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brittle PLA parts

Posted by PrintRind 
brittle PLA parts
May 25, 2013 06:18PM
Hi, I am having problems with my parts being very brittle. Especially bar clamps break very easily.
I am printing PLA at 185°C, nozzle dia. 0.5mm, layer height 0.3mm
Obviously, the layers don't bond very well.
From what I learned so far there are three main reasons for this:
A) too low temp. --> I already imcreased the temp from 175 to 185, with no improvement.
cool smiley too little material used? The weird thing here is that other printing problems I have (too small holes, thin wall object boundary (http://www.thingiverse.com/thing:37137) thicker than it should be) indicate that I am rather using too much material.
C) layer height too large --> I decreased to 0.2mm with no improvement

I find this qutie confusing. Should I print with ever higher temp. but slower?
If anyone had similar problems, I would be grateful for comments.
Re: brittle PLA parts
May 25, 2013 08:00PM
Did you calibrate steps/mm for all axes including E-steps?

It can be that your Z-axes are making more than the ordered height.

Other thing can be that your heatbed is flexing by the heat and thus lowers of heightens the printheight. Or as you say, maybe printing temp problems. But thats easy to adjust and test.
Re: brittle PLA parts
June 06, 2013 03:50PM
Just an update for those who are interested:
I've made some progress in the meanwhile, partly by printing much hotter (up to 210°C).
Another improvement was the new plastic I'm using now: the white PLA seems to be a bit softer than the uncoloured one and breaks less often.
I have the feeling that the parts I'm making are quite strong in the meanwhile. Nontheless, I've so far always failed to clip this part onto the 8mm threaded rods of my Prusa frame: frame_holder.stl (file is attached)

I have the suspect that this part is just badly designed and will always break when made in PLA because it is harder than ABS.
I'm wondering if anyone of you is able to print this in PLA and clamp it onto the frame without breaking.
open | download - frame_holder.zip (61.2 KB)
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