Anyone Tried a Removable PEI Bed?

General LulzBot TAZ
#1

I have come to love PEI. A well maintained and well cleaned/sanded PEI sheet has unparalleled stick.

Recently I have been experimenting with other build plates such as Geckotek. I love the idea of Geckotek and its removable flexible plate but after the first few prints it loses its stick as the coating cures more. (I’ve been in contact with the creator Brad and the plate is working as intended and he is also seeing the adhesion issues that I am experiencing. Hopefully future versions will have the performance I need).

Anyways, So i’m back to PEI because I can obtain better stick. However I hate part removal of the PEI. I make and sell a lot of costume props which are required to look perfect, thus I need perfect bed adhesion. This requires me to often “over stick” a part on the PEI for large prints just so a corner doesnt warp slightly.

This isnt the problem… The problem is when you go to remove the part (yes I use proper procedure, IPA soak, I take my time and the bed is set between 50-60C). But even with the best intentions and being careful, you still end up with bubbling of the PEI sheet as it pulls. Not a major issue but man is it annoying.

All this to say -> PEI is the perfect build plate material except for its inability to stick well to its sub plate.

This brings me to my next idea. Why bother with adhesion? Has anyone tried to buy a 1/8" or 1/4" thick PEI sheet and use it as a removable bed? There would be no bubbling as the bed doesn’t need to be “glued” down.

Anyone tried this? What would be the issues that you’d run into? Flatness? I’ve never messed with PEI in its raw form, I assume its pretty rigid? As in a 1/8" sheet would not flex (i’ve seen people talk about scoring and snapping PEI sheets). Why are more people not doing this?

#2

I’ve been looking into it. I found some older forum messages on other sites talking about PEI being used that way. It sounds like there is potential for the bed to be a little less flat. That seems to be an issue with any removable surface though. I was going to try it, but the Zebra was a lot cheaper so I decided to give it a go first. It works well, but doesn’t grab as well as PEI. I’m still planning to try getting a PEI sheet to use that way. I doubt 1/4" would be needed, 1/8" is probably more than you need really.

If you do try it, please post your experience.

#3

ive purchased an 1/8 thick sheet with the same idea. It came warped. I attempted to bake it to anneal it in a way. to do that I clamped it between 2 aluminum plates and put it in the oven @ 350 for 3 hours, I then bumped up to 405 for 1 hour, lastly turned the oven off it took 16 hours for the assembly to cool.

At some point it cracked in 3 different places.

I ordered another piece, I have not yet tried to flatten it.

#4

I figured I wasn’t the first who thought of this!

I looked into zebra plates but everything I read made it sound like they were more for PLA and ABS stick was “meh”.

Geckotek is promising, and I think the typical user would probably be happy with it.

Jballard could you tell me who your supplier is? Maybe I’ll try a different one?

#5

I haven’t tried ABS, PETG works quite well. HIPS is a little iffy sometimes, but usually works well. It worked really well when I inadvertently used a raft… :laughing:

#6

ABS works great on the Zebra plate. Set the heat bed to 70C, get the initial Z correct. I’d also recommend a lower extrusion temp for the first few layers… they recommend 230C, but 240C seems to be fine.

A PEI removable bed would be interesting. I’ve read the same posts about bowing of thicker plates. The sweet spot may be a little thicker than stock, using the 3M 468MP strips. The thicker sheet should spread the stress from print removal.

#7

I ordered from Amazon. I feel like this is going to be a reoccurring theme with thicker sheets of PEI.

A better idea may be to add a slightly thicker pei sheet than stock to an 1/8" substrate. if glass I would put the same sheet on both sides to try and counteract forces trying to break it. Think laminated glass.

To bad thin sheets of gorilla glass are really expensive, add PEI to each side of a .078" thick sheet would probably be incredibly strong.

#8

im actually thinking that a 1/16 borosilicate glass plate with a 16g aluminum plate laminated to each side with a stock thickness pei sheet laminated to each side would hold up to the forces just fine, while also keeping weight down.

The lamination would add to the stiffness of the glass and should hold true to the straightness of the glass, if they could be bound together efficiently, without tape.

#9

Maybe, but I still feel like you’d have problems with the PEI coming free of the subplate. It all comes down to adhesive and maybe a better adhesive just needs to be used than what lulzbot uses with their PEI sheets.

Anyone know what lulzbot uses to glue their sheets to the plate? I feel like it’s pretty lack luster, although I hear the issue is possibly more due to moisture during assembly?

A 1/8" sheet of PEI that is flat really would be the ideal situation (unless a flexible PEI “alloy” could be found, then that would truly be the Holy grail).

Is it the tolerances on the sheet that make it not flat? Or is it that it just bows? Wouldn’t an even thicker PEI sheet fix bowing? So the issue would be tolerances. So the real question is - are flatness issues unfixable because they are caused by the material? (warps during cooling ect) or are is the issue with “poor” manufacturing process. Might be time to source another vendor?

#10

i think it is just warped in general.

Binder clips would possibly hold it flat. my next post ill include a pic.

#11

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The one that I annealed is perfectly flat though, but it is cracked in a few places

#12

Pei is actually available in a castable resin form as well. I want to someday get an aluminum tool plate milled with thin slots in it, then cast a Pei top on it.

#13

If I can find the resin affordable, ill mill a plate and test it. I love having a bridgeport.

#14

This video is a bit dated, but they could be using the same DryTac machine to apply adhesive to the glass for PEI. See 3:30 mark:
https://www.youtube.com/watch?v=f4RGU2jXQiE

From the DryTac mounting adhesives lineup, MultiTac seems to be the most versatile and has a heat range of 110C-120C. Unfortunately, that’s where a lot of us are at printing with ABS. We should probably drop to 100C to be safe with the OEM film… otherwise contraction of the ABS during cooling could be causing bubbling inadvertently.

Hopefully they are using some a flavor 3M 200MP adhesive that holds to 200C. Which, BTW, is the same adhesive used in the recommended 468MP for DIY application of the PEI. Just depends on if its 2.3mil (467MP) or 5.3mil (468MP) based on this spec sheet.


Just a note on the Zebra plate… It seems to work okay, but the material seems to “bubble” from heat. I’ve tried a 240C extrusion temp with the bed at 70C, and if the nozzle is too close to the bed the combined heat causes the plate to bubble. So I’d gladly switch back to PEI if a removable solution is found or the bubbling stopped.

#15

The B.O.M. shows they get the Rolls of 3M 468MP 5.2 Mil.

#16

Haven’t had a chance to get back to this topic in a while.

So the PEI sheets seem to be uniformed thickness, they are just bowed. I might have to order some and experiment.

How would casting PEI in aluminum work? Would the PEI be removable from the aluminum or would they be one piece?

#17

I’ve throught of two approaches. cast in place non removable, where the aluminum base plate has really shallow “T slot” profiles milled into its surface, maybe 2mm deep, which would be really difficult to mill with any strength (maybe a trapazoidal profile instead) surrounded on 4 sides by a thin aluminum edge wall, or the same thing surrounded on 3 sides, but able to slide out on the 4th side, with some sort of retention mechanism to prevent that under normal operation (possibly a [ shaped hinge bracket that would swing down to allow PEI removal. Getting such a profile made is going to be extremely complicated though.

An edge retention method would work, but then you have the issue of PEI flex in the middle.

ANother thought would be a permanent vaccumme plate. Start with a 2 part aluminum plate with vaccume ports in the bottom, add a small vaccuume charge port lever on the side, push the lever down once or a couple of times, PEI is sucked down onto the aluminum. Turn the handle and the plate releases. That would work really well, but I’m not sure it could be made small enough to be effective. You could run a very small flexible vaccume line to the plate, and put the charging pump on the main frame which would make it more feasable, but you are still looking at a fairly complex milling profile, call it 7.5mm worth of space to work with, 1.5mm of that would normally be PEI and adhesive, the other 6mm would be the baseplate, so you need at least a 1mm rim around the edge, 1-2mm thick upper vaccume plate with holes in it, at least 1mm thick channels for air to travel from the holes to the pump, and at least 2mm worth of bottom plate and .5mm worth of gasket. Then you still have to put the vaccume charge port somewhere accessable with enough mass to even thread the port in (probably on the top or bottom of the plate since that would allow for a larger port without making the plate thicker.

#18

You know, now that I look at the vaccum pei plate option a bit more, its actually not that bad an idea. You can get very small threaded vaccum ports. The plate itself could be basically just 2 parts. a top plate with 3-4mm holes spaced every 2cm or so and a 1-2mm wide groove channel connecting each port. A small 24v vaccum pump could be tied off the main PSU with an on off switch and a vent valve, use RTV or similar higher temperature gasket material to hold the bottom plate with the heater attached on, a couple of low profile screws to hold the whole assembly together, maybe some artic silver thermal grease to promote better heat transfer, use the stock bed corners to hold the main plate in place and keep the PEI from moving around when vaccume is off. That way you still get good thermal transfer, a removable PEI sheet, the benifits of an Aluminum core and no worries about replacing adhesive.

That might be a good first project for my mill now that it’s almost functional.

#19

Rather than vacuum, how about magnetic? Embed magnets in the PEI base plate and the build table. Combined with an edge clip to prevent the whole thing from shifting, it seems like it would be strong enough. I use ABS clips and Binder clips on my Zebra plate, and it doesn’t go anywhere. It does, however, bow in the middle some. I had thought about cutting some holes in one side, adding magnets with epoxy or similar, then using matching magnets on the build table to attach it.

PEI is too thin to do that directly, at least, reasonably priced PEI is anyway. However, if you were to cast PEI onto an aluminum plate or similar, it might be doable.

Not as easy to remove as venting vacuum, but fewer failure points with no hoses/connections to leak etc… Either way, I like the idea.

#20

Magnets could work, the tricky bit would be how they would hold up to temperature cycles over time. The ones at the edge would be fine, the ones in the middle might not be.