[Coco] [coco] Coco CNC

[George Ramsower]

From: "Gene Heskett"
>
> IMO that chuck is a disaster with a ticket to happen.  Been there, done 
> that,
> had to find the bit where it flew off into the grass while carving wood 
> with
> it and one of those blue colored carbide rasp bits Lowes has.

 In a standard machine shop, using a milling tool in a chuck is a no-no. 
Not because they can come loose, but because the lateral forces tear them 
up.
 A collet doesn't have this issue as the tool is pretty well supported by 
the tool holder.
>
>>But as I thought on it, I realized that it would not then
>>be able to reach the slot I'm working on. The chuck does extend the length
>>of the dremmel.
>
> Humm, can the Dremel be lowered in the clamps?
>

 I could have done that but as I said below, the slot is cut and now the 
cutting is moving up and the extension isn't as bad.
 Moving the dremmel down can be done by inverting the bars it's mounted to. 
The bars that ride on the roller bearings. It would not have been easy to do 
because getting things aligned and adjusted, remounting the lead screw and 
motor and all that would have been objectionable. I'm lazy... okay?

>>Other than that, this machine worked as well as I expected.
>>The only weak point is the dremmel, as I knew this when I began this
>>project. This is why I said in an earlier post that the dremmel may become
>>only the drive motor for a new mill head. The work I did with it on the 
>>lead
>>screw slot turned out pretty good.
>> The side to side milling had issues, because the Z axis was extended far
>>beyond safe limits because it was actally milling below the slide surface,
>>which in turn began 1/4 inch below the designed work surface. So flexing 
>>in
>>the whole affair is considerable. I'll have to go really slow and make 
>>small
>>cuts to make the pocket for the lead nut.

> The coco can't run that fast of course as it probably couldn't add a motor
> output stage to the hsync IRQ, not enough time and the vsync IRQ is too 
> slow
> but would do for development of the routine.  I believe there is a timer 
> in
> the gime that could be used for this however. I believe it can count 
> either e
> clocks, or hsyncs to set its speed.  If it could count say 50 hsyncs and 
> fire
> off your the motor output loop it might be more usable.  Get that working 
> to
> drive the motor steadily, in any combination of simultainious motions and
> then reduce that count to gain maximum speed until the keyboard response 
> or
> what ever video tally for position you might cobble up starts to get
> noticeably sluggish.
>
 Quite a few years ago, I met a man that had a sign shop. He had a CNC 
machine that cut out text into such things as name plates, the formica type 
you see on doors and on desks and such. It ran from a '286 machine. It's my 
understanding that the '286 wasn't really that much faster than a 2mhz coco. 
However, this thing could spin up those steppers until they sang suprano. I 
suppose the plug-in card did most of the work of stepping and might even 
have done some of the math and other things. Who knows?
 He made the plaque for my main coco and did it for free.  It was my first 
experience on CNC stuff. I think it was fifteen to twenty years ago.
 Now that I think on this, it's hard to believe I've been using that coco 
for more than this length of time. WOW! That SCSI drive and the coco should 
be in the Guiness Book of Records, huh?

George