Issue with PETg printing

[iSenseit3dprinter 0]

Hi,
We printed with PETg, when the print was picked up, the glass plate broke.
Get the message from the supplier to use the glue, but when I use the glue the print surface is ugly and unpleasant.

what should we do about it?


Sander Voorwinden
iSense it.
06-42912111

[gr5 2,267]

1) When you say "the glass plate broke", did it just loose a tiny sliver of glass?

2) PLA doesn't have this issue where the glass easily breaks (95% of most formulations don't).  Nylon doesn't have this problem.  nGen doesn't seem to have this problem.  It's mostly PETG, CPE.

3) Using a very thick layer of glue (to provide an area that is weaker bond between glass and part) is a good option but indeed the bottom is more ugly.

 

There are many options.  I have been printing a lot of PETg and have just been lucky recently.  There are many ways to reduce the strength of the bond.  The best way in my opinion is to reduce the squish on the bottom layer just a little.  I would just turn the 3 leveling screws the same amount (clockwise as seen from below to move the glass down - away from the nozzle).  Maybe a quarter turn.  But it takes a lot of practice looking at the skirt (or brim) being printed on the first layer and deciding if it's squished enough or squished too much.

 

If the first layer is coming out like rope then you are not squishing enough and the part won't stick very well.  If it is squished so much it is transparent then it will stick very very well (which is good for some materials but not for petg/cpe).  But there is a large range "in between" that is tricky to measure.  I don't have a good answer for you.

 

Hopefully someone who prints a *lot* of PETG has a suggestion for something else on the glass.  Personally I print hundreds of petg parts and occasionally lose a bit of glass.

[AndersK 59]

I have done a fair share of PETG printing (20-30 kg) and has given up on printing on glass, it just sticks to hard.

 

Have changed to printing on PEI instead and that does magic. No need to fiddle with glue or anything to get a good match.

 

Do yourself a favour and get the flexplate system from Build-Tak makes removal so much easier.

The PEI sheets have been good with most materials I have used (PETG, PETG+Carbon fibre, PLA, TPU)

 

Mixed results with Nylon+carbon fibre, some good some got loose. Failure might be due to getting lazy not cleaning the PEI after every print since the other materials dont require that.

 

They have a special sheet for nylon but I have not yet bought one.

 

Dont use their standard build sheet together with automatic levelling if you are printing on an Ultimaker. They heat the print cores during levelling and that makes the core dig in and destroy the build sheet.  Learned that the hard way.

[geert_2 558]

I occasionally print PET. In the beginning I tried printing on bare glass, which gave mixed results. Then I tried dilluted wood glue, which gave *very good* bonding. Way too good, because at one time, it chipped the glass. This already happened while cooling down, I heard it crack violently. When I removed the print, it came off without any force, but with the glass chip stuck to the print.

 

Now I use my salt method: apply a few drops of salt water to the glass bed, and wipe that with a paper tissue until it dries into a very thin mist of salt. For PLA, and as long as the glass is hot, this salt method greatly increases bonding. But it has no bonding at all after cooling down. However, on PET this slightly *reduces* bonding, but also makes removal much easier, compared to printing with dilluted wood glue or bare glass. Disadvantage is that I have to switch off the cooling fan, otherwise corners tend to lift a bit. No cooling does reduce the quality of overhangs and bridges a lot. But most of my models have no overhangs anyway, so not really a problem. The ease of application is the biggest benefit: just wipe the glass, and ready to go. No need to take the glass out of the printer.

 

When trying new bonding methods: stay with the printer, and watch what happens. So that you see how it works, and you can stop the print in case models come off and produce spaghetti or slide around under the nozzle.

 

These models are in PET, bottom-side up: notice the little pits from the salt crystals, and the nice flat surface, squeezed well into the glass. For reference: ruler is in mm and cm.

 

This is what the glass looks like after applying salt water, and wiping it dry. This is a bit too much salt.

 

This is a better amount of salt. (Don't mind the spaghetti in the print: these are free-hanging supports to print a bridge, and will be removed later. This print is PLA, not PET.)

 

Edited March 4, 2021 by geert_2