[Coco] Proto CoCo

[Gene Heskett]

On Monday 28 August 2006 12:33, Mike Pepe wrote:
>jdaggett at gate.net wrote:
>> Gene
>>
>> I   have come across a vendor that will do PCBs 2 sided with solder
>> mask and silk screen for reasonable price. Requirements that the boards
>> need to be less than or equal to 20 square inches and minimum order is
>> 5.
>>
>> It would not take long to design a 4x5 card with the COCO 40 pin PCB
>> pattern with a bunch of holes and/or pads for smt parts. Could do
>> either or both.
>>
>> I would say that a 4x5 card with holes for breadboarding along with
>> busses for +5VDC,  +12VDC, -12VDC and ground would be in the $25 to $35
>> range. Hardest part is to route the board for the connector to fit in
>> to the MPI or expansion slot. Having a PCB house do that would increase
>> board cost significantly. Also gold contacts also increase costs.
>>
>> james
>
>I'd say with Gene's woodworking ability, a jig and a flush-cut bit in a
>router wouldn't be too hard to come up with.
>
>:)

Who needs flushcut?  Or a jig other than to hold it in a repeatable 
position from one board to the next?  Thats what cnc does, accurately 
driving the cutting bit to near .0001" accuracies, and dremel sells little 
1/8" solid carbide bits for, called grout routing bits.  I've carved lots 
of steel parts with a couple of them.  They also have one that tapers 1/8" 
down to a 1/16" roundnose, but in brass I found it just plows up the edge 
of the groove way above the surface of the brass if I try for more than 
about .003" of depth per cutter pass, like when carving brass nameplates 
etc.  So using that bit is a bit like watching paint dry or grass grow for 
a "President" nameplate.  In FR4 pcb material, I expect a pass with a 14" 
mill bastard file at an angle across the edges might be in order to remove 
the glass hair left at the board/air interfaces.

The biggest problem with the micromill is the maximum spindle speed of 
about 2400 rpm.  It needs another zero on the right for some of this 
stuff.  That would equal coolant on the walls, and is why many of the cnc 
mills (and lathes) you see today are running in a custom glued up 
plexiglass tub that contains the throwoff.  I use hand applied cutting oil 
for steel, but the power fed coolants are often 95% water with some sort 
of an emulsifying agent.  It drips/runs off, is caught, settled out and 
re-used of course in those factory floor environments, often running 24/7 
with the lights out.  Machines even handle the pallet loading/unloading, 
sometimes from bins of raw castings all the way to in boxes on the 
shelves, labeled and ready to pick and ship.

>
>-Mike

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
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Copyright 2006 by Maurice Eugene Heskett, all rights reserved.