I don’t think it can be caused by the peel, alone.
The laser exposes the correct pattern of resin on the bottom of the tank. Peel flaws generally take the form of a layer that is stuck to the tank floor, instead of the print… or supports that are fractured- shifting the entire model or a section of the model…if the peel shifted the model, then ALL the subsequent layers should be similarly shifted.
the position of the TANK has no effect on the build… its just there to squeeze a layer of liquid between the optical window and the prior layers. the platform is supposed to be rigidly fixed in x and Y. It is its rigidity that causes the printed layer to peel off the tank. and its position relative to the LASER that defines where each layer is printed.
However- if the platform has a certain amount of PLAY left to right… there might be a specific height at which the peel forces have enough leverage to shift the platform, But, again, once the model is peeled… there is nothing that would prevent the platform from re-centering… and no reason such play would manifest as gradually getting ever more misaligned and then gradually returning to near normal… it might show up as randomly misaligned layers… or a flaw running vertically thru the print.
But, again the weird thing is that the distortion is not linearly progressive… its not there, then just a little bit each layer it gets pretty bad, then it diminishes.
like a wave.
The only thing I can think of that can cause this pattern of fault is if the platform’s position in X and Y is gradually moving off to one side, to its maximum deflection, and then gradually coming back to closer to where it belongs.
Imagine there’s a slight wave in the guiderail… like a speedbump.
The moving platform follows this contour. and for that reason, the area with a maximum curve always occurs at the same height.
Yeah, I follow you. It’s a good point and I’m taking it up with Formlabs. (They currently seem to think it’s due to lack of supports and limitations of the resin. But they are deforming even in places that almost can’t have more support, and if it were the resin, the warping would not be occurring at the same specific range every time- it would occur at different places along the build.
Photo attached of a new test, done with a form file that Formlabs provided. (I took a bunch of photos but am on my way out so haven’t had time to process them all. Most of this warping was “buried” behind supports, but I did note that a few of them seemed a little bent.)
Tough is quite flexible at higher ambient temperature (>40°C, especially before full cure).
Standard resins suffer the same effect, albeit to a lesser extent
My printer sometimes gets to 37-39°C as per the temperature sensor during long prints.
One could imagine that, after a certain height, the horizontal movement performed by the tank during the peel operation might deform the part at its base because of a combination of the moment of force created (pushing the top of the print, transmiting the force to the bottom) and the ambient temp rising (resin becomes more flexible). This would explain why the deformation is happening always at a certain height, is seemingly independent on part geometry and/or orientation… and I wouldn’t rule out the idea that the support structure -being fine enough- will regain its shape while the part stays deformed.
Maybe, but it stands to reason that the warping would continue as the temp rises. Unless, perhaps the build platform gets heated up during the first few dozen layers, and ’insulates’ that heat between the tray and the plate, but once it reaches a certain height, the longer distance between the plate and heated resin, lowers the temp enough so that no more warping occurs.
Right after the weekend I’m going to try and add som ’trash’ geometry under the model, to force it up higher like Sculptingman suggested.
What version Pre-Form is that? I use the older OpenFL and supports don’t have that ladder connectors like that. As far as shrinkage is that normal for that resin? I don’t have any measurable shrinkage on the parts I print with the clear2. I have printed some beefy parts as well as thin walled cases with no problems.
If the resin has shrinkage like that then it isn’t suitable for prototyping as you will never get an accurate part for testing unless your modeling oven-mits.
John, it seems to me that given that I print in tough rather a lot, and i have not seen this kind of height specific curvature. If its the peel acting on the Preform generated support structure this should be a defect common to anyone running Tough thru a Form 2 should it not?
Have other users noticed a similar height related increase in warpage?
I noticed that on the occasion that one of my prints reached 45ºC plus the temperature fell to 41º towards the end of the print. I suspect that any temperature increase over say 37-38º is due to the effect of the laser on the resin when the ambient is high. In effect, the bigger the area of the parts being printed the more heat the laser in generating in the resin.
Maybe we should be looking at giving the printers their own A/C units?
I agree… the enclosure traps heat- great on a cold day… not so great on a hot day when the machine can not transfer heat to the surrounding air as well.
I have considered building a cooling unit into the cabinet my printer is mounted in.
My office is not air conditioned and half the time prints start without even having to heat the resin, because its already too hot.
For me the biggest culprit in warpage is the length of the print, because the temperature in the room can drop 25 or 30 degrees and then ramp back up to near 100 in a single day.
I wonder what temperature environment would yield the most consistent temperature in the Form 2?
that is, Has formlabs done any testing that shows that an Ambient temperature of X enables the heater and enclosure to hold the most consistent temp given its heater unit and how fast excess heat can be radiated away?
These are models from two model from two subsequent 11 hour builds. the one on the right was started mid-morning and the other at about 23:00. The ambient during the day was around 30º and it dropped to, I believe, around 25º during the night, though I didn’t stay around to check the actual temperature. They are basically the same model with only detail differences.
Note: Writing this on my phone an the forum isn’t coopersting with it, in case my post contains oddities.
I’ve looked for specs, but Formlabs has not listed room temp recommendations for the F2. F1 hadca max ambient room temp of around 27-28 Celsius. The room where I print has been around that. (We usually don’t have AC in apartment in Sweden, but right now we have an insane heat wave.
Wow, that’s quite a difference.
I’ll run the test Sculptingman suggested on Mondag/Tuesday and we’ll see if anything changes. Formlabs are also resting a couple of my form files, and I’ve got a test going elsewhere. If the problem shows up in all places, we’ll know it’s a universal issue.
yeah- I almost always start prints in the evening, and like for them to be complete or pretty well finished before the heat of the day builds. that way the room is cool and the resin only as warm as the Form 2 heats it to be.
Everything I build in mid day in summer time comes out pretty warpy.
So- one question regarding your repeating wave is, are you tending to initiate prints at the same time of day?
Buildings here are extremely well insulated, so indoor temps don’t fluctuate that much over a day. Doesn’t make a real difference when I start a print.
What goes on under the hood is much more critical.
Hi. I’m also printing model railways and this warping drives me nuts. I’ve printed a passenger car with roof separately and the roof bent like a banana and sides looks like your car on the right. Heating it with blow dryer helps to “un-bend it” to some degree but it is just unacceptable because every print is a new set of problems. If possible, I put connecting rods between sides of car to prevent it from warping but in your case that can’t help. Soon I 'll print 28 cm long passenger car and it will be printed in 12 parts (it has inside of the car printed as well) and I’m afraid how that will bend in the end.
The best way (in my experience) to avoid this type of warping is to add horizontal and vertical ribs to your objects, either on the surface, or if you can print your object hollow, on the interior. This is how most mass manufactured plastic casings are produced in order to retain their shape and add stiffness.
Agreed… desigining for shrinkage can really help stabilize parts as you print. the vexing part about SLA is that the temperature and humidity can change dramatically during the course of a print- so the shrinkage changes dynamically. That is really hard to correct for in design.
IN injection you KNOW the temps and you know the part is made in seconds.
Bad ball screw would have slop, do these machines use a ball screw or simple lead screw and bushing? A worn lead screw would have more backlash in the worn area.
Stupid question, the warping consistent between different resins with the same layer thickness in the same region of the tank? If so then it would be a mechanical problem.
For shrinkage, does an uncleaned part shrink the same % as a part washed in IPA? If so then the resin is shrinking from the post cure and not dimensionally stable. If the part shrinks more in IPA then it is too sensitive to IPA and reducing the wash time or substituting IPA for another cleaner would be a better option.
That was one of the first things I tried. It didn’t help at all (and in fact cracked the model when I tried to remove them).
[quote=“KenCitron, post:37, topic:19857”]
For shrinkage, does an uncleaned part shrink the same % as a part washed in IPA?
[/quote] I haven’t noticed any significant changes during washing or post-curing. The warping I’m experiencing occurs during printing.
Attaching the results of my test of raising the model a few centimeters higher above the build plate. Most of the model is now warp-free, but there is still a little bit on the lower-most part. Also, the two “pins” I added to the model, to raise it up, are severely bent.
I was able to correct most of the “bend” on this test by heating to 55C and using flat pliers to bend it into shape. Time will tell if it stays or not.
I also did a test with raising the Z-axis 0.1mm on recommendation of Formlabs (who are being very helpful in looking at this, just so y’all know), with the idea that it may have been too high pressure against the resin tank causing compression, but that didn’t seem to help.
If raising the part further away from the base helps correct it then it seems the supports are stretching. Making the supports thicker and lowering the angle of the part as much as possible should also help.
I thought that the base and supports were exposed more than the part when printing. Maybe Formlabs can adjust the profile so they are exposed a little bit more so you don’t have to go through hoops to get a good part.
Heating and reshaping the resin should hold the new position. They don’t seem to have any significant memory.
[quote=“KenCitron, post:39, topic:19857”]
it seems the supports are stretching.
[/quote] Well, the entire model is stretching and it doesn’t seem to be localized to only the supports. If it were, then longer supports would make it worse, wouldn’t it? (I mean, if the weakness of the supports were a factor.)
[quote=“KenCitron, post:39, topic:19857”]
Making the supports thicker and lowering the angle of the part as much as possible should also help
[/quote] Lowering the angle hasn’t helped at all and in fact, made it worse. The entire model went banana-shaped. Maybe I could try thicker supports, but at 0.7mm already, they are already thick enough to create major problems when cleaning up details. (Adding a lot more supports hasn’t helped either)
[quote=“KenCitron, post:39, topic:19857”]
Heating and reshaping the resin should hold the new position. They don’t seem to have any significant memory
[/quote]So far it’s been a little inconsistent with that. Some parts have gone back to their warped state. (I actually had to add some fiberglass bondo to the inside of one part to force it to stay in shape once I had corrected it.)
