Re: [CAD_CAM_EDM_DRO] motor inteference?/loosing steps

flashboiler wrote:

>
> Hello, I'm new to the group and cnc thanks in advance for any help!
>
> I recently bought a taig mill with sherline steppers, denvercnc
> control and running Mach2 controller on winXP home 2400Mhz dell
> computer.
>
> I'm having problems with what I believe is interference from the
> spindle motor or general A/C noise.
>
> If I leave the mill spindle running and have Mach2 doing nothing
> (holding the steppers at 0,0,0 and wait about 2 minutes and then
> check my handwheel zeros the steppers will have moved .002 to .035
> (or more). Mach2 still says 0,0,0. I can observe the
> servos "glitching" randomly, but they always seem to move in one
> direction. If I switch the mill motor on and off or switch my
> Sherline lathe motor on and off nearby 90% of the time one or more
> steppers will glitch.
>
> I tried running power from a different circuit down to the motor
> (extension cord) this seemed to help a little (or maybe wishfull
> thinking?) but the problem is still there.
>
> Yesterday I mounted a sherline motor/head/speed control on the mill
> and the problem got worse. It's there with the Taig or Sherline
> motor though.
>
> Should I try grounding my mill? Should I ground mill, controller,
> computer all to the same point?
>
> Thanks for any suggestions,
> Andy

I had a similar problem with my Sherline 5410 mill. Mostly the Z axis
would add steps when the X and Y axes were running. If I turned off the
spindle then no problem. Running the spindle at about 3/4 full speed
seemed to make the problem go away too. Running the spindle at a lower
speed is only a quick fix to get some work done right away.

The long term fix for me was to replace the parallel port cable from
computer to driver electronics. My old cable was 6 feet long and had one
ground wire for the 8 ground pins. My new cable is 3 feet long and has a
wire for every pin. The primary problem was inadequate ground wireing
for signals. Since the cable acts like an antenna for motor noise, use
the shortest cable necessary to do the job.

BTW, I would also see the Z axis jump amd spinlde slow down briefly
whenever I turned on the vacuum cleaner. I am guessing htat the power
surge of the vacuum cleaner generated some noise that entered the
parllel cable. Some of those glitches were interpreted as step pulses.

Anyway, nothing special about the new cable. Meets some IEEE standard
for less than $10. The old cable was about 1/4 inch diameter. The new
cable more like 3/8 inch diameter.

Open the cable connector to see how it is wired. There should be one
wire on each pin at the computer end. A total of 25 wires.

Or use an ohm meter. Disconnect the cable at both ends. Connect ohmmeter
to pins 1 and 2, then 1 and 3, then 1 and 4 up to 1 and 25. Then try
pairs 2 and 3, 2 and 4, 2 and 5, up to 2 and 25. Do this for every pair
of pins. No two pins should be connected if each has a seperate wire.

If any two pins are connected then the manufacturer went cheap on
wiring. This often happens with the cheap cable packaged with a printer.

Tom Hubin
thubin@...