Lesson learned with PEI material

Hey guys,

Just had a lovely chat with lulzbot Tec support and I thought I’d share what I learned to hopefully help some people out here as Lulzbot learns more and more what’s good and bad for your PEI surface.

The main thing to note is that the war removal temperature of parts from the bed for ABS and HIPS are 50C. Note that the bed, by default, moves forward at 60C. Removing at these temperatures can damage the PEI and adhesive in the long run.

They also have stated that letting the bed cool down completely and then heating it back up to 50c before removing the part is also not good. It needs to be removed, ideally, while the bed is cooling the first time.

The problem is the bed is at 50c for so little time. I’ve taken the time to modify the ending gcode for lulzbot’s ABS profile. The updated end code is below. It now moves the bed forward at the new correct removal temperature and holds the temperature for 1 hour to give the user time to remove the part before the bed cools down and damages the PEI surface.


M400
M104 S0 ; Hotend off
M140 S0 ; heated bed heater off (if you have it)
M107 ; fans off
G92 E0 ; set extruder to 0
G1 E-3 F300 ; retract a bit to relieve pressure
G1 X5 Y5 Z156 F10000 ; move to cooling positioning

M190 R50 ; wait for bed to cool to ABS removal Temp (50C)
G1 X145 Y175 Z156 F1000 ; move to cooling positioning
M140 S50 ; turn bed temp to ABS removal temp
M84 ; steppers off
G4 S3600 ; Hold bed temp for one hour S
M140 S0 ;Shut off heated bed
G90 ; absolute positioning

Theoretically you could leave the dwell out but it’s probably good to have so if you forget about the part, your heated bed isn’t held at 120F for days :slight_smile:

Again, I’ll test it tonight, but just thought I’d pass along the knowledge gained.

Jim

Removing parts at 50C and below is my rule of thumb also. Though, I don’t think you need to remove only at 50C… maybe I misinterpreted your post.

I do like the properties of PEI, but I’ve been thinking of removing it lately. I’m on my second buildplate and it too is getting lots of bubbles. I can squeegee them out mostly but it is just going to get worse over time.

I think what happens is that with pieces that have a large surface area in contact with the bed, if it doesn’t release well it tends to pull the PEI up a little, and then moisture does the rest. Aside from abandoning the PEI, I’m considering epoxying it down though if that doesn’t work, I’d have a serious mess.

The ideal temperature for removal according to Lulzbot is 50C for ABS. Waiting for the bed to completely cool tends to damage the bed over time. I’m getting my bed replaced under warranty and I’m going to do my best to remove all parts at 50C and see if that improves the wear on the PEI material.

I’d be interested to reading the source if that’s posted online. I havent heard that advice…

I’m actually on my third bed since purchasing earlier this year. This one is bubbling, but doing better than the 2nd bed… I’ve put silicone sealant along the edges of this bed hoping to keep the adhesive consistent. If this one doesn’t work out, I may switch to a removable plate solution. Epoxy might be a good alternative also.

From the e-mail I received my Lulzbot Tec Support:

“I did want to make sure you are familiar with bed removal temperatures and let you know that best practice is to remove the part when the bed comes forward after the print. Not letting it cool down then heating it back up to recommended removal temperatures. The link below has that information.
https://www.lulzbot.com/support/taz-cura-profiles
Don’t use those profiles, just the information about removal temps.”

I’m going to change my code to hold the bed temperature until I can remove it just to see if I see improvement in lack of bubbles in the PEI surface. I’ll report back how it goes.

-Jim

Horse pucky, trying to remove the part when the bed is hot / very warm will lead to even more damage. When it’s hot the print sticks so tight you will need to pry and whatever to get it loose.
How will heating and cooling damage anything, it won’t.

Thanks!

I still don’t read that as remove the print exactly at 50C. But I respect your interpretation… :slight_smile:

FWIW, if the nozzle height is dialed in, the print will pop off with a little force. From my experience its at 55-50C… definitely under 60C which is the temp the adhesive (PEI to glass) seems to like.

Don’t get me wrong. Nothing bad will happen if you’re around 50C. They’re giving the “ideal”. The main takeaway I got from the conversation was not to let the bed cool and then heat it back up to remove it. Originally this is what I think a lot of people did since I’m sure many people’s prints finish in the middle of the night or they’re not around and they can’t remove them until later. While cooling, the bed is in the 45C-55C range for maybe a few minutes total. Without adding the code to hold the bed temperature in the 45C-55C range, they’re going to reheat the bed and remove the part which lulzbot now recommends against to keep from damaging the PEI bed. The other issue is the bed moves forward at 60C (at least my original ABS profile does). That seems a bit too hot for the PEI sheet and adhesive. Hence why I’m just throwing out there to make sure your code doesn’t let the bed move forward until closer to 50C.

Just got another replacement bed in the mail today. It’ll be interesting to see if all this improves the robustness of the bed.

My larger prints stick a bit too well sometimes. I may have to look at changing the Z offset a bit. The trick is to make it easy to pop off after printing, but not so easy as to have the corners of the print warp up during printing.

It’s an art, I tells ya!

Happy printing!
Jim