# Towards Compensation for Servo-Control Defects in Coordinate Measuring Machines (CMMs)

## TL;DR

This paper presents new methods to improve the accuracy of CMM measurements by addressing servo-control defects, especially when measuring circles on warped surfaces.

## Contribution

The paper introduces two innovative solutions to circumvent servo-control defects in CMMs, improving measurement accuracy for specific geometries.

## Key findings

- Constructing a circle can yield better results than direct measurement on warped surfaces.
- Servo-control significantly impacts specific CMM measurements, leading to errors.
- Proposed methods improve accuracy and help meet standard specifications.

## Abstract

This study focuses on the effects of servo-control while measuring circles on warped surfaces with CMMs. It describes the methods for identifying the various parameters that affect the measurement. It offers innovative solutions to overcome positioning accuracy problems and to improve results such as circularity or runout measurements. Two practical solutions are suggested to avoid the servo-control defects.

What are the main findings?
In some cases, constructing a circle is a better solution than measuring it directly.Our study showed that servo-control can have a significant impact on specific CMM measurements.Two methods are hereby proposed in order to circumvent the effect of servo-control.

In some cases, constructing a circle is a better solution than measuring it directly.

Our study showed that servo-control can have a significant impact on specific CMM measurements.

Two methods are hereby proposed in order to circumvent the effect of servo-control.

What are the implications of the main findings?
They allow for the accuracy of some results on circles to be increased.They allow for standard specifications to be met.

They allow for the accuracy of some results on circles to be increased.

They allow for standard specifications to be met.

Coordinate measuring machines (CMMs) are increasingly used in manufacturing, mechanical engineering, and wherever special geometries need to be measured with the utmost precision. CMMs are very important in various fields including the automotive, aerospace, and military industries. For certain specific tasks, such as measuring roundness or contour, they are not as accurate as specialized measuring machines, for instance, roundness measuring machines, especially if the circle is to be measured on an oblique surface. The CMM servo loop is not as accurate as the CMM readings, as it leads to differences between the theoretical target coordinates of a point and the actual coordinates obtained. On a conical surface, for example, where height and radius are linked, these differences are the cause of errors on circle dimensions. In this case, it is necessary to construct the feature instead of measuring it directly. This article proposes innovative methods for performing specific tasks on a CMM and for taking faults due to servo-control into account. The results show significant improvements for standard parts or skewed surfaces.