PLA adhesion to a cold plate

I have a Kossel Mini, I print PLA around 205-215C onto a cold bed, and I've been having trouble with bed adhesion.

My bed is polished basalt with some small laser etching. On blue tape, anything larger than ~100mm will always warp, and it takes a lot of work with anything larger than around 60mm. Hairspray performs comparably, except that the whole part tends to pop as soon as the first corner does. Kapton and bare basalt are useless.

I had one good print with glue stick, using the last of an old stick, so I bought some new off-brand sticks. They suck. I haven't tried PVA glue since I don't have any.

My bed is around 200mm across, so I'd really like to be able to use the whole thing. What might help that? Would a heated bed help? How about heting the bed in an oven before printing? IS it worth it to try some UHU or Elmer's glue sticks?

Thanks!

IMO a heated bed is the best solution. With the right PLA filament, I can print directly on to clean heated glass. For problem filaments, I coat the glass with solvent pipe cement, diluted with acetone to make it go further.

Have you done delta calibration, to make sure that the printing plane is flat and a constant distance above the bed? Do you set the Z height accurately just before printing, after bringing the hot end up to temperature?

Edited 1 time(s). Last edit at 02/13/2015 03:44PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you!

Exactly how precise does the Z-calibration have to be? 0.1mm? 0.05mm?

Also, how do I differentiate good from bad filament?

And lastly, how likely is a ~3/8" basalt bed to crack from thermal stress at PLA temperatures? How about ABS temperatures?

I adjust the height in 0.05mm steps, but a lot of people use 0.1mm. You can get away with larger errors if you increase the first layer height in the slicing program.

You can print both PLA and ABS on ordinary float glass long as you treat it sensibly.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hairspray + cold = 40C heated bed. For smaller parts I print cold with 1-2 sprays of strong hairspray. for bigger parts I warm up 50C

I would really like to see report on the print pads reusability and sandblasted glass