## Stepper Motor Sizing

Discuss Stepper motors, Drivers, Controllers, GUI's and related Accessories here.
Engr. Wasiu
Posts: 5
Joined: Tue Nov 21, 2017 7:43 am

### Stepper Motor Sizing

I'm designing a Ball Screw system. In other to select a suitable motor for my system, i'm using The Motor Sizing Calculations Technical Reference.

I need help in defining the following three parameter as stated on page F6 of the above material:
Desired Resolution (feed per pulse):
Feed:
Positioning period:

om_tech_support_JS
Posts: 190
Joined: Tue May 10, 2016 4:48 pm

### Re: Stepper Motor Sizing

Hi Engr. Wasiu,

In regards to your post, I have the following definitions:

Desired Resolution (feed per pulse): This sets the desired smallest motion for your application. It determines the linear amount (inches or mm) that the system will move based on one pulse (or step) of the motor.

Feed: This is the total distance that you want the application to move (in inches or mm).

Positioning period: The total amount of time for the application to move to its ending position.

We also offer on online sizing tool. The tool for the ball screw application has been linked below:
http://www.orientalmotor.com/motor-sizi ... izing.html

Our Tech Support team can also help you size for the application or assist in selecting a product once the sizing has been done.
http://orientalmotor.com/contact/index.html#tp31_1

Engr. Wasiu
Posts: 5
Joined: Tue Nov 21, 2017 7:43 am

### Re: Stepper Motor Sizing

Thank you.
Another question.

In stating the total Length of Ball Screw (Inch) or (cm), are we to take only the length covered by screw or to include the length of bearing and coupling mounting section ?

Engr. Wasiu
Posts: 5
Joined: Tue Nov 21, 2017 7:43 am

### Re: Stepper Motor Sizing

What is the function of the Linear Guide?

Do we need the Linear Guide when using a bearing arrangement ?

What is the difference between positioning distance and Feed ?
If Positioning period: The total amount of time for the application to move to its ending position.

om_tech_support_JS
Posts: 190
Joined: Tue May 10, 2016 4:48 pm

### Re: Stepper Motor Sizing

Hi Engr. Wasiu,

The total length of the ball screw will only include the screw, therefore, you do not need to include the coupling or bearing.

For the linear guide, it provides two functions. The first function is to provide an anti-rotation mechanism and the second is to handle a specific amount of moment load that may be generated by the application.

Lastly, when the article talks about the feed, it is referring to the positioning difference, therefore, there is no difference.

Technical Reference:
http://www.orientalmotor.com/products/p ... RefAll.pdf

Engr. Wasiu
Posts: 5
Joined: Tue Nov 21, 2017 7:43 am

### Re: Stepper Motor Sizing

Hi OM,

Thank you for the support.

I have read the attached Technical Reference with respect to my design; a ball screw using stepper motor. I have tried out the example on page F-6 and F-7.

Please explain the following grey areas:

1) Calculate the Required Resolution: There appears to be conflict in the unit of "Desired Resolution (0.001 inch)" and "Ball Screw Pitch (15 mm)" on page F-6.

2) I tried using the online tool at http://www.orientalmotor.com/motor-sizi ... izing.html for the example but i got different answers for the following (see attached) :

A) Required Speed: 1168 [r/min] / 1200 [r/min]

B) Required Torque: 1734 [oz·in] / 71 [oz·in]

C) Acceleration Torque: 26.47 [oz·in]

D) Load Torque: 840.3 [oz·in] / 8.3 [oz·in]

E) Required Stopping Accuracy: 0.6000 [deg] / 0.72 [deg]

Kindly advice on the reasons for the discrepancy.

Engr. Wasiu
Posts: 5
Joined: Tue Nov 21, 2017 7:43 am

### Re: Stepper Motor Sizing

The attachment i referred to in my post yesterday
Attachments
Ball _ Lead Screw Sizing Tool Example.pdf

om_tech_support_JS
Posts: 190
Joined: Tue May 10, 2016 4:48 pm

### Re: Stepper Motor Sizing

Hi Engr. Wasiu,

In regards to your post, I do apologize as the value shown in the example is the incorrect value. As you stated, using the inch measurement for the desired resolution and the mili meter measurement for the pitch would result in conflicting units. With that being said, the inch units are also rounded which means that there would be some differences in the calculations. The equation should be:

Desired Resolution = 360 degrees *(.03 mm)/(15 mm) = 0.72 degrees.

When using the un-rounded inch values: 360 *( 0.0011811 inches)/(0.590551 inches) = 0.72 degrees

For the discrepancies, the major issue is your value for efficiency. The software requires the % value (90%). When you plugged in the value, you stated it as 0.90% so your torque calculations ended up being different. I have attached the revised 90% efficiency calculation which resulted in the following:

A) Required Speed: 1168 [r/min] / 1200 [r/min]

B) Required Torque: 69.75 [oz·in] / 71 [oz·in]

C) Acceleration Torque: 26.47 [oz·in]

D) Load Torque: 8.403 [oz·in] / 8.3 [oz·in]

E) Required Stopping Accuracy: 0.6000 [deg] / 0.72 [deg]

The fact that these values are still slightly off is due to any rounding that was originally done as well as any rounding in the software.
Attachments
Revised _ Ball _ Lead Screw Sizing Tool Example.pdf

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