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Has anyone who bought a sheet of PEI from Amazon had it not be a true 12"x12"? I have had mine for about a month now and just found the time to install it on my build plate. Well, as you can see from the picture it is not big enough to cover the entire build plate. Is it worth trying to make it fit, maybe center it so the clips are where there is no PEI?

This is the same one that was linked in the PEI thread (http://forum.seemecnc.com/viewtopic.php?f=36&t=7452" onclick="window.open(this.href);return false;).

[img]http://i592.photobucket.com/albums/tt6/ ... 23_iOS.jpg[/img]

The size is nominal 12x12 but that is quite a bit undersized. I'd get it replaced. If you can live with it, centering it s a good idea.

mhackney wrote:The size is nominal 12x12 but that is quite a bit undersized. I'd get it replaced. If you can live with it, centering it s a good idea.

I looked into replacing it and unfortunately I missed the return window by 2 days. Tempted to order another, but worried it won't fit either. I saw some reviews on Amazon and some have had issues with sizes not being as advertised. I would rather it fit exactly.

davec3275 wrote:

mhackney wrote:The size is nominal 12x12 but that is quite a bit undersized. I'd get it replaced. If you can live with it, centering it s a good idea.

I looked into replacing it and unfortunately I missed the return window by 2 days. Tempted to order another, but worried it won't fit either. I saw some reviews on Amazon and some have had issues with sizes not being as advertised. I would rather it fit exactly.

I would not accept it the way it is, too bad you missed the return window.
McMasterCarr sells the PEI as well as others. Google will find them. They are more expensive than Amazon but now you know why Amazon is cheaper.
Edit: After checking McMaster Carr and some other sites, the cut tolerances can be 1" off in any direction. I think we need input from other users to find the best
source for PEI that are cut very close to the advertised dimensions.

Also, another thing. The Max has a 310MM bed. That's 12.25 IN. You not only don't want to be undersized, you want over size, which most sellers are more loath to do (It happens sometimes, but most would prefer to err under). I bought a chunk from McMaster Carr, and it was 12 precisely, by 24.25. A little over, but on the wrong dimension for what I really wanted (I bought 2 beds worth, to have one as close to perfect as possible, and a backup). But if you have an enclosure, which you really want for large parts, you can't get that close to the edge most of the time, and the Max's Kinematics aren't very accurate on the extreme edges of the bed. (Which is unfortunate, but accounted for in the advertised bed size). If you go out to the edges perfectly, you actually get more than you paid for, both from the printer, and the PEI supplier.

The problem is that it will vary from batch to batch. I've ordered at least 15 sheets from Amazon and they have all been just right for the borosilicate glass diameter. I've also bought 4 sheets from McMaster and they were fine too. I don't recall seeing a +/- 1" tolerance, that is really not acceptable for this material.

mhackney wrote:The problem is that it will vary from batch to batch. I've ordered at least 15 sheets from Amazon and they have all been just right for the borosilicate glass diameter. I've also bought 4 sheets from McMaster and they were fine too. I don't recall seeing a +/- 1" tolerance, that is really not acceptable for this material.

This link to McMaster Carr shows a 1" tolerance on their sheets unless my moldy oldy eyes have done it to me again.

I'm on my second sheet in six months, both don't fit the glass fully (amazon .040)

KAS wrote:I'm on my second sheet in six months, both don't fit the glass fully (amazon .040)

4 sheets from amazon also that won't fit either.

ccavanaugh wrote:

KAS wrote:I'm on my second sheet in six months, both don't fit the glass fully (amazon .040)

4 sheets from amazon also that won't fit either.

I ordered a 12"x24" sheet from Amazon yesterday. Here's hoping the 12" direction fits.

Okay, so the new sheet arrived today and surprise surprise, the 12" direction does not fit. In fact, it is 1/4" shorter in BOTH directions. I REALLY want it to cover the entire glass plate, so back it goes.

If anyone has any sources that they have had WAY better success with, please let me know.

You really don't need to cover 100% of it. Your plate is actually larger than 12" anyway, closer to 12.25"

You also can't print all the way to the edges either. Yes it would be nice but its not completely necessary.

JFettig wrote:You really don't need to cover 100% of it. Your plate is actually larger than 12" anyway, closer to 12.25"

You also can't print all the way to the edges either. Yes it would be nice but its not completely necessary.

Agreed. I centered mine and just lift the four lips uncovered. doesn't affect prints and the clips still work fine

I've been using PEI for awhile now... awsome stuff.

My question is autocalibrating with FSRs while the hot end is at 250C.

250C is above the glass transition temperature of the material. The touch is very brief, but I didn't know if anyone had long term experience with the effects of probing the surface while hot.

I can set gcode to probe first at a lower temperature which is better than nothing, but would prefer to probe at full temperature.

I haven't had any problems at 250° C probing and I've done quite a bit of it. Like you said, the touch is instantaneous so I think that prevents any issues.

mhackney wrote:I haven't had any problems at 250° C probing and I've done quite a bit of it. Like you said, the touch is instantaneous so I think that prevents any issues.

Thanks, much appreciated!

Sorry to revive an old thread, but I noticed here someone had suggested that JBWeld might be usable for attaching PEI to glass. I've had my 'fun' issues with the 3M adhesive sheets, and saw how silicone adhesive looked good at first but then detached after a few weeks. Thinking perhaps if I squeegeed JBWeld part "A" onto the glass and part "B" onto the PEI, then squeezed them together and let them sit for a few days....? But rather than waste a sheet of PEI, it would be best to check here to see if anyone had already tried that.

Thanks

If someone has suggested using JBWeld, they're either nuts or pulling your leg.

g.

Looking at the specifications (and safety warnings!) of this JBWeld product, it would make sense for it to be working great for glueing PEI. However I think I remember more people having tried it. It seems to loosen over time. The 3M glue sheets work fine, just apply dry. Because the glass and the PEI do not breathe air, the glue never dries completely being caught in between. The easiest way is to lay the glue liner flat on a table, have some extra hands to pull it straight, and smash the glass (or alu sheet) to it in one straight movement. Afterwards apply the PEI sheet from edge to edge in one rolling movement.

I used Windex and floated the adhesive on to the pei, and once it dried I used the same technique to attach the glass plate.

g.

Bringing this back from the dead. So the 3M tape still good for everyone? No lifts after hundreds of prints?
I’ve been using BuildTak. Although, it works wonderful, the BuildTak adhesive itself is weak. It lifts and bubbles easily. Especially if you’re too close to the bed. BuildTak also has a pei version but the adhesive still sucks. On top of that, BuildTak is very expensive. I bought the flex plate to try to see how the fairs but I don’t like sacrificing heat since thickness is added.
Amazon now has a 12” version of pei, so I’m tempted to try this method again. When I tried it a few years ago, I didn’t have much luck. The pei was a pain to cut and it also lifted.

The 3M tape that came with my PEI works really well, although I did have it fail when I had it roughed up to much and printed to close with PLA. Nothing is fool proof.

The 3M tape is what the commercial manufacturers of pre-adhesive PEI plates are selling too. This tape is perfect for this application at reasonable bed temps (i.e 100°C or less).

cool (no pun intended). I'll give this another shot! thanks!

I’m still using my PEI(s) after hundreds of print, most of the time, successfully and the 3M adhesive has been sticking there with no issue.