Wednesday, January 16, 2008


Darwin on CAPA

While Vik's been blazing trails with PLA I've been trying to get our Darwin to follow suit with CAPA. Finally, the variables are coming together, and last night we printed it's first part: the y-belt clamp. I'm proud to say that this is what it looks like straight off the bed, no post-processing needed, and the M5 bolts screw straight in! (1 small square = 1mm)

My best lessons so far have been getting the temp relatively high, ~130°C (to reduce extrudate viscosity and prevent extruder stalling), and to spend time getting the layer increments spot on (to guarantee layer bonding). I'll upload my variables today into the 'tweaking' section of the wiki.

Good to hear more comments about 130c temp. The group of us in Houston on Sunday discussed the same thing... I keep having to go higher than other people suggest.

1) Partly it may be that we aren't all calibrating out thermistors equally.

2) Room temperature and airflow. We were outside in the garage with door open and we had problems as the sun started to set. A halogen 500Watt light really helped get things flowing again ;)
Yes, I think it makes sense to run it at a high value, the further away from phase change the better. There's a quick temperature test I could do to validate it... will post results asap.

Be wary of running over 100C. If your plastic has absorbed moisture, you may get steam bubbles. If they're small, no problem. If large, they interrupt the feed of fine extrusions.

Vik :v)
Ooooh. Thanks VIk, I hadn't thought of that... I'll keep an eye out, eD
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