that cure the resin in a mold instead of photo initiators creating nucleation points. We almost always annealed resin casts, which made for a more noticably durable material. So it makes sense that annealing post curing in UV results in increased strength too, as this is basically how annealing is done in resin casting. It's not always necessary to do, but even in wargaming miniatures, depending on what resin you use, such as ABS-like resins, the ductile strength of that resin remains while increasing tensile strength. TL,DR; Its almost always beneficial to post cure anneal your resin 3d prints.
I have been heat curing my resin prints in my filament dryer at 65C for a while and it helps for sure. If you look at the documentation for high end resins they specify high temp cures, somehow it just hasn't trickled down to the hobby space
Radiant heating elements, like those used in your oven DO emit light depending on the temperature/energy level of the specific element. The light just isn’t in the spectrum humans have evolved to see. High power elements glow red because they end up projecting about 80% of their energy in a spectrum that is visible to the naked eye. I love this concept and I am begging you to try to use the scientific method to determine how much of the curing process is actually because of the temperature alone vs the “invisible” light being created by the elements themselves. Thank you so much for sharing everything you have with the community and keep up the good work.
Couple of suggestions: 1. Remove prints from supports after washing but before curing. 2. When removing supports, soak in hot water for a little bit. Tap hot is good enough. Both of these things make support removal much easier in my experience. And yeah, for minis we want those things to be tough.
I bought a cheap round food dehydrator with glass clear housing to dry my filament spools (as you showed earlier) which is capable of reaching 70°C at any location inside (proved with digital thermometer). I can imagine to cure resin prints in it with 70°C or less and an UV-lamp shining from the outside in. Have to be sure to protect eyes from the UV-light with googles or a surrounding housing.
Definitely noticed that heat leads to strength. I run my resin prints in my garage where I don't have to breathe any of the vocs. During winter I use a 220v electric heater. I usually aim for about 35C during the print, after the print I crank it up to pull supports off more easily, however I have left the heater blasting my printer before and it becomes concrete esq. Good video.
Formlabs actually has a white paper somewhere (from a long time ago) showing graphs of mechanical properties with varying temperatures and time as well. The one caveat is that the optimal curing temperatures are often very close to the HDT of these resins - which means that heat curing will OFTEN result in warping if you're not careful (there are a ton a caveats and subtleties here - ask me about it sometime 😅)
I don’t do resin printing, but I do work with a lot of thermal and dual UV, thermal cure epoxies. There are default manufacturer-recommended cure schedules, but other curing schedules are possible (and manufacturers will often provide some alternatives if asked). Curing at a lower temperature means a longer cure schedule to fully cross-link the polymer. As the reaction rates increase non-linearly with temperature, lower temperature curing schedules often require a significantly-longer cure schedule.
@@JonS yeah, that all makes sense and matches the white paper from Formlabs as well. From what I recall their graphs showed that lower temperatures would "never" reach the same mechanical properties. But by "never" I mean, not in a time frame that was tested or deemed reasonable for the end user.
@@emberprototypes yes. Lower temperature cures will be less strong, so the trick is to cure as close to the recommended temperature as possible, but not to the point of losing dimensional stability. In my work, we are often limited by the maximum temperature of other components in the opto-electronic systems we are building, so we have to find the right balance by performing DOEs where we adjust each variable and measure the result.
I vaguely remember Sanladerer trying to glue 3D-prints with resin and failed, because the UV-Light was not able to penetrate the resin and the “glue” only got cured a fraction of a millimeter on the outside. So the curing after print seems to primarily cure the stickiness of the surface of the object. Even resin thats optical clear in visual lightbands absorbs UV, otherwise printing would not work. This results in me being a bit sceptic about your statement at 1:35. Maybe elevated temperature has the effect of hardening the inside of the objects. As of a rule of thumbs says that every 10 °C increased temperature speeds up chemical reactions by a factor of 2.
Yes indeed there is a lot of potential behind properly curing resins. Some factors I would think to look into for future videos on this topic are: Thermal and UV curing *times* (and as you touched towards the end if they should be done at the same time or seperately and what order), chamber temperature while printing, thermal and uv curing in a liquid/water (protected from oxygen or for some other reason) and the main one I think not considered by many, the *cleaning solution and temperatures from the cleaning process*. I have found that using cold isopropyl alcohol and especially letting the prints dry, evaporation lowers the temperature of the parts even further and this lowers the impact resistance. It indicates to me some type of thermal shock and at least making the shell of the parts weaker. By the way I have noticed also in some clear resins that thermal post-curing affects how much yellow they get from the UV post curing (and how fast the yellowing can fade away after some days).
Hi @CNCKitchen, I work in a company that's specialize in bonding manifolds with Acrylic and Ultem, the thing is that the annealing process it is especially important to cold down the material "slowly" inside the oven, if for some reason the cold down is too quick like take the part outside the oven and let it cold down, the plastic is more fragile. I don't know if have sense what I'm saying (my English is not good)
I just got in to 3DP with a Elegoo Mars 2 Pro, have only just gotten mine to play nice and work with basic gray. this will be a nice new thing to play with.
Man that’s such a genius idea! I have a lecture all about composites and one was specifically about epoxy resins, yet it didn’t even cross my mind that those same curing principles could also be used on SLA prints. (Currently doing my masters in Aerospace engineering, like you did). The strengthening is most likely through getting a tighter amorphous structure, since the heat wiggles more monomers/partially formed polymers in the previous empty spaces (through brownian motion and liberation of some degrees of freedom in the polymer bonds -> T>Tg). On a chemical level hardened epoxies look a bit like a sponge with empty spaces where no active group could reach the other active groups, due to the size of the formed polymers. Grüßle :)
Hi Stefan, thank you for doing a resin video again. I heard a lot that the exclusion of oxygen during post curing can improve the strength of resin parts. Could you test parts cured in hot water or even under vacuum or nitrogen atmosphere?
@@user-it7kg3pm4q Thanks. How do you know? Have you measured it by any chance? You could be right since oxygen is only affecting the surface. Regarding impact strength and bending strength I thought the surface properties could have an impact in regard to those properties.
even if it doesn't affect the bulk, a smooth well-cured surface can still be a major improvement of strength, by not promoting crack initiation. I use this oxygen-free curing a lot, but it's more about hand-made things... i don't have an sla printer yet
Great test, thanks. I would have guessed that it it would make the part more brittle by increasing the hardness. For my functional parts I actually prefer a bit more "give" over maximum total stiffness as most part stresses are transient rather than load to failure.
Curing in warm water has been mentioned a couple of times. Microwaves or infrared light should be able to penetrate the interior of the model much faster, thus reduce any kind of warping.
This is, as usual from this channel, really awesome. I really wish resin printing was less of a pain. There needs to be a Bambulabs esque ease of use boost to SLA where you can press print, and have the parts washed and cured automatically so you can get by without the whole gloves and mask setup. Of course, what would also be awesome is that higher temperature forced air heating for the curing station. The technology all seems there, so I guess its up to some company to implement. It feels like something it might even be possible to implement as a single person with some servo actuation only needed to switch between printing and curing. So much potential, and this type of printing looks so much more professional than FFF parts.
I cure my resin prints in water. It takes the same amount of time (2-3min, flip, 2-3min). I find they come out way less brittle and stronger. I use a UV spotlight mounted on top of a stainless steel pot so I can take advantage of the reflections of the pot but I still flip them half way through and sometimes if there's hard to get areas of the print I'll orient it so it will get more light and do another run. I haven't had an issue and I believe they come out stronger. I use room temperature water, I never thought about heat. I may have to test this with warm to hot water and see if it makes a difference. I made a load cell mount from resin for large bar style load cells (16 of them actually) and they held 40kg for over a year in a hot environment. I eventually replaced them because they ever so slightly sagged over time but I was amazed they went that long. I believe that water curing had a role in that. This was with Standard ABS resin.
i personally use a food dehydrator to finish curing my resin casts (as i already have one for dehydrating herbs) so it's nice that it's basicallt dual purpose for me. Hope this info can help anyone else even if the resin i use is chemically curing instead of uv-curing like with a resin printer
It makes sense if it works something like... heat is basically adding energy into a chemical system as well as loosening some weaker bonds (I think hence the softening). The additional energy makes the bonds jump around a bit thus finding more optimal cross connections and more numerous ones.
I have always been skeptical about UV post curing because UV only penetrates ~50 micron into even clear plastic. Thx for Stephan for finally test out this myth.
Did you take into account that the resin might react differently to the wavelength of the light used? These LEDs look like 365 nm, but if I remember correctly, a wavelength of 405 nm is required. Also the oven might mess with the light produced.
It would be really cool to see these pieces before and after different treatments through polarizing light filters to observe the stress patterns in the structures. You only need polarizing filters (cheap) and a flat monitor (blank white screen) - look for "How to find Stress Patterns with Polarizing Filters". Also would be REALLY cool to record the strength test with the filter. If I had a resin printer and a strength test machine, I would do it. Lol
Here's a thought: Print some more Blu test pieces. Check the strength of one set right away and then a second set after standing at room temperature for, say, two-weeks or a month and retest. Perhaps the strength will improve significantly just from further curing without heat.
Very interesting video. You mentioned you found no significant shrinking, but I wonder if it affects post-print warping on thin flat parts. I mention this because I usually have warping in some parts after "normal curing". If this method fixed that it would be a game changer!
Love all the tests! Would love to see a materials comparison with more than just tensile strength such as, abrasive resistance, hardness, heat resistance, durability, etc. Especially over time, how does a print made today compare with one made 1 year ago, or 3 years ago? Do different materials age differently? Those are questions I would love to see answered.
I work for a german medical company and you would be suprise what kind of photopolymers are on the market from Henkel (Loctite) or Dymax. For catheter applications there are ones for glue application which starts the polimerisation process with a tiny but of uv light then can be cured all the way in the oven with uv light, for jard to reach places. Or other ones reaching final hardness just via uv light. But one thing all of them have in common, none are long term stable! Not even Startasys manages to produce long term stable uv resin which can hold it‘s strength and toughness longer than 1-2 years. That‘s why for long term functional parts, always sls, mjf or fdm prints.
Have you tried curing parts in water? I’ve had great success using a cheap wash and cure. I wash normally in ipa, allow to dry. Then placing the partin a hot water bath in a clear vassal and curing that way. Cheap and effective!
Perfectly timed, I am trying my first round of acrylic painted prints in a food dehydrator (to speed up paint cure time) as I write this. I was curious what effect it might have on the resin prints and couldn’t really find much info on it.
Have you tried curing in water? Perhaps try curing in different temperature waters too. Including 0 degrees c up to boiling/100? This would be a way to get up the temps. without worrying about equipment's health. I know for some casting resin curing them inside vegetable glycol to remove their contact with air whilst curing helps them with burn out. Maybe trying heated vegetable glycol too so the parts can't absorb water.
Yep, some of my prints I put into boiling water (in a microwave) and this makes a big difference for white parts that have yellowed or clear parts that have yellowed plus the increase in strength and stiffness. This gets you to 100C. For opaque parts continued UV curing only cures the outer layer while the inner volume of the parts doesn't cure any more. Heating the parts helps to uniformly cure the part through the thickness and thus the increased strength.
I don’t print with resins, but in my work I make use of dual UV-thermal cure epoxies. This result doesn’t surprise me. In the materials we use, we achieve maximum strength when using the minimum UV pre-cure and complete thermal cure. Over-curing with UV results in a weaker bond. In your thermal only post-printing treatment, you might want to a longer cure time. Try increasing the thermal cure time (2 hours, 4 hours). You might not be fully cured after 1hr at 80°C.
Right on, JonS! The 3D printer resins can't be "over-cured", they can only exhaust the photoinitiators and reach their final properties when cured for the proper amount of time (ie, are cured long enough, usually at least 60 minutes or more). Crappy consumer resins [as opposed to better consumer and industrial resins] rely on under curing to hide their deficiencies [at least for a few weeks or months as is well known]. Good consumer and industrial resins when under cured [without proper temp., too] never reach their full, best properties. Curing properly in glycerol in addition is just about optimal and easily achievable by even hobbyists.
I have Formlabs Form3, and both wash and cure stations, I just assumed that cheapo MSLA curing is also done at temperature. I've always set the curing station to heat up first, then put my parts in.
Very good. It is to do the same test but with standard resins and abs from brands such as anycubic, sunlu, elegoo etc because they are cheaper resins than siraya
Another good question about curing is: to which depth gets the resin cured, with or without post-heating? Because UV definitely won't get more than a couple of mm within the print. If you leave a 1-2-3 mm center channel in your test samples, will the tensile strength be different?
I find shorter washing times in IPA also result in less brittle parts. To me it seems as the IPA damages some of the molecular bonds in the resin. I try to wash as short as possible. Rinsing parts in soapy warm to hot water before curing will bring the resin temp further up before the UV light cures it.
we would love to send you some of our latest thermal resin - it kickstarts later this month and is designed specifically with this kind of curing in mind.
A while back, I saw people curing their resin prints in a glass of water inside the UV chamber, arguing that the water better dispersed the UV light across the model. I imagine you could probably use a clear Pyrex bowl filled with hot water to achieve a similar effect.
Would love to see the results using tough and flexible resins as well. A lot of people doing miniatures use tough resin, or a mixture of flexible with other resins.
for me the underwater curing was the best, after washing, claenaing and removing the supports i put the models ina vlear plastzic container and pour warm(~40°C ) water on top, curing them in water for 5 mins. The print this case wont be as brittle as in dry curing, i dont jknow the chemistry behind it, but some says it has something with oxidation, Can you please thest this method too?
Would love to see you test out curing while submerged in heated water. Sirayatech recommends curing under water as well as many other tough resins. I've been curing my parts while submerged in 60c water and letting the part cool in the water to room temperature. I'd love to see if this has the same effect. If so, a very effective curing heating machine could be build with a sous vide or instapot
Perhaps it would be interesting to do a temperature test as well? Annealing at 40C all the way up to 160C or something? Especially the tradeoff between strength and toughness could be interesting. And of course… when serious deformation happens
Just had a random thought... rapid cooldown vs long cooldown for annealing parts, which is better? I can see few possible ways to cool parts, including just leaving it in oven as it slowly cools down.
A bit worried different time between printing and curing can have an effect too, since you printed them all together but cured in succession. May also explain how going from 40 to 60 then 80 you get more and more consistency in the results, the uncured resin had time to rest and rearrange the structure.
Does this open new possibilities for resin 3D printing?
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first
Do you have to heat them while curing?
Can you just stick them in the oven after curing?
Edit: 5 seconds after I posted this comment, I got to the answer in the video.
emerald!?
I was guessing you were going to cure with heat and an oxygen inhibiter (water). Siraya Tech actually suggests using water to cure Blu resin (in their TDS). I believe the idea is to inhibit oxygenation, which is determental to the curing process. Siraya Tech mentions its more efficient as well, generally speeding up the curing process.
@@mikejackson9585 Really good point. I'm going to try curing in hot water.
Evidently I need to make a resin-version youtube channel of CNC kitchen. When you devote 2 years to making graphene additives for photopolymer, the testing methods to get there paint a different story. Water-curing after an ultrasonic bath for specific formulas is also quite effective.
Water curing is 100% the way to go.
Yes please!
@@michaelramos4482 With a sous-vide machine for perfect temperature control. :O
Gotta try water curing next! Maybe even hot water curing😳
@@CNCKitchen Now we're really going towards the "Kitchen" part of your channel's name
One of the most important things for me in 3D prints for functional parts is creep. Rarely do I need higher than 60ºc temperature resistance, but often I do need parts to stay in shape while loaded for long times. This kills PLA for several of my projects, despite it's many advantages.
The same is true for the Formlabs Black resin, we also got the wash and cure station at work and we use the machine whenever we need to show pretty stuff to the costumers, but when it's time to make some functional prototypes to last field use, no no. It creeps way too much.
Creep tests is one thing I would like to see being explored more thoroughly, there's much more to part strength than short loads after all.
One thing I've often done with larger resin prints with heat is straightening warped walls. Large parts will sometimes get warped during printing or curing (specially that 60°c 1h curre that we go with the Formlabs station), a friendly Ender 3 with it's flat glass bed at 60°c for some minutes with correctly placed weights, then let it cool naturally until about room temperature, and we're good to go.
Same with PLA actually.
There are no non-creeping resins. They are all amourphous polymers based on acrylates or epoxy -for obvious reasons. The glass filled ones like Formlabs 4k are somewhat better, but it's always just a quantitative difference. If you want non creeping stuff you need to use ASA with CF or annealed PET with CF.
Just make parts bigger (with bigger contact area etc). That helps avoid creep. Creep mostly works at loads close to maximum
@@testboga5991What you mean is _less creep_ . We would measure creep in zirconium pressure tubes (or at least experimental analogues).
@@testboga5991 Nice addition, didn't know that far into the resins, kind of a bummer. I was wondering most about FDM as that's what I've got on reach for my own stuff (home printer), on which I use ABS when the parts are small enough and PETG for larger stuff as an in-between compromise material. At work we got the Rigid 4K too, used mostly or almost entirely for injection molding prototype molds.
That thing is a heck of an annoyance to work with tho, don't use it for a few months and you'll have a viscous paste at the vat, that also has way shorter lifespan when used with that resin.
Check out 'my tech fun' youtube channel, he makes creep tests for many types of materials, though FDM focused.
We post-cure our Siraya Tech and 3DMaterials resins immersed in a rotating hot water bath for at least 1 hour. The first 15 minutes are exposed to UV. The water will be heated to 60-80 Celsius depending on the resin used. Most of the time, the resin will be directly immersed in water, except those that are meant to be used at high temperatures or contain filles, such as ST Sculpt and Sculpt Ultra White. These will be put in a bag with light vacuum seal.
Most of the parts we make are meant for end-of-arm tools for industrial robots, manufacturing aid elements and injection molding tool components
What do you mean rotating? A submersed pump circulating water in the bath, that you change the water between post cures, or the whole bath is physically turned around during the process?
Try the same thing with glycerol instead of water and see the difference, it's equal or better than curing in a vacuum chamber.
@@pbkobolda guess,but since they are also curing under water the rotation may be to ensure even exposure.
@@pbkobolda simple rotating curing station, but you place a hot water plastic container on the turntable and drop iso-washed parts in.
@@imperatormegatron2014 agreed. I've only ever water cured my parts. I dont have any kind of rotation setup yet tho. And make sure you clean the parts well, and wait for the IPA to dry
I own a FDM printer not resin, but I use epoxy resin for projects and put them in the oven after it has had its minimum cure time.
I have always wondered why people never used heat for their resin prints and just presumed the resin used for 3D prints isn't possible, glad someone (you) have shown resin printer users this trick. Good work.
Another tip also, when I use epoxy resin, if say 60c is the highest you want to cure, start at 40, then to 50 then 60, when time is up, do not remove the part, leave the part inside until the inside of the oven has gone back to ambient temp.
I print a lot of resin dental prosthetics we use temps anywhere from 20-60c for up to an hour depending on your curing unit. Some units use nitrogen filled chambers to cure while others finish cures in a 60c water bath .
yep, my denture resins calls for curing 20 minutes in 60C glycerin bath, or sealed in a bag in a water bath.
I worked back and forth with siraya tech over a cunfusion with their blu mecha formula. One incredible technique the engineer told me to cure the resin 3D print submerged in water. I noticed a big difference in hardness and strength when doing this
water submersion UV curing at room temperature will make your resin prints so much better, especially the surface finish.
Hi Stefan! We print from BASF and Loctite resins at work (automotive prototyping) - and it is actually required to "bake" the finished prints for a while before UV curing. Not so high temperatures - around 40-50C for 30-60 minutes. So if manufacturers like these companies recommend it, there is actually some science behind :)
And with Siraya Blu You can even go higher - i did several tests up to 250 C - for 60 minutes. Interestingly - part remains in its original shape, but starts to crack at temperatures above 125 C. Resin prints dont melt into blobs as FDM prints - there are a lot of "undiscovered" areas of resin printing ...
Heck yeah! I’m testing out a new resin and they sent me a toaster oven to test it out! Excited to see a detailed explanation of how this works
Hey Uncle Jessy! “Always watching!” 🤣
@UncleJessy - do the tests with the parts you print cured in a glass jar filled with heated glycerol, too - you'll be surprised!
Are you going to make a video about this too?
This is the first time I am hearing of it.
I'm assuming once a thing gets used for resin, it never gets used for food .. correct?
@@tomthebard42 absolutely correct, stuff will stick inside of there and it off-gasses a ton. also, since working with resin (irresponsibly, i will add) I've developed 2 or 3 skin tags particularly where i've handled the resin with bare hands.
don't be like me- wear your PPE!
Important addition: beside monomers, oligomers and photoactivator there is also up to 50% filler. Filler made of some organic molecules wich didn't parcicipate in polymerisation. They made part less brittle but also less strong. And may result in developing cracks in a part over time.
Cheaper resins usually have higher % of filler.
Not long ago I aquired a new resin printer and immediatly made a curing station with a 20 dollar used microwave that I salvaged (because I wanted something with a rotating plate and a timer) replacing the magnetron with a 405nm UV lamp like yours.
There's still two 220v terminals that were originally connected to both the normal microwave bulb and ventilation fan that I now could connect to a heater and have a fully automatic Curing and Heating station with a rotating plate and timer! I could also add a thermostat for safety
I've been curing my abs-like resin in a very large glass container filled with water that I preheat with a old sous vide heater. Works fantastic. The water inhibits oxygen thus boosting curing rate, and it helps get far more even uv exposure!
Try the same thing with glycerol instead of water and see the difference!
@@retromodernart4426 Sounds considerably more messy. Does Glycerol improve strength even more, or just even better cure times?
@@MoonWind32690 Both, but the concept of "cure time reduction" is a deception - a resin needs a certain dose and duration of UV (and heat) until it competes the polymerization (aka "curing") process properly.
Undercuring resin is always bad, and will not prevent the inevitable embrittlement, warpage, shrinkage, etc., of using a defective (improperly formulated) resin when it reaches "full cure", whether in a curing chamber or after 6 months on your shelf, for example.
Proper cure duration is usually 30-60 minutes at least at 30-80 deg C depending on the resin (in a curing chamber with proper UV power and wavelength(s)).
Glycerol is completely water soluble and it's very easy to clean and work with cleanly with the slightest forethought.
What you mentioned about curing PLA vs resin is a usual behaviour of thermoplastics (everything on a FDM printer) vs. cross-linked materials (everything on a resin printer) and explained absolutely correctly. About your thermal curing experiment: nicely done. Many photoinitiators are also unstable towards thermal initiation, so I am not very surprised by your result without UV light, and any crosslinking reaction will be quicker due to heat (our old friend Arrhenius), but it's nice to see the data. I still admire your DIY tensile and impact testers.
edit: it might be interesting to do the same with non-transparent resin to see if the effect of thermal treatment is even higher compared to using UV light which would be expected since UV will not reach the interior of the part then or to vary the length of the curing to see if it is just an Arrhenius effect or you are actually starting new initiation reactions with the heat treatment.
Another banger Stefan. I always recommend your channel to newcomers to printing. Your scientific approach is such a breath of fresh air compared to so many other sources.
Appreciate it!
@@CNCKitchenyou made a typo in the title "makes then MUCH" vs "makes them MUCH"
Last month the interlocking layers now a review of the curing its great seeing how a few ideas can really improve the usefulness of prints
Great stuff. Kudos to Stefan, I generally don't look for new videos in my TH-cam subscriptions, but on weekends I always hope CNC Kitchen has a new video to watch while I workout.
Nice work! My emake-3D resin cure station has a built in heater which I never used. I will have to give this a try.
I actually discovered this by accident thanks to a messy house finch couple. Putting prints outside had been part of my post curing process already. I assumed it was more UV from the sun making the prints stronger but the finches knocked a part into the shade and it was still as strong as the rest. Turned out it was the heat.
That "use your heated bed as your oven" trick is a game-changer. We only have one climate chamber at work and it's always in use, so I could only borrow it for enough time to prove that annealing works, but not long enough to anneal every part we print. That and I can't afford a climate chamber at home!
Super interesting results! A natural progression from this topic will be how to keep the prints strong as many report the parts become brittle after a few months. So what is the difference after 3 months vs painting them vs coating with UV clear coat. Great video!!!!!
i usually post cure with the parts submerged in water - this quickly removes all stickiness from the surface (oxygen contact seems to inhibit the curing of the resin!) eg. if you didnt clean them 100%. And using hot water may double in adding strength while keeping the parts from deforming - Thanks for the tip!
Oooh, it's the oxygen! Thanks for that tip! Now the water or nitrogen other commenters write about make sense.
More SLA videos please! :) At the moment the resin printing community is sadly still at the stage "do I *really* need to buy a curing station?" as well as "do I *really* have to clean and cure my hollow prints from the inside?". But there are at least fewer people asking "but is resin *really* toxic?" and "do I *really* have to wear PPE?", which is nice.
The consensus I've found is that a curing station is for convenience more than functionality. Curing outside in the sun worked well enough for me
@@tomthebard42 Sun is a well-known consistent source of the UV-radiation.
@@GeorgMierau well known: yes; consistency *highly* depends on where you live though
@@Chaosghoul Exactly. Hence the curing station.
I do a post-wash cure in a glass jar filled with hot water. I'm able to cure prints faster in water so I don't worry much about the water cooling before I'm done. It works great!
Incredible research pushing the boundaries of 3d printing, thank you for posting this.
I've been doing this for a very long time now. And it works with most resins I've tried.
Hi Stefan, very good video as usual! Always a pleasure to watch your videos.
Regarding your test results I think I have an idea, why your last test worked:
During heat+UV cure, you split the photo initiators into radicals, which then lead to polymerization. More heat increases the brownian motion and thus increases the cure speed.
If you now do the UV cure first and the heat treatment afterwards, I think the following happens:
First you create radicals of the photo initiators with the UV light, which mostly find a monomer or oligomer due to their sheer number. Some of those radicals however end up not finding a partner to react with and thus stay in their radicak form. If you now increase the temperature without UV light, you don't create new radicals, but you increase the mobility of the remaining radicals through brownian motion and thus increase the likelyhood for those to find a matching monomer, oligomer of polymer. Repetition of the cycle might lead to less scatter in the results, I think.
So does this mean that time could act the same way? Does resin print yield strength increase with time?
@@austenite239 Not necessarily, BUT it's well known and observed that the resin continues to "shrink" and "cure" for quite some time (days, weeks) after _conventionally_ curing.
Longer cures [60 to 90 minutes in general] in Glycerol with proper UV power with temp. reaching 60 - 80 deg. C will lead to the resin properly curing to its final properties and strength.
Most people improperly under-cure the resin prints in air, which either hides the resins' deficiencies or prevents the resins from reaching their full and best properties.
@retromodernart4426 What are the benefits of using Glycerol over water?
@@joeljonker990 Copy and paste this into your favorite search engine:
"Evaluating oxygen shielding effect using glycerin or vacuum with varying temperature on 3D printed photopolymer in post-polymerization"
THANKS SO MUCH! I print a lot of rather technical stuff in resin. This for I mostly take water washable black ABS-like resin from Sunlu. Making the parts even stronger is a great thingtp look fwd to… 😃
Sunlu Water Washable is extremely underrated. It's so strong in companion to other resins in its area from testing I've seen.
I had read that the main purpose of the UV in acting on the photoinitiator is not very different from how resin polymer initiators are activated, it essentially is adding energy to the system. The photoinitiators have been found to be more sensitive to that style of energy instead of say, heat but it makes sense that heat would also do it.
Being able to throw a print into an oven post-curing is a lot more hobby friendly than trying to make a setup to cure and heat at the same time. That's exciting to hear and I hope there is more research done with it.
Such an informative video. A minute in and I've learned so much about resin printing that I missed.
Glad it was helpful!
Stefan, excellent video (as always!)
I find that curing the parts in very warm water has yielded drastically different results in the quality of my prints.
Thanks! If you say "drastically different", is that good or bad?
@@CNCKitchen a very large, positive difference between a 'standard' dry, unheated cure and a cure in warm water.
@@CNCKitchen As someone who primarily resin prints, I'd personally love to see that tested, as it's much more reasonable than buying/making a small heater lol
i just want to point out that i am happy to see how you look like... you look allmost as i would have imagined... but with more curls in your hair... has seen your videos for a long time and actually seeing how you look like is amasing :) i have allways loved your unbiased and sciantific approtch to 3d printing and i have alot of respect for your work... as someone who has a education in plastic injection molding it is amasing to see someone who knows so much about and experiment so much with 3d printing :)
keep up the good work :)
Neat! I usually cure my prints using 3 different light sources and I've also notice parts get stronger a few days post cure.
Firstly I accidentally cured some resin using a super bright WHITE light. Not sure if the LED in it kicks out some UV but it flash cures the top layer and never really penetrates. I also use 395nm and 365nm. The 395 does most of the curing and penetrates really well with minimum yellowing but the 365nm seems to cure resins extremely well and leaves a harder than normal surface but it does tend to yellow most resisn.
Secondly I was printing cupons one day for a simple comparison between different resins, colors, and additives I've been playing with and I found out that if the prints is post-cured and then allowed to rest for a few days the prints generally hardens some more, yield less and get stronger. In my experience all the resins I've been playing with do this, water washable resins, abs-like, abs water washable, traditional resins. Plus the manufacturer 3DMaterial does mention that their resins will harden some more after a few days, and no they haven't been the only brand I've tried.
All white LEDs are actually blue light.
@@BrunodeSouzaLino Blue light alone doesn't cure resins, plus I have several flashlights that don't cure any of the resins even after hours of exposure and if brightness alone was the factor then it would be impossible to record good quality video of resins in an uncured state. And, no, white LEDs aren't "actually blue light." Although a good white led emits a well-balanced spectrum from red to purple, most LEDs have spikes at specific spectrum and are balanced around the spikes. Which is why Color Rendering ratings and pantone color palates are a thing.
If you haven't been curing in glycerol for at least 60 minutes, that "hardening some more after a few days" is a side-effect of improper under-cure.
I cure as above with 300-500nm fluorescent bulbs [LC-3DPrint Box] at up to 80 deg. C, and the results are outstanding even for consumer resins like Sunlu ABS Like...
@@Guardian_AriasSome white LEDs I think use phosphoretic compounds that get excited by blue light to provide red and green
Absolutely amazing research! I just saw a video with Adam Savage and the team at Carbon who is working with Adidas. They do a combo like this but use the printer to lock in polyurethane chains the. Use heat to fully cure it which gives a durable shoe sole. Very impressive stuff. I hope we start seeing resin manufacturers design in heat cure properties for DIY guys in the near future.
anycubic came out withe Rigid 100 resin, it cures requires 1 hour of UV curing at 80C to get 100% more strength, i threw a chunk of it as hard as i could on concrete and it chipped a stone aggregate in it and resisted shattering with only deep scuffs.
I work in the carbon fiber industry and have some input! You mentioned the “giant ovens” aka “autoclaves”, but you didn’t mention the other huge property of them; they are pressurized! Carbon fiber parts are vacuumed down to get the resin into the fibers, and for high tech applications the autoclaves are also pressurized.
It would be interesting to see if pressure would net these resin-only parts any strength. Maybe putting some UV LED strips inside of a pressure cooker would make an interesting video!
Thanks for the interesting study! I look forward to more resin print videos from you! Hopefully, SLS plastic printing will someday be affordable for hobbyist too! I bet you could come up with a lot of cool videos on the topic.
This is really cool! I love the thought and effort that goes into your videos, I appreciate your diligence to find solutions and answers to questions that so many have ignored or considered unknowable. Excellent video :)
However, something important to understand about statistical analysis is that if the error bars on the graph overlap, that means there is no statically significant different. In other words, one cannot say that there is a trend upward in the tensile strength of resin as the temperature before curing goes up (for the CW1S test graph). The error bars overlap, therefore the strength cannot be considered different.
This is also the same for the graphs about heat during curing, the IZOD impact test, and the additional information about heating after curing.
However! I still think you have excellent results! You showed the results clearly and there *is* a difference between temperatures during curing, which means this **does** result in stronger prints from a statistical analysis!
As I said, I love your videos! And I think this one is very cool! It’s hard to get statistics right, so I totally understand, I’ve made many mistakes myself!
Even though I am criticizing some of the analysis, that doesn’t mean I feel like you are being dishonest! It is a mistake that I feel the vast majority of people make, especially if statistical data analysis isn’t a part of their daily lives (that being said, I don’t know what your daily life looks like, so I apologize if I’ve spoken out of turn in this regard).
All that to say, excellent video, as always, and I really look forward to the next one! I am always excited to see what new ideas, experiments, and cool techniques or methods you’ll show us next :)
For many years now, there are a lot of dental curing devices which combine UV and thermal curing. Some models even have programmable temperature ramps like reflow ovens. Another inexpensive option is to use incandescent UV light source, which produces a lot of heat (like 10% efficiency in light conversion - the rest is heat)
I bought a microwave convection oven with turn table and removed the magnetometer and installed a UV lamp in its place. It was a bit of work to invent a new control system, but it was worth it. I created a stand for my parts to insure even heat and UV exposure to prevent warping
correction, Magnetron
@@buboo_bubobubo don't try this unless you are very comfortable with electricity. The Mag and Capacitor can kill I'm told
@@alexportiiii6414 Ah, I was actually confused xD .
I've discovered this effect when I left a resin printed part on my windowsill. It was way stronger than any of the parts I cured with UV light. I wasn't sure what caused it at first, but eventually figured out the the temperature of the sun helped with curing.
You proved an idea I've had !
You mentioned composites earlier, its pretty standard to post cure parts. Most thermosets are the same. Its a heat reaction.
Ive long hypothesized that you dont need the uv. Even two part resins will cure with just heat. Even with no heat other than ambient.
I used to mix resin that had no catalyst. I had to add the reactants to the resin before we could add mekp to infuse composite parts. But even the un accelerated resin would cure after a long time in summer heat 😂
😂 Awesome 👍
This is really intriguing for functional-printing folks!
I print a ton of resin prints. The way I do it is I use a heated ultra sonic to clean my parts which heats them up and cleans them, then I put the prints on top of my radiator heated to 60c for a hour ish(i often forget and do like 4 hours no biggie lol). Move them to cure chamber while still hot or best yet put them in a small transparent container filled with warm water and UV cure to retain heat and maximize the cure process.
Fun fact, heat cure is required for Blu resins to be properly biocompatible.
I have a strong background in resin casting. Using chemical hardeners that cure the resin in a mold instead of photo initiators creating nucleation points.
We almost always annealed resin casts, which made for a more noticably durable material.
So it makes sense that annealing post curing in UV results in increased strength too, as this is basically how annealing is done in resin casting.
It's not always necessary to do, but even in wargaming miniatures, depending on what resin you use, such as ABS-like resins, the ductile strength of that resin remains while increasing tensile strength.
TL,DR; Its almost always beneficial to post cure anneal your resin 3d prints.
I have been heat curing my resin prints in my filament dryer at 65C for a while and it helps for sure. If you look at the documentation for high end resins they specify high temp cures, somehow it just hasn't trickled down to the hobby space
Super informative great presentation!! Defiantly been having trouble with brittle prints now I know to throw them in the oven for stronger results!
Radiant heating elements, like those used in your oven DO emit light depending on the temperature/energy level of the specific element. The light just isn’t in the spectrum humans have evolved to see. High power elements glow red because they end up projecting about 80% of their energy in a spectrum that is visible to the naked eye. I love this concept and I am begging you to try to use the scientific method to determine how much of the curing process is actually because of the temperature alone vs the “invisible” light being created by the elements themselves. Thank you so much for sharing everything you have with the community and keep up the good work.
Couple of suggestions:
1. Remove prints from supports after washing but before curing.
2. When removing supports, soak in hot water for a little bit. Tap hot is good enough.
Both of these things make support removal much easier in my experience.
And yeah, for minis we want those things to be tough.
I bought a cheap round food dehydrator with glass clear housing to dry my filament spools (as you showed earlier) which is capable of reaching 70°C at any location inside (proved with digital thermometer). I can imagine to cure resin prints in it with 70°C or less and an UV-lamp shining from the outside in. Have to be sure to protect eyes from the UV-light with googles or a surrounding housing.
Definitely noticed that heat leads to strength. I run my resin prints in my garage where I don't have to breathe any of the vocs. During winter I use a 220v electric heater. I usually aim for about 35C during the print, after the print I crank it up to pull supports off more easily, however I have left the heater blasting my printer before and it becomes concrete esq. Good video.
Form labs has been doing this for many years with the form cure station. Definitely a key point in making strong prints
Formlabs actually has a white paper somewhere (from a long time ago) showing graphs of mechanical properties with varying temperatures and time as well.
The one caveat is that the optimal curing temperatures are often very close to the HDT of these resins - which means that heat curing will OFTEN result in warping if you're not careful (there are a ton a caveats and subtleties here - ask me about it sometime 😅)
I don’t do resin printing, but I do work with a lot of thermal and dual UV, thermal cure epoxies. There are default manufacturer-recommended cure schedules, but other curing schedules are possible (and manufacturers will often provide some alternatives if asked). Curing at a lower temperature means a longer cure schedule to fully cross-link the polymer. As the reaction rates increase non-linearly with temperature, lower temperature curing schedules often require a significantly-longer cure schedule.
@@JonS yeah, that all makes sense and matches the white paper from Formlabs as well. From what I recall their graphs showed that lower temperatures would "never" reach the same mechanical properties. But by "never" I mean, not in a time frame that was tested or deemed reasonable for the end user.
@@emberprototypes yes. Lower temperature cures will be less strong, so the trick is to cure as close to the recommended temperature as possible, but not to the point of losing dimensional stability.
In my work, we are often limited by the maximum temperature of other components in the opto-electronic systems we are building, so we have to find the right balance by performing DOEs where we adjust each variable and measure the result.
@@JonS yup - something I'm also very familiar with because dimensional accuracy is often more important 👍
You should publish your work in peer-reviewed media, so that those of us who work in science can reference your results. Thank you!
I vaguely remember Sanladerer trying to glue 3D-prints with resin and failed, because the UV-Light was not able to penetrate the resin and the “glue” only got cured a fraction of a millimeter on the outside. So the curing after print seems to primarily cure the stickiness of the surface of the object. Even resin thats optical clear in visual lightbands absorbs UV, otherwise printing would not work.
This results in me being a bit sceptic about your statement at 1:35.
Maybe elevated temperature has the effect of hardening the inside of the objects. As of a rule of thumbs says that every 10 °C increased temperature speeds up chemical reactions by a factor of 2.
Yes indeed there is a lot of potential behind properly curing resins. Some factors I would think to look into for future videos on this topic are: Thermal and UV curing *times* (and as you touched towards the end if they should be done at the same time or seperately and what order), chamber temperature while printing, thermal and uv curing in a liquid/water (protected from oxygen or for some other reason) and the main one I think not considered by many, the *cleaning solution and temperatures from the cleaning process*. I have found that using cold isopropyl alcohol and especially letting the prints dry, evaporation lowers the temperature of the parts even further and this lowers the impact resistance. It indicates to me some type of thermal shock and at least making the shell of the parts weaker. By the way I have noticed also in some clear resins that thermal post-curing affects how much yellow they get from the UV post curing (and how fast the yellowing can fade away after some days).
Hi @CNCKitchen, I work in a company that's specialize in bonding manifolds with Acrylic and Ultem, the thing is that the annealing process it is especially important to cold down the material "slowly" inside the oven, if for some reason the cold down is too quick like take the part outside the oven and let it cold down, the plastic is more fragile.
I don't know if have sense what I'm saying (my English is not good)
Amazing. This is why I keep a bottle of Sirayatec blue and use it sparingly
I just got in to 3DP with a Elegoo Mars 2 Pro, have only just gotten mine to play nice and work with basic gray. this will be a nice new thing to play with.
Man that’s such a genius idea! I have a lecture all about composites and one was specifically about epoxy resins, yet it didn’t even cross my mind that those same curing principles could also be used on SLA prints. (Currently doing my masters in Aerospace engineering, like you did). The strengthening is most likely through getting a tighter amorphous structure, since the heat wiggles more monomers/partially formed polymers in the previous empty spaces (through brownian motion and liberation of some degrees of freedom in the polymer bonds -> T>Tg). On a chemical level hardened epoxies look a bit like a sponge with empty spaces where no active group could reach the other active groups, due to the size of the formed polymers.
Grüßle :)
Thanks Stefan for doing some Resin content!
Hi Stefan,
thank you for doing a resin video again.
I heard a lot that the exclusion of oxygen during post curing can improve the strength of resin parts. Could you test parts cured in hot water or even under vacuum or nitrogen atmosphere?
@@user-it7kg3pm4q Thanks. How do you know? Have you measured it by any chance? You could be right since oxygen is only affecting the surface.
Regarding impact strength and bending strength I thought the surface properties could have an impact in regard to those properties.
even if it doesn't affect the bulk, a smooth well-cured surface can still be a major improvement of strength, by not promoting crack initiation. I use this oxygen-free curing a lot, but it's more about hand-made things... i don't have an sla printer yet
Great test, thanks. I would have guessed that it it would make the part more brittle by increasing the hardness. For my functional parts I actually prefer a bit more "give" over maximum total stiffness as most part stresses are transient rather than load to failure.
Curing in warm water has been mentioned a couple of times. Microwaves or infrared light should be able to penetrate the interior of the model much faster, thus reduce any kind of warping.
This is, as usual from this channel, really awesome.
I really wish resin printing was less of a pain. There needs to be a Bambulabs esque ease of use boost to SLA where you can press print, and have the parts washed and cured automatically so you can get by without the whole gloves and mask setup.
Of course, what would also be awesome is that higher temperature forced air heating for the curing station.
The technology all seems there, so I guess its up to some company to implement. It feels like something it might even be possible to implement as a single person with some servo actuation only needed to switch between printing and curing.
So much potential, and this type of printing looks so much more professional than FFF parts.
I cure my resin prints in water. It takes the same amount of time (2-3min, flip, 2-3min). I find they come out way less brittle and stronger. I use a UV spotlight mounted on top of a stainless steel pot so I can take advantage of the reflections of the pot but I still flip them half way through and sometimes if there's hard to get areas of the print I'll orient it so it will get more light and do another run. I haven't had an issue and I believe they come out stronger.
I use room temperature water, I never thought about heat. I may have to test this with warm to hot water and see if it makes a difference.
I made a load cell mount from resin for large bar style load cells (16 of them actually) and they held 40kg for over a year in a hot environment. I eventually replaced them because they ever so slightly sagged over time but I was amazed they went that long. I believe that water curing had a role in that. This was with Standard ABS resin.
Try the same thing but use glycerol instead of water and cure for 60 minutes.
i personally use a food dehydrator to finish curing my resin casts (as i already have one for dehydrating herbs) so it's nice that it's basicallt dual purpose for me. Hope this info can help anyone else even if the resin i use is chemically curing instead of uv-curing like with a resin printer
It makes sense if it works something like... heat is basically adding energy into a chemical system as well as loosening some weaker bonds (I think hence the softening). The additional energy makes the bonds jump around a bit thus finding more optimal cross connections and more numerous ones.
Impressive new way of curring Rasin
Another great video from you. Thanks again for sharing your expirence with all of us 👍 😀
I have always been skeptical about UV post curing because UV only penetrates ~50 micron into even clear plastic. Thx for Stephan for finally test out this myth.
Did you take into account that the resin might react differently to the wavelength of the light used? These LEDs look like 365 nm, but if I remember correctly, a wavelength of 405 nm is required. Also the oven might mess with the light produced.
This is pretty exciting. I’ll have to try this when I get back into resin printing
It would be really cool to see these pieces before and after different treatments through polarizing light filters to observe the stress patterns in the structures. You only need polarizing filters (cheap) and a flat monitor (blank white screen) - look for "How to find Stress Patterns with Polarizing Filters". Also would be REALLY cool to record the strength test with the filter. If I had a resin printer and a strength test machine, I would do it. Lol
Here's a thought: Print some more Blu test pieces. Check the strength of one set right away and then a second set after standing at room temperature for, say, two-weeks or a month and retest. Perhaps the strength will improve significantly just from further curing without heat.
Very interesting video. You mentioned you found no significant shrinking, but I wonder if it affects post-print warping on thin flat parts. I mention this because I usually have warping in some parts after "normal curing". If this method fixed that it would be a game changer!
No the heat worsens the warping. At least that is my experience from trying different post-cure settings on a heated Formlabs curing station.
Love all the tests! Would love to see a materials comparison with more than just tensile strength such as, abrasive resistance, hardness, heat resistance, durability, etc. Especially over time, how does a print made today compare with one made 1 year ago, or 3 years ago? Do different materials age differently? Those are questions I would love to see answered.
this is awesome. I'm curious and always wanted to try a heater in the printer while it was printing to see if it made a difference to strength.
I work for a german medical company and you would be suprise what kind of photopolymers are on the market from Henkel (Loctite) or Dymax. For catheter applications there are ones for glue application which starts the polimerisation process with a tiny but of uv light then can be cured all the way in the oven with uv light, for jard to reach places. Or other ones reaching final hardness just via uv light. But one thing all of them have in common, none are long term stable! Not even Startasys manages to produce long term stable uv resin which can hold it‘s strength and toughness longer than 1-2 years. That‘s why for long term functional parts, always sls, mjf or fdm prints.
Have you tried curing parts in water? I’ve had great success using a cheap wash and cure. I wash normally in ipa, allow to dry. Then placing the partin a hot water bath in a clear vassal and curing that way. Cheap and effective!
Perfectly timed, I am trying my first round of acrylic painted prints in a food dehydrator (to speed up paint cure time) as I write this. I was curious what effect it might have on the resin prints and couldn’t really find much info on it.
Have you tried curing in water? Perhaps try curing in different temperature waters too. Including 0 degrees c up to boiling/100?
This would be a way to get up the temps. without worrying about equipment's health.
I know for some casting resin curing them inside vegetable glycol to remove their contact with air whilst curing helps them with burn out. Maybe trying heated vegetable glycol too so the parts can't absorb water.
Yep, some of my prints I put into boiling water (in a microwave) and this makes a big difference for white parts that have yellowed or clear parts that have yellowed plus the increase in strength and stiffness. This gets you to 100C. For opaque parts continued UV curing only cures the outer layer while the inner volume of the parts doesn't cure any more. Heating the parts helps to uniformly cure the part through the thickness and thus the increased strength.
I'm definitely going to have to try this with my new heated ultrasonic cleaner.
I don’t print with resins, but in my work I make use of dual UV-thermal cure epoxies. This result doesn’t surprise me. In the materials we use, we achieve maximum strength when using the minimum UV pre-cure and complete thermal cure. Over-curing with UV results in a weaker bond.
In your thermal only post-printing treatment, you might want to a longer cure time. Try increasing the thermal cure time (2 hours, 4 hours). You might not be fully cured after 1hr at 80°C.
Right on, JonS!
The 3D printer resins can't be "over-cured", they can only exhaust the photoinitiators and reach their final properties when cured for the proper amount of time (ie, are cured long enough, usually at least 60 minutes or more).
Crappy consumer resins [as opposed to better consumer and industrial resins] rely on under curing to hide their deficiencies [at least for a few weeks or months as is well known]. Good consumer and industrial resins when under cured [without proper temp., too] never reach their full, best properties.
Curing properly in glycerol in addition is just about optimal and easily achievable by even hobbyists.
I would like to suggest that you make videos on 3D printing everyday practical parts using the best material and printing methods for them.
I have Formlabs Form3, and both wash and cure stations, I just assumed that cheapo MSLA curing is also done at temperature. I've always set the curing station to heat up first, then put my parts in.
Very good. It is to do the same test but with standard resins and abs from brands such as anycubic, sunlu, elegoo etc because they are cheaper resins than siraya
Another good question about curing is: to which depth gets the resin cured, with or without post-heating? Because UV definitely won't get more than a couple of mm within the print.
If you leave a 1-2-3 mm center channel in your test samples, will the tensile strength be different?
I find shorter washing times in IPA also result in less brittle parts. To me it seems as the IPA damages some of the molecular bonds in the resin. I try to wash as short as possible.
Rinsing parts in soapy warm to hot water before curing will bring the resin temp further up before the UV light cures it.
Now that sounds like a theory that should be tested.
we would love to send you some of our latest thermal resin - it kickstarts later this month and is designed specifically with this kind of curing in mind.
Good to know!
A while back, I saw people curing their resin prints in a glass of water inside the UV chamber, arguing that the water better dispersed the UV light across the model. I imagine you could probably use a clear Pyrex bowl filled with hot water to achieve a similar effect.
Would love to see the results using tough and flexible resins as well. A lot of people doing miniatures use tough resin, or a mixture of flexible with other resins.
for me the underwater curing was the best, after washing, claenaing and removing the supports i put the models ina vlear plastzic container and pour warm(~40°C ) water on top, curing them in water for 5 mins. The print this case wont be as brittle as in dry curing, i dont jknow the chemistry behind it, but some says it has something with oxidation, Can you please thest this method too?
Would love to see you test out curing while submerged in heated water.
Sirayatech recommends curing under water as well as many other tough resins.
I've been curing my parts while submerged in 60c water and letting the part cool in the water to room temperature.
I'd love to see if this has the same effect. If so, a very effective curing heating machine could be build with a sous vide or instapot
I would love to see what are the effects of aging after annealing
Perhaps it would be interesting to do a temperature test as well? Annealing at 40C all the way up to 160C or something? Especially the tradeoff between strength and toughness could be interesting. And of course… when serious deformation happens
Just had a random thought... rapid cooldown vs long cooldown for annealing parts, which is better? I can see few possible ways to cool parts, including just leaving it in oven as it slowly cools down.
Curing with the parts submerged in water seems to give better results too, I guess I should try hot water in the future.
Better to try with 30-80 deg. C glycerol, better than water.
Makes sense about the UV. Since on a solid material the UV isnt penetrating very far into the part. Where as heat will go all the way through.
A bit worried different time between printing and curing can have an effect too, since you printed them all together but cured in succession. May also explain how going from 40 to 60 then 80 you get more and more consistency in the results, the uncured resin had time to rest and rearrange the structure.
i've found that cleaning then microwaving my parts 10s at a time gave me good results