Glassplate chipping

[AndersK 59]

I have just recently started printing PETG and noticed the glass plate has started chipping badly.

 

Is that related to the PETG or bound to happen after a while?

I have about 1000 m printed on the bed in total and of that about 150 m PETG.

I use a thin layer of glue on the plate and all prints with PETG have come off easily (let the bed cool to room temp)

[Dim3nsioneer 558]

Co-polyesters such as PETG very good in causing chipping. Renewing the glue layer for each print might improve the situation.

[ultiarjan 1,223]

And if you have trouble getting a print of the glass plate don't start hammering on it but put it in the fridge for a while (print+glass)

 

[AndersK 59]

As I said, very easy to get off once cooled but large flakes of glass stuck to the print.

Just like it chipped due to shrinking when cooling down.

 

I did put on new glue and wet wiped it smooth between prints.

 

New glass plate and a Build-Tak sheet is on route now.

[PaulK 14]

It might be nice if Cura allowed the cool down bed temp to actually be higher instead of off; I'm pretty sure there is a temp for PETG that allows reasonable removal but minimizes chipping. Some filaments even recommend not allowing full cool down before removal.

[geert_2 558]

On 2/25/2019 at 11:58 AM, AndersK said:

As I said, very easy to get off once cooled but large flakes of glass stuck to the print.

Just like it chipped due to shrinking when cooling down.

 

Yes, I have also had a glass chip while cooling: I heard the normal little ticking sound of the model coming off gradually, and then suddenly I heard much louder snapping sounds...

 

Forcing the model off while the plate is still hot, also seems a no-no to me. That would rather increase the risk, I think.

 

Try a thicker layer of not too strong glue, that can absorb the expansion/shrinking.

 

Personally, I use my "salt method" here too: wipe the glass with a tissue moistened with salt water, prior to every print. Let dry into a thin mist of salt stuck to the glass. For PLA this greatly increases bonding to a hot plate, and gives no bonding at all on a cold plate, which is very handy. For PET it does not seem to increase bonding, but rather slightly reduces it, but at least it also reduces bonding on a cold glass a little bit. I haven't had any chips since then. If you print without cooling fans, or with very little fan, it might work. With full fan, bonding might not be good enough and parts might warp. Try this on small test pieces first, and stay around to see what happens, so you can stop the print if it comes off.

 

[AndersK 59]

I think I'll try the salty mix.

I run without cooling.

 

Did the first prints on the Build-Tak today and it sticks like it was super glued, even when cooled down. Seemed little easier to pull off when hot though. Yet I put on more glue than normal.

[AndersK 59]

Tried a print over night with salt on the bed, what a difference it was.

Stuck well during print and came off with ease when cool.

The brim curled a bit at one spot but I might have used a lot more salt than mentioned.

 

Thanks for the tip @geert_2

 

 

[geert_2 558]

24 minutes ago, AndersK said:

Tried a print over night with salt on the bed, what a difference it was.

Stuck well during print and came off with ease when cool.

The brim curled a bit at one spot but I might have used a lot more salt than mentioned.

 

Thanks for the tip @geert_2

 

 

 

Wow, if all that white is salt, then indeed you used way more than I usually do. I prefer a thin layer that is almost invisible: after applying the salt, usually my glass looks a bit "dusty" like a drinking glass that has been unused for a couple of years.

 

For me, the first pic below (orange testmodel) has already too much salt; while the last one (with label "the salt method") has the optimal amount. Hardly visible when looking down vertically on it, and a bit misty when looking horizontally at it.

 

But of course, it is best if you try different methods and choose what works best for you. Different materials, printers, and environments (temp, moisture) may all have an influence.

 

For other materials than PLA, I recommend that you carefully watch the print, and don't leave it alone, until you know how well it sticks, or not. Or do a testprint like in the first pic, with inverted prisms: due to the very small bottom area to stick to the glass, and the very large overhangs creating huge warping forces, this is a good bonding test. Also, the overhangs tend to curl up, and the nozzle tends to bang brutally into these curled-up edges, making this a very hard test.

 

 

 

 

 

 

[dsp 18]

We use basic painters tape for PETG works like a charm 

 

[cyclepath 1]

I plan to try the salt method, but I currently use a raft of ultimaker break-away material under the PETG all on top of a PEI adhesion sheet. https://catalog.cshyde.com/item/3d-printing-materials/ultem-pei/36-10a-3d-12-5x-13-5

 

[geert_2 558]

23 hours ago, cyclepath said:

I plan to try the salt method, but I currently use a raft of ultimaker break-away material under the PETG all on top of a PEI adhesion sheet. https://catalog.cshyde.com/item/3d-printing-materials/ultem-pei/36-10a-3d-12-5x-13-5

 

Keep in mind that the salt method works for PLA and PLA/PHA only. It does *not* improve bonding for ABS, PET, and probably most other materials.

 

Even for PLA, use it for low and wide models: this works very well for me. But not for high models like towers and lantern poles: they tend to be knocked off: the salt-bonding obviously can not absorb repeated shocks very well (e.g. the nozzle banging into curled-up overhanging parts, especially on tall models).