lost foam casting: EXPERIMENT with thin plaster coating by VOGMAN
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- เผยแพร่เมื่อ 21 พ.ย. 2024
- I get good, consistent results when foam casting with Aluminium with my Green Sand technique, but some folks recommended I try a thin plaster coating instead. I was more than happy to give this a go. So I gave a foam pattern a thin coat of plaster of Paris, let it dry, then fired up my home made electric foundry and poured.
Here's the results of my metal casting experiment using my electric home foundry. Enjoy!
#LostFoamCasting
I used thin plaster followed by thick plaster. After drying i pour in acetone to dissolve the foam. I have no problems with turbulence from melting foam.
This was a good attempt. One thing to note for the future is all lost type castings are in a negative cavity created by what is lost- in this case the foam is lost, not the plaster. There is no need to smooth the outside of the plaster. The internal negative void of the plaster is what is most important. You can try adding multiple layers of plaster to increase the supporting structure the molten aluminum will fill into. It may also be beneficial to burnout or chemically washout the foam, before the pour. It is likely the off gassing from the foam as it melted entrained gas inside the casting. It is also beneficial to have a hot mold to pour into, in order to extend the time the material remains liquid. The sand and plaster you poured into likely acted as a heat sink to suck the energy out of the metal and sped up the hardening time.
The term "Thin Plaster" implies less than filling the entire mold with plaster.
Removing the extra plaster is not needed as the only thing needed was a solid surface to prevent the metal from mixing with and sticking to the dry sand that is not going to be holding it's shape.
Also there is no way for the gases to escape so removing/melting away as much of the foam with acetone before burying it is best, so a thicker plaster shell would hold up much better.
I am late to the party. Oh well. I don’t understand why plaster with dry sand would be used at all. As someone who owns green sand, it seems the plaster method is much more time consuming and difficult to get right just to have equal results. Is it because green sand is expensive? I am still about new so feel free to School me.
@@popermen694 I would say because with plaster you can copy very fine details and sand won't fall into casted piece. I think you could use this plaster shell with green sand.. But you don't have to, because th plaster shell is holding the shape..
@@popermen694
1. Plaster + sand allows complex casts without having to make inserts.
2. Lower skill required to start.
3. Less initial investment.
Greensand has plenty of it's own advantages. Not having to wait for the shell to dry, and easy to remake a mold being mayor advantages.
I agree with you that the green sand keeps the pattern from moving so much. I have had lots of blowouts when I try to do a lost foam casting using loose sand only. I do you like using a plaster coat and then green sand
Nice work, Sir. Ignore the negative comments. Doing something is more important than "paralysis by analysis" or never doing it because you are waiting to do it "perfectly".
Thank you for your kind help and enterprise.
Thank you for your very kind words : )
Back when you were still doing lost foam casting. Look how far you've come, with you making some excellent investment castings.
And I still haven't got it right 😁😂🤣
But the fun is in trying 👍
3:15 You could use a vibrating body massager to liquefy the sand while setting your mold. Also, I'm not familiar with this technique but it seems that you could create a thicker plaster coating and then pre-vaporize the foam to create a cleaner form.
For a first attempt that was pretty good.
Next attempt use plaster cornice adhesive, not just plaster, highly heat resistant, where basic plaster is crap with heat, and do a double layer.
It will work a treat.
To prevent the foam outgassing from impeding the flow of the metal you need more vents because the plaster is impermeable . They can be small, like the diameter of a soda straw, but they need to be arranged so the areas furthest from the pour have lots of places for the gas to exit..
hi, you can 3d print or cnc a mold (or both), then fill it with wax, then you cover the mold with thin layers of plaster-sand-dry, plaster-sand-dry during few days, then you heat that mold and recover the wax, then you use a two half green sand mold with well and venting orifices and done.
you end using only the thin layer of plaster, the rest can be reused (included the printing filament with a filament extruder)
Very good....How about not using any plaster at all....will you get similar results? ...Thanks
I have been experimenting with the foam/plaster method and have had results similar to yours. I have done some research and my next plan is to coat a foam mold with thick plaster formed with several vents, then once dry pour in Xylene (or tolulene) to completely dissolve the foam before casting. I have tried Acetone and while it does dissolve the foam it doesn't do so completely. Xylene seems to do the trick. I have also learned that plaster must dry for longer than you think... At least a week in warm dry conditions. It holds on to a lot of water.
Thanks for that Paul. Plaster is strange stuff and holds water well past boiling point.
I have experimented with thicker coatings and even whilst well vented, the results were much worse than those here.
If you enjoy experimenting (as I do) then carry on and let me know your results. I'm always eager to learn : )
If you're looking for a reliable, consistent technique, try this method using green sand - th-cam.com/video/ES1Xenom-e0/w-d-xo.html
Paul, How did your xylene experiment pan out ? I need to cast something with a fine amount of detail.
In green sand, the vaporised foam can vent through the sand, but plaster would only vent were you make vents. The foam turning to vapor would be many times the volume of the foam and that vapor caused a volcano and could have been a emergeny room deal! In investment casting, the wet clay (in this case wet plaster) would be showered with sand, clay-sand-clay-sand, six-eight times, then the wax (lost wax) melted out, then burned out, then pre heated for the metal pour. More vents may work, but I think with "not lost foam", green sand may the better way. Even in green sand, the sand can be packed to tight and also have no were for the vapors to go and all the hot metal exit with explosive force out were it entered or through the sand onto anything around and the more foam/metal, the more likely. Be safe.
Absolutely right! That's exactly what I've been preaching my friend.
Good to have your input : )
The lost foam method that introduced me to lost foam used drywall compound, a quickset hotmud(5 min), but it was used so that the caster didn't have to use green sand, but could instead just use ordinary play sand. It's a way to produce blocky low detail parts with a minimum of fuss and very little technique. It's really a technique for people that want a quick part and have to cast it because for whatever reason they can't machine it.
Well said Lowell, and that's absolutely fine. I know I've made parts before now that weren't going to be seen but required an approximate shape and good strength. Such a technique is perfect for that : )
@@vogman I am probably going to be using that technique for several parts on a CNC router. Also, thank you for the detailed video series on the electric furnace. I'm going to copy that design. When I get my own channel set up I'll send people your way when they ask about it.
Thanks Lowell, I appreciate that. To me that's what it's about... as my mate BigstackD says, "There's plenty of views for everyone." So we may as well help each other : )
Above you'll see James Burns has sent me his first video tonight which I'm happily to publicly share. When your channel is ready, drop me a line. Best of luck : D
In conclusion, always worth trying something new. And thanks to your efforts I can make a decision weather or not to try these ways myself (very limited playtime).
Hi Andrew. If you're looking for reliable, stick with green sand - th-cam.com/video/ES1Xenom-e0/w-d-xo.html - I get these results every time with Aluminium. I tried copper for the first time recently and the results weren't as favourable, but there were a number of other issues involved. Once I nail those down, I'll try again, and I'm hopeful of much better results : )
I liked the feeling of drama he gave to the process haha
Great video.
I too have learned that lost foam + thin plaster + sand is for people who like to have a lot of extra work after casting.
Greensand forever! (Even if it's d.i.y. greensand.)
The thing I like about casting is that everyone seems to find their own technique - and that's great : )
this is great info! I bought some styro pumpkins from the dollar store, they are hollow (about 3/8 thick styro walls and 7.5 inches tall. my earlier experiments with these was the sand would start caving on the inside and I would loose my $4 investment. I plan on coating the inside only with plaster then fill with sand. once I clean the 40 pounds of brass I accidently spilled in my foundry I will have a go at this and tell you the results
Thanks Jason : )
I never plan to know everything. Like you, I enjoy experimenting and finding easy ways to do things. Only an idiot thinks there's only one way.
Keep on experimenting my friend : )
I like you videos and thought I would pass along some of my experiments. I have used water thinned drywall spackling compound with very good success very similar to what you did. I have heard plaster actually has some plastic in it and will out gas and cause problems. I coated the hot wire cut foam pattern a few times by dunking it in then thinned Spackle and let it dry a few days between coats. I did not do any sanding and just placed it in the play sand and added a can as a feeder. The results actually showed the hot wire cut ripples in the pattern. Much better than any attempt with green sand! I am trying to make some aluminum gears with the method now.
Thanks for sharing that Fred : )
No casting should froth and bubble and spit AT ALL when poured. Anything that does this much is going to be a casting woefully full of gas and oxide film inclusions to the point of complete unreliability. I would expect this casting to show much porosity and may flaws when machined and to break in service unless extremely lightly loaded. Your green sand is a much better technique as plaster is NOT porous and apart from its own water content it will NOT let out the gases that come from the decomposing foam. The commercial coats used for this process are porous (they are also very thin at around 0.2 mm) and I do not believe that they contain any plaster. An interesting experiment though, but with predictable results... Martin
Thanks Martin. Words of wisdom gratefully received : )
Here's a question for you Martin, Green Sand or Petrobond?
Hey Geoff, I don't think Martin has used petrobond yet. I know that he and I have talked about it and that he's mentioned in other comments that he had not tried it yet. One of those things on the never ending list of things to try. I can speak to petrobond but not green sand as I've never tried that. Petrobond appears to be fairly porous (which I find amazing due to it using oil as the bonding agent). I don;t think it requires the venting that green sand does (again I don't understand why). Petrobond does provide remarkable detail in the casting but then again if you look at the video that Martin just published th-cam.com/video/yW4TgZoUsK8/w-d-xo.html and in fact all of his videos, he gets remarkable detail and surface smoothness using his green sand.
Petrobond does leave an burned oil film on the parts but that is pretty easily dealt with. Petrobond does also smoke quite a bit as well but I'm sure that to a guy that melts foam that won't be an issue ;-)
I believe you are correct, if I remember right commercial coats are a resin-coated fine sand or thin ceramic, many containing fine zircon powder. In some ways, it's like a cheap version of investment casting process.
My thoughts, exactly.
An excellent attempt. Perhaps some further investigation into what constitutes ‘thin’ plaster. It may need to be several millimetres thicker. Also, after the first coat or two of plaster, it may be necessary to add something to help hold it together better.
Definitely worth a revisit...
Good work.I would try a coat of plaster,then whilst wet cover with a layer of dry sand then more wet plaster,sand again.Very important to dry very well.Airing cupboard for a week ,top shelve were the wife can see,works for me.I do prefer green sand method, but your way could be an easy way for certain jobs.Thanks.
Thanks Peter. I'm a green sand fan as well, though Lost Wax is really growing on me : )
Love your videos. I need your help !
I am trying to do lost shell PLA casting. Which we all know sucks because PLA does no burn out clean and the mold keeps breaking because PLA expands and all that fun stuff. In order to do this right I would have to use wax or wax like materials from a 3D printer I know this. And also some proper investment plaster. My problem is the plaster needs a hight temp oven to burn out right and is also expensive. So I want to do zinc casts for cheap but with undercuts from 3D printed masters.
Anyhow here are my ideas and you tell me what you think Master caster =)
1. Using fire proof spray paint (800°C fireproof) and spray painting coats of the paint and mixing with sand (kind of like suspenda slurry). Then burning out the PLA in a household oven (that´s all I have, my method is supposed to be cheap and easy doable at home with little tools, material I want to use is zinc so I can melt that on a camping stove.
2. Using high temp sealant (from the caulc postol) hold up to 1300°C --> again building up coats burning out the part and casting.
3. Using castable refractory / zirconium refractory / puty repair compounds (don´t know which ones yet) and then again coating the part, burn out the plastic, casting.
4. Air drying clay ---> burn out --> cast (proper clay would need again too hight temps)
So basically I try to find a mold material comparable to investment plaster but with less heat needed etc.
Have you tried sheetrock mud instead of plaster? I've been using very thin mud (about like latex paint consistency) painted on just thick enough to add a little color. It dries overnight or less and disintegrates during pouring but it makes the surface finish exactly like the foam was, hold the loose sand back. With only the sprue (no vent), a lot of the gas from the foam goes into the sand and i get clean castings. Recently did a burner body and it hydrotested with no seeps.
Hi Andrew. That sounds interesting... I've never come across it. A quick Google search reveal nothing in the UK. Is it a branded product or the name of a substance?
I do like to hear about alternative ideas : )
Sheetrock is a brand name for drywall. What I was referring to is joint compound. Whereas plaster sets and is waterproof, when drywall joint compound sets it is still water soluble. Maybe joint filler or joint finish.
Thanks Andrew. I'll look out for it : )
I believe the sheetrock mud he's referring to is the stuff that comes premixed in a tub or pail. Unlike plaster which sets up chemically, the premixed stuff sets up by drying out, and more importantly, it shrinks slightly while drying which, in this application, would create many very fine cracks thus allowing the pattern to vent more easily.
FYI, there are also specialty plaster formulations specifically designed for metal casting, along with the plaster, they contain chemical agents which cause the water in the plaster to foam up during mixing, the resulting bubbles are very small, too small to cause casting defects but large enough to make the plaster porous .
@@85rocco Do you have a link to these specialty plaster formulations specifically designed for metal casting. I have a project that has alot of fine detail.
Makercise has had good results with this technique check his gingery shaper build out.
My thoughts exactly.
Maybe you could try adding fine sand to the plaster and applying it with a paintbush .Also poking holes with the needle as it drys might be solution to venting problems.Maybe using a cement( mix it with some fine sand ???) instead of plaster would be better idea.It would take less time to dry-especialy if made into a thin layer.I dont like plaster for casting i tried it with fishing weights several times and result was volotile even after several days of curing the plaster-that thing just keeps too much water in it.
Just couple thoughts.
They were good thoughts too.
I fine plaster takes longer than green sand, but if there's an easy plaster technique that I can share with others I'll happily try.
Thanks for the input : )
I think you should use vacume to help escape gases produced by lost foam + vacume will help improve sharp details of casting 😊
Very interesting! Your channel is awesome. Could you make a video explaining the how to of the technique of many thin plasters layers that are spread with "some unknown" powder when wet in order to obtain a hard but thin hollow mold?
Hi Victor. I think you may be talking about Lost Wax Casting. The wax is dipped in a ceramic slurry then sprinkled with a silicone compound. Once dried, it's heated and the wax drips away leaving a hollow shell. I'm sure my fellow TH-camr worldtraveler has a video or two covering this topic. Head over there and have a look : )
@@vogman yes!! But the thing is maybe it can be done with PLA pieces instead of wax or styrophoam pieces, could be very interesting to try it.!!!
I think you're 100% right Victor and I really hope to one day try it. It's certainly on my list of things to do once finances allow.
: D
Came out pretty darn good consisering that dirty trick the mold played on you!
Next time you try the dry sand method, try skipping both the coating and the vent. When you're bare-doggin' it like that, the foam can vent into the dry unbonded sand just fine. If your sand is fine enough and you were conscientious with your vibrating, the finish may be acceptable. Effective vibration is especially if there important where there are undercuts (also true when using the plaster).
Thanks for the feedback. My first attempts with casting were dry sand, though back then I had no idea about the importance of vibration, etc, so the results were poor. I may revisit just sand and foam another time : )
I just found your channel a few days ago (approx 4-6-2019) and have enjoyed your content, and learned a few things as well, of the 4 to 5 videos I have watched so far, plus, my lady enjoys hearing your Aussie accent, (reminds her of ClickSpring, Lol) but anyway... I was wondering, if doing this (thin wall plaster method) while in loose sand, just like in this video, if making an "L-shaped" runner vent or filling vent out of more plaster........ But, filling/pouring and venting the cavity from the side of the parts cavity, or maybe even doing a "J-shaped" runner/filling and vent gate, so the molten material flows in from the bottom, if that would prevent the splits areas in the finished part? Or am I making things more complicated then they need to be. I time to time, get these splits in my parts, and I don't understand why, and these splits are always at the bottom of the part, and my tiny mind, would like to think that that if the splits happened on top of the part, as if there wasn't enough molten material in the cavity to fill it up , but nope, these splits, when they happen, are always on the bottom corners/edges of my parts, if they were on top, as if it was a partial fill and gravity, they would make sense to me, but on the bottom, lol... I seen another channel about 6 to 8 months ago, talking about side filling and or bottom filling, as stated above process... I have not tried it yet, just wondering if you know why these small hair line splits happen on the bottom, and they never happen in the same location for the same part either? is the aluminum is being cooled to quickly as it has to flow around the multi faceted cavity? Meaning, I need to bring the temp up an additional 50°F to 100°F before pouring? Maybe placing something under the cast box on the vent side, so the cavity is no longer level and the vent side is higher? Maybe pouring the molten aluminum very rapidly into the cavity, and not worry about sand being knocked into the cavity? Anybody can answer this issue for me, and there is no hurry, as my next project is about a month away
Dru, you made me laugh my friend. I have a lot of Aussie subscribers and they'll all be screaming, "Aussie? He's a bloody pom" or words to that effect. I'm English, born and raised in the UK without a hint of downunder : )
Don't worry, I'm not offended and please don't mind me laughing about it. It's all in good fun.
Now, your experiments... never be afraid to experiment. The truth is there is NO single answer. Casting is one of those things that even experts disagree over and amateurs find their own way. So feel free to dabble - you may discover something no one else has.
When it comes to Lost Foam casting, if you can get Green Sand (it has bentonite clay in it) then look up my videos on the subject. I get good consistent results with it.
However, in relation to the splits, these are probably folds or porosity. Folds tend to be two seams of molten metal colliding but, critically, being at different temperatures. Porosity tends to be caused by trapped air.
It's a balancing act. Personally I try to go quick and smooth with lots of vents. Filling from underneath is an excellent technique as it theoretically pushes all air from the mold. I've used this technique a few times myself. Quick should keep a stable temperature and smooth eliminates any possible agitation that can also lead to porosity.
Anyway, I'm sure many others will chip in with their opinions, doubtless conflicting with my own - as that's the casting way. But I hope the above helps : )
@@vogman ah!!!! Aussie, or proper Englishmen linguistics, lol... Either way, she fancy's accents, in fact, I think it gets her motor running or something, lol... I am not worried so much about the resources, vs, time... I suppose, I should just leave an area of the shop set up just for my pours, and I think I would be more inspired to play often, vs, when done, I clean everything up, and put it all away... And I believe I feel like I am starting over in the learning curve every time I drag the stuff out... Or to drag the stuff out, to experiment, I think is my declaration that I am starting to get lazy, lol... Thank you for the answering of, "the unknown causes"... I don't feel alone now in that it only happens to me, as that is not the case... I may just get started a week early, and do a few tests, like the questions I was wondering above... Thank you
No worries Dru. I'm happy to help any time. My best to your good lady : )
Jeff, your videos are awesome! well done mate!
Thanks Clay : )
"Lost" casting process I have seen used wax, then a refractory mixture of plaster mixed with fine clay, silica flour, zircon dust etc. Was sprayed on with fines, then with larger refractory ballast, ie 3-4mm size pieces. All air dried, then warmed, then when ALL moisture slowly cooked out, was placed in oven to bake in the setting components, ie clay, and probably water glass, and this of course removed "lost" the wax model(s). As these were commercial castings these were ganged together in trees etc.
Results always spectacular, no gassing etc because nothing was there to burn, that is the entire concept of 'lost' process. The model needs to be 'lost' before pouring in molten metal.
And this plaster process is very dangerous, as there is still water present in plaster unless it is cooked out slowly, if the thickness is sufficient, it will explode due to the steam etc, been there, done that, molten brass is no fun when flying around.
Back in the day if I tried something and it didn't work out, the words "well that was a waste of time" would be heard. Usually shouted and with a few added expletives! In later life I have learned that it's never a waste of time buddy, I have just found another way that doesn't work is all, a step closer to getting where I need to get. Seems a long winded process fella with less than perfect results, I def think the green sand gets my vote.
Believe me Softail, I'm on your side.
For me I found it long-winded and contrary to everything I have learned. But folks still write and tell me it works. I don't wish to disbelieve them - I assume they're being honest and helpful - so I try to replicate and share the results.
Some of the finish was beautifully crisp, but some was downright ugly. All in all it was unusable.
If someone writes in telling me where I was going wrong, I will try it again.
But for now I wouldn't recommend anyone else bother : )
I think there could be difficulty with foam that lost wax does not have; the gases escaping create turbulence and eddies within the flowing metal. maybe more vents could help but compared to wax it can be done cheaper and quicker but needs certain considerations. def the volcano out of the vent is worrisome haha
What is this used for?
This was a supporting wheel designed to fit between tank tracks on my lawnmower. 😁
With lost wax casting, the wax is melted out before the metal is poured. If the plaster shell were thick enough to hold up that might be an option with foam.
You're absolutely right. The same thoughts have been running through my head. It's a puzzle.
I suppose Wax Casts tend to be vertical (at least the ones I've seen) and there's considerable use of vacuum chambers to remove air, and the plaster is cooked in stages and is generally hot when the metal is poured.
Somewhere in these differences is an answer. Guess I'll have to keep tinkering : )
Thanks for your input.
Make the plaster thicker and let sit for 2 days
Bake it for 45 min at 600c and pour
Surely it would have to be a LOT thicker. The foam would melt in the 80's I believe.
Are you suggesting using foam in the same way as wax in lost wax casting...? It might work... interesting thought : )
This was exactly what I was thinking. You could even put the dried plaster coated foam in sand and then heat the whole thing to burn off the foam just before casting which would have the added benefit of pouring into a hot mold.
Useful and interesting
Very interesting, I know when hot metal hits the foam it's vaporized but what does the metal do to the plaster, forms inside or out side of the cast , if out side what about spraying thin dry coats till it's covered with out dripshnbnm
Imagine that the foam's not there... it vanishes... so yes you're left with a plaster shell and the metal fills this like a hand in a glove. The problem is the metal isn't alone and the metal picks up gasses during the process and the foam leave plenty behind, and the plaster holds water so that's steam as well - and all of this is trying to get out every way it can which is why it jets from the vent... but that alone isn't enough.
Or at least that's my theory : )
Ideally you want a coat that's thin enough to breathe but solid enough to hold the sand back long enough for the metal to solidify.
It's a fun conundrum.
that was moister making the metal pop like that from plaster lol!
The first time I did lost foam I was surprised at the height of the flames and stopped pouring for a moment. I ended up with lines similar to the tears he mentions. 8:40
The smoke was what surprised me on my first pour 😁
@@vogman Live and learn lol
the sodium silicate method I like best with the foam it needs gas ports so you don't get the bubbling out like you did and you lose some heat in the exchange proses and if you use a very fine sand you can get a very good finishes as well the best is the lost wax . and I know how to make sodium silicate if need to know how ask me :)
I'd love to hear how you make that, yes please : )
I'm always eager to learn and try new techniques.
sodium hydroxide and the cat letter that is like beads with blue spots in it you will need a hot plate do out side and water be careful with the sodium hydroxide its drain cleaner , it works a lot faster if you crush the cat letter before hand or you will be mixing it for a long time the recipe is on youtube were gloves and eye protection and don't have any kids around when doing this ,it has many uses . its also called water glass ,and store in in a air tite container and were no kids can get at it or it will become glass hard it washes off fine as long as its not hardened if you get it on your close its not going to come off and don't breath the fumes us a fan to blow them away when working with this stuff .
Hey thanks for the info were could I buy this etruded foam?
It's very common. You just don't realise it's around : )
Model makers use it a lot, so try any hobby type place. I found it quite cheaply by searching on the internet.
you need to plaster dip and then slowly spin out of the dip
also it my help your surface finish to use a denser foam
also turbulence is generated from the burning chemicals that the foam consists of, It defeats the method of foam casting but if you were to burn out the foam first, that would help turbulence
Thanks for the input.
What would happen if you used a thicker plaster coating?
With thick plaster the results would be poor. The gases within the metal as well as the air that's trapped inside the mold all need to go somewhere. Even venting doesn't help : )
@@vogman good to know
Sweet!
Thanks Tyler : )
@0:57 VegOilGuy; is it your wife doing the video graphics overlays? :D
Hi Björn. No my friend, I do it all myself : )
What type of foam are you using there???
Hi Johnathon. It's extruded foam. It takes a little more energy to burn but it's fabulous stuff to work with as it can be machined, filed, sanded, etc, where normal expanded foam falls apart. With a little preparation, you can achieve some amazing results. Have a look at this video if it interests you th-cam.com/video/Bv1uV2MHMKk/w-d-xo.html
I think your plaster is too thin.. and perhaps you should have done this with the cast object oriented vertically to reduce trapped gasses...
I'm not sure the thickness would help, but the vertical alignment is an interesting suggestion. I may have a tinker with that some time : )
Why does the plaster have to be thin? I am not following. It seems to be that all you have to do is have the part coated. The sand holds the plaster in place while the metal is poured in. It seems to me that the thickness of the plaster is irrelevant other than being thick enough to coat the part. What am I missing?
That's a fair question and one I haven't explained properly.
The issue is gasses which get trapped in the metal during casting (and which come from the foam and moisture in the plaster). If the gasses cannot be released sufficiently, they can get trapped in the metal, weakening it and producing a spoiled cast.
Many believe (and I'm one of them) that plaster is not the best coating as it cannot breathe - so I'm guessing that folks that insist on it being thin presume that thinner coats might allow gasses through - but they don't.
What's required is something to make the plaster more porous, which is either an ingredient or a technique. Hopefully if such a thing exists someone out there might let me know... but we'll see : )
Hope this helps.
Thank you for explaining this. You just taught me what might have taken hundreds of castings to figure out on my own. Your channel has been my favorite since I recently found it and this is why. Your need for perfection in the process and your need to understand what is going on has driven you to not only a better and better process but also an understanding and with the ability to teach it to others.
At 47 I find my self back in school learning robotics and electronics and there are many types of instructors at our local college. There are some that are so smart that they gloss over the process because to them it is just so simple and easy. Then you have others who can read a book and explain the process, but do not understand the "why" and therefore the lessons are vague.
I have been a hand tool collector and user for years and have always wanted to cast some of my own stuff. This last quarter of school, I took an engineering drafting class where I learned to use 3D modeling tools, both Inventor, and Solid Works to be used with the schools' 3D printers. This was the key that opened up doors to possibilities that I never knew existed for me. I am now able to draw anything my imagination can come up with and print it. Within one week of class, I decided to purchase a printer (on its' way) and begin a TH-cam education in casting. My goal is to eventually be able to print in wax and use the investment casting process to make my own designs.
That is how I found you originally, looking up casting methods. I did, however, find that you have much more on your channel that crosses many of my interest paths and I really enjoy your channel.
You, sir, go beyond the what and how and explore the why as a way to continually improve your process, and that is the heart of a true craftsman.
Thanks very much for your kind words.
We're of a similar age and could be brothers (though I'd have to call you junior) and I'm amazed how similar our interests are. But you're much braver than me... I don't think I could face a college education again, even just night classes. So I explore, experiment and generally self-educate. I tend to learn best that way and have met every one of your tutors by the sound of it.
How interesting that you are exploring 3D printing and casting... watch this channel closely in the next few weeks (hint, hint).
What CAD software are you using? I'm looking into that one.
Good luck with your studies and don't be afraid to ask questions or chip in with comments if you think I'm going wrong - I like to learn... it's wasted on the hormonal young - at least in my case ; )
Here is a hint: Inventor 3D modeling is a great program. It costs about $20,000 US but if you are a student (have a student email) you get a free 3-year license. Go to your local college and take 1 or 2 credit class for a next to nothing and get a student email.
Going from 3D modeling to a print is merely downloading the model you made as an STL file. The great thing about the software is that the tools you are given allow you to create the most complicated model with ease. I took Inventor the first half of the quarter and the second half is Solid Works. Solidworks has some things I like about it, but for just using something that is intuitive and without getting too overly complicated, I like Inventor better. Also, I get it for free as a student and take it home on my laptop. When my lisence runs out, I will go back to school and take a jewelry class or something so that I can reup my lisence.
I like your style : )
👍☺
I think the plaster inhibited the escape of gases.
Exactly! Without anywhere to go, the gases remain in the metal and form faults. That's why I prefer green sand : )
VOG what if you used investment powder as it is porous and should allow gases to vent plus it would last longer as there is no negative space to fill as it’s not cheap.
Suspendaslurry is available in the uk👍👍
It seems to me sanding off the plaster did nothing but cause issues.. why sand it off? the thickness of the plaster should not even matter..it's going to burn off just the foam and hold its shape better inside a thicker casing of plaster. thinning it out only lets the loose sand give way and intrude into molten aluminum..
ok I have never tried it this way but it just seems logical...
Why thin? Because the whole thing was an experiment. I was answering requests to test the idea that thin plaster could breathe like sand.
@@vogman hmm..I see,,,so it off gas's to the sand is the idea.. I never considered that it needs to..I'll have to try both ways too.
either of those could be machined, plenty good enough.
Unfortunately I cast it back to ingot without taking any notice of its inner properties, so we'll never know for sure : )
inquiring minds want to know! (lol)
i don't think this is how it's supposed to be done. you should use multiple layers of plaster and sand on the mold.
Hi Steven. You may be right. That's not something I've personally tried.