Small prints stop sticking
Hello Everyone,
We just assembled our Prusa 3 MKs last weekend. We did the live z adjust like an older post in this forum suggested and were getting pretty good results around -1.140 . So we decided to start printing a "Cali Cat" which my wife seems to love ( https://www.thingiverse.com/thing:1545913 ). However we seem not to be able to finish the print. If we print the Cali Cat with the default settings it prints up to the ears and then it stops sticking to the surface and starts getting dragged around. If we print the same cat (for quicker results) scaled down to 50% it stops sticking and being dragged around relatively quickly (much sooner than with normal size Cat).
Friends of ours have the same type of printer and they can print both sizes easily without any problems of the cat sticking to the powder coated bed. If we print the cat with brim we don't have any issues, same with prints that have a bigger surface on the bed. Can anyone recommend something that we can try to make "small prints" stick better to the bed?
RE: Small prints stop sticking
Usually, that is an issue with either the z calibration (have you read this thread: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/paged/1/ ?) or the cleanliness of the surface.
If you're using PLA, your bed has to be clean. I don't habe the powder coated bed yet (should be in the mail...), but with the smooth bed, I take a new kitchen sponge and a drop of my dishwashing fluid and a bit of water and then foam up the bed (with the smooth side of the sponge) with the sponge, then rinse. Repeat until the water runs off as a smooth film without any preference to stick to any part of the bed, then carefully wipe dry with some kitchen paper - DO NOT TOUCH THE SURFACE WITH YOUR FINGERS!. Before printing, I spray on a bit of Isopropanol and again wipe with a fresh piece of kitchen paper. Usually, that's enough.
On the other hand, if you're printing PETG, after the iso, I spray a bit of windex and wipe it off again (with the same piece of paper as before) - otherwise, PETG sticks too good.
It would help if you posted pictures of your z calibration test patch, the underside of the failed print(s) and the surface of your bed.
RE: Small prints stop sticking
All Prusa sheets need to be thoroughly cleaned with soap and water before printing PLA ... alcohol is only useful if you use enough to thoroughly rinse the sheet after scrubbing. Most of us don't have gallons to spare. Rinsing with hot water at a sink has those gallons.
Hot Water wash: often, as needed, and after any of the following
(not recommended for daily use on Powder Coated sheets)
- Handle the bed only by the edges.
- Wash the bed in hot water, use a fresh paper towel as a wash cloth, with a few drops of plain dish soap (Dawn, unscented, no anti-bacterial, etc.).
- Rinse well in hot water - if you have very soft water, rinse a bit longer.
- Dry the bed with a fresh paper towel.
- Handle the bed only by the edges.
- Place bed on printer.
Alcohol wash: every few prints as needed
- Gloves recommended.
- Once in a while, an alcohol rinse is helpful to remove PLA residue. It does not remove finger oils well.
- Pour a 5 cm puddle of 91%+ alcohol in the middle of the bed, with clean hands use a fresh paper towel to scrub the bed. Wipe up all the alcohol.
Acetone wash: infrequent as needed
(Not recommended for USE on Powder Coated sheets, but some find it necessary)
- Pour a 2 cm puddle of acetone on the bed, scrub it around with a fresh paper towel. It will evaporate fast as you clean. This step removes PEI oxides that form over time and with heat, and improves PLA adhesion to a like new state.
Streak test: when contamination is suspected
- With a fresh piece of paper towel, and very clean fingers, dampen the towel with 91%+ alcohol, and wipe the bed side to side moving back to front, like you're painting it with alcohol. The alcohol should be thin enough on the towel it quickly evaporates from the bed. If you see any streaks, the bed is dirty and needs a wash.
RE: Small prints stop sticking
Hi,
thanks for the replies!
We haven't done any cleaning, besides using IPA yet. Will do that today and report back!
I attached the pictures to this shared folder: https://photos.app.goo.gl/3Fx97Pzbnze1DmB38
- Two pictures of the calibration patch with -1,15 and -1,14. (Both look VERY similar)
- One of the failed Cali Cats. (Note: there is some warping at the front feet, maybe you can see it), the third cali cat was printed on a borrowed PEI Sheet.
- The last picture is of our powder coated sheet.
RE: Small prints stop sticking
You never actually say what filament you are using. We can deduce you are using a powder coated sheet, but it would be easier if you would say those up front, along with head and bed temperatures.
My first sheet was powder coated. It took me a good two weeks to get PLA to stick satisfactorily. Major scrub with Dawn helped the most.
While I was fighting with PC, I ordered a PEI sheet from Prusa. This is worlds better for PLA.
I am happy with my PC sheet now. It continues to improve with age, and I can use it for PLA and PETG. These sheets seem to vary a lot. Yours may be better - or worse - than mine.
RE: Small prints stop sticking
Yeah my bad, sorry!!
We are using PLA.
Btw, cleaning improved our issue! The tiny cat with 50% size still keeps failing, but we can use brim for that.
I tried the normal cat once yesterday after cleaning and it sticked to the board and didn't warp. I hope it stays that way.
Thank you so much for your help!
(We will order the PEI sheet later as well, probably. :))