[awetmore]

I have a 3 axis Taig with a Super-Tech driver. I bought a rotary table and would like to be able to use all 4 axis at once. I'm also jealous of the higher rapid rates that people seem to get with the G540.

My stepper motors are Pacific Scientific Powermax II P22NRXB-LDN-NS-00. That means they are 214oz-in torque when wired bipolar. The other specs are:
2.3amps
1.52ohms phase resistance
8.4mH (typical)

I'm wondering if the 24 volt power supply that came with my current controller is good enough, or if I'll want to upgrade to a 48 volt power supply.

The Gecko docs say that I want a PSU voltage that is at most 32 times the sqrt(mH). For my motors that would be 92 volts, which is well above the G540 rating.

How can I figure out my maximum rapid speeds to make the decision between a 24v and 48v power supply?

[Crevice Reamer]

Hi awetmore. Arnold? Arthur? Andie, Audi? Allan? Anthony?

You don't HAVE to upgrade the 24V--The G540 will give way better performance even with that, but double the Voltage equals double the power. The idea is to get the Voltage as high as possible, but not to exceed 50V.

Stepper motors do not run on steady current, but pulses of current. Higher Voltage lets the coils charge faster during a pulse and hence more speed.

Your motors will run at LEAST twice as fast with 48V. If you get the Keling 7.3A PSU you can even adjust the Voltage up to the max 50V.

CR.

[Jeff-Birt]

How can I figure out my maximum rapid speeds to make the decision between a 24v and 48v power supply?

The short answer is you won't be able to come up with a rock solid number as there are too many unknowns. The stepper motors, power supply, drivers and machine all have to be well matched for best performance. Since the Taig has 20 TPI screws you have a tremendous amount of built in drive reduction and a 'fast' motor is more important than a 'torquey' motor.

You have some well made motors, that are a higher inductance than ideal for the G540/Taig combination but still should offer good performance. With my G540, MeanWell 48V power supply, and 166 oz-in motors I can easily do 100 IPM rapids. (I've posted some Youtube videos of it several times on the forum.) But keep it tuned to 40 IPM as I have no need to traveling faster than that with a 10k RPM spindle (guys that cut wax with high speed spindles can benefit from higher feed rates.) I would suspect that you should be able to do 40-50IPM with your motors.

I would suggest the 48V supply due to the high inductance of your motors. But it would be easy enough to try it with your existing power supply and see if the performance is what you need. As CR mentioned you do NOT need a huge power supply, the G540 has a built in 7A very fast blowing fuse so you know that is the limit. A good quality switch type supply between 300 and 350 watts is a good choice. For a linear unregulated supply you have to go with a unit about 30% larger to keep the output voltage at a reasonable level over the entire range of current draw.

With all of this talk about power supplies and G540s lets not forgot about the PC. With a Taig and G540 and typical 1.8 degree/step steppers you wind up with 40,000 steps/inch! If your PC won't put out a stable pulse stream from the parallel port then your fancy new G540 won't be able to live up to its full potential.

With 40,000 steps/inch at 50IPM that is 40,000steps/inch * 50IPM = 2 million steps/min or 33,333 steps second. So your PC will need to be able to provide a pulse stream at least that fast. (My personal choice is to use a SmoothStepper.)

[Andre' B]

Listen to what Jeff says.

A good while ago I ordered a 540, and setup an old computer with EMC2. I pulled a 24 volt power supply and some steppers out of the junk box. The steppers were exactly the ones Mariss says to stay away from. They were some old blue, round, 6 wire, Slo Sin brand, 1 amp at 5 volts, 32 in-oz.
Played with that for a while with machine concepts and hardware store threaded rod. Used it to convince the money people where I work that instead of just replacing an old mill we really should get a better machine a quick change fixtureing system and some custom automation, and the extra 150 grand would be worth it. Sometimes takes more then words and a drawing to get the idea across, a functioning model goes a long way.

Anyway then I ordered a Taig CR and put the above motors and stuff on it. Managed to get a usable 10IPM out of X and Y and after counter weighting the motor it would do 6IPM on Z.

Run that for a while and then about 1 1/2 weeks ago order 4 166 motors and a 48V power supply from Jeff.
Now I can get 60IPM on X and Y limited by the computer, and 40 on Z, could maybe use a little bigger motor for Z but with the short travels of the Taig it does not matter much. I did back X and Y down to 50 because the mill just does not sound happy going that fast.

[Jeff-Birt]

I have my Z tuned the same as X and Y, never had a problem with Z except a few caused by a dull bit or excessive feed rates. No counterweight should be required either. Your pulse stream not being smooth will create more problems the faster you try and go. If you hear any rhythmic ticking sounds it is most like a pulse stream issue. You might try lowering the acceleration on Z but as you say the Z axis is short and most of the time you will be limited by the plunge rate of the cutter not the rapid rate of the Z axis.