Thursday, January 31, 2013

Beds, beds, beds

One of the things that makes or breaks a 3D printer (other than the linear motion, extruder, hot end and countless other things...) is the build surface. The key is to get a print to stick well enough to not fall off during a print, but also being able to remove it from the surface afterwards.

Adhesion is a fickle mistress. What works great with one plastic will suck with another. in my experience, the following is generally true:

Cold beds:

PLA loves to stick to clean Kapton tape. It can stick to blue painters tape, but this is less desirable than Kapton (Kapton adheres more strongly to the bed, and is a glass smooth surface. The papery texture of painters tape is imprinted upon each print). PLA can maybe stick to glass, if it very clean, but don't count on it. There is very little warping that occurs, and the prints pop off quite easily.


ABS hates everything. Cold glass? No way. Blue tape? I don't think so. Kapton? No chance in hell. The main reason for this is really because ABS has a tendency to warp so much more than PLA. More often than not, it will simply pull itself off the bed.
The fix for this is a slurry of ABS dissolved in acetone. It should not be clumpy, but very liquid and flowing. when you apply the juice (or sludge, or goop, or whatever), to the surface, you want as little as possible. More sludge results in an uglier bottom finish.
I first put down painters tape, then put the slurry on top of that to protect my actual build platform. The warping of the ABS was enough to pull the painters tape right up and off the wooden platform. I then went and got a sheet of glass, and gooped right onto that. That did the trick; the part couldn't pull itself off the bed.

...

Unfortunately, there are still forces due to warping at play, and my print would quite literally pull itself apart! Some layers would delaminate with a *PING*, and the print would be weaker in that area. This was what drove me to a heated build platform.

Heated beds

I have not tested my bed extensively, as I have only had it for a week or two, but it has already vastly improved my prints. First layer adhesion (onto Kapton tape) works fairly well without any sludge. Some parts with very low surface area (one of which will be featured in my next post) still need a bit of goop, but that's only extreme cases.


Final thoughts, before I away to sleep...
Heated beds are not entirely necessary, but can definitely improve your print quality.
ABS cement is invaluable in sticking down difficult pieces
ABS bonds permanently to polycarbonate (You can test this if you want... But I'm pretty confident that that particular print will never be seperated from the bed)

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