Problem with setup on new powder coated PEI sheet  

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mark.c20
(@mark-c20)
Active Member

I have just got a powder coat PEI sheet for my mk3 and have an issue.

I have reset the first layer calibration, it prints great and takes far less effort to pop the successful prints of the new sheet.  The problem I have is that 4 of the first 9 prints have failed because the print head knocks the print off the bed at various heights.

It may have had a problem with the print head touching the print before but the print was so well attached to the old style sheet that it didn't detach from the bed or this may be to do with how I have the new powder coated sheet setup somehow.  When it knocks to print of the bed you hear a very clear click as the print detaches so it was a firm push.  Any ideas would be appreciated...

Posted : 20/05/2020 7:52 pm
Kaiede
(@kaiede)
Active Member

I just received a MK3s as my first 3D printer, and for some reason thought it was a good idea to get the textured sheet. That said, I'm starting to notice a couple things with the textured sheet:

  • I have better luck with 70C as the bed temp instead of 60C for adhesion. But I'm seeing advice (elsewhere) saying that this comes with the risk of warping when using PLA.
  • I'd really use the "Life Adjust Z" method to get the live z value right if you aren't already. The textured plate seems to have a smaller "ideal range" than the smooth plate, and I noticed the quality of the first layer could change quite a bit with a change of +/-0.010. I find I have to go by touch dialing it in with the squares towards the end. Visibly two settings can look very similar, but one is starting to get scratches etched in by the nozzle and the other isn't. Especially when I'm trying to do this with the Galaxy Silver which is semi-translucent.
  • I'd check for warping of the first layer. It might not even warp at first, but if it warps some layers in, you can get nozzle collisions as it gets higher on the print.
  • As a final troubleshooting step, consider attacking the plate with hot water and dish soap like you would the smooth. But someone else on the forum suggested drying it quickly and doing a pre-heat afterwards to help evaporate any remaining water. I'd follow that advice to avoid rust. 

My unit was pre-assembled, but I hit on pretty much all this:

  • Factory first layer calibration seemed "fine" out of the box. Bottle opener printed fine. Seemed okay so far. 60C bed temp.
  • Printed a Benchy, it popped off the plate at the top of the port/starboard doors. Caught it before it made a mess. 60C bed temp.
  • Tweaked settings, tried again, this one still popped off the plate, which is when I noticed the warping.
  • Played around with settings again, but didn't get a good print until I upped the bed temp to 70C and backed off the Z a step. It was still warped, but not as badly as the ones before.
  • Tried printing a simple scraper this morning a couple times, thinking it'd be like the bottle opener, both curled badly off the plate and caused collisions/scraping with the nozzle. So warping is clearly a problem plaguing my prints and causing problems.
  • I wound up deciding to go all out on this thing, so I cleaned it with dish soap and hot water, and went through the "Life Adjust Z"  process. Doing this I backed it off from -1.072 to -1.030. Huge difference in the first layer. Much more consistent. 
  • Printed another scraper, which completed successfully. It did still warp after a few layers, but I had let it start at -1.035 by accident, and fixed it part way through the first layer. The part that warped was where the first layer was still at -1.035 and the layer was showing "gouging" on the bottom of it in that spot like when I had the Z set at -1.072, which could explain why it was allowed to warp, so I don't think it's conclusive one way or another that it's "fixed" or "still broken". 
  • Printed another Benchy at -1.030 which just finished a couple minutes ago. No brim, just the default gcode off the included SD Card + tuning the bed to 70C. No warping off the bed during printing, no popping off the plate or collisions. The first layer was still flat on the plate. 

New to the hobby, but maybe my stumbling troubleshooting adventure can help?

This post was modified 9 months ago by Kaiede
Posted : 20/05/2020 11:13 pm
Kaiede
(@kaiede)
Active Member

I’ll also add that there’s a couple threads in here about the textured plate in the first prints forum, which I’ve been reading to try to get some idea what’s going on. 

But I’ll add the problem I’m having is definitely a tug-of-war between warping/curling and adhesion. Below 60C bed temp, bed adhesion just isn’t happening for me, and I’ve had to catch/clean a couple extruder blobs already. But going up in temp causes curling in the corners of larger prints for me (trying to print card trays for board games at the moment). I’m still experimenting a bit here, since I feel like I may need to tweak the bed temp a bit more.

I also wonder if using PLA with the textured sheet makes it more vulnerable to drafts. I see folks talking about getting good circulation for PLA, while wanting enclosures for ABS/etc to keep thermals more controlled. But I’m wondering if air circulation could help cause curling that can overcome the adhesion the PLA has with the plate. Being more sensitive to environmental conditions would explain why it works fine for some and not at all for others. I’m tempted to make a cardboard box semi-enclosure to see if it helps reduce the curling as an experiment. 

(And yeah, I’m mostly just experimenting and watching the prints, while making note of the effects of the changes)

Posted : 21/05/2020 6:04 pm
Graham
(@graham-2)
Trusted Member

@kaiede

Hi i have been using the textured plate for petg , you  are right i found it difficult to get things to stick.

my solution was to give it a good wash in the sink , then i now print at 70.

never had much luck at 60. what is of interest is i checked my bet with a raytek temp gun and are about 6 degrees under what it says on the display

dont think it really makes any difference as i know its under temp, this is the same for all the plates i have

yes i have have made a surround out of depron sheet, this i used in the winter, as i was printing some parts that had very small foot print.

recently i have been doing the bed level correction, this has seemed to help quite a bit, may be worth a look

Posted : 21/05/2020 7:01 pm
Kaiede
(@kaiede)
Active Member
Posted by: @graham25fox

yes i have have made a surround out of depron sheet, this i used in the winter, as i was printing some parts that had very small foot print.

recently i have been doing the bed level correction, this has seemed to help quite a bit, may be worth a look

Yeah, I'm trying something similar at the moment to see if I can reduce drafts. Our ambient temps can be 17-20C during the day, lower at night, and don't really reach above 20C until summer (where it can wind up around 27C). Something simple like the photo tent idea suggested by Prusa seems like it would work in my case during the cooler months. 

Bed level itself is generally not my problem. Most of what I'm printing at the moment fits in the 75x75cm test square, which produces a very consistent result. It's more that once I get a few layers up, something starts to curl, the nozzle collides, popping it off the bed like the OP (which is what made me think it might be similar). It's kinda annoying since the Prusa logo print at 215/60 is perfect in PLA off the textured bed... but the Batman sample print will curl even at 215/55. Ugh.

Posted : 21/05/2020 10:09 pm
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