Stepper settings

[VCParticipant @vc44480]

Some help need please

Trying to drive the X axis on my mini mill with a stepper nema 17 (200) steps /rev this is hooked to a easydriver -arduino uno – usb- EFL program.

Need help with these settings comes std with step/mm 250 at these settings asking for a X1 and checking the DR way off.

Tried this (stepper) 200*8 (micro steps)*20 (lead screw) = 32000

Tried that in step/mm and the stepper just makes a noise that's like a high pitched squeak.

Thanks all

[VCParticipant @vc44480]

[EmgeeParticipant @emgee]

VC, is the stepper driver board called "easydriver" because the arduino won't drive it direct. Normally setting details are included with the driver. Are you testing off load, ie not connected to the leadscrew.

Emgee

[VCParticipant @vc44480]

Thanks for the prompt reply Emgee

The arduino has been "flashed" with GRBL

sounds like I know what I'm talking about just a little parrot talk

Testing on the mill. had too up the voltage to 24v

Thanks again

[Les Jones 1Participant @lesjones1]

Hi VC,
Have you checked the torque required to rotate the leadscrew is within the rating of your stepper motor ? Are you using ballscrews or the original leadscrews ? I am using a 180 Nm stepper motor on my rotary table and I think that is easier to rotate than the X axis leadscrew on my X3 mill. Have you tried stepping at a lower rate ? If you step too fast the current through the coils does not reach its full value due to the inductance of the windings. My gut feeling is that the stepper motor is too small.

Les.

[Russell EberhardtParticipant @russelleberhardt48058]

Nema17 motor sounds a bit small to me as well. I'm using nema23 motors on my X2 mill which has an identical table to some X1s. Try running with the motor disconnected from the leadscrew. Does it turn OK then? If so are you running it at it's maximum current? You do need high voltage for fast stepping as well as it takes some time for the current in the motor to rise to the set value.

Russell.

[David JuppParticipant @davidjupp51506]

Posted by VC on 01/03/2016 08:55:21:

Tried this (stepper) 200*8 (micro steps)*20 (lead screw) = 32000

Tried that in step/mm and the stepper just makes a noise that's like a high pitched squeak.

That suggests 1 full turn of stepper motor gives 0.05mm movement of the axis. Are you sure that is correct?

I agree with others that NEMA 17 is likely to be a bit on the small side, unless geared down quite a lot.

Also check that traverse speed and acceleration aren't set too high – set to minimum for initial testing. It's very easy to ask the steppers to do more than they can manage in accelerating the carriage and overcoming friction.

[Clive FosterParticipant @clivefoster55965]

Have you got any acceleration control so the step rate builds up from nothing when the motor starts or are you starting off at the preset rate? Most stepper motors will bog down and not move under load if the start step rate is too high. Basically the motor needs to move round a bit after each step so the next step can get hold of things and move it a bit further. Think of turning a loaded gear wheel via a springy ratchet system. If the gear doesn't move far enough for the ratchet to engage properly on the next tooth it will just slip back past the spring.

For any given motor torque and load there is a limiting step rate above which the motor torque is insufficient to shift things round far enough for the next step to continue the movement. If they step rate is slower the motor has more time to move the load so a lower torque will suffice.

Clive.

[VCParticipant @vc44480]

[jason udallParticipant @jasonudall57142]

Size 17 motors…seem a bit little for that if direct drive

Firstly try it with no micro step or only half…the torque falls off as the degree of micro step goes up..and not in a linear way

Also mm/step
I think it goes like this…
Steps per rev x microsteppes /mmper rev…
Ie one rev =leadscrew pitch and that is achived( say 200 x8) by sso many steps..so
20 mm / (200*8) steps…
Ie 1/80 mm per step

[VCParticipant @vc44480]

[VCParticipant @vc44480]

Thanks All

Yes bigger steppers would be better

But still think I would have the same problem

Need to add code X.050 and watch the stepper do ! rev

[David JuppParticipant @davidjupp51506]

What pitch is lead screw ? and are steppers direct drive to screw?

My guess without knowing the mechanical arrangement is that when multiplying by 20, you should have instead divided by leadscrew pitch.

[Les Jones 1Participant @lesjones1]

Hi VC,
Try writing a little program to run on the aruino that just sets the direction signal and sends 200 pulses to the setepper driver. There would be less unknown factors that way.

This looks like a template for what you need to do.
 

Les.

Edited By Les Jones 1 on 01/03/2016 15:21:07

[jason udallParticipant @jasonudall57142]

This isn’t hard.
200 (steps per rev)
8 (micro steps)
Thusly 1600 steps per revolution.
20 mm lead also per rev

Thus 1600 steps will advance 20 mm

So. 80 steps per mm

[mike TParticipant @miket56243]

Does you mini mill really have a leadscrew with 20mm lead per rev?

I would have thought something like a 5mm lead would have been more likely for a ball screw, or a 1mm lead for a conventional screw/nut leadscrew.

[John HaineParticipant @johnhaine32865]

I think the lead must be 2mm per Rev, not 20! So 800 steps per mm. I think this is trying too hard, the stepper may not generate much torque until you have fed it a number of steps. A step of 1.25 microns isn't practically very useful IMHO.

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