Thursday, May 01, 2008


Anti-ooze - the first design

Untitled from Adrian Bowyer on Vimeo.

Here is the new polymer valve in operation.

A solenoid pushes a short length of piano wire across the flow. This stops it instantly, giving a much better finish to constructed objects, and also stopping the polymer oozing from the nozzle when it is idle.

The AoI files for the design are in the subversion repository here. The solenoid I used is from RS: 250-0827.

I have also checked into the repository the changes to the host Java code and the firmware for the Arduino needed to drive the device. Note that, in the latter case, the new firmware disables the maximum (but not the minimum/zero) optoswitches on the RepRap machine's axes. Few people use these anyway, and - as pins on the Arduino are tight - it is better, I think, to use them to add new functionality.

Exactly the same code will drive the metal deposition head that I blogged here.

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Damn! The extruder controller electronics becomes a little more complicated. :-s

No seriously, great work Adrian!
Actually, the driver was already there in Zach's design. All I had to do was to run two extra wires between it and the Arduino. :-)
Where do those wires go in the arduino? I think that all of them are taken up, or am I mistaken?
I use pins 16 and 16 - as I said, I've disabled the axis max opto endstops to free up pins.
For which read pins 15 and 16...
Can you save pins and yet keep your end-stop functionality by OR'ing together the max and min endstop pins? The software will only know that you hit an endstop - without knowing which one - but it ought to be able to deduce that from the direction it was driving the motors at the time.
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