Nophead's techniques for using Skeinforge

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from the Software forum:,10772,page=7

messageRe: How to print Gcode from Host Posted by: nophead (IP Logged) (RepRap Guru) Date: October 07, 2008 01:15AM

   I don't know if Nophead and Brendan have done the same thing.

While waiting for the nozzle to change temperature my extruder oozes (the plastic falls due to gravity if you leave it hot long enough). That means I have to run it for a few seconds to refill the barrel. After that if has a few cm of filament dangling, so I wipe it off before moving to the object.

My build procedure is this:

Warm up to raft temperature and wait 1 minute for PTFE nozzle to expand and filament to melt above the PTFE / brass junction.

Wipe the nozzle.

Go to near the first raft position, run the extruder for about 1s to make a blob and then do 5mm of lead-in to the raft. This is needed to get the first line of the raft to stick. The reason is that by the time the head has moved from the wipe station to the raft position a few mm of filament will have oozed and be too cold to stick. It curls upwards and prevents the rest of the first line sticking.

I do the first layer of the raft: sparse zig-zag of 1mm filament at 4mm/s, height 0.7mm.

I set the temperature for subsequent raft layers, but don't wait for it to get there (it would ooze and need a wipe if I did). Do the next two layers of the raft, a close, but not solid, zigzag of 0.5mm filament at 16mm/s.

I then place the fan over the raft and cool for 2 minutes to get a reliable raft temperature. I turn the temperature down while the fan is running so as not to stress the heater, which would stress the PTFE.

I then warm up to the first layer temperature (at the home position) and wait for 1m minute again and then wipe the nozzle again.

I return to the raft corner and draw a rectangle round the object, 1mm from the edge of the raft (the raft overlaps the object by a material dependent amount). This ensures the filament is flowing properly and no cold ooze to prevent sticking.

I then do the first layer of the object at half speed and a little lower (0.15mm) to make it stick. 0.05mm makes all the difference.

I then increase the temperature for the other layers, but do not wait for it to get there.

I then extrude the rest of the object at full speed with no pauses between layers. I do slow down on layers with not much on them to avoid overheating. On low temperature plastics I run the fan after the first layer.

Ideally I would always wait for temperature changes to take effect, but I have no clean way of starting a new layer after a pause. I would have to wipe the nozzle, but by the time I move back to the object it would have oozed. HydraRaptor only moves at 32mm/s. I am hoping to solve these problems by moving 5 times faster with my turbo charged Darwin. I also plan to revese the extruder motor to stop the ooze. That will give a pause before it starts again, but with the shaft encoder that should be repeatable.