CR-6 SE glass build plate - no lifting possible

Question

I've been dealing with 3D printing for 1.5 years, but now own a CR-6 SE myself since the beginning of 2021. Most things are already quite clear but for 2 days I have had a problem with the adhesion of the prints.

Nearly all prints I have done so far used the filament shipped with the printer (PLA 1.75) and they came off the building plate after some cooling time by themselves. I used the default printer settings for PLA: 200 °C nozzle temperature, 60 °C printing bed.

Then 2 days ago the prints began to not stick to the bed anymore and I thought this could be because of dust and from touching the bed. So I cleaned the bed with IPA. The microfiber towel was yellowish afterward - so I thought that this must have been printing residues. Since then every print is kind of "welded" to the bed. There is no chance of loosening it without more IPA or way too much force.

I already tried:

• cleaning the bed with clean water - unfortunately, didn't work
• setting the Z-offset from 0.1 back to 0.2 mm - also no success

Today I also tried a spool of brand new PETG, with the following recommended settings: 240 °C nozzle temperature, 80 °C print bed - but the problem stayed the same.

Am I doing something wrong? Did I destroy the "Carborundum" coating (silicon carbide) of the glass plate?

Answer 1

I have had similar issues, and I have learned three tricks:

1. Some slicers (i.e. Cura) let you specify the height of your first layer, and I have found that slowly incrementing up from 0.16 mm by 0.2 mm to find the sweet spot of adhesion without warping. Every brand/type is different. But, usually, for me, fall between 0.18-0.22 mm.

2. Blue painters tape. If you don't need the glass flat finish of printing directly to glass, I always use blue tape. It makes for great adhesion, and also easy removal of super stuck prints, and you can just peel it off the build plate. With blue tape, I tend to add 2-3 °C to the bed temp.

3. Glue sticks (instead of hairspray). But, Elmer's glue sticks that go on purple and dry clear. When you use these, if a print is stuck, you just need to spritz some water around the print. The print and the glue will wick the water under the print, and reconstitute the glue. Once the glue is tacky again, the print will pop right off. The only downside is a slight texture to the print and not glossy glass flat.

The reason I like the colored glue, as it reconstitutes it activates the cobalt chloride and turns purple again. This is great for knowing when it is good to start printing again. And also tends to become less of a sticky mess than hairspray.

Answer 2

It is likely the surface was damaged by the chemical cleaning, based on your description and octopus8's comment. If you are unable to mechanically release the print, there is a chemical method that has worked for me (and at least one other SE user) in the past.

Bring the bed up to about 40 °C and turn off the heat to the bed. Apply with a dropper or swab a 50/50 mixture of denatured alcohol and water. It will seep under the part as well as evaporate. Attempt the mechanical release. If it fails, apply additional mixture and repeat. Continue to do this until the mixture does not evaporate as quickly.

If the part has not released, it may be necessary to repeat the heating and application.

If you wish to return to "normal" circumstances, a bed replacement is indicated.

Answer 3

Am I doing something wrong? Did I destroy the "Carborundum" coating (silicon carbide) of the glass plate?

I doubt it. Silicon carbide is tough stuff: it's a 9.5 on the Mohs hardness scale, just half a notch below diamond. They make router bits and end mills and the teeth of table saw blades out of it, and people clean all of those with much stronger solvents than isopropyl alcohol. I don't know what other ingredients Creality uses in their carborundum coating or whether they might be susceptible to solvents, but I'd be surprised if the alcohol you used did any real damage.

So I cleaned the bed with IPA. The microfiber towel was yellowish afterward - so I thought that this must have been printing residues. Since then every print is kind of "welded" to the bed.

I had a similar experience, except that I cleaned with acetone instead of alcohol. My impression, too, is that the yellow stuff is some sort of residue left by PLA. If you print the same object several times in the same spot on the bed, you can begin to see a slightly shiny footprint of the object on the bed. You'll eventually notice a loss of adhesion in that spot, and the bed will feel a bit slick there. A small amount of acetone on a paper towel removes the footprint entirely, but you end up with a yellow spot on the towel that doesn't appear if you use the same procedure in a spot where there's been no printing.

I've also had object stick so strongly to the bed that they seem like they won't ever come off, and I think it's just a sign that a clean carborundum bed does its job very well. The best way to get them off, at least for me, is to apply a liberal dose of patience. I usually want to remove the part right away, but I find that if I let the bed cool down even to 50 °C, it's much easier to pop the part off.

Update: With the carborundum bed, adhesion is very sensitive to the height of the nozzle above the bed. If you have the bed set a bit too close to the nozzle, the PLA seems to really smoosh into the bed and grab on making the print hard to remove. If the bed is set lower, the PLA lines sit on top and don't smoosh in at all, and you don't get enough adhesion. There's a sweet spot in between the two, where the print sticks well enough that it takes a little effort to remove, but pops off with some coaxing. For me, using a sheet of printer paper as a gauge, it's about where I can feel the vibrations of the fan through the paper, but just barely, and the paper still slides easily between nozzle and bed. Your results may be different depending on the paper you use. Another way to tell you're on the right track is that the individual lines in the skirt should fuse together, but you want to be close to the point where they don't.

Answer 4

Sounds like the bed came with a coating on it. If you can't find out what the coating is, but believe you already removed it, you could try glue sticks or hair spray. You can also find glue sticks specified for 3D printing. Elmer's glue sticks work. I'm yet to try glue sticks specified for a 3D printer. You can Search on 3D Printing for answers where people used adhesive sprays. The link in octopus8's comment mentions a resin coating. There are resin coatings being sold for a bed adhesive.