[Coco] [Color Computer] Re: [coco] Coco CNC

[Paul T. Barton]

--- In ColorComputer at yahoogroups.com, "George's Coco Address"
<yahoo at ...> wrote:
>
> 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
>


George,

You may find that microswitches "never" click at the same location.
Found this out when working with them at Tektronix, years ago.

Opticals could work.

Paul