Re: retrofitting an older CNC

Just did it!

What type of Shizuoka did you get? A knee mill or a bedmill? They
are A+ amazing machines of super quality.


I bought a Shizuoka B-3V bedmill with a Fanuc 6M controller for
$2500. It has a z axis head with 16 inches of travel and 28 inches
of x travel and 20 inches of Y travel. I got it cheap because the
Fanuc motherboard was missing a axis control chip and the Fujitsu
spindle drive for the 5HP dc spindle motor was fried. (Cost to
replace drive from Shizuoka was $9000!!!).

I ripped out ALL the Fanuc 6M stuff and sold it on ebay for about
$2800, including the servo amps, heh heh. I then bought a 4 quadrant
regenerative KB electronics 5HP dc drive for $350, three gecko G340
drives for $140 each (went with the G340 over the G320 because the
encoders on my 60V dc Fanuc model 0 (x,y) and 90V dc Fanuc model 1
(z) motors are 2500 ticks, TEN THOUSAND in quadrature!!! Couple that
with a 5 pitch ballscrew and you need 100khz steprates to do 120ipm
rapids. That is mighty hard to do in EMC or mach 2 out of the
parallel port, thus the G340 with its internal 2,5, or 10 step input
multiplier. Works for me, and who needs .00002 inch resolution
anyway? :-)

Lets see, what else did I do? I made the whole machine operate from
single phase 220V by using the aforementioned KB spindle drive and
also by purchasing a small (1/2 HP) hitachi variable frequency drive
that takes single phase 220V and outputs three phase 220V. That is
used to run the spindle lubrication pump, which cycles spindle oil
through the geared mill head and back to a small radiator near the
rear of the mill. The mill has a 1:1 and a 6:1 gear reduction,
making it ideal for hogging steel with an insanely huge cutter and
cut depth :-)

I wired up the air solinoid for the spindle drawbar (It is a BT40
taper and uses things on the tools called pull studs). Let me tell
you that is a joy to use (my last machine was a sherline, heh heh).

After talking a bit with Marris at Gecko (amazingly cool guy), We
discovered some noise on the error pin (pin 5) of my drives that was
causing them to fault. When I jumpered pin 5 to pin 7 of each drive
without tying them together I can get 120ipm rapids with acceleration
so fast that it is scary. I am running the 60V motors at about 42
volts and the 90V z axis at 72 volts. Marris told me he has fixed
the error noise problem in the newer g320 and g340 drives so I may
just go ahead and buy the new ones.

I plan to run the encoders back to the computer also, as soon as I
figure out if EMC can support 100khz encoder rates...

Here are a few pics of the mill, along with my first "Hello World"
piece cut into MDF. It is the name of a mmorpg my wife is a software
developer for.

Overall view of the mill:
http://www.skyko.com/cncstuff/P1010035.JPG

View of control box where spindle drive used to be. I was able to
fit the new KB electronics spindle drive, the VFD, the 3 gecko
drives, and the 42V motor supply with room to spare where the old
spindle drive used to reside!!!:
http://www.skyko.com/cncstuff/P1010037.JPG

I really did try to be neat on the wiring, but then I got impatient
and wanted to mill something :-)


Mill cutting MDF (note that I have now found high density foam to
make a much cleaner cut!):
http://www.skyko.com/cncstuff/cutting.JPG

Finished part (except I didn't have a small enough bit to do the
details justice):
http://www.skyko.com/cncstuff/finished.JPG

Let me know if you have questions.

Rick