Welcome to the SeeMeCNC Community

+1 for Windshadow. Read my posts in this thread or the synopsis thread - I use a can of spray "refrigerant" aimed at the base. The part pops right off. You could also put your build plate in the freezer or outside if you are in Maine.

I have destroyed one part with a localized thermal swing technique. (poured cold water in to the print and cracked the PEI) {It should be a FEW posts back}

The PEI has been in the freezer as well but did not do much good. I have little bits left on the sheet, no part of it is thicker than 5mm, and they are max 3 layers high (usually 1 layer).

I am tempted to use acetone but that would leave a very thing abs juice layer on the pei negating any benefit from the pei.

Water has a much higher heat transfer than a gas so you really shocked your plate. The gas can is a little more gentle and more directed. I've been doing this since day 1 and 1000s of prints on multiple PEI beds with no problems. Try the gas!

Not quite sure it will work with such small parts. I need to find a can of the cooling spray.

teoman, do you think your first layer is too smooshed? I never have this "can't get off" problem with ABS. If it is sticking that well, something is not right. Maybe lower bed temp, check Z=0, etc.

mhackney wrote:Water has a much higher heat transfer than a gas so you really shocked your plate. The gas can is a little more gentle and more directed. I've been doing this since day 1 and 1000s of prints on multiple PEI beds with no problems. Try the gas!

I tried hooking my wife up to a tube but the air was too hot!

So, I ended up developing wrinkles in my PEI bed. This was a result of carelessness with a heat gun to pre-heat the bed (it's 8C in the shop right now) And I don't have heating set up in the chamber yet. So I recently pulled the PEI to reform it, and take care of some air bubbles from the first time (I plan to use the Windex float method). I've been experimenting with reforming the PEI. I've got it sandwiched between two aluminum plates, both flat (one is the heat spreader it gets bonded to). Some observations thus far

A) getting the tape off AL plate is a bitch. quite a bit of goof-off, wire brushing, and scraping later, and it's mostly clean.

B) A heat gun is not sufficient to reform the PEI, but it will wrinkle it. Be careful with those.

C) 425, and 430 F are not hot enough to reform the PEI in an oven, despite being over the glass transition point. So far 450F seems to be working (it has taken much of the curvature out, but there's still some left). I plan to try again at 460. half an hour in the oven between the plates, and then a similar amount of time, again between the plates, cooling, seems to work well, and I just toss the plates in before I start the oven

D) If this all doesn't work, I have another two beds worth of PEI on the way, so I can't fail!

Of all the methods I have read about on the Forum, the Windex Float method seems to work best to eliminate bubbles. People don't seem to like to wait
the time for everything to dry though.

teoman wrote:I use isopropyl alcohol (have lots of those medical pads) to clean the PEI.

While experimenting i have some parts that I have managed to weld firmly on to the PEI. I have been doing my best to peel it of using my fingernails, but i do not have much fingernail left

How would one go about removing the ABS that has been welded on to the PEI? All i can think of at this moment is acetone.

I have always used acetone to clean even on a hot plate. Has never been an issue and I have never seen any damage to the surface. Not even the gloss on the smooth side has been effected.

mhackney wrote:+1 for Windshadow. Read my posts in this thread or the synopsis thread - I use a can of spray "refrigerant" aimed at the base. The part pops right off. You could also put your build plate in the freezer or outside if you are in Maine.

I also use the spray refrigerant. A quick blast of -60F does wonders especially in the bottom of hollow parts.

Yes my layers may be squished a little bit and my temp may be high as i am tuning the system.

Hi

I have finally mountet the thin PEI shett to the glass plate, and desided to check the surface temp. on the PEI sheet, as expectet it where significant lower than the printer displays. I have measured the surface temp on the Onyx directly, that is in sync whit the displayed temp on the printer. SO I have so far found that tha printbed as is today, actually need's the print bed to be set at 100C to have a sorface temp of ca 88C.

My prints stick pretty good so long the printbed is at working temp, when it's coolsdown, at around 70C on the display, you can hear a small pop when the part release the grip in the PEI sheet.

How much time did you allow the temperature to equilibrate? I've found that after about 10 minutes the surface of the PEI is right where it needs to be. If you rack up the temp to compensate for a non-equilibrated system you will create all sorts of problems later - too much "stick", especially for ABS.

I also have a 1/8" aluminum heatsink under the glass and PEI stack that might tend to hold heat better too.

So far it has been working for an hour, and the surface temp is around 82C. the room temp is about 22C. I don't have an alu heatspreader

Ok, then you probably have reached equilibrium. Go with it!

An 18C differential between the bottom of the glass and top of the PEI strikes me as a lot. While I use a 1/16" copper plate my differential is closer.

Out of curiosity, how "thin" is "thin"?

Not sure I understand your question nitewatchman, what do you mean?

the PEI sheet is 0.8 mm thick, and the 3M 486MP tape.

I will measure this temperature a few more times on long prints, so I can se if it's a stable difference.

Okay, same thickness as mine. I will check mine also, I will also check the temperature offset between the display and actual temperature. The "guessmistor" can sometimes report something very different than a measured actual.

MH, how "thin" is his "thin" PEI. I have commonly have people report a "thin" layer of untempered martensite on a broken steel face. Usually means it is between 0.0004" and 3/8" thick.

After a few long prints, it is still a difference of 12 - 18 degree. It works as it should any way, when the print is finished, i wait until I hear a pop from the printer, the bed has cooled about 30 degrees, then is just to pick up the loose part.

Viking wrote:After a few long prints, it is still a difference of 12 - 18 degree. It works as it should any way, when the print is finished, i wait until I hear a pop from the printer, the bed has cooled about 30 degrees, then is just to pick up the loose part.

I have painfully learned several times that "if it works, it don't need fixin".

Full speed ahead - don't look back.

offcourse I used it this way until it fails. Then it will be time to adjust. The prints turnes out excelent i ABS.

If it ain't broke, don't fix it till it is.

g.

When I lived in Memphis just after the "Great War of Northern Aggression", I had a small side line business rebarreling and restocking target rifles, tweaking wheel guns, etc.

One of the business cards I had simply said "Fixed Guns Repaired".

gary

Opps removed it was meant to be a private msg. sorry all