Positioning Accuracy Vs Repeat Positioning Accuracy

Positioning accuracy and repeat positioning accuracy are two different concepts

Commonly used in industry to describe the performance of mechanical systems.

Repeat positioning accuracy is higher than positioning accuracy

positioning accuracy

Positioning accuracy is a certain value, not a range; while repeated positioning accuracy is a range.

Positioning accuracy refers to the degree of deviation between the target position and the actual position that the mechanical system can achieve in one movement.

It reflects the accuracy of the mechanical system in reaching the target position in a single movement.

In layman's terms: it refers to the error between the actual position reached when the machine equipment stops and the position you requested.

Positioning accuracy is a definite value (for example, 0.01mm), not a range (for example, ±0.02mm)

The positioning accuracy error depends on the manufacturing error of the transmission components.

Example: An axis is required to travel 100mm, but in fact it travels 100.01mm. The extra 0.01 is the positioning accuracy.

For example: Set the screw movement distance to 100mm. As a result, the actual movement distance of 100 screws is 99.99mm to 100.01mm, and the positioning accuracy is 0.02mm (100.01-99.99=0.02)

Repeatability

Repeated positioning accuracy refers to the accuracy with which the mechanical system can repeatedly reach the same target position in multiple movements. It reflects the consistency and repeatability of the mechanical system in reaching the same target position in multiple movements; repetitive positioning accuracy is important for multiple movements. The application of repetitive movements is very important.

In layman's terms: it refers to the error caused by positioning the same position multiple times in the past.

Repeat positioning accuracy is a range (for example ±0.02)

Repeat position error is related to the clearance of transmission components.

In addition, repeat positioning accuracy is not only related to the accuracy and resolution of the grating scale (displacement sensor), but also to mechanical system errors, such as guidance systems, transmission systems, and structural rigidity.

These factors will reduce positioning accuracy and affect repeat positioning accuracy to a certain extent.

Example: An axis is required to travel 100 mm.

As a result, the first time it actually walked 100.01mm, and after repeating the same action, it walked 99.99mm. The error between this is 100.01-99.99=0.02mm, which is the repeat positioning accuracy.

Repeated positioning expression method: expressed by ±x, the above error is expressed as ±0.01mm, which is ±(0.02/2).

For example: set the moving distance of the screw rod to 100mm, and the actual moving distance is 99.988mm to 99.992mm after 100 movements.

Its repeatable positioning accuracy is ±0.002mm.