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Setting Z Offset Not Working Right...
#1
I'm going to try to be concise, because this one is beyond me.

So I first got the printer, calibrated the z offset, and printed the rook.  When I hit print, it went to the offset, and started printing.

Fast forward to a few prints later, when I go to print, it brings the print surface all the way against the lcd and seizes the motor.  At first, I thought it was just getting to low.  I recalibrated, and the same, again and again.

I had a hunch I knew what it was doing, so I tried a test; here are my steps exactly.


  1. loosened the two screws on the print arm.
  2. clicked home on the manual motion control.
  3. raised the arm by .1mm until I could move the paper on the lcd.
  4. did NOT tighten the screws on the print arm.
  5. set the z offset.
  6. raised the print arm to 15cm
  7. selected a file to print to test arm motion.
The arm comes all the way down, back to home, does the home test up and down, THEN goes to the offset.

Why did it start doing this all of a sudden?  When printing, shouldn't it only return to the offset?

I tried the above again but set the z offset to 1cm above the lcd surface and same thing.  It goes to home, then goes to the offset.  It makes absolutely no sense.

From looking around the web, it apears I'm not the only one that has experienced this problem.  Is there some solution that just isn't getting shared?
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#2
(01-13-2022, 03:29 PM)coaxfun Wrote: I'm going to try to be concise, because this one is beyond me.

So I first got the printer, calibrated the z offset, and printed the rook.  When I hit print, it went to the offset, and started printing.

Fast forward to a few prints later, when I go to print, it brings the print surface all the way against the lcd and seizes the motor.  At first, I thought it was just getting to low.  I recalibrated, and the same, again and again.

I had a hunch I knew what it was doing, so I tried a test; here are my steps exactly.


  1. loosened the two screws on the print arm.
  2. clicked home on the manual motion control.
  3. raised the arm by .1mm until I could move the paper on the lcd.
  4. did NOT tighten the screws on the print arm.
  5. set the z offset.
  6. raised the print arm to 15cm
  7. selected a file to print to test arm motion.
The arm comes all the way down, back to home, does the home test up and down, THEN goes to the offset.
Why did it start doing this all of a sudden?  When printing, shouldn't it only return to the offset?

I tried the above again but set the z offset to 1cm above the lcd surface and same thing.  It goes to home, then goes to the offset.  It makes absolutely no sense.

From looking around the web, it apears I'm not the only one that has experienced this problem.  Is there some solution that just isn't getting shared?

Your alignment procedure is flawed because of the printer's basic functioning. There are two "zero" positions used by the printer, one physical determined by the hardware limit switch, and one logical attained ONLY by the firmware's interpreting a gCode "goto 0" command--and this only after the Z-axis has been dropped to the physical "zero". Your process of raising the Z-axis without the screws tight will cause the platen to push down into the LCD when the printer attempts to "get it's bearings" by dropping to the physical (limit switch determined) "zero" position.

Going "home" and rising to the "offset" (Z=0 setting) is how it works--it has to go the physical home to figure out where "zero" REALLY is, it has to do this to determine absolute "zero". It can then do the math, and determine how many lead screw turns are needed to move to the logical zero "offset' position when commanded to do so.

The alignment process should be as follows:

  1. loosen the locking screws;
  2. lower the Z-axis to the "home" position (with a sheet of paper over the LCD);
  3. press down lightly and evenly on the platen;
  4. tighten (firmly, these are not lug nuts) the locking screws--front screw first;
Done... Do NOT raise the platen manually or use the "Z=0" function--it is not needed except in unusual situations to compensate for odd models and long-term creep. It is NOT a needed part of a standard alignment and if it were not exposed to the average user many people's printing experiences would be much improved.

See my posts here for more the "Z=0" function and my exchanges with Elegoo support re: same...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#3
So you go to home, raise it to the appropriate height, tighten the screws and that's it?  It just knows that's the new offset?
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#4
(01-14-2022, 09:18 PM)coaxfun Wrote: So you go to home, raise it to the appropriate height, tighten the screws and that's it?  It just knows that's the new offset?

No, you do not have to raise it at all, no "offset' is needed--when the printer starts a print job it will drop to the absolute physical zero position and then rise for the first layer all by itself...

What you describe "go to home, raise it to the appropriate height, tighten the screws" would cause the platen to be set below the surface of the LCD when the printer first performs its drop to figure out where the physical "zero" limit is...

The alignment procedure is as I listed above:

[Image: PlatenAlignment-00.jpg]

There is NO "raise to appropriate height' on that list...


Why do you feel you need to set a "Z-offset'? Even if necessary the minimum motion available is 0.1 mm, 100 microns = 2 50 micron layers which would likely be too much and create platen adhesion problems...

If you want to tweak Z-axis height then use 2 or 3 layers of paper to perform the initial alignment.

Also, I have found that standard 20 lb. per ream copy paper is only about 0.1 mm thick. the FEP is 0.15 mm so performing the alignment using just a single layer without the vat/FEP in place sets the platen 0.05 mm INTO the FEP. i use a single layer of 24 lb. "parchment" paper which is 0.015 mm same as the FEP....
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#5
I got what you're saying.  Essentially you go home, tighten the screws, done.
If you want to, you can set an offset, but that's only adding a little room, it's still going to home first (thus, if you tighten at the offset, it won't be able to go home).
I'll try this procedure today.  Thank you, this makes so much more sense than the stupid manual.
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#6
I don't know why the later manuals added use of the "Z=0" function as some required element of aligning the platen--it is not, in fact in two years I have never used it except experimentally to see what it did.

I just downloaded the Mars 2 Pro manual and find their description of the alignment process to be incredibly complex--that nonsense about raising (or lowering) the platen 0.1 mm manually and setting "Z=0" to decrease pull-out resistance of the gauge paper is ridiculous--the paper is only 0.01 mm thick, .1 mm is 10 times the thickness of the paper!.

Just loosen the screws and don't press down as firmly next time is all it takes; that raising/lowering and "Z=0" garbage is absurd...

Here is the entire alignment procedure from my original Mars manual:

[Image: MarsPlatenAlign-00.jpg]

Note there is no gibberish about pull-out resistance of the paper, or manually raising/lowering the platen. I guess too many users pressed down like a 600 lb. gorilla before tightening the screws (they were originally socket set "grub" screws that people were always stripping when they tightened them like it was a wheel on their car). Elegoo changed them to socket cap screws in the later models. They do indicate that the front screw should be tightened first in the referenced "Picture 3"

One "gotcha" here: if you have messed with the "Z=0" function in the past you need to reset it to coincide with the real "home/zero"position.

So,  DO use it after you have properly aligned the platen as I described--this will ensure that he physical "zero" home position and the logical "Z=0" firmware recorded position are the same so that a gCode goto(0) command (generally the first command in a print file) does not send the platen to some crazy position.
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#7
It worked perfectly!  Thank you for your help, it was getting quite frustrating.  I hope this thread helps other owners.
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#8
Good news! Glad it worked out--those directions In the manual make a simple task far more complex than even remotely necessary...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#9
No offense but the instructions in the booklet were very clear so I don't get the confusion
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#10
https://drive.google.com/file/d/1zdtTx4z...rxdyY/view
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