2 Jun
2006
2 Jun
'06
9:32 a.m.
At 03:54 PM 5/31/06 +1200, you wrote:
On 5/31/06, Tony Duell <ard at
p850ug1.demon.co.uk> wrote:
I bought a CGP-115 new about 20 years ago and had the same gear problem.
I went to a TRS "computer store" and tried to order a gear but they
insisted that I had to have the printer checked out by their technician
before they would sell me one. After a bit of intense questioning they
finally admitted that there was a one hour minimum charge at something like
$40/hour! I told them to stuff it and I've seldom darkened the door of an
Trash Shack since. A year or two later I meet the manager of another TRS
store and I told him the story. He ordered 3 or 4 gears for me and they
only cost about $1. So the gears WERE available.
I've seen a crude but effective method of cutting gears by turning a
shaft of the desired od and then mounting it horzontally on a verticle
milling machine so that it can turn freely. Then mount a TAP vertiaclly in
the headstock and spin it slowly and then moving it slowly in against the
shaft. The tap will cut longitudinal (actually nearly longitudinal) threads
(teeth) in the shaft as you move it in. (You only need to move it in by the
depth of threads for the gear once you contact the shaft.) It will also
spin the shaft and cut threads all the way around. You will need a tap of
the same od and pitch (or as close as you can get) as the gear that mates
to the one you're trying to make. This will yield a lantern post shaped
gear instead of a straight one but for this application that should be even
better.
Another way to cut the gear is to turn a shaft of the correct od and
mount it in a lathe. Lock the headstock so that the lathe spindle, chuck
and shaft can't turn. Make a cutter that matches the shape and size of one
of the spaces between the gear teeth. (1) Mount the cutter in the tool post
holder and move it back and forth taking light cuts on the shaft until you
get the desired depth of cut. (2) Unlock the head stock and turn it exactly
the angle between the gear teeth and then lock it again. Reapeat steps 1
and 2 until you've cut all the teeth. The advantage of this method is that
you can cut a gear of just about any length. You can then cut them off to
the desired size and that will yield a number of individual gears.
FWIW THE standard reference for gear cutting is 'Gear Cutting Practice'
by Colvin and Stanley. My copy is dated 1937.
Joe
There was also a standard controller IC (it was a
mask-programmed
microcontroller, I forget which one, but it was something standard --
maybe 6805-like), which was used in some of the desktop printers. It had
Centronics and 600 baud serial inputs.
The controller in the C= 1520 is a 6500-family masked-programmed
controller and only implemented the C= IEC bus, not serial or
Centronics.
I have the Alps service documentation for this
mechanism, but it doesn't
show the motor pinion separately from the motor.
That's a shame.
I've contemplated what it would take to make a "negative gear" in some
durable material like aluminum and experiment with extrusion molding
of a "slug" which would then be cut down to the right length. Since I
have a few bare Alps mechanisms, I've also contemplated experimentally
turning down the motor shafts if I were to ever find a matching gear
that was the right size except for shaft diameter. Anyone else here
have any ideas on how to solve the perpetual cracked gear dilemma?
-ethan