Friday, September 11, 2009
Printing with 2mm filament
I use a pinchwheel consisting of a small brass spur gear. A ball bearing is on a lever and presses the filament against the pinch wheel due to the force of a rubber band (with multiplication from the lever). There is not much holding a 3mm filament from sliding sideways and out from between the spur gear and the bearing, but 3mm filament is stiff enough that it is not a big problem. When I tried the 2mm filament, I had to modify the level a bit to allow it to come close enough to the spur gear to press the 2mm filament against it. I also printed out a better filament guide to prevent the 2mm filament from moving sideways.
Once I had done these modifications, and had tweaked the skeinforge settings (halved the feedrate and decreased the expected extrusion width slightly), I was able to print well with the 2mm filament. Here is a paperclip (http://www.thingiverse.com/thing:655) by "unfold". While I was extruding, I heard a slight popping noise (frying?) which I do not hear with the 'natural' colored 3mm ABS filament (from Village Plastics). I suspect that I may be running the tip a bit hot for this material.
Interestingly, I got good results with a 2mm filament in a 3mm+ hole, which holds 3mm filament fairly snuggly. When I pulled out the 2mm filament from the extruder, it looked like this:I described the heater end of my extruder here recently (builder's blog of August 29, 2009). It looks to me like the 2mm filament is just pressing up against the dished end of the acorn nut and not spreading out much. I am probably deluding myself, but it looks like this is a hint at a simpler extruder.
I've been thinking along similar lines, but using a 3 mm filament, with a 3 mm PTFE thermal break, but then a 4 or 5 mm ID barrel. I think it might reduce the force needed to extrude, along the lines of Nophead's tapered melt zone.
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