Anyone Tried a Removable PEI Bed?

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ttabbal
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Re: Anyone Tried a Removable PEI Bed?

Post by ttabbal » Mon Apr 04, 2016 2:47 pm

Either way, make me one for a Mini, OK? :D

moejt
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Re: Anyone Tried a Removable PEI Bed?

Post by moejt » Mon Apr 04, 2016 3:01 pm

No offense but a vacuum just sounds like over engineering.

Magnets would be a better option and are currently being used by the Geckotek plates. I believe they use ceramic Magnets to hold up to the heat.

I've currently reached out to some local plastic manufacturers around me regarding a thicker PEI sheet that isn't bowed and has correct tolerances. I'm waiting to hear back from them. In the mean time I see McMaster Car is also selling PEI and they are claiming +/- 0.003" thickness tolerance on their 1/4" thick sheets. (and +/- 0.0125 on their 1/8" sheet (not nearly as good)).

If their tolerances hold true and the sheets are not warped. This seems like a viable and the best option to me. McMaster is know for higher quality.

I figure a thick enough PEI sheet won't raise up in the middle of the bed, even if the print pulls on it.

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mirage335
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Re: Anyone Tried a Removable PEI Bed?

Post by mirage335 » Mon Apr 04, 2016 3:09 pm

Having ordered a thick ~1/4in sheet of PEI, like most plastics, it warps badly after exposure to moderate ~65C temperatures. Supposedly though, fiberglass reinforced PEI was originally chosen by the reprap project, prior to bonding thin plastic sheets to glass. High cost eliminated the material at the time. Only link I can find to this now is here - https://groups.google.com/forum/#!topic ... 7FN_Zpb6v0 .

Resin casting is extremely interesting though, because it raises the possibility of using additives. We could try making fiberglass, carbon-fiber, or even kevlar reinforced PEI. Another possibility might be to include ferromagnetic particles, allowing the entire bed stack to be clamped with strong magnets.

moejt
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Re: Anyone Tried a Removable PEI Bed?

Post by moejt » Mon Apr 04, 2016 3:27 pm

Interesting, this stuff is supposed to be heat resistant and it's glass transition is way higher than anything it gets close to. I'm shocked to hear it warps.

So basically the community started with Ultum 2300 (30 percent fiber glass infill) and got cheap and moved to. Small layers on glass.

Am I seriously the only one dealing with bubbling? A typical build plate is $50. And they all tend to have weak points. I'd gladly spend $100 on a far superior build plate.

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piercet
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Re: Anyone Tried a Removable PEI Bed?

Post by piercet » Mon Apr 04, 2016 3:41 pm

moejt wrote:No offense but a vacuum just sounds like over engineering.
I take it you haven't seen the rest of my Taz then?

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mirage335
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Re: Anyone Tried a Removable PEI Bed?

Post by mirage335 » Mon Apr 04, 2016 3:49 pm

Ultum 2300? Where can a sheet of this be bought, and at what price? If this stuff proves rigid in testing, then it would definitely support the case for further research with custom resin mixtures.

Also, keep in mind that 3D printers have tight tolerance requirements. When I say "badly warped" in this case, I am talking about 4-5x 0.35mm nozzle first layer heights. FWIW, IIRC a roughly 150mm * 150mm square in the middle of my 300mm * 300mm sheet of thick PEI seemed to remain usable.

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piercet
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Re: Anyone Tried a Removable PEI Bed?

Post by piercet » Mon Apr 04, 2016 5:24 pm

It's Ultem 2300 PEI. Basically this stuff
https://www.sabic-ip.com/gepapp/eng/wea ... ype=Online

You can buy sheets of it here for $450, which is about the best price I have seen https://www.onlinemetals.com/merchant.c ... &top_cat=0

Or a remnant sheet for $130
http://www.ebay.com/itm/25-x-16-x-16-Na ... SwDk5T6lvQ


There are also all sorts of other percentage of glass fill resin types out there for PEI sheets, some of which may be cheaper because no one is looking for them.
https://www.sabic-ip.com/gepapp/Plastic ... rchresults

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mirage335
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Re: Anyone Tried a Removable PEI Bed?

Post by mirage335 » Mon Apr 04, 2016 6:13 pm

Thanks!

Paying $450 for a new sheet sounds ridiculously expensive though. No wonder this stuff hasn't been used much in production!

jballard86
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Re: Anyone Tried a Removable PEI Bed?

Post by jballard86 » Mon Apr 04, 2016 7:09 pm

piercet wrote:...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.
I may try this, I really like this idea. Im going to add a dovetail cutter to my next mcmaster carr order.

I think if the sheet is slid in with the cup facing up it would cancel out.

moejt
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Re: Anyone Tried a Removable PEI Bed?

Post by moejt » Mon Apr 18, 2016 3:41 pm

For anyone wondering. I asked McMaster what their vendors tolerances on flatness were for their PEI/ultem sheets.

"I spoke to the manufacturer of the Ultem sheet and while the material is very flat, because it is cut from larger pieces a tolerance for flatness is not available. The larger piece they are cut from is within a tolerance of 1/8" over 4' length."

Nothing we didn't already know, but I like knowing the hard numbers.

And Piercet... I've seen your printer, its spectacular. I'm currently adding your Z-wobble nut to mine since my Z-wobble has recently been getting significantly worse (zero wobble out of the box, but 1000 hours of printing later...). And I plan to soon after add the open rail modifications. All awesome mods that I do NOT consider "over-engineering". Sophisticated does not necessarily mean its over engineered if its necessary. I just question if a vacuum on a print bed is necessary! haha. Maybe it is, just sounded like there might be a more simple solution. You probably hear it all the time, but thanks for the mods and support you give to this community!

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