What Does Concentricity Mean?

Concentricity is a value used to calculate the extent to which a geometric shape in CNC (Computer Numerical Control) matching is closest to its ideal form. This measurement is commonly taken in CNC machining to ensure high precision and quality during the production stage to ensure manufactured parts fit perfectly together and minimize errors. There is value to measuring the concentricity of a product during CNC machining, including a greater assurance that the dimensions of prototypes will not exceed their manufacturing tolerances. In this article, we dive deeper into the meaning of concentricity and how it is used in metrology to expedite the product development pipeline.

Why Do We Need to Measure Concentricity?

The bottom line in the pursuit of product development is to ensure that workpieces do not vary too from having perfect symmetry, especially when a machine processes it. In many cases, deviation from having the ideal symmetrical balance can be costly, resulting in material waste and higher production costs. Most importantly, it will create flaws and issues later in the production process. Therefore, it is usually measured in an axial or radial orientation to examine the extent of the error in the different dimensions. However, as this process is considered complex and difficult to implement, it is only used in specific situations and when needed.

How to Measure Concentricity?

The value of concentricity is usually calculated using the two diameters of the hole – one for the hole and the other for the shaft. They signify the outer boundary and the inner line, respectively, and both are necessary to examine the deviation in surface measurements. Additionally, depending on the company’s protocols, they can be measured in imperial units (inches) or metric measuring (millimeters). As mentioned before, measurements in CNC machining are made in the axial or radial orientation; therefore, three methods are considered relevant in this aspect.

  1. Radial Error – The measurement variation between the feature’s center on one side and the corresponding point on the other.
  2. Axial Error – This is calculated by subtracting the distance from machine zero to a datum line and then calculating the deviation from this line at two locations along its length.
  3. Overall Accuracy – This value is obtained by adding radial and axial errors together, or it can be pre-calculated (empirically) because certain machines provide complete concentricity

A Common Challenge in Concentricity Measurement

The dial indicator is one of the most common ways in which engineers measure concentricity and it is usually done in both directions. It will measure at a 90-degree angle to the longitudinal axis and at a one-sided offset. However, it poses the challenge of requiring sufficient space of up to 18 inches to inset the spindle tip of the equipment. Additionally, you will need to be extremely cautious of any accidental breakage or deflection of the rotating components during the measurement process.

What We Offer

Here at Willrich Precision, we have almost half a century of experience in the metrology, gaging, and inspection fields. We offer a great variety of products such as basic measuring tools, metrological technology, and equipment like vision systems, laser systems, and micrometers. We are a pioneer in measurement instrumentation, and we are dedicated to helping you make informed and intelligent decisions for your business operations like CNC machining.

For more information about the product and services Willrich Precision Instrument offers, please do not hesitate to contact us today!

by George Chitos