3D Printing engine discoveries

One of the problems that Graham, Alvaro and I ran into was that the
current ink jet printers do a "dance" before printing. The dance was
intended to run the print head cleaning station. The older HP printers
don't do this. They have a separate stepper motor on the cleaning
station. The lack of this dance makes these a much more suitable donor
for a 3D printer.

The logic board on these older printers is separate from the motor
drive and optical paper feed encoder which makes it much simpler to
separate the paper feed from the print head/logic. To separate them
all you need to do is extend a 6 or 8 wire (depending on the printer)
bundle.

As the printer does not "dance" you can use the original feed
mechanism, basically unmodified, to drive the print mechanism with a
capstan/cable drive.

The print cycle consists of a paper feed until the paper switch is
tripped where the printer will start to print. Some of the
professional printers (HP 960c) also have a sensor on the print head
that have to sense white paper under the head (after the paper switch)
after the paper switch before starting to print. In any case it is
very easy to manage and I have bench tested.

As the printers use a DC motor on the paper feed the motor is very
easy to hijack the motor with a relay to allow a simple controller to
handle the required rewind and spreading cycle using the existing
paper driver.

The older printers use the highly desirable (cheap, large volume, easy
to refill) HP 45 cartridges.

The specific printers I have examined are the HP 960C and 722C. I'm
sure many printers of this vintage have the same characteristics.

All of this being said I still haven't had an opportunity to proceed
much farther. I hope, sometime this fall, to assemble a flat bed
printer with one of these older printers. Owing to the lack of dance
The slides can be short as the smaller 3D System printers only print
about 6". I am sure ball bearing drawer slides would be completely
acceptable for testing and probably in a finished machine.

If anyone gets there before me I am still committed to getting the
Rhino SLC to print working. It already seems to work for simpler parts
although Alvaro found a problem printing a bearing. We need to walk
before running.

Roger