The right voltage for my Stepper Motors in order not to lose steps

[johnansaro]

Hi there
I have put together a 3 axis router CNC machine. It is a 4 meter By 2 Meter long machine. The machine has 4 Leadshine stepper Motors (Model 86HS45 4.5 N.M --- 637 OZ-In --- NEMA 34), The motion system for Y and X axis is Helical rack and Pinion (spring loaded with 3:1 Pulleys). The Drivers are Leadshine M880A with Electrical Specification as follow:
Min current of 1.8 A --- and Max 7.8(5.6 RMS) A
Supply voltage --- Min 24 VDC --- Max 72 VDC --- and Typical 68 VDC
The Machine is working fine in Short Runs. It can actually cuts 16 mm MDF in one Pass without any Difficulty. But In Long runs (Over one Hour) For example when is Cutting a Relief like a Lion Heads and so on, IT Loses some steps and when it moves to its zero Position it is off target by few mm mostly in X Direction. I am wondering what would be the probable cause or Causes?
I have some questions on its Voltage supply.
1. My power Supply is a Hittachi 32 A --- 57 VDC. I think I am OK with Current, But as far as the Voltage goes as you can see My Driver Typical Voltage requirements is 68 VDC, and my PS has a Max of 57 VDC, Could this be the cause of the problem?
2. Can I add a 10 or 15 VDC --- 10 A in Series with my Original PS? And If I do so, Wouldn’t this sort of burns my Smaller PS?
3. I am also considering of Upgrading my motors to a Higher NEMA 34, Like 86HS85 with holding Torque of 8.5 N.M --- (1203 Oz-In ), On this issue what do you think of Stepper Motors with Brakes? Are there any better for my machine? And How about the Closed loop Steppers? And If I use them do I need to change my BOB?

Regards
jhonansaro

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[ger21]

Lost steps are typically the result of trying to run the motors faster than they are capable of. The simplest answer is to reduce the velocity by 25%, and possibly the acceleration as well.

No, you can't add a 10V power supply. But bumping up 8-10V higher probably won't make a lot of difference.
What are the full specs of your motors, or the model #? You want motors with an inductance of 3mH or less.

Going to larger motors will likely result in more lost steps. The bigger the motor, the faster it loses torque, as rpm's increase. So a larger motor may have less torque at higher rpms than the ones you already have.

[johnansaro]

Hi Ger21

Thanks fro the respond.
Can I reduce the speed by modifying or reducing my feed rate? or do I have to do it in my mach3 settings?
i am attaching the spec file for the driver, as you can see it clearly says "Higher supply voltage can increase motor torque at higher speeds, thus helpful for avoiding losing steps"

Regards
Jhonansaro

[louieatienza]

1 - The voltage more so determines how fast the stepper can spin while retaining torque. You probably do not want to run at the max rating of your drive.
2 - No
3 - I wouldn't use those huge steppers. What you could do, however, is get NEMA34 steppers that are maybe 15-20% higher torque rating than what you have now, with a low inductance rating. The torque curves on them are a bit flatter than NEMA23, and you won't have issues with cogging and resonance that can happen with large steppers that are overcoming not much more than their detent torque. Closed loop steppers can be good, but I would tend to address your mechanical issues first, and possibly not run the machine as fast.

[johnansaro]

Hi there

ger21 please let me know that If i could reduce the speed by lowering my feed rate? Or do I have to do it in mach3 settings?

also as i mentioned from my user manual the typical VDC for my Stepper is about 68 VDC, but my Power supply outputs is only 57 VDC.

Off course in some places it says the typical is 48 VDC, but if the 68 VDc is the typical, could this 9 V difference cause a problem?

Regards
jhonansaro

[ger21]

It should be reduced in the motor tuning.

There is no "typical" voltage. Voltage is determined by a variety of factors.

Speed is roughly proportional to voltage. Going to 68V might give you 10-15% more speed, but it's close to the max, and may cause the drives to blow from back EMF.

[johnansaro]

Hi there

Thanks for reply Gerry
I rather reduce the speed by lowering the feed rate, Is this a total wrong procedure? As you know if I reduce the speed in motor tuning then I think it will have a direct negative
effect on my Jogging speed. Correct me if i am wrong.

On the issue of voltage Knowing that presently my speed in motor tuning is only 4000 mm/min, (and I believe this is my Max Speed), And knowing that the
my pinion has 13 pitch each at 7 mm apart and I have pulley ratio of 3:1 Then For that Speed I only need RPM of 4000/(13*7)*3 = 131
And from the Graph and/or Tables I am almost at max of my available Torque, which is about 3.5 N*M,
and It appears neither by lowering the speed Nor Increasing the voltage, I am not able to gain much on Torque. (If You want I can send you the Graphs)

Therefor I think I should look for some other causes or solutions for my Problem,
I Should mention that at this speed of 130 RPM with stepper 86HS85 (8.5 N*M), I am able to output the 5.5 N*M Torque

Regards
Jhonansaro

[ger21]

I rather reduce the speed by lowering the feed rate, Is this a total wrong procedure? As you know if I reduce the speed in motor tuning then I think it will have a direct negative
effect on my Jogging speed. Correct me if i am wrong.

If you are losing steps, it is most likely occurring during rapid moves, acceleration, or both. Lowering the feedrate will have no affect on these issues.

Yes, it will lower your jogging speed.


If you are only spinning your steppers at 130rpm, you need more reduction. What is the pitch diameter of your pinion?

Ideally, you should have about 10-20mm of travel per revolution of your stepper motor.

[johnansaro]

Hi ger21

I think I have already given you that info : 13 teeth, distance between them 7 mm therefore, circumference = 91 mm then Pitch Dia almost to be 27 mm

On the travel issue, if my travel to be 10-20 mm, let's say 10 mm then in order to reach 4000 mm/min (which is not even very fast), Then I need RPM of 400

With that RPM from the Graph I will end up with only about 2 N*M from what I already have about 3.5 N*M

Please correct me If i am wrong, but I think there is a problem in your statement.

regards
jhonansaro

[johnansaro]

Hi there

On the issue of Step Pulse and Dir Pulse, From my driver's Manual I think, I have to set these 1.5 us and 5 us in my Motor Tuning Setup config.?
If it is so, presently their value is set at 0 for both of them. Would this change be any good to me?

do you have any recommendation for the general Logic configuration page settings?
also on sherline mode, and Kernel speed do you have any recommendation?

Regards
Jhonansaro