PID vs Bang-Bang Temperature Control
ฝัง
- เผยแพร่เมื่อ 20 พ.ค. 2024
- While configuring my new DUET 3 Mini 5+ control board that I put into my broken Prusa Mk2.5, I noticed weird surface artefacts that did not come from a wobbly z-axis! Let me show you how I found out that the heated bed was the problem and how I fixed it!
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🛒 Equipment used in this video:
DUET 3 Mini 5+: e3d-online.com/products/duet-...
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Lumpy Bumpy Vase: www.prusaprinters.org/prints/...
Gayer-Anderson Cat: www.myminifactory.com/object/...
📖 Further Links:
Prusaprinters Blog Entry: blog.prusaprinters.org/dev-di...
Marlin PID Autotune: marlinfw.org/docs/gcode/M303....
DUET PID tuning: duet3d.dozuki.com/Wiki/Tuning...
Choosing and connecting a bed heater: duet3d.dozuki.com/Wiki/Choosi...
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Chapters
00:00 Introduction
00:55 Quality Problems
02:53 Bang-Bang Control
03:50 Thermal bed deformation
04:43 Z-Wobble or a bad bed?
06:43 Surface Marks despite PID
08:01 Bang-Bang or PID?
09:25 Prusa bed & DUET
#3Dprinting #duet #tips - วิทยาศาสตร์และเทคโนโลยี
*To bang or not to bang? What's your opinion?*
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Hey there!
i opinion is I need a 3D printer to find out but I would like to flash my bang is better than yours just look at it
On my Ender 3 Pro I left the Bang Bang when I switched to the Btt skr e3 mini 1.2.
I have no issues with it. The temperature is only fluctuating by a couple of centidegrees. I guess it will not improve that much changing to PID.
I plug my bed to a lab power supply. I made a Voltage/Temperature calibration curve.
That's it: constant current and constant temperature; no noise, no fluctuations whatsoever.
@@urano1988 do you manually set the bed temp or did u put the curve into firmware? how does that work
Wow, interesting finding, I wasn’t thinking that could have such a big effect.
Now I’m thinking to put some dial gauges on the bed and see how much it deforms while doing some heating tests.
Many thanks for the insights Stefan, very useful 🙌😎
For large 4-point constrained PCB beds it can be really dramatic. With the PCB bed from my BLV cube kit, you could see it moving by eye if you parked the nozzle over the middle.
I'll have to do that!
@@CNCKitchen And it would be super to compensate this in firmware during print with automatic z-baby stepping :D Like mesh bed leveling, but temperature mesh compensation.
@@JanVokas That would be really neat, but you would only be able to compensate for the bed lifting/dropping. If your bed were warping during the heat cycling, you could compensate for the first couple layers, but after that, the part geometry will result in unpredictable part movement.
@@Kineth1 You are correct, but what if the mesh compensations were applied to the X, Y and Z? This might be harder to predict, however! Perhaps, piezoelectric sensors could be placed under the print bed to monitor any bed deflections and compensate in real time!
Wow, One degree variation doesn’t seem like it would affect the bed warp that much. Im surprised. I can’t help wondering if the change in current draw from bang bang switching fully on/off is causing issues with the stepper drive current thus causing those issues where PID is a more gradual change in current draw. Wonder if a better power supply would also correct it. That buzzing in the bed seems more like a power supply noise (ripple) which made me think of current as a possible cause.
Very interesting video Stefan. Well done.
I might have a closer look at that though I don't think that the steppers are a problem due to their discrete steps, though who knows what happens to the microsteps?
@CHEP I think you might be on to something there. I had a problem in my printer with the Z-axis not moving enough upon layer change. The firmware would indicate the correct height but the actual height was about 20-25% lower. This only happened to me when I would print ABS with the bed at 105C so drawing a lot of current. When I would print PLA with smaller bed temp it would print just fine. My fix was increasing the Z-motor Vref voltage. I too believe that a minute 1-1.5C variation in bed temperature wouldn`t affect the print quality that much. This needs further investigation.
@@CNCKitchen Full steps on stepper motors are fairly accurate when stationary. Any microstep step is not precise and can be within a small number of actual microsteps of the position you think your at. Take a strip of paper and rip it in half, now do the same thing again and again and again and again. You now have 16 smaller pieces of paper. You have increased resolution but the resolution does not equal precision. Each piece of paper is not precisely torn, not precisely the same size as the others.
With the ripped paper you can separate two objects by 3 micro-pieces of paper and the position will be more accurate than if you were limited to 1 full strip of paper. But, the spacing is not precisely 3/16 of the full paper strip. It may in fact be closer to 2/16 or 4/16 because our paper micro steps are not precise.
Microsteps increase resolution of movement and smoothness of movement at low speeds. You don't get something for nothing though. With microstepping as the RPM increases the potential power output of the motor decreases. Some stepper drivers will 'morph' steps from n-microsteps to full steps as RPM increases (all done internally, you are still sending microsteps to the driver). This gives you the best of both worlds. Increased resolution, increased low speed smoothness and all the power out of the motor at high RPMs.
Please see my post about indicating to your bed when the bed it stationary and heated to measure any deflection in Z. My suspicion is that if your bed is deflecting with a 2C delta T then it is due to it being held at the corners thus any thermal expansion/contraction can only be relived by the center of the bed bowing in the Z direction.
Best comment exactly what I thought. Its a power issue. Electrical noise affecting the steppers. If say a second power supply was used for the bed heat this would also fix it.
@@HeyBirt ripping a piece in paper in half ??? please put down the crack pipe buddy, you've had enough.
The title looks interesting
the first line too.
Spoiler: the conclusion is to not bang if you don’t want z wobble.
Please try this experiment. Keep the bed stationary, use a sensitive test indicator, something with 0.01mm graduations, to indicate the center of the bed. Now try each heater control scheme and see how much your bed is actually moving in Z due to fluctuations in temperature.
The issue with that kind of a measurement is that your indicator is also growing and shrinking as the temperature fluctuates, and needs to be accounted for.
@@TurkishLoserInc introduce a thermal insulator, such as a 3d printed object. if the effect is real it doesn't matter whether or not the dial indicator is directly in contact with the bed
in case one part of the bed doesn't expand and another part does i would use multiple dial indicators to take into account that distortion
@@ikbendusan Laser interferometry should be able to illustrate minute changes in form and placement.
@@TurkishLoserInc Let's be realistic, if a change of 2C disturbed the test indicator that much it would be utterly useless in real life.
Congrats to the 300k! You really deserve them! (btw. as I watch it is 300.000)
Thanks!
Still shows 300.000. 🙈 can't be the true amount. I think it stays at 300k for a while to celebrate?
@@REDxFROG some time ago youtube stopped showing precise sub counts
I love how refined the fdm process is getting
this video helped me out a lot! Thank you!
Very interesting never thought such small temperatures lead to such visible artifacts. Awesome investigation and presentation. As always ;-)
He is a real resource. Totally agree.
Thank you so much for bringing this to my attention! I've been pondering where the "banding" in my prints was coming from. My build platform is 600x600 and heating via a AC heating element controlled by a SSR. It makes sense that a bang-bang controller would cause the bed to flex and result in print distortions. Thank you!!!
Minor correction - @6:00, it's only the PIDTEMP line that needs to be commented out (undefined) to use bang-bang. You would need to leave "BANG_MAX" defined. Note line 483 only says to comment out the one line.
Hello, 3D printer users new to CNC kitchen! Congratulations, you've found it. This is the channel. It's all here.
omg I needed this two years ago when I built my HEVO with a duet... I had this same artifact and it took me FOREVER to figure out because as you noted, if the print speed changes (shorter layer times for instance) the banding changes. I printed so many vases and spent a lot of time on duet's help forums before someone had me try changing the bed to PID and like magic it disappeared.
Super informative, thank you Stefan!
I had similiar problem, but I discovered, that my problem was in suppling power. If power was switched to bed, nozzle temperature also fluctuated and I belive that this was the problem. My solution was new power supply.
Your videos are still on of the best in 3dprinting and keep up good work!
Absolutely incredible analysis and troubleshooting. Thank you for this!
Thank you Klipper for making a PID tune as easy as a few commands in the terminal.
Great information! I had this problem on one of my printer, and it was clear to me that the problem is in the Z Axis but after seeing this am going to try your method to know which one is really the problem! Danke Stefan!
Nice video. A few years back when I built my Hypercube Evolution I had both lead screw induced Z-wobble and bed heating induced layer inconsistencies as shown in the video. That combination was "fun" to figure out...
Thanks for making this, I had no idea that running bang-bang could cause those kinds of issues.
Hi Stefan, good video. This problem also annoyed me for some time. Easier way to see if this problem is the cause: print without bed temperature. Then you don't need to compare with the threaded rod
Cheers
Good idea. Just put some tape on the bed or use a thick raft and it should be fine.
This has totally changed my mind in one of my printers. Looks like I've got a load of PID tuning ahead of me tomorrow!
Thanks for the information. You do a great job on all your videos (and your podcast)!
You are totaly on point. I know this problem for many years. But in my case I had a huge problem to configure correct PID values, because everytime i run the autoconfiguration it gave me different results and they were not good. Turns out this was problem with stability on 5V stepdown on my MKS Gen v1.4 board which is used asi reference for calculations. (It was the same for all boards at that time - old RAMPs, Rumba, MKS Gen L, all have bad architecture). In the end adding capacitor and endless tunning of PID values helped and now my bed oscilate +/-0.1. But it was pain to get there.
Amazing
Thank you for so much knowledge Stefan!
Awesome work, not many people catch these flaws.. kudos to you my friend!
Noticed this a long time ago back around ~2014 when i used my MakerBot Replicator Clone with wooden frame as my main and only machine. When i figured the temperature swing was causing the parts to come off over time despite hallow or solid parts that would cause more "pull" from shrinkage, i started using insolation under the bed and found wool not only insolated beautify but also damped the vibrations on fast prints or sharp edges. I also used Kapton tape on the Y axes bed frame to reflect the heat upwards. From that experience i quickly noticed the banding gone and put two and two together. Massive improvement for ABS print bed adhesion
*I didn't get any data back then but i did for an i3 machine i have now, It went from ~5 degree swing while printing a large vase (to simulate air pumping though and over the bed) to a ~1 degree swing
Thank you so much. I have been fighting this kind of Z banding for over a year. Have not been able to correct it. Thank you so very much!!!! I am now Z Band FREE!!!!!!!!!!!!!
Great info Stefan. Congrats on your sub count, it's finally getting up to the numbers it should be at 👍
Great video. Love the witty humor to keep me engaged so much so I almost forgot Im learning XD
Glad you enjoyed it!
This is a good argument for a bed that is only fixed at one end and the other is able to slide when it expands rather than the whole thing bulging in the middle.
Did you calculate the thermal expansion? With only + -1 K I can't believe it will be enough to see them rings.
I don't think it's that. It must have something to do with the "power shocks" on the Mainboard itself. They are strong and happen less frequently than mini burst of PID.
It is, at least on the original printer that bed pid was implemented for in Marlin, the mendel max. It had a 250w heater and a glass bed. The math is all in the git commit to prove it.
The slow nature of temp sensors could mean the temp swing is greater than indicated.
@@stephenmcdonald3781 the temp sensors are super quick? It only depends on often you poll it. You could basically get 5 different values within a second when you heat it up.
However the temperature transfer in the bed is slower and thus you will get a different temperature through the entire bed. The temp sensor can only tell what's in the center of the bed.
This happened to me exactly a couple days ago with my Anet ET5! Instead of the bed fluctuating it was my extruder. I Had to flash marlin 2.0 since the stock Anet firmware won't let me do a PID tune through pronterface. After PID tuning I've had much better prints :)
That’s very interesting about SSR controlled beds. I have one that seems to struggle getting to temperature. I blamed it on lack of insulation and the fact it’s trying to heat through a magnetic bed to the spring steel / pei surface
Great, i really was about time For Someone making a Video about this topic! Took me several de-and reassemblies until I found Out about this issue
Oh wow, very very well documenting, Stefan. I have learnt the way to scientifically document my researches and projects through your video over the years.
Great to hear!
Amazing. It seems to make sense but I would never have thought the bed temp variations to cause this.
I think my Ender 3 has the same problem. I added a glass plate to the print bed, which of course changes the thermal capacitance. The graph of the bed temperature in octoprint is oscillating and some pattern is visible along the z axis in the prints. I will definitely try tuning the PID loop!
Those exaggerated heat expansion animations were fantastic!
the best 3d printing channel
✌
Glückwunsch für die 300k brudaaaaa
👌💪
I once reduced bed temp from 40c to 30c during a 40hour print. It caused very noticable artefacts in the wall.
Omg, I have this issue for half a year now since I last flashed firmware. I have to take a look, thanks.
Hey, another reason for z-banding other than lead screws and heatbeds might be an extruder feed gear that is not concentric with the stepper motor shaft. This can be pretty easily checked by printing two different sized towers and seeing if the z-banding happens at the same frequency on both of them, if it does not, then your feed gear might not be concentric.
interesting had not considered that could be a problem, thanks for sharing
You sir are a genius!
You want to put some insulation on the underside of the heated bed, I have mine insulated, I put that on when I was building it since it worked well on my Anet. Temperatures are more consistent (within 0.2C) and it saves a small bit of energy when printing. You want a silicon sock on the hotend also of course for the same reasons.
Great update from your, Like it
Good points about the Z wabbling!
Thanks for sharing your experience with all of us :-)👍
Also, depending on how much load the heater is applying, turning it hard on and hard off could also cause voltage dip on the extruder heater, or the motors
I've been chasing that Z(?) banding issue for some time.
Consequently I now have Single Start Z screws and Dual Collet type couplers fitted which helped Z banding... a LOT.
But there remains similar artifacts to what you are showing in this video.
Believe that the source is My OverHyped Bondtech extruder mechanism..
The main filament gear uses a Grub screw. Which shifts the drive gear Off center when tightened. Lovely !!
Add on the other rather imprecisely machined driven extruder gear and the foolish variable diameter Hobbed drive teeth detail..
and I get a pulsed (and a visible /measurable ! ) extrusion flow variation.
Backing off the Idler spring tensioner Helps.. Noticably.
It seemingly lets those gears have a wee bit of wiggle room for slightly improved flow consistency.
Replacing that idler gear with a suitable Ballbearing race... improves the situation .. notably more..
In process of finding / building a Better quality (verifiably concentic) Extruder drive setup.
Likely a Single Drive gear version.
I have seen similar behavior on one of my printers before. I have an Intamsys Funmat HT that I use for high temp materials, and due to breaking the ceramic plates, I bought and machined a sheet of garolite to use as the bed, and it was about twice the thickness of the original ceramic plate. I started noticing a very similar pattern of z banding issues on the first print with it. I always let the printer warm up for an hour and a half when printing high temp to let the chassis heat soak, so I didn't think it was due to any heating issues at first.
I switched back to the ceramic plate, and the problem went away. So I purchased a carbon fiber plate from Vision Miner, and I haven't noticed the problem with that plate, either. Garolite is supposed to be fairly stable from a thermal expansion perspective, but I can't find any data on it's thermal expansion characteristics on MatWeb, but all else being equal, the only thing I can think of is the thickness of the bed was changing slightly with the heating cycles.
One other possibility I can think of is the bed is held down by magnets that screw together through holes in the bed, and rest in cups at various points on the bed. If the x and y directions of the bed were expanding enough, it is possible that the magnets could be forced to ride up the side of the cups they are in, which would force the rest of the bed up.
I think the firmware for this printer is pretty well locked down, so I can't dig into the settings to look and see what it's doing unfortunately.
Thank you for this video.This solved issues i had.
You are my favourite 3d printing Nerd (no offense) :-) Well explained, very very good video! Now I check immediately if my printer is crap or only misconfigured...Thank you!
I just had a problem with thick and thin layers and if I hadn't have watched this video a week previously, I'd have tore my hair out 😄 Thanks for the great info!
In fact I like that "digi" singing noises. My first CNC machine (Tron CNC) did make a huge variety of sounds, especially when going through curved paths. It was a music to my ears. Most annoying sound came from the spindle,compressor or vacuum. No matter if the vac was used to hold down material or to suck the debris off the milling path.
One of the causes could be also voltage drop caused by bed current draw, as MK3 PSU works close to its limit. Anyway, I never thought about it, I am pretty sure my bed works at bang-bang and I spent more than healthy amount of time chasing z-banding. Thanks!
You can get around the bed ringing by wiring the bed with an external SSR and use the board controls to trigger the SSR.
Instead of printing the 2nd cylinder at 200% speed, print a 2nd cylinder of half the diameter of the 1st, ensuring the printing speeds are equal (don't let auto-cooling slow down the smaller one). That way the material load on your extruder will remain equal, eliminating an extra experiment variable.
Bang bang, he shot me down
Bang bang, I hit the ground
Bang bang, that awful sound
Bang bang, my baby shot me down
..... 🤣
Very informative video. Thanks.
OK Nancy
I was looking for this reply 😂💕🤘
#TeamTarantino
I think you can sidestep the problems somewhat by having a high thermal mass bed, IE glass. Thanks again for more high quality research.
Good point and this is also what you can find on the RepRap Wiki. If the thermal mass is big enough, Bang-Bang can be fine.
even with a large thermal mass for example if the glass isnt thermally bonded (bed clips) there is still maybe an isulation gap causing the metal plate to flex under the glass causing the glass the pulsate with the metal plate though on my large printer i use bang bang, with thermal tape under the glass and its fine
@@meky0 Wouldn't it be the reverse? If the glass is bonded to the metal, it's forced to follow the erratic motions of the metal. If the binding is loose, the glass bed can sortof ignore whatever the metal underneath is doing. Not too sure about this though.
@@CNCKitchen The original pid bed implementation in Marlin was specifically because of a glass bed. The heater side of the glass swinging around in temperature by just a little while the top was more stable would cause bowing that led to banding. Although that was with a 250w heater, which is a bit large.
Very interesting. This was a very good one.
Great find! My printer has been using bang-bang forever, and I've had issues like this before (although not entirely sure if Z-wobble or this).
Something else to consider : If using bang bang, the 0% -> 100% duty cycle change has a large impact on supply voltage to the rest of the system (on my printer at least). I hear the drop in RPM (therefor voltage) to my part and cold-end cooling fans when it periodically turns on. Could this also contribute to this anomaly, and to what degree? I wouldn't think that a +-1 degree temp change on the bed could be the sole contributing factor. Maybe a test with a bed heater with an independent power source could provide some data on this.
Thanks for a great video as always!
Great video. I will now investigate my printer.
My first 3D printer was a Solidoodle 3. There was a design flaw that resulted in a large lag between the heater and the thermistor on the extruder. It would take over 30 seconds for the thermistor to see a change in the temperature after the heater would turn on, and vice versa when it turned off. This became quite a problem when I upgraded to newer firmware because the thermal runaway kept tripping. It also meant that, even with a reasonably-well tuned PID control, the temperature varied by +/- 5C from the setpoint. I believe this was the cause of some very noticeable inconsistencies in the surfaces of the printed parts.
Thanks for sharing your troubleshooting process. My printer is so old, I'm sure it's using bang bang.
I learned something today. Thanks.
Yes also the LEDs on the heatbed flickered annoyingly so i used PWM few. 5Hz and it works perfect 0.0°C differences and low switching good for my FET :)
That's the issue/artifact that's bothering me for months!! Danke, Dude
Cheers!
Fascinating! I never knew the bang bang was called... well... that. Always just thought it was a realllly slow kind of PID. :P
Amazing how much those bed temps affected the print quality, I would never have guessed!
The power drain when the heated bed activates in bang bang mode may affect the motor or heatter of the extruder???
The voltage of the PSU drops a bit but if it's powerful enough the impact shouldn't be too big.
@@CNCKitchen but you should check the voltage/current on the Mainboard traces itself. The bed instantly sucks full power causing little spikes which could also drain/hit capacitors and cause a quick shortage of current. The fan of a JGAurora A5 always lowered the rpms once the bed banged.
But of course I'm not as much inside this tech as you are. Just trying to guide thoughts in another direction.
@@CNCKitchen Could ultimately be skewing the thermistor though. Would be interesting if you could rule this out. You could remove the heatbed (leave it attached, but don't actually print on it - i.e., just leave it sitting behind the machine). So you have the same electrical load, but you're not heating the actual print surface.
A quick and easy test to eliminate the heatbed cycling as the issue is you can turn off the bed after the first few layers and you can see the results quite well. It will go from the regular layer issues to completely smooth. I just print with the bed off since I am too lazy to change firmware.
Wow, it never occurred to me that the thermal expansion & contraction of the bed would affect prints in such a way.
I have a Prusa i3 Mk3 because I wanted a matured product where I wouldn't have to try and diagnose odd issues like this, just build it, tune it a little and endlessly print. 2.5 years of ownership has shown that strategy paid off :)
My lack of money made me go the complete opposite direction for my 1st printer: an entirely scratch built project, not even a clone, only just similar to the i3 style in montion design (and even that just similar - mine runs on lead screws all the axis), and Marlin on it.
Sure as heck is quite the ambitions project and I have quite a bit on my hands to tune and test, tho I'm glad to report to anyone that cares that it's indeed moving and heating correctly right now!
Can't wait for the video where you switch boards. I really want to do that on my MK2 as well. Does the duet mini have silent stepper motor drivers? That is my only concern because I'd love my MK2 to be quiter
great content! thanks!
Muy buen video, pero entiendo que una cama de vidrio deberia solucionar el problema tambien ? De esta forma no habria deformaciones en la base. O si ?
I have created an external plate based on 300W mosfet for bed contol. With 12V 200W Webasta heater it need about 5 minutes to reach real 90 degrees on glass. PID control work really great, temp hold in coridor about 0.1 degree. I must mention that 220W Ac relay is really dangerous in this mode.
I would love to watch a test of the PCTG filament from Essentium
Exactly the problem I had with my Anycubic Mega S. I never imagined only +/- 1°C could have such a huge impact, but apperently it does. Even the part cooling fan could decrease bed temperature and cause an overpronounced elephant foot if set to 100% too early - a badly designed fan duct could make things even worse if air stream blows too much towards the heat bed or hits the nozzle. And when the hotend is PID-tuned without having the fan enabled, it might cause undershooting or dips in temperature when you actually use the fan - in the worst case even introduce or worsen clogging...
I wish I had seen your video back then, as it took me a few weeks to actually figure this out. Anycubic's support first sent me new threaded rods and brass nuts, but there was still significant Z-banding. After quite a few test prints I noticed, pretty much by coincidence, that printing with the heat bed turned off didn't result in what I thought to be the usual Z-wobble.
Turns out the latest official firmware from their website (that I downloaded and flashed right after I got the printer) was either using bang-bang or badly tuned PID values. But since PIDTEMPBED was disabled, I had to switch to knutwurst's firmware to be able to PID auto-tune the bed at all. Anycubic's support is pretty awesome, though - They quickly sent me an updated firmware with bed PID auto-tuning enabled. Now I have an officially supported firmware and completely got rid of any Z-banding.
I would have thought that the change in voltage (because of the power draw of the bed) would have more of an effect on the heating ability of the hot end... This is very interesting. I wonder if the PID tuning of the hot end would be different with and without the bed being heated (as a result of the different drive voltage). Great video. Thanks
That's it !
Nothing to do with thermal expansion/contraction.
More like voltage fluctuation affecting the board...the power supply, and consequently the motors.
Bang-bang control create two distinct levels...while PWM control spread out the influence.
Been fighting similar issues for days now after upgrading to a new print head on a BLV AM8.
I wonder if that lack of the magnet in the center of the Prusa bed and the cooling fans are causing the spring steel sheet to expand at a different rate than the heated bed itself?
Last time I heard such title was something about tinder or so... Anyway, thank you for the video and congrats, just saw your subs are exactly 300.000!
Thanks!
For everyone saying it could be an issue with the voltage drop in the PSU. I had this problem with a 230v heated bed run on a different circuit via a SSR. And the problem was solved by using PID instead of bang bang. That being said in a 12v bed there might be other effects as well.
It blew my mind when I first saw how pronounced the artifacts can be from the bed expanding and contracting. It’s definitely important to use PID for the bed, and there is little reason to use bang-bang heating today.
I've been having this issue on and off for months. It tends to show more when using this one brand of filament so I just assumed it was that and been using other stuff if I needed to look nice at all. Going to try a PID tune to see if that works.
Yay, there is one issue with older or cheaper heat beds. PID may trip thermal runaway. Likely during preheat as when the bed gets close to set temp, it starts pulsing to slow heating to prevent over swing. But that makes it rise slower than the min “degrees per minute” even when set at the lowest setting. Been considering figuring out how to leave Bang Bang, but put in slicer gcode to switch somehow after preheat.
I've been trying to diagnose such things on my printer too. I also did notice that prints in an enclosure come out perfict whereas those printed in open air have slight and near regular variations. So, right now, ABS prints come out better than PLA for me.
I had the same issue a couple of years ago. The way I found out it was due to bang-bang was that the issue disappeared when I printed PLA with the bed off. PID solved it.
Great to hear!
For AC powered beds you could use a PWM input phase cut triac dimmer heated beds would be almost perfectly resistive so those will work fine.
I have to try this with my Anycubic I3 Mega. The slow on/off led under the bed indicates bang bang. It's a big issue with a 4mm thick glass ultrabase. I'd love to see that effect go away. It's the last hurtle I have to clear with my printer!
Very usefull!!! thanks!!!!
Awesome video! Never though of this
How do you think a vibrating table (really high frequency low amplitude) would effect layer adhesion
I had the same issue in one DIY printer. It was driving me crazy although someone in a forum suggested me to perform a PID tunning. In my case I was already using PID, but the values were not tunned.
Does the prusa have the standoffs integrated into the bed? Did you test it on the ones that have screws? Since they have a little more movement tolerance when the bed expands, so it would indicate a problem that is more prusa based
Hallo Stefan,
Danke erstmal für das Video, endlich mal eine einfache und verständliche Erklärung der Unterschiede zwischen PID und Bang-Bang, das hat mir wirklich geholfen!
Ich hätte aber noch eine Frage (gerne auch an die Community) unzwar zeigt es mir bei meinem Hevo mit DuetWifi und Chimera bei dem 2. Hotend durchgehend -273*C an, beim Aufheizen des Hotend verschwindet das Problem, beim Abkühlen taucht es wieder auf...
Kannst du mir erklären woher das kommt?
Can't wait for your creeping tests, a topic not that well documented.
What about variation in extruder temperature? causing flow to slightly change and lead to layer lines like that?
Hmmm, I didn't notice it tbh. I think when my prints come out of my printers, I'm happy with a very decent result. The fine-tunings I need to learn
Suggestion for an experiment: Take a 2nd bed board, flip in over and epoxy it to the bottom of your working bed board. Wire both heaters in parallel. In this manner, any strain force generated by one board will (approximately) be compensated by the strain force (in the opposite direction) of the other board. I anticipate that you only need to measure the temperature of the top board. If you have concerns about double the wattage, then heat the bottom board, and measure the temperature of the top board.
I had the same problem after I changed the firmware/hardware configuration. It took me weeks until I found an article about that phenomenon. After changing the Z setup multiple times! 🙄😅
Same here on another printer.
Can't you tune the hysteresis to have it react earlier / more often? I mean unfortunately heating is usually slow to react but maybe the issue can be minimized even when bang bang