Re: [CAD_CAM_EDM_DRO] Re: NEW conversion project....

I have three Compumotor nema42 frame motors with encoders. They are
rated at 700 oz.in.. I am in the process of dealing with how to drive
them. I have tested the knee feed with one of my Oatley kit drivers. I
had to set the feed speed on the low side to get things going. The
motors seemed to like getting more voltage. I bought a Vexta driver to
try a chopper drive but it has a bad phase and wouldn't run any motor.
What I would like to do is convert the mosfet Oatley drives to choppers.
My motors are 6 wire and I am running them bipolar series connected so
they might pull as much as 1000 oz.in. with the right driver. I tested
the knee feed by trying to drill a 3/8" hole in a piece of steel(no
pilot hole and dull drill) and caused the belt to jump cog. Probably
need a 1" belt and will most likely use a kevlar belt(no stretch). I
also have a 1850 oz.in. motor that will probably drive the knee with the
Compumotor going to the quill. Same mounts. I just want to do my testing
first.
The downside to using the knee as Z is a lot of the software only allows
a single motor setting. Which means all of the motors share the same
settings. That could slow things down a bit. Hopefully, if that is a
problem, that big honking Sigma motor will allow a faster setting.
My main reason for going with the knee feed involved rigidity. I often
have to bore something that is not a complete circle. The single point
cutter really works the quill feed as the cutter comes in and out of
contact with the work piece. I did notice while doing that type of cut,
that if I cranked the knee as feed with the quill clamped that it was
much easier on the machine. Hence the knee feed. Besides, I can still
use it as a drill press. I guess that i could set tool heights quite
easily also. Just run the tool down till it touches and lock it. There
is a commercial CNC website that listed the pro's and con's of knee
feed and that convinced me to give it a try.