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Mars Pro WILL NOT ZERO - HELP !
#11
The firmware has only one absolute reference for a "zero" position--that is the optical limit switch at the base of the Z-axis mast. It calculates all other Z-axis positions logically based upon the number of "pulses" (steps) it has submitted to the stepper motor since determining the physical lower limit.

Without first dropping to the hardware limited empirical "zero" position it has no idea where the trolley is actually positioned, other than it's accumulated history of stepper motor commands. This is why in initial startup of a print it doesn't matter where the logical "Z=0" position has been set--the trolley nust drop to the hard limit to get "it's bearings". It is not ignoring the logical "Z=0" setting, it's just that that setting is meaningless without knowing where the real bottom is.

The "Z=0" function only sets a "logical" "zero" (home) position, an offset from the physical zero point--it has nothing to do with vertical calibration and planar/axial  alignment¹ of the build plate when the Z-axis trolley is physically positioned at it's lowest point (as moved to by the "Home" button alignment function, and as determined by the printer's firmware sensing the lower limit switch's state change). Read more about "Z-0" here.

If at the bottom of the Z-axis travel your printer is "grinding" (I.e. the stepper motor is not turning and "cogging") the possible problems are: a) miscalibration of the build plate; b) the trolley is jamming up in the rails; or c) the optical limit switch is faulty.

The limit switch can be tested as follows:
  • remove the build plate from the trolley;
  • press the "Home" button;
  • the trolley should fall, stop, then rise 4-5 mm and fall again, then finally rise just a tiny bit;

If it does this the limit switch is OK and the problem is most likely calibration/misalignment of the build plate.

To calibrate it properly do this:
  • place 2 layers of common (20 lb) printer paper on the LCD screen;
  • loosen the build plate lock screws;
  • press the "Home" button;
  • when the trolley comes to rest adjust the build plate so it's edges are squarely aligned with the LCD's edges;
  • press down LIGHTLY (you're not cooking a Cuban sandwich) on the build plate;
  • snug up the front locking screw, the the side screw; 

I have never used, or found any need for the "Z=0" function, which Elegoo describes as a way to adjust the vertical calibration "on the fly" as opposed to performing the complete physical calibration and alignment (as might be done in production runs when alignment of the build plate was not needed).

Note that I said "snug up", not tighten. You are not replacing a wheel on an F-250 "dually". Many users stripped the socket set screws supplied with theearly MARS units (which were not a poor design choice, but chosen with a missing knowledge of what "tighten" means to the average American) because of overzealous tightening of same.

I would also strongly recommend removing the lock screws and filing/grinding off the ridges that are artifacts of the thread forming process--a ball end would be best:

[Image: CapScrewRidges-00.jpg]

They will almost certainly cause the split sleeve that clamps the build plate mounting ball to shift when tightened (or even "snugged"). I do this also to the M8 screw that clamps the build plate assembly to the trolley, and the small thumbscrews that clamp the platen in place. It prevents those ugly ridges from chewing up the aluminum on the trolley bracket and resin vat frame.

---------------------------------------------
¹- I do wish the misleading and just plain wrong term leveling could go away--with our printers there is no act of "leveling" involved in the vertical calibration and alignment of the build plate--unlike with filament deposition printers where the build plate is actually leveled.
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#12
I still can't print properly.... the print grows all distorted... I think the plate doesn't align properly... when I turn the screws to set Z=0 it moves as I turn them.. there's no way the plate stay still... and when I attempt a print I have to move manually the plate a tiny bit in order to avoid the grinding sound.. it's ridiculous... and I am sure I am not expert.. but this printer is not user friendly and it's really annoying losing days trying thousand times to set the plate with a paper sheet.. two sheet.. maybe 3... it's honestly very frustrating
I tried to set my room temperature to 25 degrees in order to avoid the resin to be too dense.... but I failed all my prints and the grow deformed even if they have tons of supports...

more the plate is closer to one of the anchor points for the resin tank.... so I'm starting thinking my printer is not ok... and could be assembled badly...

at the moment... only the the test print worked.... every other... no way....
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#13
You need to disassemble the build plate ball mount as I described above and make sure it's not damaged and is clean. Reassemble with a tiny bit of grease, but first roudf off (or even flatten) the ends of the lock screws. If the build plate is moving when you snug up the screws (front one first) then you are making them too tight or the ridges on their ends are making the sleeve "walk about" as you are snugging them up.

I have done it this way since day one (October of 2019) and have never had a problem with the platen shifting as I snug up the screws.

Again, SNUG--NOT "tight"...

I jut last night/this morning printed this (a 9 hr print with 0.02 mm layers) at 68° F (20° C):
[Image: LockIndicator.jpg]

Used Elegoo's Standard Gray resin, no problems.

See my post here for more about disassembling the ball mount.
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#14
Hi Cliffyk, thanks for the comment, I'll try to disassemble the plate.

I suspect it will not work for this reason
what I saw in my print has been that:
- tightening lightly the screws, stopping when I feel resistance.... the print starts... and it ends with the plate loose moving around and a curved.. deformed print
- tightening more the screws, the plate rotates a bit (this must be what you say I'll flatten the screws)... but again... the print start... and after a while I see the plate loose moving around.. and the print fails ..deformed print...

I think there must be a problem with the direction of the vertical movement for some reason....that pushes the plate in a non flat way... causing the screws to untighten and the position goes bananas whot the print.
I'm not an expert, I have my Mars 2 Pro a few days... but this is the feeling, observing how lose is the plate when I stop the print.
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#15
"tightening lightly the screws, stopping when I feel resistance" is not correct--they need to be "snugged up"--I.e. about 1/16th turn past when you feel resistance, same as tapered seat spark plugs...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#16
After reading these posts it appears lot of people are over thinking this issue or have found work arounds. I have a Elegoo Mars Pro and also experienced this issue when I first started 3D printing.  I'm a knuckle dragging mechanic, not an engineer, so hopefully I can explain the set up in layman's terms. The most important thing to realize is that Home is the mechanical limit of the unit. Set Z=0 is entering an offset in the program to take into consideration the thickness of the FEP in the resin vat.

The first step is to loosen up the build plate so it moves freely. Put a piece of paper on the LCD screen and press the Home button. Remember to square up the build plate as it goes down. The only reason why the paper is inserted is to prevent the build plate from making physical contact with the LCD screen.

Next step is to tighten the allen head screws on the build plate. Start with the screw on the front. Turn it a quarter of a turn then turn the screw on the side a quarter of a turn. Repeat this until you feel a little resistance on both screws. Then you will want to tighten up the screws using the "two finger torque" method. Which is tightening the screws as much as you can using only two fingers. You can confirm the level of the plate by manually raising the build plate 0.1mm then tug on the paper on both sides. If there is more resistance on one side than the other then repeat the entire process.

Once you are happy with the level of the build plate, manually raise the plate another 0.1mm or 0.2mm so the paper will pull out with slight resistance. Once the paper is removed press Set Z=0. Manually raise the build plate, inset the resin vat, and you are ready to print. NEVER PRESS HOME WHEN THE RESIN VAT IS IN PLACE!!! Doing this will cause the unit to try to drive the build plate to the mechanical limit. It won't be able to reach that limit because of the added thickness of the FEP in the tank. This is what causes the popping and grinding and will put a heavy load on the stepper motor.

It is possible to set "zero" without using the Set Z=0 function. Doing so will basically set the mechanical limit higher to accommodate the FEP thickness. This method will allow you to press the Home button without over driving the motor but it will not allow you to adjust the "zero" if the gap between the build plate and the FEP is too great. If you wish to set it up this way I would recommend using a piece of replacement FEP instead of multiple sheets of paper.

I hope this clears up any confusion and solves your issue. Good luck and happy printing!
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#17
(04-11-2021, 12:23 PM)Jmac Wrote: After reading these posts it appears lot of people are over thinking this issue or have found work arounds. I have a Elegoo Mars Pro and also experienced this issue when I first started 3D printing.  I'm a knuckle dragging mechanic, not an engineer, so hopefully I can explain the set up in layman's terms. The most important thing to realize is that Home is the mechanical limit of the unit. Set Z=0 is entering an offset in the program to take into consideration the thickness of the FEP in the resin vat.

The first step is to loosen up the build plate so it moves freely. Put a piece of paper on the LCD screen and press the Home button. Remember to square up the build plate as it goes down. The only reason why the paper is inserted is to prevent the build plate from making physical contact with the LCD screen.

Next step is to tighten the allen head screws on the build plate. Start with the screw on the front. Turn it a quarter of a turn then turn the screw on the side a quarter of a turn. Repeat this until you feel a little resistance on both screws. Then you will want to tighten up the screws using the "two finger torque" method. Which is tightening the screws as much as you can using only two fingers. You can confirm the level of the plate by manually raising the build plate 0.1mm then tug on the paper on both sides. If there is more resistance on one side than the other then repeat the entire process.

Once you are happy with the level of the build plate, manually raise the plate another 0.1mm or 0.2mm so the paper will pull out with slight resistance. Once the paper is removed press Set Z=0. Manually raise the build plate, inset the resin vat, and you are ready to print. NEVER PRESS HOME WHEN THE RESIN VAT IS IN PLACE!!! Doing this will cause the unit to try to drive the build plate to the mechanical limit. It won't be able to reach that limit because of the added thickness of the FEP in the tank. This is what causes the popping and grinding and will put a heavy load on the stepper motor.

It is possible to set "zero" without using the Set Z=0 function. Doing so will basically set the mechanical limit higher to accommodate the FEP thickness. This method will allow you to press the Home button without over driving the motor but it will not allow you to adjust the "zero" if the gap between the build plate and the FEP is too great. If you wish to set it up this way I would recommend using a piece of replacement FEP instead of multiple sheets of paper.

I hope this clears up any confusion and solves your issue. Good luck and happy printing!

I have tried everything in this thread. I have a brand new Mars 2 pro and am having issues.

Without the plate on if I hit home it goes down then up and then down and settles no problem. (Just as the gentleman above described in his steps 1-3) Everything seems to work as normal.

As soon as I put the plate on and tighten the arm, loosen the nuts holding the plate in place to level, it will go down and start grinding. It never settles. It won't stop. It can't be bargained with, it cant be reasoned with, it doesn't feel pity or remorse or fear, and it absolutely will not stop... EVER.

After doing a bit of research, I've tried putting spacers on the arm that control how far the metal tab sticks down to hit the sensor at the base. This hasn't done anything to help.

Any suggestions?

Thanks in advance.
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#18
I got my Mars 2 Pro today and was having exactly this problem.

I did find a solution. Not ideal but it's worked.

I calibrated the plate with the tank on and filled with resin. I'd already been through the piece-of-paper approach a couple of times to no avail.

I loosened the Allen bolts on the plate, pressed home, the plate adjusted.
Next I tightened the bolts (front first then side).
I then took the plate up with 4 presses on 0.1mm.
Back out to the parent menu and hit the button to set Z.

Crossed my fingers, no grinding motor noise and printed the rooks perfectly.

I think the order of button presses is also very important but the piece-of-paper approach just doesn't seem to allow enough room for the FEP sheet.
It's very possible that I just got lucky and I'm bracing myself for plenty of "You cannot do that!"

[Image: 219376667_140996901496865_19728302714923...e=611FF59F]
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#19
I've got an original Elegoo Mars and I'm not sure whether the design has changed (suspecting not seeing as the initial set up appears to be unchanged) and ran across the same issue. When telling it to home it would hit the build plate and start grinding, took a look at the little peg at the rear and noticed it was getting nowhere near the sensor. So I took the build plate off and pressed home and saw that it was correctly doing the homing sequence which told me it was something to do with the build plate.

As some here have suggested the secret lays in the ball joint. This joint tilts in the x & y directions to allow for horizontal leveling but it is also on a spring in the z direction. The plate should be able to push in and spring back in the mounting bracket. If it isn't you may need to take it apart and check the spring, and make sure it has some light greasing. When homing and leveling the plate needs to be loose so it can push in and out.

The reason mine had started grinding out when homing was because the plate had pushed further out in the joint (likely due to me being heavy handed when removing the previous prints, plus i did drop the plate once).
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