Swapping Build Surfaces?

[Gwhite]

I have the regular glass & polyimide build surface that came with my M2E. I've leveled & adjusted the Z-height for that. I just bought a plastic "PRINTinZ" build plate to experiment with for PLA, but it is a different thickness from the standard glass plate. At a minimum, I will need to recalibrate for that. The main computer I use with the machine is about 8 feet away, so in order to do any hands on tweaking like leveling or the like, I need to bring a laptop down into the shop to set up right next to the printer. I'm trying to figure out what I can get away with to avoid having to do that frequently.

Several questions:

1) If I change build plates, is it a good idea to re-level as well, to account for any thickness variations, or is that down in the noise?

2) Is it a good idea to mark the build plates to they go in the same way each time?

3) If re-leveling isn't necessary, can I read out the Z-offset from the firmware for one plate, and restore that value later if I switch back?

A lot of this depends on how much variation in thickness and/or level is considered OK. If I'm printing at 0.2mm layers, that is ~ 8 thousands of an inch. If my build surfaces are +/- 0.001 inches in thickness or less, I would think variations of that magnitude aren't too critical. On the other hand, the amount of extra "squish" used to print the first layer could be on that order.

I'm going to get out my good micrometer & do a little research as well, but that will give me a very limited sample (although one that will matter most to me...).

Comments & suggestions welcome.

Thanks!

[Gwhite]

Well, I dug out my good digital micrometer, and measured my new "PRINTinZ" build surface. The results were more than a little disappointing. In one corner, it measured around 4.45 mm thick. In the opposite corner, it was ~ 4.21 mm. With a total variation of more than my typical layer thickness, I will have to re-level any time I switch to this, and if i remove it from the printer to release a print, I need to make sure it goes back in exactly the same orientation.

I'm guessing the glass build plates supplied by MakerGear are much more uniform. When I get a chance, I'll check mine. I've already done the experiment of turning the plate over to print PETG with hairspray on the glass without any adjustment. It worked just fine.

[sthone]

1) If I change build plates, is it a good idea to re-level as well, to account for any thickness variations, or is that down in the noise?

It depends on how far off they are but you are never going to get all of your bed corners all within .04mm anyway so I personally wouldn't worry about it if it's that close.... I think you'll find your glass isn't any closer than that anyway.

2) Is it a good idea to mark the build plates to they go in the same way each time?

Don't know how much it matters but I do this because it can't hurt that's for sure.

3) If re-leveling isn't necessary, can I read out the Z-offset from the firmware for one plate, and restore that value later if I switch back?

Yes..... From the command line in S3D

First Type M501 to read the EEPROM parameters
Look for the M206 line. (it should look something like M206 X0.0 Y0.0 Z4.20) Write down the Z height offset (Z4.20 in this example) this will be your measurement for this plate.

Put on your different plate and run the quick start app to reset the new z height to the new plate then run M501 again and write that number down.
Now when you want to change plates you can enter the new numbers with the command M206.

M206 Z[new value]
and then M500 to save it to the firmware.

You can also use this method to make small changes to your z height with out running the app every time.

-Steve

[Phil]

You got me to thinking...How much is the bed raised/lowered per 'click' of the Z-adjustment knob?

[sthone]

You got me to thinking...How much is the bed raised/lowered per 'click' of the Z-adjustment knob?

Mine measure at roughly .006" (0.15mm) it's pretty common practice to pop the Z-Knob on the fly to adjust the gap too.

-Steve

[Gwhite]

I'm switching from PLA to PETG for now, and I flipped the factory build plate over to print on the glass side with hairspray. While I had it off the machine, I measured the thickness at all four corners & edge midpoints with a high end digital micrometer. The total range was from 3.301 mm to 3.317, or 0.016 mm. One long edge ran from 3.314 to 3.317 mm, while the opposite edge went from 3.301 to 3.307 mm, so it is ever so slightly wedge shaped.

Out of curiosity, I ran the leveling software, which was last done a month or so ago with the polyimide side up. Because of the way I flip the plate, I should get the worst case error of going from the thin side to the thick side. The software said everything was fine, and that no adjustments were required.

So it looks like the factory glass & polyimide build plates are VERY flat & consistent. I have a spare tucked away, and at some point, I will measure that as well & report back. It will be interesting to see if they are repeatable enough to allow swapping without re-leveling.

[Gwhite]

You got me to thinking...How much is the bed raised/lowered per 'click' of the Z-adjustment knob?

Mine measure at roughly .006" (0.15mm) it's pretty common practice to pop the Z-Knob on the fly to adjust the gap too.

-Steve

That seems very coarse. The leveling software operates down to 0.01 mm increments, so I assume that is close to the smallest increment it can control to given the combination of the stepper motor & ball screw. I'm surprised one "click" is 15 times bigger, but I guess a "click" must correspond to a bigger step than the minimum. I'm not that familiar with stepper motors, and assumed one tactile "step" ("click") would be equivalent to the finest step the motor can make.

[sthone]

That seems very coarse. The leveling software operates down to 0.01 mm increments, so I assume that is close to the smallest increment it can control to given the combination of the stepper motor & ball screw. I'm surprised one "click" is 15 times bigger, but I guess a "click" must correspond to a bigger step than the minimum. I'm not that familiar with stepper motors, and assumed one tactile "step" ("click") would be equivalent to the finest step the motor can make.

Sorry ....I misunderstood what he was asking... I though he meant if you manually turn (pop) the z-knob by hand during a print that was running. Common thing we use to do during the first layer to adjust the gap if it was off and you didn't want to stop to mess with the nut and bolt.

[Phil]

I finally did my own experiment:
One complete revolution of the Z-axis knob is 50 clicks.
10 revolutions of the knob changes the Z by 1.250".
1.250"/10 rev/50 clicks = 0.003"/click
Is that the same as what you get?

[Gwhite]

I finally had a chance to measure my spare MakerGear glass/polyimide build plate. The thickness was measured at all four corners and in the middle of each edge. The range went from 3.335 mm to 3.346 mm, so the plate is flat within about +/- 0.005 mm. Not too shabby!

My original build plate measured around 3.310 mm, so the new one is about 0.03 mm thicker. I typically print with layers of 0.2mm, so that is small enough I wouldn't worry about re-leveling or adjusting my Z offset if I needed to swap in a hurry for some reason (oops! crash! tinkle tinkle...).