[Coco] Little Johns 8 slot MPI

[Gene Heskett]

On Saturday 21 September 2013 13:04:47 Gene Heskett did opine:

> On Saturday 21 September 2013 12:01:09 Louis Ciotti did opine:
> > How about all the files?   Would like to see them myself, both
> > schematic and layout.
> 
> I found part 2, at
> <http://www.coco3.com/community/2010/07/this-is-part-2-
> of-3-of-an-8-slot-mpi-multi-pak-interface-design-for-my-friends-at-coco
> 3-
> com-andor-the-maltedmedia-list-members-from-your-friend-johngimechip-co
> m/>
> 
> There is a link there to the part 1 files I already have, but it turns
> out part 2 has the whole mary ann in it.
> 
> But when loaded into eagle, I find the .brd is 6.05" wide front to back
> and I would need about 1.5" more Y axis travel than my mill has.  So,
> short of building a new machine, which I might not have time to finish,
> I can't make it. On ebay, the cheapest I can get a machine suitable for
> this accuracy OOTB because it has ball screws is $1050, FOB Hong Kong,
> the only one I could find with ball screws for drive.  Ouch...  I could
> do it, but I'd have to make lots of boards to pay for that.  Unforch,
> it comes /with/ the motors drivers, something I really don't need if I
> switch cabling, or I'd need to find another atom based computer kit &
> monitor, another $350 & who knows what customs would want coming in
> from Hong Kong.  Thats a long boat & truck ride to WV, USA.
> 
> The $650 model is big enough, but has 2 start trapezoidal screws,
> whatever that means, I think 2 threads per revolution of the screw.
> They might be accurate enough if the nuts were molded in place out of
> delrin, but they would also use 90% of the motors to turn them, where
> ball screws are very low friction.  The molded in place delrin nuts
> are, according to what I've read very long lasting, like ball nuts if
> kept clean.  The spindle motor has an ER11 collet and only spins 8
> grand where the bigger one spins at 20 grand max.  I can't justify it,
> but I'm still thinking. ;-)

As a PS to that if I was to buy another such machine, I would be looking 
for a 4 axis about that width, but about 4 feet long, with lots more z 
motion, z being up and down.  Then toss in a 5th axis to tilt the Z, and it 
would be big enough to carve a thumbhole style gunstock when it wasn't 
carving PCB's.  Unforch, with the required rigidity of the longer frames 
needed, the price goes up at about the cube of the length. :( I've got too 
darned many hobbies, if thats possible. :)
[...]
Cheers, Gene
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