The CNC machine we have up and running has a positional accuracy of
+/- .001 inch. Most of the cost of these things goes into making them
rock-solid, repeatable, and precise. Our little baby is built for
accuracy. We have two versions. One is BIG (the repeatability goes
down just because of expansion/contraction). The other is quite
small and is used for precision engraving of jewelry, among other things.
We can actually reproduce photographs on jewelry with this thing
and a diamond engraving tip.

The small unit has a travel of about six inches in XY and an inch
in the Z direction. Jewelry tends to be small.

It helps when you have friends who are machinists!

If we were designing something like a vinyl cutter, then we would
not need the accuracy we went for. Accuracy costs money.

Fr. Tom McGahee

-----Original Message-----
From: Randy A. <Cnc002@AOL.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Friday, February 18, 2000 4:35 PM
Subject: Re: CNC machine language


>I didn't see the original posting.  If he already has the better part of
his
>controller designed then yes, you are correct.  I assume that no great
>accuracy etc. is required just the cutting of shapes etc.  The only
>experience I have had with controllers of this type was around 9 or 10
years
>ago.  They were being used on machines that were extremely lightweight and
>for cutting vinyl material to be used in signs, trophies etc.  The biggest
>problem seemed to be that they couldn't cut closer than +/- .010 to .020
>inches.
>
>If, however there have been improvements in this type of control (PIC or
>otherwise) it would be of great interest to me.  Regarding the use of
>Windows, it isn't the program that causes the problems, it is Windows
itself.
> For that reason you must use either DOS or Windows NT or now, of course,
>Windows 2000 will work fine.  Windows 95/98 is just too unstable to be safe
>for use in running any type of machine.
>
>Randy A.
>