Powder-coated sheet damage  

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stefano.f5
(@stefano-f5)
New Member

Hi guys, I recently printed some Prusa ABS on my powder-coated sheet using the default ABS Prusa profile.

The print turned out really good, it also detached itself from the print bed. The small line of priming plastic was a bit stuck but with almost no force it came off easily as well. However, that pesky strip took off a little chunk of PEI leaving a small mark on my powder-coated sheet.

To ensure first layer adhesion, I always clean the steel sheet with IPA before printing while everything is at room temperature, and I wait for it to cool down when it finishes.

So, any ideas why this happened?

Also, the steel sheet was almost new, I used it before like 4-5 times.

Images:


 

This topic was modified 1 year ago by stefano.f5
Posted : 11/09/2019 12:00 pm
cwbullet
(@cwbullet)
Illustrious Member

I have one like that.  I still use it.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 11/09/2019 3:49 pm
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 --
(@-2)
Illustrious Member

I've seen other images of the same type of damage mid sheet; seems it is the nature of the beast.  Also, read posts that Prusa has responded to the owner with the equivalent of "print sheets are consumable objects that wear over time" ... 

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 11/09/2019 5:47 pm
Chocki
(@chocki)
Prominent Member

There is some custom G-code you can use in Slicer which raises the nozzle a bit for the initial purge line, this stops it being squished so hard into the bed. I'm at work ATM so have no access to my home PC, but if someone else has not already posted, I'll do it tomorrow morning (GMT).

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 11/09/2019 6:04 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: chocki

There is some custom G-code you can use in Slicer which raises the nozzle a bit for the initial purge line, this stops it being squished so hard into the bed. I'm at work ATM so have no access to my home PC, but if someone else has not already posted, I'll do it tomorrow morning (GMT).

A bit of convergent evolution at play. I added some gcode to raise my nozzle after mesh bed leveling to avoid heating it too close to the bed to avoid forming a small divot in the bottom-left corner. I realized later I'd re-invented the "easy lift" prime line routine. My startup looks something like:

G80 ; mesh bed leveling
; Final warmup routine
M117 Waiting for final bed & nozzle temps
G0 Z5; Raise nozzle to avoid denting bed while nozzle heats
M104 S[first_layer_temperature] ; set extruder final temp

This causes the nozzle to move down to the bed to start the prime line, resulting in a smoother start. I also put a swipe of gluestick along the prime line area to avoid build up. I played around with routines to vary the prime line position but didn't realize any real benefit.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 11/09/2019 6:39 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: stefano.f5

[...] The print turned out really good, it also detached itself from the print bed. The small line of priming plastic was a bit stuck but with almost no force it came off easily as well. However, that pesky strip took off a little chunk of PEI leaving a small mark on my powder-coated sheet.

Part of the problem with wear in the prime line area is that the prime line is printed independently of your slicer settings. The nozzle is moved to a fixed 0.15mm height after homing and -- without modification -- simply prints fixed gcode commands independent of nozzle, print or any other settings other than temps. I find that the prime line region on all my sheets started wearing a bit. As noted in my other post, a swipe of glue stick and raising the nozzle slightly after homing helps.

I have had bits of the powder-coated sheet come off on my prints as well. Mostly with higher-temp PETG, but also with some PLA. Not enough to expose the metal underneath, but some of the texture coating it seems. It makes sense, the raised bits are subject to stress, but it can be a bit unsightly printing with lighter colors.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 11/09/2019 6:43 pm
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