I'm running Mach 4 with an ESS smoothstepper. I'm having issues running a closed loop Nema23 at anything like a speed I expected. I've been advised by the supplier to change the duty cycle to 1:1. Can anyone advise how to check / change this in Mach 4 ?

My guess is that would be a setting in the drive?

The supplier said change duty cycle of mach 4 to 1:1, And keep it below 125k. Not sure if mach 4 dictates the duty or the ESS. I need to check it with a scope later.

Oh, he's talking about the pulse width.......

The duty cycle is the portion of the pulse that is high and lo. A 1:1 should be 50% high and 50% lo. The pulse width is the hi and lo combined. Thats my understanding anyway 😊

Hi,
the duty cycle of the ESS step outputs is fixed by the ESS and is not able to be programmatically controlled.
I have observed the step outputs of my ESS/BoB combo on occasion with an oscilloscope and they are already nearly
bang-on 50% duty cycle as is.

The ESS can produce pulse streams up to 4MHz, so 125kHz is scarcely a crawl for the ESS.

The limitation here is the ability of the driven device, in your case the stepper driver. The manufacturer specifies a max
of 125Hz, but you would be advised to stay well below that.

What microstepping regime have you in place?. Its not uncommon for inexperienced CNCers to specify a way to high
microstepping regime on the misunderstanding that it is better and gives better resolution. It does not.
With a two phase stepper (ie normal) resolution beyond half step microstepping is fallacious. The real advantage
of microstepping is smooth motion thereby avoiding mid-band resonance.

I would recommend a microstepping regime of about 8 micrsteps per full step or 1600 pulse per rev.
If you wanted your stepper to spin at 1200 rpm (ambitious for a stepper) then the pulse rate will be:
pulse rate=1200 / 60 X 1600
   =32kHz

That is comfortably within the spec of your drive.

If however you choose an unrealistic microstepping regime of 64 microsteps per full step or 12800 steps/rev
the calculation becomes:
pulse rate = 1200 / 60 x 12800
   =256kHz

Which is well outside of the spec.

What voltage power supply have you provided the drivers? The general rule is that it should be as high as the drivers
will stand because the steppers will run fastest.

Craig

Thanks for the response.

Warp 9 tell me the pulse width is 10us below 50k then it's 50% duty cycle up to the 4m max.

I'm running on 36v, i've tried 45 but it didn't make a massive difference.
I have the driver set to 800 steps/rev, and was trying to run at a feed rate that worked out at 360rpm. The motor was stalling but not alarming, without load just running on a bench.
I workd it out at a 4.8k pulse, way below the 125k they said was max.

I'm trying to get a feedrate of 3000mm/min, but to do that i had to set to 400 pulses per rev, way below the accuracy i wanted on a 5mm pitch screw.

I think a refund may be whats called for and try a different supplier.

Motors laying on a bench will tend to stall easily, due to resonance. Set your microstep to 1/8 (1600 steps/rev), and it should stall less. If possible, bolt the steppers to a board while testing, and that should also help.

Hi,
well it certainly sounds like you have experimented enough and have the calculations well in hand.

As I stated in my previous post that it is unrealistic to expect better that 400 step/rev resolution from an open loop
two phase stepper. You can set a microstepping regime with apparently far better resolution but that theoretical
resolution is not actually obtained. There is a sound explanation for that....but I would not, unless you require it,
regurgitate the reason for it.

A closed loop stepper is still a stepper with all the limitations of a stepper, reducing/vanishing torque at high speed.
A closed loop control system does not prevent that. For this reason I do not recommend that the premium paid
for closed loop steppers as opposed to well engineered open loop steppers and drivers.

One area where closed loop steppers do offer an advantage is resolution.
An open loop stepper can reliably be at either a full step position or a half step position. A half step position occurs when
both phases are energized and the resulting magnetic field 'drags' the rotor to a position midway between the two
full step magnetic poles on either side.

A closed loop stepper enjoys a distinct advantage in this regard. Should your required motor position required  to be
14% CW of the last full step position (therefore 86% away from the next full step position). As a guess you would reduce the
phase current in the 'leaving' phase  to 86% of max and increase the current in the 'arriving' phase to 14% of max.
It is almost inevitable that the rotor will not achieve its 14% position as required. However it actual position is measured by
the encoder and therefore signaled to the driver. Thus the driver will adjust the current balance between its two phases
such that the rotor indeed achieves its desired position. It may require a current distribution of 84% and 16% respectively.

This constitutes the sole major benefit of a closed loop stepper. The question obtains 'does the increase in resolution
justify the expense'

Lets compare open loop resolution vs closed loop.

Open loop at half step, resolution = 400 step/rev, with a 5mm leadscrew resolution = 0.0125mm or 12.5um
Closed loop (Leadshine encoder 6000ppr encoder) =6000 step/rev, with a 5mm leadscrew =0.833um

Clearly close loop has an advantage....but the minorest amount of backlash or flexure and that resolution is wasted.
Unless you have the need, and are prepared to build a sufficiently rigid machine with backlash free components, I would
recommend open loop steppers and drivers.

If you go that way you absolutely MUST buy steppers with low inductance, its as important as holding torque. With
23 size steppers you should aim to get steppers of 1mH or less inductance. Pair those with a good highvoltage
stepper driver like Gecko or AM882 drivers from Leadshine and you in business.

You should, excepting very heavy loadings, achieve 1000 rpm or with a 5mm leadscrew 5000mm/min.

Craig

Craig,

Thanks very much for that comprehensive answer.
I've seen videos of closed loop working far faster than what I am achieving, and set to a 1000 steps, I don't think any on the ESS though. I'm only looking for about 3000mm/min, at the moment I'm getting to about 1800. The drivers default, and lowest division is 400, so I've set it to that and got to 4000mm/min, I was hoping to keep to the 10um accuracy, so it's not that far off.
My current open loop drives are set to a 1000 and I'm getting a stall free 1800 out of those.
The closed loop is certainly smoother sounding and feeling and much cooler.

I think the problem is the signal to the driver, I think the driver is just not getting the faster signal from the ESS. I'm going to experiment a bit and generate my own signal to see if it performs as the vendor describes with a 1:1 square wave, then look at my options.

Many thanks

Carl.