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

[George's Coco Address]

David,

 I'm not really sure what I'm talking about either. I'm learning this stuff 
as I go.



----- Original Message ----- 
From: "David Roper"
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Monday, February 12, 2007 12:10 AM
Subject: Re: [Coco] [Color Computer] [coco] Coco CNC


> Hi George,
>
> I don't have a clue what you're talking about, but it was an interesting
> read, none-the-less!
>
> Kind regards,
> David
>
> George's Coco Address 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
>>
>>
>>
>>
>>
>>
>>
>
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