Reply To: Hacking the Canon BJ-21 Printhead

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Well, I have the color head (yes, I agree, the black is junk for my purposes), but I have just today, as I was disassembling my BJC-4550, found another good reason to use this head:

It Just Fits!

The Canon BJC-4550’s head, X carriage, and control electronics package all fit on my existing base.

My plans are now considerably simplified, and I might just be able to get a working printer chassis by the end of the month:

* Make sure the ‘reverse line feed’ function works as advertised
* Configure BJC-4550’s Y stepper motor drive to drive my Y axis
* Modify Gutenprint’s BJC driver to support the ‘page size’ of my part bin
* Attach powder roller to back of the Y axis carriage.
* Get a USB to Parallel adapter

The Z-slice process would then work as follows:

* Start in ‘waste’ area at front of the part bin.
* Send Z-slice as raster to (via Gutenprint) to BJC-4550’s parallel port
** Y carriage is now between part and feed bins
* Continue to send linefeeds until Y carriage is at rear of feed bin
** This triggers a limit switch, which causes the Arduino to move the feed bin up one slice
* Send reverse linefeeds until Y carriage is in waste area
** This rolls the powder into the part bin area, and any excess into the waste chute
** At the end of the powder roll, the Arduino sees a limit switch, and drops the part bin down one slice.
* Go back to start.

The Arduino software is now trivial, and could probably be replaced by simpler electronics.

The BJC-4550 head control and frame could probably be ‘faked’ into believing a cartridge is present when it is not (it just needs the heater thermal diode to be replaced by a fixed resistance), and I could use the 24v + logic to drive other extruders if needed.