Paper resistance is imbalanced during calibration

[andywood]

Hi everybody

I have three Mars 2 Monos all with the same issue:

When I calibrate and pull out the paper, it has more resistance on one side than the other. This suggests an imbalance in the build plate I think?

I am experiencing a lot of failed prints which seem to be due to calibration problems.

With one of the printers, it didn't start off this way. It calibrated fine first time and printed very well 3-4 times. Then I had another issue with it where it wouldn't print beyond the first layer (I brought this up on another thread), and now it's printing files completely again but is having this calibration problem.

I'm corresponding with Elegoo about this but the response so far has not been helpful.

At any rate, I've made a video to demonstrate the issue. You can see the paper has resistance on one side, but not on the other, which is why it can be rotated from the point where there is resistance.

I'm wondering if anybody else experiences this, and if so, is it actually as problematic as I think?

[rbbraman]

I have been having a similar issue you described on my mars pro 2 where only the first layer prints. Were you able to remedy that issue reliably?

I've been back and forth with elegoo support but have just been getting the "re-calibrate the print bed" suggestion to no avail

[cliffyk]

IMHO the "calibration paper pullout resistance thing" is significant overstated. During calibrations over the year I have had my Mars the paper has never  never been entirely evenly entrapped. and I have has no calibration related printing issues.

When performing the adjustment I press lightly and as evenly as possible can on the platen¹ while snugging up the locking screws (front screw first as recommended by Elegoo support)--also note I said "snugging" up the screws. You are NOT replacing a wheel on your car.

I have also found that rounding the end of the locking screws to remove the typical cap screw end ridges causes less induced motion when snugging up same. Given the design of the ball joint clamping mechanism this should not matter but it seems to help anyway:



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¹- Do not press too hard as it will flex and deform the LCD (within it's limits) and result in the platen being set to the plane of the deformed LCD--when the excess pressure is release the LCD returns to its relaxed state and the platen is then misaligned.

[andywood]

Rbbraman: The issue where files wouldn't print beyond the first layer was resolved, but not reliably I'm afraid - I don't know what was causing the problem nor why it suddenly resolved. It just started working again after recalibrating, but this wasn't the first recalibration I'd tried. I suggest you read the thread as Cliff gave some great troubleshooting directions which might help you: https://www.elegoomars.com/forum/showthread.php?tid=802

Cliff: That's fascinating about removing the end ridges from the screws. Unintentional movement while tightening the screws has been an issue for me so I will look into this.

Regarding inconsistent paper resistance: I have had some success by employing the method in this video: https://youtu.be/6HmKLrMBYqM?t=289

Also I have been calibrating so the paper resistance is super tight (although I'm aware this isn't the recommended method). This has given me successful prints when the regular method was giving only fails.

Another aspect to this was supporting the files. Although the files printed fine on other machines, I was finding they printed so far then slipped off the supports on 2 of my printers. I believe they were just on that knife edge where the tiniest calibration issue would mean failure. I added thicker supports and more supports and then the files printed okay on these two machines.

[cliffyk]

i just reread that other thread--don't know why I missed it previously, however the lift speeds you indicated;

Bottom lift speed: 90 mm/min
Lifting speed: 100 mm/min

are VERY aggressive. The higher the inter-layer lift speed the higher the force required to tear the last printed layer from the FEP--which can tear the last printed layer from the platen instead.

Try reducing them to 60/80 (bottom/normal) and see if it helps consistency.

[andywood]

Thanks Cliff. I'm about to have many orders come in to print so will circle back round to this when there's time to test it! All the best.

[cliffyk]

In pondering the Z-Axis adjustment/calibration "paper resistance" thing it has occurred to me that any significant resistance--other than to be expected slight static resistance ("stiction")--to pulling out the paper would have to be an effect of the paper being "pinched" between the LCD and platen--I.e. "too tight'.

The OEM FEP is 0.15 mm thick, normal 20# printer/copy paper is 0.10 mm, a poor substitute. Way back I began using a sheet of 24 # parchment of 0.14" as a spacer ans have generally ignored the whole "pill out resistance" thing--just make sure you hols the platen down evenly and gently, and snug up (as previously defined) the clamp screws.