Re: Mill retro-fit info available...

Accuracy... Well, for the 2/100,000ths, I used a friends Starrett
Bench Micrometer accurate to 5/1,000,000ths ($800 for an indicator is
a little rich for my blood). I then cut some T-6061 Aluminium on
either side with an small end-mill (about 3 inches apart), and
measured the distance between the cuts on either side. Did this a
few times and took an average. Then did it again with the same
already cut part to check for repeatability. Just the surface
distorion was a factor that had to aceraged as well. I had to play
with backlash settings quite a bit to get it repeatable, but in the
end I nailed it. So the 2/100,000ths accuracy is over a range of 3
inches. I noticed that accuracy sightly degraded when repeative cuts
were made further apart (around 5 inches or more, to about
4/100,000ths). Although the servo drives would start to compensate
for progressive error over time and improve the accuracy. Feedrate
between moves was approx. 100ipm.

For the 500IPM, the machine is rated to 472IPM, to verify this I used
a yard stick and stop watch with the switchs remotely wired at each
end. I doubted I'll get 2/100,000ths accuracy when it's flying
around at 500ipm, I have not performed that test yet.

Ironically, I've got a hobby machine (a Shop Task) that I converted
to CNC with stepper motors and Ah-Ha system to drive it. It was
pretty accurate for a small machine (2/10,000ths). However after
adding ball-screws so it would run faster... I could only get
accuracy to about 4/500ths repeatable accuracy! So I've got some
work to do on that machine!


--Scott

--- In CAD_CAM_EDM_DRO@y..., Matt Shaver <mshaver@e...> wrote:
> scottleatham wrote:
>
> > Galil: I'd like to talk with people that use Galil controllers!
I
> > like the card a lot, I'm getting incredible speed and accuracy on
my
> > machine, close to 2/100,000ths of an inch at about 500 ipm!
>
> This is very impressive! How did you measure it?
>
> Matt