max step rate

Hi again all,
Just seeking clarification regards the max step output on a ramps.
I was just reading the wiki on step rates and it mentions the arduino ramps
combo has a max step rate of 16KHz.

Is that per output to each stepper or is that the total step rate of all steppers?

This might be an obvious question but I haven't been able to locate this answer
else where.


Many thanks,
Andrew

It depends on firmware/hardware possibilities.
A good programmer will write step commands for all steppers to one variable and then send it out to one register at once. That way it´s fast and synchronous, but the step-pins have to be in the same register to do that ( depends on hardware eg. Ramps ) That way all steppers would be able to run at 16kHz.

I´ve seen a comparison table where max. feedrate was listed for different controllers/steppers, but that´s probably the page you´ve already mentioned?
-Olaf

Edited 1 time(s). Last edit at 09/28/2015 03:07AM by o_lampe.

Hi Olaf,
yes, it is a page from the wiki on reprap. I keep losing it and refinding it.
If the figure of 16KHz for max steps per second for a ramps/arduino r3 is
correct then it is a handing fact to know.
It also helps explain why running a 0.9/ 1/32 stepper at 10mm/s just
don't work and gives me a reality check.

Thanks for the info on internals Olaf,
Andrew

Quote

It also helps explain why running a 0.9/ 1/32 stepper at 10mm/s just
don't work and gives me a reality check

According to the table, it should run at max. 40mm/s.
Do you see different behavior? What printer, LCD are you running?
-Olaf

Forget that old table. This table needs an update.
The important thing is how much steps/mm do you have?
40,000 divided with this number is you absolute maximum. Some AVR are slower, some faster. I would prefer a number of 30,000 divided by your steps/mm.

---

Triffid Hunter's Calibration Guide

--> X <-- Drill for new Monitor

Most important Gcode.

Hi folks,
thanks for the replies.
The actual printer is a rework tweaked with a 12864 lcd.
The current steps/mm is 4000 but I might increase it to 1/16 8000. The steppers are still
very noisy.

I seem to have problems especially in the z once I start playing with 4mm/s+.
But I have another problem that has reappeared. It seems that once I start having
xy moving above 120mm/s, actually figure is really iffy, then the endstops stop working.

But I think,as was suggested elsewhere, moving the second z motor over to e1, means
I can start running them both at 1.5A+. Which should calm them down.


Many thanks,
Andrew

Quote
friarfish
But I think,as was suggested elsewhere, moving the second z motor over to e1, means
I can start running them both at 1.5A+. Which should calm them down.

Why not just connect the two Z motors in series (as the better kit manufacturers do e.g. RepRapPro) instead of in parallel? For the types of motors generally used in RepRaps, series connection makes far more sense than parallel connection. The reasons most people connect two Z motors in parallel are (a) they don't know any better, and (b) RAMPS makes parallel connection easy.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

But wouldn't that then mean I have the same old problem of the Drv8825 not
being able to provide anywhere near the amps required?
Or can the Drv8825 automatically adjust the volts to power two steppers
on one channel?

I know best solution is to replace the steppers with some decent 1.2A model
but the old piggy bank is empty.


Many thanks,
Andrew

The drivers automatically adjust the voltage to the motors to achieve the current you have set.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks dc42.
that might be another problem knocked off down the track.


Many thanks,
Andrew

For completeness, I should point out that if you use low current high voltage motors, parallel connection is better. But for typical motors used in repraps with a current rating in the range 1.3A to 1.7A and a corresponding voltage of between 2V and 4V, series connection is better, even if you are powering tour electronics from only 12V.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].