RPM on steppers & StepServos - Page 4

# Thread: RPM on steppers & StepServos

1. ## Re: RPM on steppers & StepServos

Originally Posted by imitheo
Have anyone ever look at the TBI MOTION ballscrew designing PDF ?

TBI MOTION Ballscrew

I used this design guide to know the Torque i would need to drive my gantry. If anyone could take a look with for me to be more confident about these calculations.

To get the cutting force on my endmill i used this KENNAMETAL calculator:

KENNAMETAL Calc

To see the maximum cutting force my end mill could hold, i got the milling parameters for the endmill i am using from kennametal and then inserted in the calculator.

So with the maximum tangential force i maxed my parameters using my spindle power. Finally i got 90N as my cutting force.

Anyone could take a look at these ?
Yes, take a look at my thread here:

Ballscrew Sizing Options

Look at post #21. There is a sample calculation.

You can try to recreate my graph in post #5 using an excel spreadsheet or whatever kind of math program you want to use. Then if you get the same results, both of us will know that our spreadsheets are good and you can then put your specific parameters in your spreadsheet for your machine

The motor torque table is here:
http://www.cncrouterparts.com/cdata/...rque_curve.pdf

That is two motors driving an 800lb gantry at 0.25G, And calculating how much force is left over at different RPMs. I didn't include preload drag or bearing drag and assumed an efficiency of 90%. See if you can recreate that graph.

Some references are here:

http://www.engr.sjsu.edu/bjfurman/co...iaformulas.pdf
https://www.aerotech.com/media/85449...d%20sizing.pdf
http://www.hiwin.com/pdf/ballscrews.pdf pages 26 and 27

Also, HSMAdvisor gives cutting forces and will tell you how much HP you need. Your machine is light and I doubt (correct me if I'm wrong) that you will have a really powerful spindle, so I don't think you will be making really aggressive cuts or subsequently need much cutting force.

But you can check it out and download it here if you wish:

Post your results when you're done, let's see what you come up with.

2. ## Re: RPM on steppers & StepServos

Hi again, long time no posts, i was testing some stuff with my steppers. Anyway i didn't had the time to make the calculations because my team is all over me, okay, i have some questions regarding the speed that i noticed under my tests and i would like to share here:

First of all, the parameters and the motor:
KTC-HT23-401 Datasheet
Running on 48v PSU
I am using a frequency generator to generate the square wave to pulse the motor.

1) Okay, i first tried to run at full step and i noticed that it was really hard to accelerate it really fast, the motor was suddenly stopping all the time. Then i raised the resolution to 1/4ustep and bam, it was so easy to accelerate and deaccelerate it, anyone can explain me why ? And the vibration also lowered.

2) I was trying to measure the current in one phase to get the total average current, so i set my multimeter to AC and it's a True RMS one, and measured it. The values that show on the display(RMS) and the values that datasheet shows are the same ? Or the value in the datasheet is the peak current ?

3) Also that value that shows on the driver, what current is this? Average, Peak?

4) Another question regarding the driver, the motor i am using shows 4.3A/phase, so i bought a driver that runs 4.5A, ON MY UNDERSTANDING, as they sell the motors with CURRENT/PHASE, the AMPERAGE rating on the DRIVER, ALSO WAS PER PHASE. BUT i am doubting this.

The driver i bought --> 4.5A Action Motors Drivers

Why i doubt this ? I set my driver to 4.5A, and i expected to see on my multimeter display, 4.3~4.6A RMS, but i'm getting 2.2A on my measured phase. SO am i correct? The amperage rating on the drivers is for the total current that the driver can handle, and the vendors rate their motors with A/Phase ?

And i should get this bulky, 8A driver ?
Bulky Hardened Super Hulk 8A Driver

5) (ASSUMING EVERYTHING I ASKED BEFORE IS CORRECT)My motor is getting pretty hot with 48V 2.2A/Phase, and it's rated for 4.3A, if i get my bulky driver and set for 8A max, this thing is going to fry ! Some fans around it should do the job ?

3. ## Re: RPM on steppers & StepServos

Originally Posted by imitheo
4) Another question regarding the driver, the motor i am using shows 4.3A/phase, so i bought a driver that runs 4.5A, ON MY UNDERSTANDING, as they sell the motors with CURRENT/PHASE, the AMPERAGE rating on the DRIVER, ALSO WAS PER PHASE. BUT i am doubting this.
https://www.linengineering.com/resou...-vs-amps-peak/

"Amps/Phase * 1.41 = Amps Peak current. Regardless of whether you remember the reason behind the 1.41 value, it’s crucial to understand this relationship because in most manufacturers, drivers only care about what peak value it can output. And step motors only care about listing the Amps/Phase value. As long as you understand what the difference is, you will be able to talk in the same language to both driver manufacturers and step motor manufacturers."

That is a quote from the article I posted. That's according to Lin Engineering. You can tell me if this is correct, I don't know.

And someone can correct me if they disagree with these two statements:

Also, the motor will not draw full amps unless running at full torque and low speed.

The stepper motor can only draw fewer amps at higher speeds before it starts to loose steps, and has less power, and less torque available. This is different from a spindle motor that has more power at higher speeds, but also less torque.

Originally Posted by imitheo
5) (ASSUMING EVERYTHING I ASKED BEFORE IS CORRECT)My motor is getting pretty hot with 48V 2.2A/Phase, and it's rated for 4.3A, if i get my bulky driver and set for 8A max, this thing is going to fry ! Some fans around it should do the job ?
You'd have to limit the current with the switches on the driver. No, you can't run that motor with 8 Amps. That's 4.24 amps, and if you believe Lin Engineering, that's 6 Amps max peak current, but before doing that I'd recommend having a very good look at the driver manual to determine what they are talking about and what their current settings actually mean. It won't help you get better performance at faster speeds as a stepper motor uses less amps at faster speeds. Please do some tests to verify if what I've said is true. I'd like to hear about the results. You'd have to test it under load.

Increased voltage gives better performance at faster speeds.

For the heating, what is the insulation class of the wires on that stepper? Also, I'm guessing that a Nema 23 can't dissipate heat as well as a Nema 34? If you heat sink your motors with a fan, well, I've not heart of it on a CNC router, but it would be interesting to see the results.

NEMA Insulation Classes

4. ## Re: RPM on steppers & StepServos

Originally Posted by NIC 77
https://www.linengineering.com/resou...-vs-amps-peak/

"Amps/Phase * 1.41 = Amps Peak current. Regardless of whether you remember the reason behind the 1.41 value, it’s crucial to understand this relationship because in most manufacturers, drivers only care about what peak value it can output. And step motors only care about listing the Amps/Phase value. As long as you understand what the difference is, you will be able to talk in the same language to both driver manufacturers and step motor manufacturers."

That is a quote from the article I posted. That's according to Lin Engineering. You can tell me if this is correct, I don't know.

And someone can correct me if they disagree with these two statements:

Also, the motor will not draw full amps unless running at full torque and low speed.

The stepper motor can only draw fewer amps at higher speeds before it starts to loose steps, and has less power, and less torque available. This is different from a spindle motor that has more power at higher speeds, but also less torque.

You'd have to limit the current with the switches on the driver. No, you can't run that motor with 8 Amps. That's 4.24 amps, and if you believe Lin Engineering, that's 6 Amps max peak current, but before doing that I'd recommend having a very good look at the driver manual to determine what they are talking about and what their current settings actually mean. It won't help you get better performance at faster speeds as a stepper motor uses less amps at faster speeds. Please do some tests to verify if what I've said is true. I'd like to hear about the results. You'd have to test it under load.

Increased voltage gives better performance at faster speeds.

For the heating, what is the insulation class of the wires on that stepper? Also, I'm guessing that a Nema 23 can't dissipate heat as well as a Nema 34? If you heat sink your motors with a fan, well, I've not heart of it on a CNC router, but it would be interesting to see the results.

NEMA Insulation Classes
As i expected, the drivers rate the total peak current, so the stepper is rated on amps/phase, actually amps rms/phase. So my motor, that is rated 4.3A/Phase, should be run at a driver that is capable of reaching 12A. THATS A LOT :/

My team is probably giving up on this stepper, it may reach our purpose but a 12A driver is insane and the price reaches the price of a 200W Servo Motor. It may not need this amount of Amperage for our machine, but we don't have the money or the time to start testing stuff, buy a expensive driver, buy a PSU, everything. We probably go for a more safe option.

IF we try the tests and i heatsink it with a FAN, i'll inform you guys.

5. ## Re: RPM on steppers & StepServos

For speed you need voltage. The problem with your driver is not the current, but the fact that the operating voltage is maximum 40V. You can't run that driver with anything higher than that. Current is only important for the torque, so assuming you will not have high load you won't need high current. Generally speaking NEMA23 motors are better with high speeds than NEMA34.

On the temperature, I'd not add any fans, though I have heard about somebody using fans, I never understood why. If your driver is OK then heat should not be an issue. Motors can get very hot and that is normal. Temperatures between 60-70 degrees C are not unusual and you can't really feel that with your hands. Measure it if you are worried, but note that high heat may not be caused by the current but also by a badly designed driver. I don't know the driver you plan to use, but I'd go for the very common DQ542MA or a better, newer digital version of it. The one you have looks like based on the Toshiba chip, which generally is not the best for your purpose.

6. ## Re: RPM on steppers & StepServos

Originally Posted by imitheo
As i expected, the drivers rate the total peak current, so the stepper is rated on amps/phase, actually amps rms/phase. So my motor, that is rated 4.3A/Phase, should be run at a driver that is capable of reaching 12A. THATS A LOT :/
No, nooooo, no no. Goodness! No!

Originally Posted by A_Camera
For speed you need voltage. The problem with your driver is not the current, but the fact that the operating voltage is maximum 40V. You can't run that driver with anything higher than that.
Good catch, I didn't check the driver voltage specs.

7. ## Re: RPM on steppers & StepServos

Originally Posted by NIC 77
Good catch, I didn't check the driver voltage specs.
I didn't check the specs just the picture and it says 9-40V. Regarding specs... that's another issue... also I have no idea what the maximum frequency is for that driver, maybe too low to run it fast anyway. A driver which is not speced for at least 200kHz is not a very good one for speed running.

8. ## Re: RPM on steppers & StepServos

've switched to StepServo's AKA Integrated Closed loop steppers I'm using JMC-motor.com iHSS57-36-20 NEMA 23 2nm 36v steppers (\$124ea). I feed them 36vdc, step, and dir from my Break Out Board from Linuxcnc. So my control box is basically a power supply for the spindle 48v and steppers 24v, PWM spindle speed control for my DC spindle and the parallel breakout board. I have lots of room now in the box. The steppers run about 5-15F over ambient temperature and get a bit hotter when really running them. Since they have encoders in the with an integrated driver, they're not sitting there with 100% holding current all the time, just enough to not free wheel and it actively holds position. It's well worth the little extra money to try some. In NEMA 23 and 24 they have 1nm, 2nm, and 3nm. In NEMA 34 I believe they go to 35nm for hybrids. I'm getting 1500rpm at 24v with mine which is good for 141 inch a minute (236in/min theoretical)

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•