Updated leveling process


#1

Hi Moai users,

With feedbacks from multiple users, we have drafted a new way to check leveling so it is less subjective and second-guessing. This has not made into the official Wiki yet, and we are looking for feedback from the community on this.

Updates to leveling process:

Leveling is the number 1 reason why print does not come out correctly, and we have been testing ways to make leveling less subjective.

Here is the additional step we are going to insert into leveling:

After the nuts are tightening and z-reset position is set to 1877. Please print following corner test g-code:
https://drive.google.com/open?id=1REhwgXPzffKO1UOH15q6oeZvWlj-A3Lv

This GCode prints four cylinders with a total height of 11mm. There is lettering on top of each cylinder, identify its position on the platform:

This GCode takes about 15 minutes to print at default system settings with a laser power of 58. Please make sure room temperature is above 20C.
When the four cylinders are done. It should look like:

After cleaning it in with Ethanol or IPA, you can check the total length with a caliper.

And you can do this for four corners. Since the amount of compression on heights is a good indicator how much pressure the build plate is putting on the PDMS layer. This set of numbers gives us a good idea about leveling in each corner.
The ideal plate pressure would lead to cylinders with 10.7-11mm height. If it is over 11mm, you may find your print not sticking well and require extra laser power to keep it on. And if it is under 10.5mm, you may find your PDMS layer is wearing out quickly. In some cases, too much pressure on PDMS cause artifacts and shifted layers.

Now you have the leveling indicator number for each corner, how can you get them to into the preferred range.

  1. The numbers are close. Let’s say 10.45, 10.51, 10.42, 10.49. This shows the plate is relatively parallel to the PDMS layer; only the height needs to be adjusted. In this case, you can add 0.4mm to each corner’s height by reducing Z Reset Position by 4. This should get all four corners into 10.8 range. So if you are on 1877, you can lower it to 1873 and test print again

  2. If the cylinder height numbers are pretty far apart, say 10.65. 10.85. 11.00, 11.15. You may want to just do the leveling process again to get them close to each before taking step 1.

  3. If you have three height numbers pretty close, but one is far. Say 10.49. 10.69 10.73. 10.75. Instead of completely relevel, you could just modify the problem corner. Tightening the nut half turn will increase cylinder by about 0.3mm while loosening the nut by half turn adds about 0.3mm.
    So in this case, you tighten the nuts for the 10.49 corner by half turn (matching the letter on the cylinder) and then reduce z-reset position by 1 to get everyone in the 10.8 range.

  4. If you have any corners failed, check for damages on that corner’s PDMS and make sure system settings match to the recommended level. If the setting is ok and there are no damages, it is recommended you redo leveling before printing again. The plate press on the failed corner is too lower.


Level and XYZ calibration
Advanced Leveling
Z Height slightly squished
Show Us Your Bits
Help with fine tuning ring test
Print speed settings
Vat Tilting Issue
Updated Leveling Process Clarification
Advanced Leveling
#2

Hi
I just finished the updated calibration print. Only one thing is not clear for me. Do i messure the total lenght before or after UV-Curing?


#3

I would say before curing, test parts don’t need to be cured unless you are going to keep them and want them to be stronger.
Curing could also skew the results due to shrinkage that can happen during the curing.


#4

Well, this was quite enlightening :slight_smile:

I really like this idea as it gives you a lot more feedback as to whether you are getting it right. Of course, now I found out I am quite far out:

A - 10.60
B - 11.30
C - 10.59
D - 11.57

Not really what I expected as I figured I would have the left or the right high or low but seems like I have the back high and the front low. At least I know where to look now.

Of course even while I’m printing this test I am admiring the crazy resolution that is resolving the text on top of the posts :slight_smile:

Given how far out I am I guess I will go for redoing the levelling process. I think this concept will make a great addition to the guide though.


#5

Lossen both back nuts 1 1/2 turn and print it again. That will shorten the long ones 1.05mm and you will be pretty good then.


#6

Just finished my calibration procedure. To get a better fealing for my messurements I started with a little repeatability test.
I printed the test structure 3 times and compare the result.

results

As you can see, the repeatability is excelent. This is a very importand step from my point of view.
I continued with the calculation of the adjustments. As you can see was vat a little off on the right side. So i adjust the two screws by 120° from the side of the maschine (without cover). Additionaly I couse to readjust my z-reset position to 1869 to achive a total height of 10.80 mm.

After the next calibration print the leveling was near perfect. I choose to readjust the two screws again. This time by 60° while pushing position C a little further. A print later the adjustment was perfect.

From my observation the quality of the calibration print rised significat while adjusting the levels. But I would change the adjustment for the screws from 0.4mm/hal-fturn to 0.6/full-turn.

Generall settings:
Laser power: 58
near new maschine
Peopoly resin (grey)


#7

That looks handy, are you going to share your spread sheet?

The thread on the nuts are 4mm diameter x .7mm pitch. Meaning .350mm for a half turn and .700mm for a full turn.


#8

Of course i will share the spread sheet:

https://1drv.ms/x/s!AnQjmF7qULqhkghyZZpofRyGgzXi
(Link to OneDrive; non edible)

Feel free to change and re upload if you want.


#9

Thanks for the advice, now at:

  • A 10.44
  • B 10.46
  • C 10.68
  • D 10.41

So I guess I should slightly adjust C then use the Z Reset position to give get it into the 10.7-11mm range.


#10

Given the Cura build plate is flipped if this is going into a guide, to remove potential confusion it would be great to explicitly state what A, B, C and D are in terms of where the printer is viewed from.

Viewed from the front of the printer (i.e., looking at the door):

A - Front Left
B - Back Left
C - Front Right
D - Back Right

While it might seem small, I find the mental remapping of what I am seeing in Cura to the actual nuts I need to work on allow room for some confusion.


#11

A little less than half a turn loosening C should bring it in. Don’t be surprised if B is effected some due to a pivoting action on the other two screws.

If it does then you are correct to adjust the Z reset to bring the results into the right height range.

Now with the vat level to the build plate the adjustments to the Z reset will control how your first layers stick.


#12

It took a few more goes (about 5 actually) and adjusting the Z reset but here is where I am at now:

A 10.83
B 10.81
C 10.85
D 10.84

I think once the nuts are loosened to the point that the springs start to have an effect the 0.6mm per turn rate slows quite a lot, I found I needed to turn a lot more to get any effect. Do the above numbers look close enough?

Regardless of the need to repeat the process a few times, it is significantly better than having no way to gauge it except by how full prints go. Definitely think this will be a good addition.


#13

I would say it looks good.

How far off were you in the last 4-5 tests?


#14

Starting point was:

A - 10.60, B - 11.30, C - 10.59, D - 11.57

Then adjusted B and D 1.5 turns and got:

A - 10.44, B - 10.46, C - 10.68, D - 10.41

Probably should have lived with that but wanted to adjust C a little, so I did that as well as subtracting 4 from the Z reset position to put it in the real range and got:

A - 10.83, B - 10.85, C - 10.73, D - 11.02

Wasn’t happy with C and D then so calculated roughly the turns needed for those based on the 0.6mm per turn and did that then got:

A - 10.82, B - 10.84, C - 10.75, D - 10.97

As I mentioned, it seemed like the springs were limiting the effect of the turns at that point so I pushed them further and got:

A - 10.81, B - 10.82, C - 10.76, D - 10.89

Then I had a last go at it and got to:

A - 10.83, B - 10.81, C - 10.85, D - 10.84

In the last three cases I was only adjusting C and D. Hopefully that gives some feeling for how the process went for me. I would say that I am pretty hopeless judging anything other than a full, half or quarter turn, to the point that I had to draw a line on my driver handle just so I could see how much it had turned.


#15

So your Z reset is at 18773?

@peopoly should change the guide to reflect thread on the nuts have a .7mm pitch. Meaning a half turn = .350mm and a full turn = .700mm .


#16

I’m actually at 1871 now because I was starting from following the very original levelling guide rather than the updated one.


#17

Built myself visuals while waiting for test prints :slight_smile: - got it down to 10.8 all round… immediate change …

  • I’ve been also thinking how to make some pressure sensor thing or something to help us make this really quick and painless - something that would beep when you hit the right pressure on a screw… indicating it’s at same pressure all over the edges… gonna think about how to solve this better…

  • until then, this is finally 100% working right


#18

@robob3ar these are great. I am adding this to the guides and also to wiki

@RonUSMC


#19

Oh, I so could have done with these last week :wink:
Cheers !


#20