singing motors, no torque

i have a 3 axis mill with Sanyo Denki 103-845-6741 steppers. the labels read: 12-300volts 6.7 amp nema 34. holding torque 486 ounce inches. rotor inertia=21.5 oz/inch .winding inductance=2 mh. I am also using gecko g201s with the current set resistor at 270k or 7 amps. The power supply is running at 40 v @5 amps. I am also using turbocnc v4. The problem is i have no torque, or more correctly i am missing steps like mad. And one of the motors is singing like mad. I find the quotation 12-300 volts on the label to be pretty strange. Thats a huge range. Does anyone know what would be a correct current range for these motors? Also do you think the singing , low torque and missing steps are related? DUH!! i would assume thats a given. One last thing...I have been running it from windows as i havent been able to get it to run from DOS. I know thats alot of suspect variables but i am pulling my hair out trying to get this thing running. MARISS!!! Are you out there!!?

Randy,
"One last thing...I have been running it from windows as i havent been able to get it to run from DOS."
This is the biggest problem you have! Windows has a lot of overhead and you cannot get a good stream of data out of the port this way:{(
Which flavor of windows are you running? If XP, you will have to find a disk image for dos and boot up with that as XP is not dos based. If you are running 9x, you can tap the F8 key during boot up to get to the menu and then select command prompt only. There are other ways, but my favorite is to use "Tweak-UI" (a power tool) and set it up to have the boot menu come up at each re-boot. On my machine in the shop, (98SE), it is configured to start in dos all the time and when I need windows, I enter the command "win" and it will load windows. Then to run TCNC, I re-boot to be sure NO extraneous junk is running either. You must have a clean autoexec and config sys file to eliminate problems.

Bubba

Running TCNC from Windows will cause messed steps and rough running. What version of Windows? Also, you should never run steppers over their rated current. Run them at a little less, like 6.5a. Too much current will cause damage.