PEI issues/ effectiveness at temps 90-110

[nocen 1]

I just added a PEI sheet on top of the glass of my UM2 (100% abs "fail" rate before PEI btw). Using stock ABS settings the corners warped >30% of the print's radius/length/width...size (xy plane). I raised the temp up to 99c and speed down to 80%, warping decreased to like ~10%. So I moved the bed ~1 turn of the leveling knobs closer after scouring every problematic PEI post and wet sanded lightly with 1500 grit. This helped but I still get 1-2mm of warping (zx plane and xy planes).

One thing I saw in PEI research was 110&50c seem to be the magic numbers for PEI, 110 being the temp where the surface adheres to abs and 50 where it rejects it.

This brings me to my issue, UM2 specs say 100c is max for the bed. The controls let you go above this, but prior experience with various brands, types, sizes, etc of heaters (and printers in general) have made me  very apprehensive of going above a certain value (100 for most, 110 and 120 for a couple) since most seems to degrade in performance when pushed beyond that level.

So, whats the max "safe" temp for the UM2 bed, will it last at 110c? and I guess while we are at it who else still has issues with PEI after reading every other post that end at "wash with alcohol and run at a high bed temp, #goodluck"?!

ps PEI is pretty fricken sweet but at this point it's being out performed by failed-prints-melted-in-acetone-smeared-on-a-stock-SD4-bed :(

psps, the printer is mostly enclosed and I had a couple successes but the buildplate was even closer and the print wouldnt come off even after putting the plate in the freezer.

Edited August 30, 2015 by Guest

[dintid 6]

Read this.?

http://forum.seemecnc.com/viewtopic.php?f=36&t=7452

I always print at 110c on bed. Not an UM though.

Why should it degrade?

[gr5 2,172]

The bed can handle high temperatures (>120C no problem) but the wattage doesn't provide enough power to keep it above 100C with air temp at 20c. So to get it hotter than 100C you need to start enclosing things and get the air up to 50C. I found 50C to be a good safe printing temperature for the steppers. I don't recommend letting air get above 50C unless you make major changes (move steppers outside the box or add fans to cool steppers).

[nocen 1]

that article is one of the ones i read in prep for the upgrade and proved one of the best/reassuring.

the different brands degraded varying reasons, most of the pcb showed signs of burning/warping and/or cracking, the silicone ones were harder to tell since i didn't do any destructive investigation since they all still "functioned" to a point.

just adding a door seems to have brought the warm-up time to within 5min of its original time. the um2 never seems to amaze me. i had planned on making an elaborate enclosure but its good enough for now. i have some heat sinks on the way for the steppers and ill have fans flowing up from the bottom once i measure and cad everything out, but till then the motors seem happy.

its such a fine line between the abs adhering too much or too little, if this is the beginning of a pattern when i test on other models i think the "holy grail"-ness of pei is a bit oversung

[h3nno 0]

Hey OP, I'm looking at also getting a PEI sheet for my UM2.

What dimensions would you recommend? Also, after sticking it, do you just re-calibrate the bed and all is good?

Hope you can sort out this issue. I've also been having some warping with PLA on bigger prints.