Setting up stepper motor drivers

**croy** · 26-02-2012

Hi, i need some help/advice on setting up stepper drives, Currently trying to CNC my lathe i have a 14mm dia x 4mm pitch ballscrew for the leadscrew and a 8mm dia x 2mm pitch for the cross slide.

i have a Nema 23 on the leadscrew and a nema 17 on the cross-slide. these are driven MSD542's powered by a 50V DC 10A power supply.

I have setup the micro drivers to 8 microsteps, Is this possible too much? as the motors sound rough.

Some background ( i had the drives etc working on the old 8 TPI leadscrew) so there is no problemas with power motors or drivers..

Thanks
Roy

**John S** · 26-02-2012

Roy,
Have you tried any other settings ?
How are you connecting the motors to the screws ? Oldhams or lovejaw type couplings ?

**JAZZCNC** · 26-02-2012

50V supply on 50V drive is bad idea.! . . . your in danger of back emf frying them on de-acceleration. On a lathe it probably won't be a massive issue because it wont be de-accelerating from high feeds but @50V your on the edge.!!

First I would double, triple check all your wiring, esp the motors phase connections.

Check your amps are not set too high on drive, then like john says try other settings.

What model motors are they.?
How have you got the motors wired.? Parallel or series or unipolar.

**croy** · 26-02-2012

I think it is just my settings. as the only thing that changed was to replace the myford leadscrew with a ballscrew.

coupled with a belt 20 tooth on the motor and 40 tooth on the screw.

Originally Posted by JAZZCNC

50V supply on 50V drive is bad idea.! . . . your in danger of back emf frying them on de-acceleration. On a lathe it probably won't be a massive issue because it wont be de-accelerating from high feeds but @50V your on the edge.!!

First I would double, triple check all your wiring, esp the motors phase connections.

Check your amps are not set too high on drive, then like john says try other settings.

What model motors are they.?
How have you got the motors wired.? Parallel or series or unipolar.

**JAZZCNC** · 26-02-2012

Originally Posted by croy

I think it is just my settings. as the only thing that changed was to replace the myford leadscrew with a ballscrew.

coupled with a belt 20 tooth on the motor and 40 tooth on the screw.

Please dont take this wrong way but you have changed the steps per to take into account the gearing.?

**croy** · 26-02-2012

Hi No i dont think i have.

Dont worry i am not offended just grateful for the help

**croy** · 26-02-2012

Thanks John,

i been fiddling with the settings in MACH since the screw changed from 8TPI to 4mm pitch. so i am guessing this is the area of problem.

PS, assembling the PCB this afternoon to test. will keep you posted.

Originally Posted by John S

Roy,
Have you tried any other settings ?
How are you connecting the motors to the screws ? Oldhams or lovejaw type couplings ?

**John S** · 26-02-2012

Try different velocity and acceleration settings in Mach

**irving2008** · 24-09-2012

John,

The z-axis on a lathe is always a challenge. Have a look at this thread http://www.mycncuk.com/forums/lathe-...onversion.html to see one approach that should work on any lathe...

**JohnHaine** · 25-09-2012

Hello Roy,

That could be interesting! I am thinking of fitting the leadscrew in the normal location and making a replacement apron (really just a bracket) to carry the nut. What pattern nut do you have please? Problem with my approach is that because the L/S is slightly recessed into a kind of channel in the bed there doesn't seem to be much room for a flanged nut and I would have to use the type that has a threaded spigot. And how much would you want?

Regards, John.