PETG wear on PEI Sheet  

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benjamin.r8
(@benjamin-r8)
Eminent Member

Hi, I'm running an MK3 with a smooth PEI print bed.   I have owned it for about two years with light to moderate use on both sides of the sheet.

I have just started dabbling in PETG, having only used PLA until now.

My first large print was very hard to remove.  I was aware that I needed to take care, but it was very difficult.  The removal left a small bubble on my bed.  It appears that the bubble is the start of some damage to the sheet surface.

So, I'm trying to look for things I can do to reduce sheet damage when I print PETG.  Maybe my sheet is just too old to release the PETG well?  I can design fillets around the bases of my parts to help give me a way to start removing the parts, and I also know that bending the sheet can help with part removal. 

However, when I remove the parts via bending or prying, the marks on my bed, the bubble, and the amount of force required are concerning.

Does anyone have similar experience with PETG who can share some advice?  I don't like the idea of chewing though bed sheets.  Thank you.

Posted : 02/06/2020 1:19 am
Area51
(@area51)
Honorable Member

Nearly all my printing is in PETG and I use diluted windows washer before every print on the smooth PEI build plate. I have a sponge in a small box I use to wipe it with. Any windows cleaner can be used as long as it is free of additives and ammonia (damages brass).

The textured build plate can be used as is, no need for windows cleaner.

Have been using the same build plates without damage to the surface for years.

Have a look at my designs on Thingiverse or on PrusaPrinters ;)...
Posted : 02/06/2020 1:31 am
erik.t2
(@erik-t2)
Active Member

I've had the same experience with PETG (very high adhesion). I also have small bubbles in clusters where parts were affixed; bubbles are 0.25-1mm in size. I've also been printing using the same PEI spring steel sheet for over two years, now. The bubbles eventually go away, in my experience.

As counter-intuitive as it seems, try some purple glue stick. It creates a layer between the PETG and the build surface. Try it on small parts first, though.

Posted : 02/06/2020 1:56 am
Kevin Reid
(@kpreid)
Trusted Member

For PETG, get and use the powder-coated (textured) sheet. The PEI then sticks better to the steel so you don't have to worry about peeling it off with a print. Way less bother and mess than glue stick.

Posted : 02/06/2020 2:37 am
gert.l liked
charles.h13
(@charles-h13)
Famed Member

I found this to be much less of an issue if you let the bed cool before removing  prints.  

Posted : 02/06/2020 3:08 am
ian.p liked
benjamin.r8
(@benjamin-r8)
Eminent Member

Thank you all for the wonderful advice!  I really really appreciate it.  I feel much better now that I have some ideas.  It is also good to hear that the bubble could go away.... I might have accidently "picked" at it before I realized what it was Yikes!

Also I had been using acetone occasionally on my print bed, never tried window washer but now I will.

Posted : 02/06/2020 11:59 am
Protoncek
(@protoncek)
Reputable Member

PETG goes off by itself from textured plate when it's cold, while  getting it off from smooth plate can be very painfull, especially if item is big (even if it's cold). So i, too recommend use of textured plate for PETG and smooth for PLA.

I print PETG on smooth only when items are small when adhesion on textured can be too low.

Oh, and using Acetone only causes PETG to stick even more. And using it too often degrades PEI sheet, so be carefull with it. For plate cleaning/preparation use isopropanole or alcohol for PLA and windows cleaner for PETG.

This post was modified 5 months ago 2 times by Protoncek
Posted : 02/06/2020 6:32 pm
gert.l liked
erik.t2
(@erik-t2)
Active Member

There are a multitude of different contaminants that can find their way onto your build surface; some with major consequences for the success of your print, some less important. Your hands have both oils and salts that you secrete yourself in addition to anything that you have acquired through touching other things. There are also contaminants in your environment; dust-off cans (use propane and other petrochemicals as propellants), household cleaners, waxes, sunscreens, lotions, etc. Also, there are compounds in the filament itself that can leave behind residue. 25 years of experience in the automotive refinishing sector has taught me that surface preparation is the single easiest thing to get right, and have the worst consequences if skimped on. Trust me, having to spend 30 hours preparing and repainting a Mercedes is a lot more work than redoing a 30 hour print, so the lessons are hard earned. Nevertheless, nobody ever had to redo a print because the bed surface was too clean. I keep a couple different solutions on hand for cleaning the spring steel sheet, whether powder-coated or PEI.

  • Windex (straight-up name brand ammonia-based, no "Earth-friendly" fru-fru vinegar or such; you're printing with plastic, not saving the planet)
  • IPA (rubbing alcohol). 91% that you get at your local pharmacy or grocery store is probably ok, but unless I'm mistaken, Prusa recommends 95% or greater. 99% is available on Amazon, and it's what I use. I've tried denatured alcohol as well, but IMHO it doesn't do as good a job as IPA.
  • Acetone. As noted above, for infrequent use; it degrades the PEI especially. I'm not sure about the powder-coated; it feels like it's been affected (read on for more about that).

Procedure for any of these is to have two (or three) paper towels or other absorbent cloth. I get and use cotton makeup removing pads on Amazon that work great for everything besides Windex. With window cleaner, you simply want more material to soak up the fluid.

very important part to consider when cleaning is to have an applicator and a remover. Simply swabbing your sheet with a moist towlette is going to spread contaminants around; instead, wet (but don't saturate) your surface with one pad, using a little bit of pressure; you want some mechanical friction in addition to the solvent. Then immediately use a second pad/towel to absorb the solvent. Give your soluble contaminants somewhere to escape to. With alcohol and acetone, you have a short window before they evaporate and you have to re-wet; cleaning the sheet when it's hot accelerates the evaporation, so always do it cold . And if you're removing pad is not drying the surface with a swipe or two, it's effectively saturated and you need to use a fresh one (if you're concerned about the environmental impact of using three sheets of paper towel instead of two, consider how much wasted energy and material there is in having to redo a 30-hour print because it broke loose. Also, the "select-a-size" rolls of paper towels offer the perfect size sheets for build plate cleaning. I just wish all the cotton makeup pads weren't organic... anyway, I digress). A properly cleaned surface will have a "drag" to it as it transitions from wet to dry. (My concern with acetone and the powder-coated build sheets is that the drag that occurs with that is actually opening up the surface of the film and breaking it down to some extent. Acetone can be particularly harsh in this way).

A final note about safety, again hard-won through experience working safely in hazardous environments and many, many hours spent in OSHA Right-to-Know training classes:

  • Store your cleaning solutions as far away from your printer (or any heat source) as possible. Always. No exceptions. Alcohols and petroleum-based solvents are volatile at room temperature, and are a source of flammable vapors. Many are also heavier-than-air, and using acetone anywhere near your hot printer is just begging for a fire. And even if the combination of solvent and heat didn't cause your fire, an ill-placed can of accelerant can easily escalate a small issue into a catastrophic one.
  • If you buy your solvents in large containers (liters, gallons, etc.), transfer them into a smaller (solvent-proof, obviously) container that is easier to dispense small quantities from, and keep it closed and well-labeled. Do not assume that your bestie isn't going to come over and assume that the unmarked container of clear smelly liquid is rum and drink it. Absolute best practice is to buy a small container of your solvent(s) of choice and refill that container with a larger one. 
  • Do not combine your solvents. Different solvents (alcohol, acetone, etc.) have different properties and clean their own contaminants best. Combining them doesn't give you all the properties of all in one super-solvent. And (in case it needs to be said) your bedroom (or wherever you keep your printer) isn't the place to be experimenting with chemical reactions. Leave that to trained professionals in the appropriate environments.
  • Best practice overall is to separate your printing area from your cleaning area. As in, keep your cleaning supplies in another part of the room, or a different room entirely; DO YOUR CLEANING THERE, then take your immaculate steel sheet to your printer and begin your warm-up/print. Skimping on cleanliness can cost you a print; skimping on safety can cost you everything.
  • Dispose of your cleaning towels/pads immediately in a fire-proof container. Most people don't have a vapor-proof canister on hand, so next-best option is an all metal trash can or empty paint can, which is kept outside. Do NOT dispose of solvent-soaked media in your household trash. Just don't. Don't be that person.
  • Wear gloves. Latex and vinyl are ok for very short exposures, but something like nitrile is best for long-term use. Gloves will save your hands from the exposure to solvents, and also keep you from transferring your body oils/salts/etc. to your work surface.

Some of these things may seem like overkill for a problem you have never experienced, but nevertheless they're good (and some, essential) practices.

 

/WoT

This post was modified 5 months ago by erik.t2
Posted : 03/06/2020 7:34 pm
Protoncek
(@protoncek)
Reputable Member

Great post! I will only add that Prusa especially says NOT to use acetone on textured plates at all. Supposely coating can crack. Only IPA and soap solution is allowed.

On smooth plate acetone is allowed only occasionally, when plastic doesn’t stick anymore to refresh surface.

Posted : 03/06/2020 8:14 pm
erik.t2
(@erik-t2)
Active Member
Posted by: @protoncek
 I will only add that Prusa especially says NOT to use acetone on textured plates at all. 

Yes, you are right; thank you for the correction. I'll edit my post so it's clearer.

 

EDIT: It appears I can't edit my post. Oh, well...

This post was modified 5 months ago by erik.t2
Posted : 03/06/2020 10:50 pm
charles.h13
(@charles-h13)
Famed Member
Posted by: @protoncek

Great post! I will only add that Prusa especially says NOT to use acetone on textured plates at all. Supposely coating can crack. Only IPA and soap solution is allowed.

On smooth plate acetone is allowed only occasionally, when plastic doesn’t stick anymore to refresh surface.

True but lots of people still use it if prints start failing to stick.  I have used it and see the value for occasional use.  

Posted : 04/06/2020 3:02 am
Protoncek
(@protoncek)
Reputable Member

I guess that it's nothing wrong if you can't get adhesion otherwise. It's just  that PEI sheet will wear out sooner if you use acetone more often. I think that since textured plate is sprayed the chance of coating gets cracked is bigger than in smooth plate, where there's a sticker on it. That's why acetone is not recommended. But, if you can't get it to stick it's useless anyway, so basically you can't loose much by trying acetone, right?

When i cant' get adhesion sometimes it helps so reduce Z offsett a bit, to print first layer somewhat closer to plate.

Posted : 04/06/2020 11:41 am
charles.h13
(@charles-h13)
Famed Member

@protoncek

I understand the risk.  I will tell you I am still using the same sheet for 16 months.  I use acetone.  Except for some nozzle dings and scratches caused by the nozzle getting too low, I have had no chips or cracks.  That being said, it should be used very sparingly.  To be honest, I have used it 3-4 times in 16 months.  I think it resets the bed and improves adhesion.  

Posted : 04/06/2020 3:53 pm
bobstro
(@bobstro)
Illustrious Member

There have been a few posts over the years of PEI sheets cracking due to acetone over-use. That said, acetone is recommended for its ability to remove oxidation, so was promoted to "renew" the PEI early on. The textured sheets apparently use much thinner PEI application, so it makes sense acetone is not recommended. That said, there's no real warranty on any of the sheets. If you have one that's not working, there's little to lose by trying other methods. Ultimately, they are consumables.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 04/06/2020 3:56 pm
charles.h13
(@charles-h13)
Famed Member

@bobstro

I agree.  I think if you are at the point where you are thinking of tossing a sheet that is not sticking well, there no harm trying acetone.  

Posted : 04/06/2020 4:01 pm
darcshadow
(@darcshadow)
Trusted Member

I do powder coating occasionally and acetone is one of the few chemicals that will remove it, although not easily. It essentially melts the powder coat and can turn into a sticky mess. 

Posted : 04/06/2020 4:18 pm
charles.h13
(@charles-h13)
Famed Member

@darcshadow

Have you seen this?  This is very doubtful.  Has never happened in any of the applications I have placed.  Then again, I dod not let it sit and I immediately remove it with IPA.

Posted : 04/06/2020 4:23 pm
darcshadow
(@darcshadow)
Trusted Member

Never used it on a printer sheet. Just saying Acetone will somewhat dissolve powder coating. If I put some on a rag and rub it on a object with a high gloss powder it'll remove the gloss easily. I can eventually get down to bare metal.

Posted : 04/06/2020 5:03 pm
charles.h13
(@charles-h13)
Famed Member

@darcshadow

This is not standard powder coating and will not just become a sticky mess.  Then again, I would not leave it on soaking - spray and wipe, followed by the same with IPA.  

Posted : 04/06/2020 5:41 pm
Graham25Fox
(@graham25fox)
Trusted Member

interesting post, My original smooth has a couple of bubbles on the surface.It dont seem to make any difference to it.

never used Acetone, always IPA

i have a spare smooth plate and last night i was printing with petg, just like i have been doing for months now.

just print straight on to the plate, this now i know was a mistake.

Could not get the part of , and when i did it pulled some of the PEI with it.

I have been reading that some say this can happen, but i did not think it was true, any way it dont really matter as i have a textured plate bought for petg

Posted : 05/06/2020 9:31 am
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