Duet Wifi and nimble acceleration issue

dc42

The relationship is:

max_extruder_acceleration_during_printing_moves = min(configured_extruder_acceleration, jerk/pressure_advance)

where jerk is specified in mm/sec. You have set jerk to 72mm/min, so with PA 0.05 the max extruder acceleration for printing moves will be 72/(60 * 0.05) = 24 mm/sec^2. That is indeed a very low acceleration.

Does the Nimble need the jerk to be set as low as 72mm/min ?

garyd9

@dc42 said in Duet Wifi and nimble acceleration issue:

You have set jerk to 72mm/min, so with PA 0.05 the max extruder acceleration for printing moves will be 72/(60 * 0.05) = 24 mm/sec^2. That is indeed a very low acceleration.

Does the Nimble need the jerk to be set as low as 72mm/min ?

I can't answer that with a clear "yes" or "no", but I can give you a bunch of numbers that might put it into context.

For the Zesty Nimble (both the older v1.2 with a 30:1 ratio, and newer v2 with a 20:1 ratio), they suggest a "jerk" of 40mm/min with an acceleration of 120mm/sec^2.

I can understand the limits with the 30:1 ratio: A jerk of 60 (1mm/sec) is an instant movement (or stop) of ~2700steps. (2700steps/mm with a 1.8 degree stepper and 16 microsteps.) That's over 4/5's (84%) of a full turn of the stepper shaft as instant movement. Not only does the extruder shaft have to move 84% of a full revolution, but so does the drive cable and worm gear...

For my own configuration, I started with their suggested numbers and did a bunch of testing. I don't have my physical testing notes anymore, but I did leave this tidbit in my config.g:

M566 E125 ; zesty suggest 40. 350 works, but clicks madly. 125 works smoothly even on retractions when printing a 0.8 nozzle at 50mm/sec (print speed, not extrusion speed.) Possible (?) that a jerk too high can damage the plastic nimble worm gear

I also have acceleration working at 900mm/sec^2. (At 1000mm/sec, there's a risk of the stepper shaft not turning.)

I'd guess that the flex3drive has the same or a similar issue due to it's 40:1 ratio. (However, I've never used or installed that particular remote direct drive extruder, so I am only guessing.)

max_extruder_acceleration_during_printing_moves = min(configured_extruder_acceleration, jerk/pressure_advance)
where jerk is specified in mm/sec.

I'm trying to reconcile that formula with my actual experience, and it doesn't quite match. (I'm not saying that you are wrong - I'm just trying to fit it into my real world simulated experience.) In all the tests I mention above, my accel was at 900. In every test case I made, that 900 would be greater than the result of jerk/PA, so the jerk would always be slowing down the print.

For example, a jerk of 500 (8.33mm/sec) and a jerk of 0.02 results in 416.65 (which is less than half of the 900 accel.) Yet, my testing showed that a jerk of 500 had no impact on the print time with any PA value from 0.0 to as high as 0.1. (0.1 resulting in 8.3/0.1 == 83.)

(I need to add this line to my signature for work emails: "I'm not saying that you are wrong - I'm just trying to fit it into my real world simulated experience.")

garyd9

@deckingman said in Duet Wifi and nimble acceleration issue:

@garyd9 That is one of the most interesting and useful pieces of testing that I have seen in a very long time. I never considered using simulation to quantify the correlation between E jerk and PA. My machine is in pieces again at the moment. Could you possibly establish the minimum jerk that does not slow down the print time for a PA value of 0.5? If not, no worries - I'll add it to my to-do list.

I long ago deleted the gcode file for the print, so any newly sliced file wouldn't have any relation to the existing results.

As well, simulations on my machine with my config would have different results from yours. I'm using a delta with high accel and movements speeds in x/y/z due to having a very light effector, but with low "E" values for max movement, accel, etc. I'm going to assume that your printer has much higher "E" values, but much slower X/Y/Z speeds and accel due to (sarcasm) you moving 48 nozzles and heaters, 14 diamond hot ends, a dozen bondtech extruders, a few boulders, and the entire population of at least one major city. (Or, at least that was my impression the last time I saw a video of your machine running.)

Seriously, though, while the PA vs jerk would raise/lower the print times, I don't completely understand how all the other variables might interact to impact the results. I'm sure my limited E accel would play a part, but I don't know what else would.

arhi

@garyd9 said in Duet Wifi and nimble acceleration issue:

I'd guess that the flex3drive has the same or a similar issue due to it's 40:1 ratio.

doesn't that's the major difference I find between the two f3d is way faster, you only need to get E motor that can go fast. I had some issues with high impedance motor but when I found a better one it's crazy fast, attm I'm running jerk 500 and accel 2000 for the f3d. I'm not happy how PA works with f3d with the old shaft but new shaft they supplied (I broke one of the old shafts) seems to be working ok for PA too (they switched to a thicker shafts, differently wound and they come in "no clue what but not ptfe any more" new type of slieve.

fcwilt

Hi,

What does PA do for a Nimble?

I've been happy with my two Nimble setups using the recommended settings.

Frederick

deckingman

@garyd9 Yes it's true that my machine is a CoreMostOfTheAlphabet etc. . But I thought DCs comment clarified something that I've been wondering about. In other threads, it has been suggested that what would appear to be silly high jerk values should never be necessary. But my multi input beast needs a PA value of around 0.5. Which means that my "silly high" E jerk of 3600 translates to extruder acceleration of 30mm/sec^2 when PA is set to 0.5.
I'll run my own tests when I get my machine back together. Could you describe what your test part looked like? I'm guessing it had lots of curves or cylinders.

garyd9

@deckingman said in Duet Wifi and nimble acceleration issue:

I'll run my own tests when I get my machine back together. Could you describe what your test part looked like? I'm guessing it had lots of curves or cylinders.

Based on my notes, the file name was "2x ear protector v5 (08 nozzle).gcode" If you really, really want, I can go back into fusion360's history to get v5, but here's v7 of the same file. (It's one of those surgical mask ear protectors, but oversized for people with big heads.)

When I print those with a 0.8 nozzle, the first layer has a height of .4 and the remaining layers are at .3. Print speeds are fairly slow at 40mm/sec. I can send you the full cura profile if you really want (but can't post it directly in this message due to file extension limitations.)

Anyway, here's the stl file: ear protector v7.stl

@arhi said in Duet Wifi and nimble acceleration issue:

f3d is

I'll respond in a private message. This thread shouldn't turn into one of the many (now closed) ProductX vs ProductY threads.

bot

@garyd9 said in Duet Wifi and nimble acceleration issue:

[...]
@dc42 said in Duet Wifi and nimble acceleration issue:

max_extruder_acceleration_during_printing_moves = min(configured_extruder_acceleration, jerk/pressure_advance)
where jerk is specified in mm/sec.

I'm trying to reconcile that formula with my actual experience, and it doesn't quite match. (I'm not saying that you are wrong - I'm just trying to fit it into my real world simulated experience.) In all the tests I mention above, my accel was at 900. In every test case I made, that 900 would be greater than the result of jerk/PA, so the jerk would always be slowing down the print.

For example, a jerk of 500 (8.33mm/sec) and a jerk of 0.02 results in 416.65 (which is less than half of the 900 accel.) Yet, my testing showed that a jerk of 500 had no impact on the print time with any PA value from 0.0 to as high as 0.1. (0.1 resulting in 8.3/0.1 == 83.)

(I need to add this line to my signature for work emails: "I'm not saying that you are wrong - I'm just trying to fit it into my real world simulated experience.")

You have to keep in mind, the result of that formula is EXTRUDER acceleration.

Jerk/accel for E axis is a slightly different game, because their relationships to the X/Y axes is based on volume of extrudate.

[edit: though, I may have misunderstood your post. I thought you were talking about your X/Y acceleration. I need a second coffee, sorry.]

arhi

@garyd9 said in Duet Wifi and nimble acceleration issue:

This thread shouldn't turn into one of the many (now closed) ProductX vs ProductY threads

I agree 100%, just answered the question with my experience

I found many had issues with remote direct and PA and I have same experience, I can get high jerk/accel but no luck with PA on remote direct

dc42

How much PA is needed on a RDD extruder anyway?

arhi

@dc42 said in Duet Wifi and nimble acceleration issue:

How much PA is needed on a RDD extruder anyway?

That's a good question as the tension of the cable buffers the pressure in the hotend. The problem I had was I was getting zero quality improvements with change of PA and I was getting huge slowdowns so I gave up setting PA on RDD

garyd9

@dc42 said in Duet Wifi and nimble acceleration issue:

How much PA is needed on a RDD extruder anyway?

More than I thought, if I use the python script test that has been posted on the forums (and comes up every now and then.) It's the one that prints a double thick wall with motion speeding up and slowing down while printing - and slowly increasing PA over the vertical space.

Based on that test alone, the 30:1 nimble on a smart effector with a standard E3D v6 setup needed a PA between 0.15 and 0.20 PA before the "fast" and "slow" sections started getting near the same thickness. To compare to that, I used to use a titan extruder with a precision piezo orion module and v6 heat break, all hanging from my effector. That only needed a PA of 0.04, and the length between the extruder hob and nozzle was about 15mm longer than what I have with the zesty nimble and smart effector assembly.

What was interesting with the nimble PA test is that the resulting print didn't "tear" at very low levels of PA (as pictures I've seen seem to indicate happens with bowden setups.) In fact, the print looked nearly identical all the way from PA 0 to PA .12 or so.

That leads me to guess that there is some pressure build up in the drive cable causing the issue. Perhaps M572 is entirely the wrong answer to that issue. Unfortunately, PA is the only tool that I know of that deals with that kind of symptom, so it's what I try to use. (If you only have a wrench, but you need to drive in a nail... that wrench starts looking like a hammer.)

I will mention that when I print "normal things" with a higher jerk (250 or so) and a PA of 0.04, as long as I can ignore the noises, the prints do look slightly better than prints with a PA of 0. In particular, it's nearly impossible for me to identify where lines of extrusion start/stop with a PA of 0.04.

All that being said.. I just (about 20 minutes ago) replaced my NEMA17 pancake stepper that was driving the nimble with a 1 amp NEMA14. It has less torque (12.5Ncm vs 16Ncm), but half the rotor inertia, so I'm hoping it behaves better with the sudden direction changes from higher jerk and PA. I think I'd be happier if I could keep jerk at 250 (and not have slowdowns with PA 0.04.)

Alexander Mundy

I did away with all the settings and interaction problems by going to Portescap P430 258 005 01 3.6 degree ultra low rotor inertia disc permanet magnet steppers for my Nimble extruders. I'll never go back to conventional steppers with a high ratio extruder after using them, they are like a sports car vs a Yugo for starting, stopping, and reversing direction in comparison to the suggested Nema 17 pancake and Nema 14. Expensive new, but they can occasionally be found used at a decent cost.

fcwilt

@Alexander-Mundy said in Duet Wifi and nimble acceleration issue:

I did away with all the settings and interaction problems by going to Portescap P430 258 005 01 3.6 degree ultra low rotor inertia disc permanet magnet steppers for my Nimble extruders. I'll never go back to conventional steppers with a high ratio extruder after using them, they are like a sports car vs a Yugo for starting, stopping, and reversing direction in comparison to the suggested Nema 17 pancake and Nema 14. Expensive new, but they can occasionally be found used at a decent cost.

Where did you get yours? I cannot (so far) find a vendor in the US.

Thanks.

Frederick

Alexander Mundy

Used on ebay

fcwilt

@Alexander-Mundy said in Duet Wifi and nimble acceleration issue:

Used on ebay

It seems that there are currently none there.

Too bad, I would like to try one.

Frederick

svalsorim

Just wanted to thank you all very much for input and sharing, don't want to be ungrateful. I had some success with 120 E acceleration and 0.03 PA. On a side not my prints look a little different since moving from direct to nimble, walls have weird "pattern". I need to test more to eliminate speed factor. Also ill be looking to get that portescap stepper it seems to be a way to go. Again Thank You!

OwenD

@svalsorim said in Duet Wifi and nimble acceleration issue:

On a side not my prints look a little different since moving from direct to nimble, walls have weird "pattern". I need to test more to eliminate speed factor.

The patterns are command and a known issue in V2 extruders. They are apparently caused by 2nd order resonance in the helical gears. (Us old farts would remember the diff howl typical in pre 70's cars)
You'll need to go to the discord channel and register to have the gears replaced when a fix is available.
My experience was that no amount of tuning would get rid of it completely.
Also be aware that the breech will soften if exposed to much heat. They advertise 60 degrees.
In my case, printing ABS generated enough ambient heat (unheated enclosure) to make the breech soften and cause under extrusion.
I like the design philosophy, so when they can sort the gears I might get it out of the draw again, but I was unable to realize the benefits that the design promised.
And I'd have to make a breech to work reliably at ABS temps.
Others seem to love them, so perhaps it comes down to the sum of the manufacturing tolerances in the particular unit you get.

fcwilt

@OwenD said in Duet Wifi and nimble acceleration issue:

They are apparently caused by 2nd order resonance in the helical gears.

Why wouldn't a speed change allow avoiding the resonance?

Thanks.

Frederick

Alexander Mundy

@fcwilt 4 times what I paid but still way cheaper than retail:

https://www.ebay.com/itm/192599739125

If you look at the pics it is the same part#. In fact mine came with the "theta assembly" label pigtail also. Escap is Portescap's old name.