Friday, May 15, 2009
Small Melt Zones Look Good
The difference in operation of the no-lathe extruder with different barrel lengths and a heatsink leads me to suspect that the main factor in reducing friction is to reduce the size of the zone where the plastic is actually melting.
As you can see in the photos I've chopped an old CPU heatsink (easily salvaged or made from copper/aluminium stock) into 10mm slices, and clamped a pair around the barrel. There is a recess in the middle of the two halves made with a drill 0.5mm smaller than the barrel's external diameter. I have experimented with moving it up and down the barrel. The barrel above the heatsink does nothing useful in this setup, but might be useful for guiding the filament later.
The heatsink stops the plastic melting on entry, keeping the top part of the barrel under 60C. I've rewound the heater to start the coil as close as possible to the nozzle, and to keep the windings close together. Kapton tape is great for this!Best results definitely seem to be had with a small, powerful heater (1A@13.8V max, running at about 60%) and the heatsink placed as close as possible to the heater windings. This is much more successful than my earlier experiments with heatsinks.
The extruder works continuously, or in bursts, and I checked that it will restart after cooling. It still needs no lathe!
Vik :v)
Labels: melt, no lathe, reprap, zone
