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Speed of my stepper motors

Posted by flydeprutten 
Speed of my stepper motors
August 31, 2017 12:10AM
Hi,

I'm building my first 3D printer, and I'm struggling with a challenge. I'm testing my stepper motors and, although I can make them move correctly, I can not make them move very quickly without them stalling. If I move the engine more than approx. 1500 mm/min in octoprint they stop moving and just make a terrible noise. The engines run freely, I have not yet put a load on them.

My printer is a CoreXY design, and I have only connected the x and y motors to my RAMPS 1.4 card. I am using DRV8825 drivers that are set to a voltage of 0.650V, which should give a current of 1.3A. I have until now only connected drivers to the x and y axis. The drivers are set for 1/16 microstepping. The power comes from a PC power supply and I have only connected the 12V to the 5A-port of the RAMPS.

The motors are RTTM 17HS8401:

[www.aliexpress.com]

Am I doing anything wrong, or can these motors not move faster?

Edit:
I just wanted to add that Marlin is set up to 100 steps/mm. :-)

Edited 1 time(s). Last edit at 08/31/2017 12:19AM by flydeprutten.
Re: Speed of my stepper motors
August 31, 2017 12:33AM
What acceleration are you using? Reducing it may help.

The torque from a stepper motor starts to fall off above a certain speed, and that speed depends on the supply voltage to the drivers. To maintain torque to higher speeds, you need a higher supply voltage. See [duet3d.com] and work out whether 12V is sufficient for the top speed you want to achieve.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Speed of my stepper motors
August 31, 2017 03:24AM
That is a wonderful document. Thanks. smiling smiley

My max acceleration is set to 300 mm/s/s (no thought is behind this number).

If I set a desired speed of 100mm/s (6000mm/min) I get a peak back emf of 5.8V and an approximate back emf of 5.5V.

12V, according to what you write on duet3Ds page, should be ok. But I can not get over 25 mm / s (1500 mm / min).
Re: Speed of my stepper motors
August 31, 2017 09:09AM
Yes the speeds you are looking to achieve are quite modest, so I would expect 12V so be sufficient, assuming they are 1.8deg motors.

Are you certain that the drivers are running at 1/16 microstepping and not some lower value? Check that the jumper settings you are looking at are for DRV8825 drivers, not the more common A4988. Also, some RAMPS boards have all the jumper positions shorted by PCB traces, so the jumpers don't do anything. If you run the motors at a slow speed, you can count the revs/second and work out whether it is what you expect at that speed.

Edited 1 time(s). Last edit at 08/31/2017 09:10AM by dc42.

Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Speed of my stepper motors
August 31, 2017 01:31PM
Oh no. This is really embarrassing!

Yes I had set it to half-steps instead of 1/16. I discovered it because my big boy was disappointed that it was not moving yet. When I put all the belts on, I could see that when I moved it 10 mm in octoprint it moved significantly longer. Actually exactly 8 times longer. smiling smiley

The reference image I used to set the jumpers from was up side down compared to my RAMPS. This was probably something an experienced builder would catch immediately. I could clearly hear a difference in motor noise after I set the jumper correctly.

However, I have learned more about the speed of stepper motors, and I am grateful for that. Thanks smiling smiley
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