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OK, here's a conundrum

Posted: Fri Jun 10, 2016 7:42 pm
by dramsey
Sorry. I should have used a better title, but I couldn't think of one that both summarized the problem and fit within the title limits.

I'm trying to print the elaborate T. Rex skeleton that Makerbot has made available for free on Thingiverse. (Originally, they had just the skull, and you had to pay for the rest. Now it's all free.) I've had a few things I've had to tweak to get everything to print--- a raft here, a support there-- but overall it's been pretty easy going.

Until now.

The very last part that I want to print, "TRex_Tail_B_D", comprises three parts: a very thin tail end; a much thicker mid-tail, and a support that snaps the two together. These are all one print job, but I've used Meshlab to isolate each item into a separate file. The problem child is the thick mid-tail...let me see if I can describe what happens...

The top extensions from the vertebrae-- the ones that would be at the top of the spine when the T. Rex is assembled-- are the problem. They're pretty small, a couple of mm or so wide, and taper almost to a point as the extruder moves along the "Y" axis. As the extruder renders this taper, and starts to move back, the plastic at the very end of the taper rises a little. That is, instead of being flat with the rest of the layer being printed, it's higher. This difference increases as more layers are added, and the extruder starts hitting the raised plastic on every layer. Eventually a chunk of the model breaks off, or, in one case, the model snapped in half.

I've tried increase and decreasing print speed, but neither tact seems effective. Any ideas?

Re: OK, here's a conundrum

Posted: Fri Jun 10, 2016 10:27 pm
by Jules
Try including a Retraction Vertical Lift of about 0.6 mm.

Re: OK, here's a conundrum

Posted: Sat Jun 11, 2016 1:37 am
by jsc
If you are printing in PLA, make sure you have full fan going except for the first layer. If you are still getting curling on overhangs, get more fan. A desktop fan will work, as well as a more powerful 24V bed fan. More cooling = less curling, for PLA.

Re: OK, here's a conundrum

Posted: Sun Jun 12, 2016 9:05 pm
by dramsey
Jules wrote:Try including a Retraction Vertical Lift of about 0.6 mm.
That works beautifully, Jules. Thanks!