Finer step angle

Hello,

I was looking for a NEMA17 stepper motor for the second extruder I am making. I stumbled on to this web site, which sells a few variety of stepper motors. The price looks decent, too.

However, the motor I would like to get has step angle of 0.9 degree, which is half of the step angle of all the other motors I have on my printer.

If I want to use this smaller step size motor in my printer...

1. I have to make updates to the firmware, and my RAMPS will be able to control this motor more accurately.
2. I don't have to make updates to the firmware, but it will be a good idea to do so b/c my RAMPS will be able to control this motor more accurately.
3. I don't have to make updates to the firmware, this motor will be automatically more precise thanks to its smaller step size
4. I have to make updates to the firmware, but there will be no gain in accuracy
5. I simply cannot use this motor.

Which one of above will be correct?

1.

In particular, you have to increase the steps/mm value to the double ... which also limits top speed to the half.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Traumflug Wrote:
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> 1.
>
> In particular, you have to increase the steps/mm
> value to the double ... which also limits top
> speed to the half.

Having to double steps per minute value sounds like the motor will have the same revolution per minute... Wouldn't that be the case?

0.9 degree step size motor would take twice as many steps to complete on revolution, compared to 1.8 degree step size motor... but now that we doubled the number of steps per minute for 0.9 degree step size motor...So, both will take the same time to complete on revolution, and wouldn't that mean the speed is the same between the two?

At very small steps (or high microstepping), speed isn't limited by the stepper, but by the processing speed of the controller. The more steps you have to generate, the earlier to hit this limit.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

But to be realistic, you will not hit the microcontroller speed limit with 0.9 steppers and 16x microstepping.

I am using 0.9 degree motors, and I am very happy with them. More accurate printing.

jkoljo Wrote:
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> But to be realistic, you will not hit the
> microcontroller speed limit with 0.9 steppers and
> 16x microstepping.
>
> I am using 0.9 degree motors, and I am very happy
> with them. More accurate printing.

Can you kindly tell me the configuration changes you had to make? I've been told to increase (double) the steps/mm value, but not quite sure where that setting is. Also, are there any other places I would need to make changes?

I'm using Marlin firmware on RAMPS 1.4 by the way.

Thank you.

You only have to change the steps/mm value, and you will have to do that anyway when you set up a new printer. In Marlin you make the change in configuration.h file, you will find the correct place when you look for it.

Edited 1 time(s). Last edit at 08/18/2013 05:29PM by jkoljo.

jkoljo Wrote:
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> You only have to change the steps/mm value, and
> you will have to do that anyway when you set up a
> new printer. In Marlin you make the change in
> configuration.h file, you will find the correct
> place when you look for it.

Is this it?

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,4000,870}

If I what to use a 0.9 step angle motor for Z axis (just for an example) I would change the third number, 4000, to 8000, is that right?