Strange Movement

[tuffduck]

The power supply is a Meanwell SDR-960-48
https://www.meanwell.com/webapp/product ... od=SDR-960

[martyscncgarage]

Question, did you choose the steppers and power supply combo?
There is an equation for figuring out max stepper voltage. I found it a little odd that you have 3 different stepper motors on the machine.

Marty

[martyscncgarage]

The power supply is a Meanwell SDR-960-48
https://www.meanwell.com/webapp/product ... od=SDR-960

I saw that when I went back and looked at your photos, your big Z axis stepper motor is capable of much more than that buy taking the square root of its inductance and multiplying it by 32. I come up with 90volts peak voltage (wired Unipolar, off the charts otherwise). Further, that is an 8 wire motor, how do you have it wired to the Gecko drive?
(note, many buy stepper motors based on advertised torque ratings but don't understand the importance of matching it up correctly to the available power supply. Geckodrive published "Stepper motor basics" a good read: https://www.geckodrive.com/support/step ... asics.html)

There is nothing wrong with stepper motors provided they are selected and sized properly. There is usually a 30% safety margin added to the torque rating to compensate for open loop system. You also need to be careful setting rapid speeds. Get to close to the max, you can loose steps. Setup is also important.

I can not find inductance ratings of your other motors

Specs I found on the Z axis motor:
Electrical Specification
Manufacturer Part Number: 34HS38-3008S
Motor Type: Bipolar Stepper
Step Angle: 1.8 deg
Holding Torque（Unipolar）: 5Nm(708oz.in)
Holding Torque（Bipolar）: 7.07Nm(1001oz.in)
Rated Current/phase（Unipolar）: 3.0A
Rated Current/phase（Bipolar Serial）: 2.12A
Rated Current/phase（Unipolar Parallel）: 4.24A
Phase Resistance(Unipolar): 1.6ohms
Phase Resistance(Bipolar Serial): 3.2ohms
Phase Resistance(Bipolar Parallel): 0.8ohms
Inductance(Unipolar): 8.0mH ± 20%(1KHz)
Inductance(Bipolar Serial): 32.0mH ± 20%(1KHz)

[tuffduck]

Thanks for all of the help. I didn't choose any of it. The machine frame was made and it came with a bunch of parts. The guy building it, never completed it. He was supposed to finish it but after 5 months during the Pandemic he never did.

The Z-axis is wired bi-polar parallel.

I am retired. I have to earn what I put into the machine. That takes a long time. Currently, things aren't good in my community economically.

[Richards]

Being retired makes things different. I'm 71, but I have enough consulting work so that I can dabble when an idea hits me.

Marty's figures are exactly what I would computed if I had taken the time to look things up. 90 volts is a lot of voltage. It may be more than your drives can handle. The Gecko stepper drivers that I used in the past are limited to 80 volts. The Leadshine that I now use is limited to 50 volts, but there are other leadshine drives that handle much higher voltages. My testing in the past showed that voltage is more related to speed and current is more related to torque. In other words, a stepper supplied with 48V would not be able to run as fast as a motor supplied with 75V, but it would pull about the same load with either power supply.

On my Taig mill with its little Nema 23 motors, I don't push things. It doesn't miss steps with the light loads that I give it. When I learn what I want to know from the mill using steppers and replace the steppers with ClearPath servos, I expect to push the mill to its limits, mechanical or electrical, whichever gives in first.

When I had my Shopbot PRT Alpha with 3hp spindle, I expected to make full depth cuts in 3/4" MDF and melamine coated particle board. That was just a dream. I learned that shops doing that used at least a 7hp spindle. My home shop didn't have power enough to use a 7hp spindle along with all the other 240VAC things that had to run at the same time, so, I resorted to making multiple passes. It worked. There was still enough profit to warrant the shop. In other words, I had to adapt the way I did things to work with the things that were available and practical. It looks like you're doing the same thing.

[tuffduck]

Thanks Mike, I had to adjust things alot over the past 14 years. I would love to use servos but the cost here in Canada by the time I pay exchange, duty and taxes makes them very expensive. Almost double what you would pay in the US. I will probably get 2 larger steppers for the X and Y axis, degrease the passes to about 1/8" and go from there.

[tuffduck]

Motor on Y

[martyscncgarage]

You clearly have a mishmash of motors.
This Y axis max voltage is 46VDC

I don't think the guy knew what he was doing.
What are specs on X?

It might be better to replace the Z axis with one more suited to running at 48VDC and give it a try....lots cheaper....

Marty

[tuffduck]

Here is the one on X

[Richards]

The specification that you need to watch is inductance. As Marty posted, by using the GeckoDrive formula, to find the maximum voltage to use with a motor, you take the square root of the motor's inductance and multiply that number by 32. That gives you the maximum voltage to use without overheating a motor. Inductance is listed in mH (millihenry). Using that formula, I would look for a motor that had about 2.5mH inductance (or slightly higher) if I were planning on using a 48VDC power supply. I would also look for a motor that had only 4 wires for easy connection to the driver. The 6 wire motors from Oriental Motor that I have, need to be wired half-coil (black/yellow and red/white). That reduces the torque but gives me greater speed than wiring the motors uni-polar (black/green and red/blue). I also have some 8-wire motors that I have to wire bipolar-parallel. So, if I were looking for a new motor, I would look for one with 4 wires.

Also, it's important to note that if a motor has too high inductance, it will run slower than a motor with lower inductance. You can run a motor with inductance higher than 2.5mH from a 48VDC power supply, but the higher the inductance, the lower the performance.

If you use a switching power supply to power the stepper motors, you might try adding a large filter capacitor to the power supply's outputs. Snap caps with a capacitance of 20,000 uF or higher and a voltage at least 1-1/2 times the voltage of the power supply will make life easier for a switching power supply. Switching power supplies are generally used to power devices that need constant current. Stepper motors need varying current, so most switching power supplies struggle to handle the varying current requirements when used with stepper motors. I prefer using linear power supplies with toroidal transformers, such as those sold by antekinc.com. I've had good results with that company. Those power supplies run cool and their large filter capacitors keep the voltage ripple to a minimum when used with stepper motors. Right now, I'm using a 48VDC switching power supply to power the three PK268-02AA motors on my Taig mill. I'm NOT using a filter capacitor, but I'm not driving those motors very hard. There is minimal ripple because of the light load on the power supply. If I planned on using that power supply long term, I would add additional filter capacitance to the outputs.