[Coco] [color computer] CNC with a Coco

[George's Coco Address]

----- Original Message ----- 
From: "Gene Heskett" <gene.heskett at verizon.net>

>
> Now I have to install it next weekend.  For you on your day job, piddly, 
> for
> me, big deal.  Makes me grin from ear to ear just thinking about it. :-)
>
> -- 
> Cheers, Gene

 I no longer work at that sweat shop. I'm now back in the construction 
equipment rental business and making six smackers an hour more. Yeah!!

 I'm about to buy another lot on the east end of my property, so the 
increase in pay is VERY welcome. Soon, I'll be able to build a real shop to 
play in.

> I HAVE TO DO IT ON A COCO FIRST!
>
> It's a coco thing.

:-)  That it is George, that it is.  There is a certain cachet to be able to
say you did it with the coco.  But, there is no way the coco can drive 3
axis's at up to 30,000 step/sec, or turn a nema 22 motor .01 rpm using an 8
step microstepping drive amp, doing it so silently you don't hear the 
stepper
at all, when a single step is 1/1600th of a turn, and keep track of where
every motor is so they all get to the end of the move simultainiously.
I can tell emc2 to move from -1"x, to +3"x, -5"y to +_2"y, and 0z to -3" z, 
at
the same time and the cut will be well within a micron of a straight line
electronically.  Now if you think my little harbor freight mill, even with 
my
mods can actually do that, donbesilly.
----------------

Gene, even if the coco could do that speed, the machine can't. Not enough 
power. The coco can actually drive the steppers as fast as the machine can 
grind. So speed isn't an issue until I build a mill with more power. The 
issue now is the software.
 I've learned a lot working at the machine shop and the stuff that those CNC 
machines are capable of is mind boggling.

 The coco can step the motors just fine. However, doing the math to 
determine the steps of the motors takes a long time.That's the bottleneck in 
this project.
 To do a simple four inch circle, with resolution of 12800 steps/inch takes 
about twenty minutes. I placed an ink pen cartridge in the dremel and drew a 
circle with that. I think I may have gone into a coma waiting for it to draw 
that circle.
  My original intent for this machine was to make tiny parts and this hasn't 
changed. I think it will work fine for making tiny parts. I really believe 
this.

 When I need to make engine blocks or cylinder heads for my Ford truck, then 
it just won't do it. A small gear or sprocket to fit a small steam engine 
should be a piece of cake, if I can get the software right.

  This mill can repeatedly move to within .0005 inch (more or less) to the 
designated position. My test indicator only promises .001 accuracy. Heck, 
that's close enough for me.

  Of course, the coco and the math says it's within .000078125 inch. Your 
Harbor Freight and my Northern Tools mill/lathe  won't even consider this to 
be attainable.

 I'm lucky if I can turn a part within .001 on my lathe. Even luckier if I 
can mill the Z axis within .030. However, I don't even try to make tiny 
parts on that machine.

 As for micro-stepping, yes, a coco can do that to 1/1600th of a turn using 
all eight bits from the data latches I've put on that coco. It's just 
hardware/electronics. However, it would take years for the software to draw 
that circle if we attempted that. What I need is a coco with at least a 
100mhz clock. Then I can make more mistakes in less time.

 With 400 steps per turn and a 1/32 inch pitch on the lead screws give me 
12800 steps per inch. The lead nuts are Teflon and really tight, about an 
inch long. So there isn't much room for slop. The steel in the frame of the 
whole setup will flex more than the lead screw/nut assembly will slop. I'm 
not disappointed with it.
 The X and Y axis both have six inches of travel. The Z axis has about four 
inches travel. This should do nicely for making parts no larger than about 
an inch. The next step, after I get these three axis working correctly, is 
to make the 4 axis. The 4 axis is going to be a rotary table that can turn 
the part(for making gears). At 400 steps/turn and a worm gear, the 
possiblilties are limitless, except for the time it will take the coco to 
turn it. Now it's to the point that I can make a gear in about three hundred 
years. But, it will be a perfect gear.

 Coco lives! PCs die.


George