stepper getting hotttt??

[chrisw765]

hello i just built a 3 axis roughter im using 2 116oz stander sci pacif steppers x/y but on z i bought a thk liner z axes witch has a smaller sized stepper made from " japan servo ltd part number kh42jm2-901" i running a xylotex board witch i can ajust the current from .75a too 2.5a and a 24v supply.i fired the system up for the first time and ill be damed after a year of building it works the too sci pacifc stepper didnt even get warm but after about a 1 min run time the z motor ie the smaller thk one got so hot i could not touch it i shut it down.ajsted the current to min ie .75a at 24v it still got hot so i scalled the 24v back to min 15v still got hot after 1min?? i guess it just dosnt like the high volts even thow the amps arnt there??any help pls could i put 2 resisters in a# and b# to cut currnt/volt to work?? this is a 6 wire stepper i wirred the the too winding in sers for a totel of 7ohms pls help i want to start cuting but i dont want to fry anything more. thx chris

[ger21]

What's the current rating of the motor? Steppers can run hot, usually they are rated up to about 200°F .

[coherent]

sounds like your small stepper is rated much lower than even .75 amps. There are lots of small steppers out there so it's hard to say without exact specs. You can figure the motors rating by using a meter and checking resistance across the motor windings. I'm sure if you do a search you'll find more info on that. Lot's of folks want to put a tiny stepper on their Z, when in practice Z can require nearly as much motor torque when plunging as your other axis's. Once you determine the motors specs, you can use a power resistor to lower the voltage, but I'd put the time effort and money on getting another pac sci or simular motor like you're using if thats working ok. Take advantage that you've got a board that allows adjustment of the voltage to avoid having to mess with resistors, and avoid the hassles. If you want to add resistors to a bi-polor chopper board, look here (under tutorials/bi-polar stepper tutorial) http://www.stepperworld.com/ for info on connecting current limiting resistors to your curcuit. Make sure you use power resistors at the correct rating (the large ceramic or aluminum finned type) otherwise they will overheat and fail.
-marc

[MrBean]

If you have the 6 wire motor, wired in series, making it bipolar (4 wires connecte d to the drive). Then I'm pretty sure you should run the motor at half the rated Amps. Try running the motor with one coil end and the centre tap connected for each phase. That should leave one coil end un-connected on each phase. This should keep the motor cooler with the same settings on the drive.

Regards Terry.....

[Mac T. Knife]

I just googled that part #,,, it's rated .88 amp per phase, and only 33 in-oz of torque,,,, Ouch.

[chrisw765]

yes that correct but its belt reduced before the lead screw its a factor thk setup so tork isnt a problem in fact it feals more locked in then the bigger sci pacific ones ,ok of ther web site its a uni-pollar motor 6 wire 3.42v and 1.2a how ever my contrale boared is 4 wire so i wired it bi-pollar series it put the ohm at 6.8 per phase. according to some info ive seen and also in this post i could wire it to use only one set of coils is bi-pollar half winding but if i did that it would cut my resistance in half for 6.8 to 3.4ohm per phase so lest resistance=more current=more heat ??right or am i wrong and when i set the driver boared for the current setting it ajust for the lower ohm and scale back the pwm lowering the current?? im not sure but according to the specs operating temp is 0-50c with a 70deg alwable clim so 50/122degf plus70=192deg alwable?? if any one know any info pls help im new to cnc but not new to maching. im so close to cut my fist cnc part in fact this is the onlything im waiting on i just dont want to smoke somethink thx chris

[H500]

Chris: Your motor is overheating cuz you're putting in twice the rated power. If you're running bipolar series, you need to cut the rated current in half.

I suggest you run in the bipolar half winding mode at the rated current. That will fix the overheating and also give you much better speed.