I've been trying to figure out the maximum speed my stepper motors can theortically turn at. The reason this came about is to get the maximum retraction and travel speeds possible, and maybe print speeds if I can get my hobbed bolt to stop grinding filament past 70mm/s at 0.2mm layer height.

At the moment I am using a RAMPS 1.4 board over an arduino mega 2560, with the regular A4988 polulu drivers at 1/16 mictostepping, and some no-name 1.8* 5Kg/cm steppers. I was using a printrboard until I fried one of the drivers.

Does anyone know what is the theortical maximum steps per second rate? The reprap forum briefly mentions 16000, but I also read somewhere it's 40000. Neither of these sources mentioned how they got these numbers.

If I somehow just missed a writeup or something during my research, please just post the link.

Thanks.

Edited 1 time(s). Last edit at 06/07/2015 11:08PM by Masterjuggler.

See: [reprap.org]

Thanks, that link helps a lot. It doesn't say how it got those numbers, but I'm not sure if I would understand the explanation anyway, haha.

That wiki page references "Quadstep-Mode (uneven step distribution)" as a means to get up to 67kHz with marlin on a RAMPS board. I can't seem to find anything about that either, but it sounds like it would give the same effect as reducing the microstepping to 4x. Do you know what quadstep-mode is?

Speaking of reducing microstepping, I might just do that for my extruder, because it's geared to 847 steps/mm. Man I'm feeling dumb today.

67kHz is more a theoretical value. 40.000 is much more realistic on an Arduino Mega.
Quadstepping is needed for that high stepping rates. Normally 10.000 steps/s is the maximum. This is because there are some expensive calculations. This calculation are only done every forth step on quadstepping or every second step on double stepping. Also the steps are done in the fastest way after that calculation. That's the reason of the uneven step distribution.

Time for execution
------------------------------
expensive calculations
cccccccccc
step execution quad stepping
ss ss ss ss

calculation + stepping
------------------------------
cccccccccc ss ss ss ss
= enough time

calculation + single stepping
------------------------------
cccccccccc ss cccccccccc ss cccccccccc ss cccccccccc ss
= not enough time

So at 800steps/mm you can't get faster than 50mm/s (40.000/800) with quadstepping or 12.5mm/s in single stepping.
Don't spend much time to think about quadstepping, this is done in the backround and allways active if the steps/s goes to high.

Edited 2 time(s). Last edit at 06/08/2015 04:57AM by Wurstnase.

---

Triffid Hunter's Calibration Guide

--> X <-- Drill for new Monitor

Most important Gcode.

... with finer microstepping you'll need higher stepping rates to achieve the same speed, but you can position finer, the motors runs smoother and you can drive even faster than with coarser steps for higher possible accelerations.

One of my old CNC-mills with only full- and half-stepping is limited to 10kHz, what was common around 1990 ... but it can run as fast as 4m/min (67mm/s) with it's mechanical resolution of 400 steps per 5mm (one full turn of the spindle) at half-stepping.

I have other drives with 5mm-spindles too, which are driven with 325 VDC motors and 20kHz at fullstep with 1000 steps per rev. or 200kHz at 10x microstepping with then 10000 spr., what's resulting in a much higher mechanical resolution, but only 6m/min (100mm/s) max. speeds, so not really that much faster than the old mill.

I have some other stepper-drivers with max. 1/256 microstepping and max. 10MHz stepping rates, what could result in superfine resolution and ultrafast movement (max. 58,5m/min, 976mm/s on a 5mm-spindle with then 10240 steps per mm or 97 nanometers resolution!) -- but until now I don't have a CNC-controller which is capable of this clocking speeds to test it ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

With a 200 step/rev motor, increasing ustepping beyond 16 smooths the motion but doesn't increase resolution because the ustep size becomes smaller than the 5% typical error in the full steps.

If the motor is running quietly enough at 16 usteps, leave it there. Microstepping reduces torque as well as limiting maximum speed.

You can get back some of the torque lost to microstepping by running the motor at higher voltage. Steppers are often run at 10x their rated voltage.

@ Masterjuggler

Hi,

Did you read the Discussion tab in the wiki page that the_digital_dentist pointed you to?

In reality, maximum retraction and travel speeds possible for any given 3D printer are in 99% of all cases limited by mechanical factors, and not by the electronics max. theoretical step rates.

Apart from that, microstepping does not reduce overall rotational torque, it reduces incremental torque for each microstep, see [www.micromo.com] for the details.

Without getting into the nitty-gritty of it all, the simple conclusion is that you can and should run your RAMPS + A4988 Pololu setup at 1/16th microstepping for all the steppers in your RepRap 3D printer.

I run my Prusa i3 and various P3Steel's at 1/16th microstepping for the extruder and Z-axis and 1/32 microstepping (using DRV8825 drivers) for the X and Y-axis without any problems whatsoever.

... this discussion about max. 1/16 or higher microstepping and lower torque with microstepping isn't new, but is mostly focussed on a specific type of application - here with the typical 3D-printer setup.

While it's mostly true for the common setups with cheap NEMA 17 motors and pololu-type drivers, this will change when using high quality (much more expensive) steppers with higher torques, bigger sizes and higher currents, as used with most CNC-milling or high torque drivers.

The small steppers used for 3D-printing are close to their mechanical/electrical limits and max. possible torques.

When used 'oversized' motors+drivers, this numbers changes rapidly.

I'm using stepper motors, servos and PZT-drives for micro-applications with stepping resolutions and accuracies in the sub-micron ranges, where the internal building accuracy of the motors is much more relevant than electrical or driving properties ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

@AndrewBCN - I didn't even notice the discussion page, thanks for pointing that out.

As far as mechanical vs electrical limitations go, if my theroetical max steps/sec is 16000 and my extruder steps/mm is 847, then I can still only acheive a maximum realistic 18mm/s retraction speed.

I actually already read through the micromo page and understand for the most part what it's getting at with how microstepping affects torque. As I understand it, while torque per microstep is reduced, overall torque per full step is not, which means microsteps may need to piled onto each other in a sense to get enough torque to move under load. Of course, I haven't researched enough to be able to understand some of the more technical stuff.

All my other axes are 88.89 steps/mm for a max of 180mm/sec, so I'm not really worried about those. The only reason I would want to go fatser is if I wanted to experiment with crazy speeds, or if I wanted to get the travel speed up there. Right now my travel speed is at 170mm/sec, so I don't skip steps.

I just tried redicing the extruder microstepping to 8x to experiment with higher retraction speeds, which I'll play around with later. I have to say though, while I can hear the steps a little more distinctly, it is no louder than at 16x. In fact, I'll even call it less annoying because of the lower pitch.