DIY collet chuck questions

[strantor]

That's what I get for not previewing the post. I was going to quote something and lost it. Thought I had deleted all the quote stuff.

Any bad experiences from the other polymers? I have only done abs and a little pla. Not that impressed with abs. It always tried to shrink and curl off the bed with larger prints. Adjusting the bed temp didn't really seem to solve much.

I've actually done extensive strength testing on various polymers, and the conclusion I've come to is that any polymer, whether carbon fiber infused, or just plain "badass," is that a printed part is only as strong as its bond between layers. Published tensile strength, flexular modulus, etc. numbers for printing filaments (for those manufacturers that actually publish numbers) are just about meaningless because the tests to derive the numbers aren't carried out using 3d printed test objects and therefore not subject to the woes of layer adhesion. Layer adhesion, if published (it isn't), would be a much more valid measure of a filament's chance of success in a high strength application. In 3d printing, unless you're printing something really small and printing really hot, with any polymer, your layers aren't truly bonded; they're just "got hot and stuck together."

I devised a standardized printed part strenth test which tests a 3d printed part's strength in all 3 axes and also pull-out tensile strength in 3 axes, using a calibrated load cell in my drill press. What I found is that with any polymer, printing very very too hot so that the layers get melty and part gets deformed, actually makes the part stronger as the layers are closer to "bonded" together. Aesthetic value is inversely proportional to performance. I got excellent results with nylon645 and taulman t-glase in this way. Nylon printed part are strong but not rigid. They will deform quite a bit before breaking (or they might just break, if layer adhesion sucks). T-glase performs as well or better than nylon, but only if printed very hot and melty. When I say that these things need to be printed hot an melty, I mean so hot and melty that the part is unrecognizable and unusable for its intended purpose. PLA sucks all around. ABS can be surprisingly strong if post processed with acetone, but only for smaller parts that can thouroughly absorb the acetone.

In short, 3D printing by layer extrusion cannot make a part that is strong and stable in all axes. It took me several hundred dollars to reach that conclusion, despite being told that before hand - what can I say, I'm hard headed. Next avenue to explore is 3D printing by UV curable resin with a laser. I must save up a bit to get into that game. Failing that, 3D printed molds for casting with a more suitable polymer. My intent is to find a method of making DIY (that the average joe can actually DIY) prosthetics that can withstand unreasonable abuse, like being slammed in a car door, smashed with a hammer, used to pick up hot objects, be resistant to accidental cutting, etc.

 

[David Kirtley]

I wasn't impressed with the strength of the parts either but I think it is well within it's original purpose of just cranking out a prototype or pattern. There is just a lot of hype associated with them as "desktop manufacturing" that really goes beyond their capabilities. We have one of the fancy resin laser machines here at work but the consumables are really pricey. One of the kids did a print and left it as solid fill. Ended up with a *very* pricey 2" x 2" x 12" block of resin :*(