[Coco] [Color Computer] [coco] Coco CNC
George's Coco Address
yahoo at dvdplayersonly.com
Mon Feb 12 00:55:18 EST 2007
I've been working on my Coco powered "Tiny CNC" machine this weekend.
What a task! I discovered that the axis designations were all messed up.
(You learn a LOT when working in a machine shop)
All three were wrong. X, Y and Z were wrong. So I renamed them and in the
process, I lost the driver(B09 driver) for the REAL Y axis.
No problem, I thought. Just rename the X or Z axis driver. Well, it didn't
work. After two days, I discover several problem with my hardware that
proved that the port for the Y axis was wired incorrectly, the cable that
connected it was also wired incorectly and the software to correct this
error is now lost.
No matter about the software. I repaired my mistakes with the hardware and
now the software to drive the servos works correctly. I can swap the cables
to each of the servos and it works correctly.
Since I've been working at a machine shop, I was forced to buy some
precision instruments such as a dial caliper. My old vernier caliper was not
acceptable at work.
Hmm. I really can't see any accuracy difference except for the fact that
the dial is easier to read.
Anyway..... Math always works......
All three lead screws are 32 TPI. The three servos are 200 steps per inch.
Doing the math, this comes to 6400 steps per inch, or precision to
Not bad, but not as good as what I work with at my job.
I've learned that offsets and HOME are important. (I did have trouble
figuring into this on my coco)
Originally and even now, I use brute force to drive the axis into a
mechanical stop. The stepping motor would stall there and hum until the
software stopped driving it. At that time, I set the software to assume it
was HOME. Actually, it works! However, it isn't elegant. So I'll add some
micro switches to the sytem to fix this. Besides, I can move that switch to
a more convenient place for each project.
My coco takes a long time to step these motors to where they are supposed
to be. Basic09 is a lot faster than RS Basic, but it doesn't hold a candle
to ML. .....Someday, maybe!
I envy you folks that can "whip up an ML program".
So far, I can move each of the three axis from home to the limit and back
and my dial indicator reports a return of exactly zero. This implies that my
stepping motors, power transistors, software and math are working correctly.
The only problem is finding home. The micro switches will take care of
Backlash on each of the three axis are different. The Y axis is only about
two steps on the stepping motor. This is incredible!. However, I took
extreme care to minimize backlash when building this thing. I won't go into
detail on how I did this until later.
I've learned at work, that extreme brute force and extreme mass of
machinery is important to get the results necessary. Heavy metal is good!
However, it's expensive. The machines that I work with cost a TON of money.
We're talking 600 thousand dollars for a small one. My first 4k coco was
$300 and took a couple of pay checks to pay for it. So, I won't expect to do
what those monsters can do. I just want to make some small gears, sprockets
and pulleys. Later, I want to do some 3D stufff, small things.
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