[Coco] [Color Computer] [coco] Coco CNC

[George's Coco Address]

Okay!

 I've been working on my Coco powered "Tiny CNC" machine this weekend.

 Whew!

 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 
.00015625.

 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)

FINDING HOME:
 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 
this.

 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.

 More later....



George