Unable to exceed 60 inches/Min without stepper stalling

I am new to CNC routers, so I hope my question is not too stupid. My CN will not go over 60in/min on any axis without stalling. I have no idea what I am doing wrong, so I am hoping someone can help me out. I know my little Ebay 3018 runs at about twice the speed of this beast. Here is my current setup:
NEMA 34 Steppers - 34HS59-5004S
1.8 deg/200 steps per rev
Stepper Driver - DM860T
Set to "8" for a total of 1600 steps per rev
60vdc power supply (57.4vdc out)
Lead screws are 5mm (.1969') pitch
Mach3 setup:
Steps Per - 8125 (.9) - I rounded down

The motors are tuned correctly. 1 inch is 1 inch.

I just read in a post the inductance of the steppers my be my issue. It is 11mh. However, when I run the numbers through a stepper motor max RPM calculator, I end up with a max speed of like 16 RPM which I know is wrong. When I do a little reverse math, it come out at about 253 RPM which seems to me much closer.

I guess my actual question is "Is the inductance of the stepper motor the issue?".
If so, what would recommend for replacement steppers?

Hi,

Quote:

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I guess my actual question is "Is the inductance of the stepper motor the issue?".
If so, what would recommend for replacement steppers?

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Your driver and microstepping sound about right as does the ballscrew.

I would guess that 11mH will prevent your stepper from performing at speeds much over 100rpm. Low inductance is mandatory for steppers to operate
at high speed followed by highest possible voltage drivers.

For 23/24 size steppers look for 1mH-2mH and reject anything above 2mH.
For 34 size steppers look for 2mH-4mH and reject anything above 4mH.

Craig

That is what I was afraid of. Any thoughts on a decent NEMA 34?

You're 5mm pitch ballscrews aren't helping either, as they require high rpm to get any speed. 10mm pitch would be a much better choice.
How big is the machine? How much weight are you moving?

A motor like this may work
https://www.automationtechnologiesin...r-single-shaft
Or this one
https://www.automationtechnologiesin...-8b-dual-shaft

The machine work area is 32x51 +/-. It's about 3'x6' and all aluminum. Of course it is 3/8 plate and 1x3 bars. It is one heavy beast. The axis moves easy enough if the screws are detached.
The pitch was also a concern, but I can't seem to find one with a bigger pitch. If you look at the torque curves for the motor, they run all the way to 450 RPM. My best guess is 60IPM is about 255 RPM (.1969" per rev). I also tried changing the steps. I took it all the way down to 2000 and it still stalled out on all three axis's. I would rather have more power than I will ever use than be short.

Hi,
I don't think 34 size motors are the way to go.

You have a 5mm pitch ballscrews so you don't need lots of torque to get good thrust and acceleration but you will need high rotational
speeds to get fast traverse speeds...ergo 23/24 size.

A stepper of say, 1.2mH, could be expected to have 45%-50% of its holding torque at 1000rpm with a 60V-70VDC driver.

This forum is littered with posts not dissimilar to yours, people have bought steppers because they had very good holding torque while
not realising that the manufacturer has deliberately made a high torque motor to attract first-time buyers but only at the expense of crippling
high inductance.

You will find that its the rotational inertia of the ballscrew followed by the rotational inertia of the stepper armature that dominate the motion equation,
not the machine mass at all. This might sound counter-intuitive but is in fact the case. The rotating components are 80%-90% of the inertial load with the
axis mass 20% or less.

This thread has now got to about 80 replies so is quite a read but in it I presented the formulas derived from first principles that demonstrate why
that is the case:

https://www.cnczone.com/forums/servo...es-servos.html

Craig

Hi Ernie- Have you dialled the accel back? If the acceleration is set too high your motors cannot reach the velocity at that acceleration. ie it can't provide the torque at that accel and velocity so it stalls. So choose a very low accel and see what happens. Cheers Peter

JoeAverage
I did find a NEMA 34 which should bolt up to the machine as is with 5.5mh of inductance. I still need to look at the rest of the spec's but in my little mind 5.5 is half of 11, so I should get the speed I would like to have without breaking the bank. The post you noted is talking about servo's instead of steppers, but I just don't want to dump that much money into it right now. Thoughts?

Peteeng
I have the accel set to 1 right now. It will go a few or several inches and then stall. As soon as the RPM's come down, it moves again. Of course it loses position when it does it.

Hi Ernie - 1 (one) what units? Peter

Inches?? If I remember right, Mach3 says 1 or 2 seconds to full speed.

The first motor I linked to (465oz) would probably be the best with those screws. 1.65mH

The one I found on ebay (KL34H280-45-8A) is 640 oz-in and 2.2mh in parallel. That would give me a lot more speed than I would ever need.... Unless I was launching something into space. I am still leaning towards the one I found on Amazon (34HS46-6004S) with 1200 oz-in and 6mh of inductance. I just can't translate oz-in to anything I know. I do know the NEMA 34's I have on it now will drag my fat butt across the shop... Until I get over 60IPM.
Both motors are about the same price, so cost is not an issue. I't just Lack of experience and learning the hard way. I am surprised I didn't find anything about the inductance anyplace except on one question here.

Hi,
2.2mH is still on the high side, go lower if you can.

Craig

Quote:

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I am still leaning towards the one I found on Amazon (34HS46-6004S) with 1200 oz-in and 6mh of inductance

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The 465oz motor I linked to will probably be at least 5x faster than that 1200 oz motor.
Bigger is NOT better with steppers.
You're 5 mm pitch screws give you a huge mechanical advantage, so you don't need a large motor.

And be aware that a steppers torque rating is when they are not spinning. At 500rpm (~100ipm), a 465oz motor will likely have the same or more torque than a 1200 oz motor. At 1000 rpm, the smaller motor will be much more powerful.

JoeAverage,
Lower than 2.2mh? Wow, I have seen any of those, yet.

Ger21,
JoeAverage said 23's would be fine and you are backing him up in the bigger is not always better position. The one you linked to says it has a 1/2" shaft the same as the one I found on ebay. The ones that are on it say 14mm, so I will need to do some more hunting. I will take a measurement just to be sure. I really, really want a plug and play, so a NEMA 34 size is a requirement unless I redrill everything.

I am confused. I looked at one stepper and it said 2.2v on one page and 60v on the other. I know my driver is supposed to auto configure to the motor, but I am not sure what they are talking about. When I look at torque curves they reference what I assume to be the input voltage, not the voltage supplied to the motor. Now if I use the power supply voltage for my driver, the max RPM's for my stepper is 163.8 (60v, 11mh, 5a). This is a lot better than the original figure of 13.2 RPM using the motor voltage (5v, 11mh, 5a) and may be correct.
So when I use the online Speed and Power calculator, should I use the supplied voltage and ignore the motor voltage? I just don't know how the input voltage could affect motor speed without frying the motor.

Hi Ernie - I'm not a M3 user but acceleration will be in inches per sec per sec. If its set to 1 sec to max then thats a very big accel. Make it 5 secs and see what happens. Peter

It APPEARS!! in M3, 1 is 1 second to max and 1 second to 0. 2 is 1/2 second to max and 1/2 second to 0. The issue is not with starting. It's mid move. It drives me nuts!!

The Nema 34 standard uses 1/2" shafts. If you have 14mm shaft motors, they are not standard Nema 34's. You may not be able to find a low inductance motor with a 14mm shaft, as they are usually only available from China in limited configurations.

While a Nema 23 might work, Imo a small Nema 34 motor is better. I was assuming you had standard Nema 34 motors, which is what I suggested.

In Mach3, acceleration is inches/sec/sec
Try setting your accel to 5.