[Applesupnorth]

Hi there, I've been lurking around this sight for a couple years now, and figured it was time to finally actually post a question. I purchased a ModularCNC Mini-mill kit off ebay a couple years ago to play with while I got around to building my own 3 axis router. Here are the stats to everything I am running.

Vextra PK266M-01A .9 degree steppers 166 oz
Item # PK266M-01A, Stepping Motor on Oriental Motor U.S.A. Corp.

Univelop 5 Axis Driver
http://www.cncgeeker.com/images/manu...rCNCGeeker.pdf

1- 24V 25Amp PSU for the steppers
1- 12V 10Amp PSU for the BOB & cooling fans
ACME leadscrews 1/2-10 single start

I got the 5 axis driver because I got a MUCH better deal on it compared to the 3 or 4 axis models, which gives me 2 spare driver cards. I plan on upgrading to 5 start screws once $$$ allows. Ok, now that I have given a little background here is the issue.

Before I get into this, I just want to say, I KNEW NOTHING about steppers when I bought these....now after countless hours of research I think they are the problem.

When I have these steppers and electronics hooked to the ModCNC minimill, I was only able to produce 20IPM with no load(15-18IPM while cutting wood, very shallow cuts). I didn't think this seemed very fast at all, but because of only having 6"x4" of travel it wasn't too bad. Now that I have moved these steppers/drivers to my new router which has 20"x16", it seems SO slow! LOL. My new machine is WAY easier to turn the leadscrews manually, it is VERY smooth, but yet I can't get any more speed out of the machine.. Still stuck at 20 MAX. I have tried playing with all the settings in MACH3, and switching between all microstepping settings on the drivers, and full step gives the best speed/torque without stalling. I see that my motors seem to have a WAY WAY higher inductance than many other motors on the market...is this where I am losing my speed??? I've read that higher voltage=higher speed. Using the MAX voltage calculation of Inductance sqrt*32= 228volts.....Yet these motors get REALLY hot at 27volts(24v PSU cranked up to max), so going to a bigger PSU, 36V is driver max, seems like it would just create MORE heat and probably won't give much more speed.. Am I totally off on this? I basically guessed when I bought everything b4, and looked at prices more than stats of everything.. Do I need to buy new steppers or am I setting something up wrong?? I'd like to get up into the 50IPM range while cutting... I don't want to pick the wrong equip again, so if someone could suggest motors and/or drivers with reasonable pricing that would be great. Ok, I guess I am done rambling on, so THX to anyone that can help..

[jschmitt]

These steppers are .9 degree instead of 1.8 degree. you need 400 step per rev instead of the normal 200/rev. You didn't say if you were microstepping with the drive. try half or quarterstepping to see if that helps.

[Applesupnorth]

Ya, I have Mach3 set up with 400steps/rev in mind, and have tried microstepping with 1/2,1/4/,1/8, and Full, which gives the best results. I have adjusted the steps/in in Mach3 when trying these microstepping settings on the drivers. It drives me crazy that I can't get this thing to turn any faster...It is SO SO easy to turn my axis' by hand..I've got them so perfectly aligned. The fact that I gained NO speed when going from my little MiniMill(which was hard to turn the axis) basically tells me, that I was already at the highest speed these motors were capable of at my given Voltage, and I'm not plannin on pumping 220VDC into them any time soon. It almost has to be the HIGH inductance giving me trouble...I think if I gave it the crazy high voltage it would give me the speed.... I think I'm gonna have to just buy new motors, and possibly drivers too. The 2.5amp/phase of the drivers kinda sucks, seems like every 300 oz/in stepper needs atleast 3amps, so I am very limited there.. Should just quit bein' so cheap and buy some low inductance 300+ steppers and Gecko 540s..OUCH $$$ Grrr live and learn I guess...I mean spend and learn

Anyone else have any ideas that I might be missing? Thx in advance

[doorknob]

How much current have you set the driver to deliver?

Have you hooked up your 6-wire motors according to the diagram on page 8 of the driver manual?

If so, you may find that you can improve your motor speed by hooking up "half coils" instead of "full coils". That will help by reducing the winding inductance substantially. See Figure 9 of Support.

[Applesupnorth]

Thanks for the advice doorknob. I will try that tonight and see what happens.. I remember looking on this page when I originally wired my system, and now that I know a little more about things...this may be the issue. It says having them wired Bi-polar series leads to 4X the inductance and 1.4X the torque, and I think I did it that way because of seeing the 1.4x the torque, but if I don't have the Volts to give them, the torque won't be gained because the inductance is so high.. Am I thinking correctly here?? I'll let you know what happens! I'm a little excited here! LOL

UniPolar vs BiPolar wiring schemes for 2-phase Stepper Motors

OH, also....my drivers don't seem to have adjustable current settings...No pots, or anything like that.... They didn't come with resistors either, so I'm guessing that they are just getting the FULL current the drivers can deliver??? which is 2.5 amps/phase.... Man, this has me really thinking I need new equip. grrr

[jaypeeshinmac]

Hello i had this TAKAMAZ machine model X-10 and i want to buy a full type collet chuck.Where could i find a supplier for this machine?im from the PHILIPPINES.

[doorknob]

Am I thinking correctly here??

Yes, I believe that you are on the right track.

OH, also....my drivers don't seem to have adjustable current settings...No pots, or anything like that.... They didn't come with resistors either, so I'm guessing that they are just getting the FULL current the drivers can deliver??? which is 2.5 amps/phase.... Man, this has me really thinking I need new equip. grrr

If your driver is trying to push 2.5 amps through each phase, that would help to explain why those motors are getting so hot.

[aarggh]

I have a set of these same drivers, and I must say they don't handle the heat too well, as the heatsinks (what there is of it) are pretty crap to be honest, and especially, take note of the warning about disconnecting any of the leads with power applied, you will more than likely blow the chip. I did!

Apart from that, they aren't too bad at all. I would though ensure you have a fan blowing across the heatsinks as they can get very, very hot.

cheers,
Ian

[H500]

Bipolar half coil will increase the speed.

Ask the vendor how to set the current. I'm sure they were not dumb enough to design it with no provisions for that. Otherwise, you will burn out your motors eventually.

[wildwestpat]

Just a thought - check the chip type - almost certain to be Toshiba TB6560 - if so then the current is set by the two large resistors on the driver card. The values are chosen to give half a volt feed back to the chip at the desired current. You can check this from the colour bands on those resistors and using Ohms law half a volt divided by the resistor value will be the motor maximum out put current. i.e. 0.2 ohms for 2.5 amps.

The resistors should be close tolerance to avoid unequal magnetising currents in the windings.

Suggest you consult the chip makers catalogue data sheet for heat-sink requirements.

Stepper motors by their nature run hot and this is why modern drivers include the current reduction when not stepping. The motor data sheet gives the temperature limit.

For the low value resistors here is a link to the colour code :- http://www.hobby-hour.com/electronics/e24-resistors.php

Regards - Pat