Monday, April 24, 2006


Extruder updates

Oh, did I mention the extruder firmware problem is fixed? :) It was actually a wiring problem in my electronics, but I have discovered several other issues that I have fixed and committed.

I have also committed to CVS some more work on the java drivers for the extruder. There is also a test application for extruders that you can access from the Tools menu of the RepRap application. It lets you specify a temperature and the extruder will automatically maintain that temperature. You can also drive the extruder motor.

The PIC firmware supports both "chop-chop" and dynamic heating. Chop-chop heating results in a temperature that wobbles around the target temperature while dynamic heating gives much more precise and stable heating. Currently the Java code only supports the chop-chop heating because it's a bit simpler. You need a little bit of a thermal model to make the dynamic heating work properly, so we can get to that later. The chop-chop heating doesn't seem too terrible anyway judging from my experiments with it today.

There are new preferences settings for specifying the two thermistor parameters that are needed to determine the thermistor temperature. I have also put a page on the Wiki that describes how to measure the parameters for a thermistor if they are unknown (as mine were) and how to calculate the other figure needed for the RepRap preferences (R at 0C). For more, see

Oh lord! The moment I have to take some time off from working on Godzilla to log in some billable hours so that I don't go bankrupt you guys take off like a bunch of fireworks rockets doing all sorts of interesting thing that I'd love to take advantage of. :-p
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