Friday, December 21, 2007


Encapsulated Extruder Hopeless - Built New One

The previous extruder got trapped in a ball of PLA. The family wishes me to keep it as a memento and it looks fairly dicey to excavate so I've built a new one. Still no JB Weld about, so it's held together with BBQ paint again. I have learned through my mistakes though:

1. The thermistor is now mounted on a copper tag for easy removal.
2. The dome nut nozzle has been reshaped to a thinner point.
3. No insulation - it just absorbs plastic.
4. Heavy copper wires crimped to the nichrome heating coil.
5. Actually did wrap both ends of barrel in PTFE before assembly this time.
6. When drilling barrel using drill press, drill in half way from each end to keep hole central.

The first one I built had a pinhole leak in the barrel where my lousy drilling clipped the thread. I discover this after assembly. Moral: Check for leaks.

During testing I blew up 3 PICs. Moral: Insulate your thermistor leads well.

I also discovered that thermistors with a very low (<500 ohms) resistance at operating temperature spook the PIC's temperature measurement causing the heater to operate intermittently. If you've got one of these, stick a 560 ohm resistor in series with it and all should be well. You'll have to recalibrate of course. Moral: Try to use stock parts.

And now, she works again.

Vik :v)

I'm very interested in details on your mods; the copper tab for the thermistor is of immediate concern... are you installing that before you screw on the extruder tip?

Trying to think what copper parts I have around of use ;) I guess a visit to the hardware store is in order.
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