Shrinkage with ABS isn't a big problem if you test your production lot of plastic up front and scale as needed. (Which is something we do in the real world of production with most materials, Gabe knows a lot more about this than I.)
If I'm working with ABS, I print a 2cm cube then measure the actual printed dimensions for a lot of plastic then resize my model and print it out. I usually had to scale the model up %1-%3, which isn't that much if you're dealing with bolt holes and basic angles. My CNC machined lasersaur parts from Mitsumi were often off by a percent or two if I bolted it up without a machinist square. The straight pieces (what we use on the Mendel) were CNC cut but the brackets (what we 3D print) were cast metal with some variations.
My personal concern with PLA is that it simply isn't rugged enough for public use. I have no idea what it's going to do if someone spills a soda on it, oversprays machine oil, etc. I think it's great for public handouts of printed novelties, I simply don't trust it for structural components used by the public.
On 3/17/2013 10:45 PM, Elijah Richter wrote:
Ok, I figured that's what you meant. So are you saying that PLA tends to crack if used as a structural component? I was looking online a bit and the only cautions I came across regarding using PLA was not to use it for components that are subjected to heat. The reason I was thinking about using it is that I've read that it's less prone to shrinkage and I would therefore expect more dimensionally accurate. -Eli On Sun, Mar 17, 2013 at 9:38 PM, j. eric townsend <jet@xxxxxxxxxxxx <mailto:jet@xxxxxxxxxxxx>> wrote: gah, "with PLA" is what I meant. ABS is much better for structural components. On 3/17/2013 4:40 PM, j. eric townsend wrote: I wouldn't print any of the structural parts with ABS due to all the vibration and tension. But things like LED/display holders and other non-mechanical parts should be fine. Plus, you can compost/recycle the parts that don't work... On 3/17/2013 4:00 PM, Jeremy Herrman wrote: No 3mm PLA but I do have a bit of 3mm nylon, and plenty of 3mm ABS including some cheap Chinese stuff if you'd like to see what printing with bad filament is like. -Jeremy On Sunday, March 17, 2013, Elijah Richter wrote: Do any of you printing folks have some 3mm PLA filament lying around that you aren't using (perhaps you changed to 1.75?) The mendelmax is coming along and I'd like to start testing with PLA filament. I have a few parts I'd like to eventually print for the bot itself, so I'd prefer black filament to match, but any color would work. -Eli -- @jherrm <http://twitter.com/jherrm> linkedin.com/in/jherrm <http://linkedin.com/in/jherrm> <http://linkedin.com/in/jherrm__> facebook.com/herrman <http://facebook.com/herrman> <http://facebook.com/herrman> -- J. Eric Townsend design: www.allartburns.org <http://www.allartburns.org>; hacking: www.flatline.net <http://www.flatline.net>; HF: KG6ZVQ PGP: 0xD0D8C2E8 AC9B 0A23 C61A 1B4A 27C5 F799 A681 3C11 D0D8 C2E8
-- J. Eric Townsend design: www.allartburns.org; hacking: www.flatline.net; HF: KG6ZVQ PGP: 0xD0D8C2E8 AC9B 0A23 C61A 1B4A 27C5 F799 A681 3C11 D0D8 C2E8
