Im now testing an LDO NEMA 17 motor OverTheMoon LDO-42STH25-1004AC which is a High Temp High Speed pancake motor.

And I think I found the real root cause, aside from not-ideal stepper choices, I was using a Jerk speed of 200 mm/min, which is a value I found online as a recommended "extreme" setting. The default value is 40mm/min. When I dropped this down to 100mm/min and combined with the new light and fast stepper I can now achieve a pretty impressive 400ma current on the Stepper driving the Nimble (and still at high speeds).

As per the wiki
https://duet3d.dozuki.com/Wiki/Pressure_advance

For setting multiple Drive pressure advance, the command suggested above doesnt seem to work, ie:

“ M572 D0:1 S0.3:0.1 “

then if you send a M572 and you get

" M572

Extruder pressure advance: 0.300, 0.300, 0.000, 0.000 "

Instead of D1 having "0.1" it appears to just keep the D0 setting?

Firmware Version: 2.05.1 (2020-02-09b1)

@droftarts

Alright, an update and progress. I tried two smaller half height Nema17 steppers from my junk box. I also isolated a piece of movement from the actual print Gcode and made it into a macro. This was the most "offending" section, the last two fast extrusions back to back.

Macro:
G0 F2500
G1 X39.245 Y28.111 E12.53808
G1 X38.845 Y30.238 E.65933
G1 X11.598 Y57.486 E11.7389
G1 X39.245 Y28.111 E12.53808

This piece of GCode causes stalls on both the full size, high torque Stepper motors (the Wantai and the StepperOnline), Ie both fail, no matter the current (amps).

Conversely both the smaller Steppers could complete it with the following settings:

Working with 17HS3001-C5X (without gearbox, so its now a low torque direct motor)
M906 X1250 Y1250 Z1250 E1615 I25

Working with unnamed (it literally only has "XY" written on it) half height stepper
M906 X1250 Y1250 Z1250 E1545 I25

So basically the cheap ass, no name small Stepper works the best in this scenario. Im going to look for a better option online, annoyingly not mentioned in the Zesty Manuals but is on their old product page is a specific recommendation: https://www.omc-stepperonline.com/nema-17-bipolar-1-8deg-16ncm-22-6oz-in-1a-3-7v-42x42x20mm-4-wires-17hs08-1004s

@dc42
Thanks, was able to make progress by making that suggested runonce.cfg a macro instead and running from PanelDue. It was not executed automatically, presumably as it only gets "run once" a network is connected (ie the thing thats broken) per the docs. But Im back in operation again! I took the opportunity to move to a newer faster SDCard and now I have a nice little macro to reset Wifi should I need it in future.

PS: I must have had the old Wifi Firmware version and just not have noticed, which caused this to begin with!

@dc42

Just updated from Duet Wifi from 3.5 RC3 to RC4, just used the big Duet2and3Firmware-3.5.0-rc.4.zip file and let it do its thing. Unfortunately on reboot Im greeted with Wifi Module No Known Networks found (and M587 says none saved) and constant Wifi Idle errors.

Ive tried reverting to the older RC3 (via SD Card sys file changes and also have a Paneldue to run its console) to no avail... Im stuck now!

Im now testing an LDO NEMA 17 motor OverTheMoon LDO-42STH25-1004AC which is a High Temp High Speed pancake motor.

And I think I found the real root cause, aside from not-ideal stepper choices, I was using a Jerk speed of 200 mm/min, which is a value I found online as a recommended "extreme" setting. The default value is 40mm/min. When I dropped this down to 100mm/min and combined with the new light and fast stepper I can now achieve a pretty impressive 400ma current on the Stepper driving the Nimble (and still at high speeds).

@droftarts

Alright, an update and progress. I tried two smaller half height Nema17 steppers from my junk box. I also isolated a piece of movement from the actual print Gcode and made it into a macro. This was the most "offending" section, the last two fast extrusions back to back.

Macro:
G0 F2500
G1 X39.245 Y28.111 E12.53808
G1 X38.845 Y30.238 E.65933
G1 X11.598 Y57.486 E11.7389
G1 X39.245 Y28.111 E12.53808

This piece of GCode causes stalls on both the full size, high torque Stepper motors (the Wantai and the StepperOnline), Ie both fail, no matter the current (amps).

Conversely both the smaller Steppers could complete it with the following settings:

Working with 17HS3001-C5X (without gearbox, so its now a low torque direct motor)
M906 X1250 Y1250 Z1250 E1615 I25

Working with unnamed (it literally only has "XY" written on it) half height stepper
M906 X1250 Y1250 Z1250 E1545 I25

So basically the cheap ass, no name small Stepper works the best in this scenario. Im going to look for a better option online, annoyingly not mentioned in the Zesty Manuals but is on their old product page is a specific recommendation: https://www.omc-stepperonline.com/nema-17-bipolar-1-8deg-16ncm-22-6oz-in-1a-3-7v-42x42x20mm-4-wires-17hs08-1004s

@droftarts

Well that certainly does sound like a promising lead!

The Zesty is a remote drive extruder, my V1 is has a 30:1 multiplier on the torque input.
I found the screeching stall happens when exceeding 32mm/s on a sustained (ie more than second) extrusion on the 1.2mm extruder and 0.7mm layer height. I have a 1000w 24v PSU.

Zesty recommend the following ideal stepper specs:

--
Low rotor inertia
This allows it to start and stop rotating fast.
A value lower than 15 g-cm2 is desirable.
This often isn’t shown on the specification sheet, In this case an overall weight of the stepper of 120 to 150 grams is way to get something close to the target.

Low inductance
This means that the currents set up by the pulses are not too strong.
This allows the stepper to spin fast without the pulses interfering with each other.
Aim for a value of 3.5mH to 4.5mH

--

Now, where this interesting is the spec's of the two steppers I tried.

1. My original (supplied as part of the Anycublic tower motor I think) Wantai 42byghw811p2 has a Rotor inertia: 68 g⋅c㎡ and an Inductance of 1.8 mH
2. The replacement StepperOnline motor, which in practice was no better at all, has a Rotor Inertia of 105gcm2 and an Inductance of 3.0 mH.

So basically the StepperOnline motor is much worse for this application, lol. Im pretty sure in my junk box I have a half size Nema17 that was part of a geared setup (it had a little gearbox on the end of it) that most likely better than both of these Steppers.

@engikeneer said in Nimble + 1.2mm Nozzle - extruder stalls unless Amps increased 4x:

@Kodachrome doesn't matter whether it is the motor skipping steps because it doesn't have enough torque or the extruder gear slipping against the filament. Fundamentally the extruder system cannot push the filament through the nozzle at the rate you are asking. Apologies I have kind of used the terms interchangeably

Ok, cool, so it will be interesting the change when swapping out the 4200g-cm (at 2.5amp) torque Wantai 42byghw811p2 for the StepperOnline Nema17 rated 5900g-cm (at 2.0amp) stepper. On paper, thats maybe closing on 50% more torque for a given Amp rating (since Im not running the Wantai at the full 2.5amp its not actually pushing 4200g-am torque).

@engikeneer
I'm really confused on why both of you are mentioning melt rates and temps. The issue isnt an Extruder skipping problem, I said the Stepper motor driving the extruder stalls. The stepper stops spinning (well, it vibrates slightly) and the stepper motor (not extruder) makes high pitched noises. If I just had the basic and known clickly-skippy extruder noise then yeah, whack up the temp (which I tried but as I said, its irrelevant due to the fact the stepper motor isnt feeding the extruder anything when its stalling out!). But I suspect this has nothing to do with the extruder actually. I am running at 24v. And as I said, the problem is "circumvented" with a now confirmed 2150ma (of the 2500ma the motor is rated at). But this makes be uncomfortable due to high heat of stepper motor and the fact its so way over the top of Zesty doc's (which dont mention any nozzle or flow specs).

Did you misread me or did I misread (misunderstand) you both?

EDIT: Just found out that Zesty, who I assume are now out of business based on having no stock for a year now, once made a High Volume version of the Nimble, the Zesty Giddy. Never heard of it before right now!?
https://zesty.tech/products/the-nimble-giddy

To reiteration, the key issue in my case isnt melting of filament, its an electrical issue with the Stepper, the Zesty isnt skipping or hitting resistance with the filament. The Extruder stepper itself visually stalls to a standstill and "screams" on fast moves with extrusion. I dont know if this is a Duet Driver or Stepper motor issue. Further testing is showing that even 2200ma isn't enough.

I will try a 3rd stepper motor soon, ordered a SteppersOnline model, which has about 25% more holding torque.

@T3P3Tony Sensible stuff, though your last paragraph has me thinking, while its not actually acceleration, it actually only craps out on sustained straight lines (ie top speed, sustained for a few seconds). But its a crazy looking thing when going (with the amps high), the filament reel is just spinning constantly, it is actually quite impressive. There is also a crunchy-creaking sound coming from the Zesty, but I think thats the filament which is a quite hard PLA (branded as High Speed PLA+).

As to the drawbacks, heat in the Stepper is one, which may eventually cause its to also shutdown when over heating and also this poorly explained logic (IMO) from Zesty themselves:

Because the Nimble has so much torque available, you can/must run a much lower vref for your stepper than normal. This also helps getting the pulses across properly as you are not fighting decay in the pulses caused by too much current.

Well yeah, but while the flow rate is higher, the effort to push it is lower. Like it's really easy to push it by hand on the 1.2mm vs the 0.6.

I thought these would kinda negate each other. I did try slowing the print significantly though too, to no avail. Also the Zesty instructions make no reference to flow rate or nozzle size at all, only that the torque it generates so huge you need to start at 500ma and drop it from there till you get clicking sounds.

I had also tried ramping the temp way up, which is what I thought would solve it but made no difference.