[Coco] [color computer] CNC with a Coco

[George's Coco Address]

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

> I replaced the z axis screw on mine with a 1/2" 10 tpi acme with two nuts 
> to
> adjust the backlash.  But the head itself rocks a teeny bit on a direction
> reversal, limiting how well I can compensate the backlash in software.  If 
> I
> always move the z in the same direction during the cut when making 3d 
> parts,
> its well within a thousandth.  Do a reverse at the top of a crown and you 
> can
> catch a fingernail on the ridge. :(

 A couple of months ago, I found an outfit that has a ball-nut and lead 
screw at a very affordable price. When I find it again, I'll post it for 
you. I think it was a 24 pitch. With a ball nut/screw, your steppers need 
some sort of brake to keep it from moving. They are virtually frictionless 
and will turn under load. My lathe/mill is so sloppy, it isn't worth the 
effort to convert from ACME to Ball.

>
> But ISTR you are using a Dremel grinder, and its spindle accuracy is so 
> bad
> there is no real use trying for .001" accuracy.
>
 This Dremel is fairly elegant inasmuch as the chuck is mounted in ball 
bearings and driven from the motor through a flexible coupling. However, I'm 
thinking of using the dremel to drive a new head via gear or belt reduction 
to reduce the speed and increase the torque. This should stop the bits from 
glowing a dull red and live longer. 25 thousand RPM is too darned fast.

> As for that lathe, 2 or 3 thou at best, the carriage fits the ways way too
> sloppily.  Not to mention the tailstocks height is off about .020" even if
> set for min taper on a long turn supported at both ends.  Correcting for 
> that
> make life very confusing.
>

Mine uses a dovetail type of slideways and they totally suck. If I get them 
tight enough to reduce the slop, then I can barely move them. There are ball 
type slideways but I can't afford that now.


>
>> Coco lives! PCs die.
>
> No, PC's running winderz die.  Running linux they're fine, cuz they are 
> doing
> what YOU want them to do, and NOT what Bill might want them to do behind 
> your
> back, like phoning home with the contents of the firefox password file,
> including all your bank numbers...

 I've replaced a lot of motherboards on my PCs, but only once have I had a 
Coco just up and die. I've killed a few of them myself.

 When I kill one, it's usually totally shot. Too many parts to change and 
another coco is cheaper and easier.  I have repaired a coco a few times. 
Usually it's a CPU or a PIA. That was back when you could buy them new and 
they were expensive. Now, I just will just go out to my storage shed and get 
another one. However, I haven't killed a coco in years.....

Knock wood.

George