Thursday, 29 September 2011

Printing Surfaces

So there was a little discussion on #reprap the other night about what is the best surface to print onto.
I have tried a few different surfaces and have come to the conclusion glass seems to be the best, its easy to clean, but hard to work with when making your printer.. as you (should be)  printing more than assembling the difficulties in working with the glass should not really be an obstacle.

I have tried several surface materials with ABS (haven't tried PLA yet), l will list them for you..

MDF (plastic doesn't stick well, i suspect it sucks too much heat from the plastic for it to stick)
MDF with kapton tape (plastic sticks ok but will warp up once it cools.)
White masking tape ( sticks ok but my settings were not right and i was applying too much plastic so the nozzle knocked the cube free before it finished.
Bare Aluminium works well but can scratch up really easy.
Glass Unheated. Plastic does not stick!!!
Glass Heated plastic only sticks when its hot enough. ABS110'c. this works like a charm.
Glass Heated with sandblasting surface finish. (0.5 welders slag for sandblasting grit) plastic sticks to this like turd to a blanket.. and is just as hard to clean... when you scrape the top clean there is a little bit of plastic crud that is left behind and cannot be removes by scraping. need to soak in a chemical (acetone for ABS) this level of cleaning (IMHO) is not really required unless you have some real contaminant on the glass bed (eg lard used on crappy nylon bushes on your x axis.) then you may need to really remove the excess plastic that may be harboring some grease or something that will stop the plastic from sticking. there is a caveat to the sandblasted glass, it will efffect the finish on the bottom layer of the object being printed, you will get a surface texture that is the same as the sandblasted surface.
 you can by all means get smaller grits for sandblasting but the 0.5mm grit was what was at hand.

here are some pics of the bottoms of objects that i have printed..

 the two pictures above are of things i printed on a high gloss piece of glass

the above three pictures are objects that i printed on the same piece of glass as above but after the surface was sandblasted with 0.5mm welders slag. this finish is not too bad if you ask me.. i kind of like it better than the full gloss finish. the result of the sandblasting was the plastic stuck really really well at one point i thought i was not going to be able to get the objects off..

for my new printer i am considering sand blasting one side of the sheet of glass that way i have the option to turn it over if i do or don't like one...

there was discussion of getting the glass chemically frosted, as well as frosted with a laser. the chemical treatment would probably work, but from what i learned about how the laser is used i am doubtful that this will have an effect. the laser treatment is performed by submerging the glass object in mineral oil and then directing a laser at the area to frost. the frosting (as i believe the process goes) is a result of the heat of the laser liquifying the glass (maybe to the point of plasticity ) and inducing boiling bubbles in the middle of the glass not the surface. I think the surface will still be flat and smooth. this is only an aesthetic change not a surface treatment. we need the surface to be flat and grippy.  if you look at the pictures of my first printer you will see the glass that i was printing on, there is two pieces one is sandblasted the other is not. they were scrap pieces of glass from some old kiosks at my work.

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