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Better Raft sticking / Raft Pull up

Posted: Fri May 18, 2012 4:16 pm
by whryly
I keep having this problem with the print head pulling its own raft off the perfboard during the first 1/2/3 layers.

It is specifically related to when the print head finishes a "trace" on the first layer - when it stops one trace and starts the next, but still on the first layer.
The Z-axis pulls down and then back up to start the next run.
When it moves down it is pulling the raft "trace" off the board just a small bit, but enough that when it makes the 2nd layer, it pulls it up more.

Is there a way to alter the first raft layer so that it does not actually move the z-axis? Seems that it could achieve the same effect by stopping the filament feeder, and moving the head, just leaving a small trail?

Is this just heat related? (happens both with perf at low temp and at 100°C.)
Do I need to treat the perf with something to make it more sticky?
Is the nozzle temp too low and causing the ABS to be too sticky and not release when the z-axis moves?

Is this humidity related?

I can submit a video of this if it would help.

W

Re: Better Raft sticking / Raft Pull up

Posted: Fri May 18, 2012 8:10 pm
by wackojacko
Ensure your platform is level, ensure the distance between nozzle and platform is about 0.1mm to 0.2mm. Ensure the platform is hot to the touch on all corners, check the perfboard is relatively clean, and finally check that your nozzle is not blocked- do an extrude and make sure it comes out straight and doesn't curl back up to the nozzle.

How long have you had your UP

www.3dprintingsystems.com

Re: Better Raft sticking / Raft Pull up

Posted: Fri May 18, 2012 9:17 pm
by whryly
We've had it for 6ish weeks, but our first unit had multiple problems, one of them being a bad z-axis, both rails & drive system.
I've had the current unit for two weeks.

Platform level: Check
Nozzle height: Check
Hot: Fingers Burned - Check!
Clean board: for sure
Extrude: straight and makes a clean cone. (although sometimes the very first bit does curl, after it has started, its' smooth and clean)

I have checked everything you mention - in fact I am having trouble getting the perfboard holes cleaned out because the ABS is so jammed in there.

The raft is very secure, it's just when the trace ends and the platform jogs down, it's actually pulling the trace up, which then gets ripped up over the next several passes.

I've been trying to get a video, but the camera is having a hard time with the movement.

W