Sped up peel?

So, each layer, the peel process progressively angles the tray away from the build platform. If the last layer printed before a peel only cured resin as close to the hinge as let’s say 1/2 the tank, could the peel be optimized by only running 1/2 the cycle? There would be no speed difference if a layer extended to the hinge side of course, but it seems that for layers that are on the far side of the tank only, things could be sped up significantly.

That would make printing on the peel (as opposed to hinge) side more failure prone.

If anyhing, the peels should be slowed down if a significant cross section is detected on the peel side, not sped up or cut short.

Not sure you understood the question, Ante, or maybe I’m not. The tank hinges during the peel, as we all know. The distance the surface moves away from the build plate is a function of its distance from the hinge. For each step of the tilt motor, closer to the hinge moves less distance vertically than locations further away from the hinge. Presumably, the amount of rotation around the hinge isn’t the primary factor, it’s the vertical distance moved relative to the build plate. There’s some minimum distance move required to generate enough strain to peel the print off the tank bottom. So in order to guarantee the minimum vertical distance move near the hinge, the distance moved at the opposite side of the tank is much greater. If you printed on the side of the tank away from the hinge, the amount of stepper motor required to achieve the desired separation would be less. If you took advantage of this, you could move through the layers faster, since the tank tilt movement would be minimized based on the print’s position.

Except, it appears to me that the build platform steps down as the tank tilts. If you watch the build platform when the tilt completes, it moves up much more than the layer height would make you think it should (at least it does to my eye). So if I’m seeing what’s going on correctly, the motion is more complicated than just the tilting would suggest. It’s both a peel and a shear I think.

But even so, the motion at the hinge side is inherently less than the stepper-driven side. The print peels first in the area away from the hinge since that’s where the motion is greatest. And once the print is peeled, any additional motion is just wasted time. So if the print is in the area away from the hinge, you could conceivably stop the peel process sooner and print faster.

Randy, that is exactly what I was thinking, thanks for articulating.

You could conceivably measure the current drawn by the stepper motor. Since current is proportional to motor torque, the torque required to move a step must go down significantly once the print is peeled. You could terminate the peel at that point and optimize regardless of where the print was on the build plate.

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My point was that the fact the prints on the peel side get peeled sooner than the prints on the hinge side is an unwanted “effect” (of the peel mechanism). Ideally, the prints on the peel side should be peeled as slowly as the prints on the hinge side.

Hence, i’m saying that stopping the peel sooner for objects on the peel side is the wrong way to go - yes, it makes the peel faster, but it should not be possible for it to be stopped sooner in the first place, if you catch my drift.

Ideally, when there’s a big cross section on the peel side, the peel should be slowed down so it’s as slow (from the perspective of the object, not the actual peel duration) as if it were on the hinge side. I guess it could be stopped sooner in addition to that, but the net result would be - the peel would last exactly the same (and longer if there was also an object on the hinge side, as then it could not be stopped sooner, but would still need to be slowed down).

That’s all i’m saying, not sure if i’m expressing myself clearly enough - typing under fever is not fun :smile:

Ideally the software would recognize how far from the hinge side the tray is being used and adjust the peel stepper velocity profile to give a constant peel rate only where the part is touching. for most parts that would mean a slow peel motor step rate initially then the speed would increase as the sine of the angle. Once the side of the tray closest to the hinge is adequately separated from the part the peel would stop so there would be no time wasted trying to peel something that is not there…

With those two changes made to the peel algorithm, some smaller parts could print 10x as fast. I.E. a part that is small and that is placed away from the hinge side. Most parts would print significantly faster without any drawbacks. It would be a relatively simple process to calculate the two lines in the tray, parallel to the hinge, where the part stops and stops. The rest is simple trig and a firmware update for the peel stepper.

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Yes, that’s what i was aiming at!
Except stopping the peel based on the algorithm would not work, because the actual PDMS thickness is unknown.

As it is right now, the designers had to base the peel angle on some assumed worst case geometry. The algorithm change I’m talking about would simply subtract from the peel angle based on that geometry and the distance of the closest and furthest part edges from the hinge axis.

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True. Although in extreme edge cases, it might cause prints to not peel correctly over the entire PDMS area.

The most extreme edge cases would simply use the same peal profile that’s being used now and not have an associated time savings.

I meant extreme edge cases of PDMS thickness / variation in thickness.

Remember that the whole system is designed to accommodate a multitude of individual Form1+'s with varying specs of all of their components, not just one sample with strict and exact specs. That is one of the reasons the top (horizontal) position of the peel mechanism doesn’t have an endstop, but simply rams up until the stepper stalls, among other things.

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