Discussed here is accuracy requirements of stepper motors using a simple single axis robot with a timing belt and a stepper motor.

(1) Calculating rotational accuracy needed for the motor

For converting motor rotations to linear motion, accuracies needed for the linear motion mechanism and the drive motor are as follows.

This equation is a conversion of needed linear positioning accuracy and rotational accuracy per 360 degree rotation, easily understandable by the [Fig.2] show below.

(2) Example

1. If timing belt and pulley selection candidates are as follows...

If linear positioning accuracy A is to be: A = ± 0.1mm...

2. If a ballscrew is used

The accuracy equation above can be used for ballscrew cases by replacing the pulley's lead pitch P with a ballscrew lead pitch.