Why is Diameter Measurement Important to Industry?

Before we get to that answer, here’s a brief 101 on the different types of diameter measurements. In general, there are two types of diameter measurements:

• Outer diameter (OD)
• Inner diameter (ID)

The outer diameter is the distance from one point on the outside of a product, such as a pipe, tube or cable, through its center and to the opposite point on the outside. The inner diameter of a hollow circular object, like a pipe, is the distance from one point on the inner wall of the product through its center and to the opposite point also on the inside. The inside diameter is dependent on the outside diameter of the product and its wall thickness.

Another important, and related, set of measurements include the ovality and wall thickness of a product. The ovality is the amount of “out-of-roundness” of a tubular or cylindrical product in the typical form of an oval. The wall thickness is what it sounds like. It’s the thickness of the tube wall or the thickness of insulation of wire or cable, for example. So, by having the inner dimensions (ID) and outer dimensions (OD), you can calculate the wall thickness of a product. By subtracting the ID from the OD and then dividing by two, you get the wall thickness.

So why are these measurements important?

Because many products in this world need to be produced to exact design and performance specifications. For example, tubes are often put into applications such as medical devices that require precise outside diameters. Producing any medical tube product with an “out-of-tolerance” diameter or roundness, often down to ten-thousandths of an inch, affects the performance of life-critical devices such as catheters, drug delivery and surgical tubes, and other medical devices. With communication cables, such as coaxial and twisted-pair LAN products, any error in the diameter or roundness of the conductor or insulation directly impacts the cable’s performance characteristics – rendering the product useless for the designed application.

Integrating precision and reliable diameter measurement capabilities into your process enables you to automate process control. This allows you to instantly detect changes in the product diameter and automatically make adjustments at the extruder to effectively produce more products faster and with higher quality results. In turn, you’ll reduce scrap and significantly lower manufacturing costs to maintain a profitable production operation for the long term.

What types of non-contact gauges are available to measure the diameter of products?

There are several types of laser-scanning gauges available to measure the diameter of products – each offering a different degree of accuracy. For instance, single-axis diameter gauges perform measurements from a single viewpoint that is perpendicular to the measurement field. Two-axis diameter gauges perform measurements from two viewpoints. Four-axis diameter gauges perform a similar measurement but from four viewpoints. The larger number of measurement axes, the greater the measurement coverage and degree of accuracy. So, a four-axis scanning capability provides the most comprehensive measurement coverage around the product’s circumference compared to single- or two-axis gauges.

Which diameter gauge is best for me?

Depending on your application, you may only need a single-axis gauge to measure just diameter. Two-axis gauges give you the capability to measure both diameter and ovality dimensions. For applications requiring the measurement of critical dimensions, and certain profiles, you may require more precision such as a two- or four-axis gauge. It’s good to note that Nordson is the only company in the industry that offers four-axis laser gauges. In addition to diameter and ovality measurements, our four-axis gauges offer fault detection capabilities to catch lump and neckdown flaws on products. Diameter, ovality and flaw accuracies are the highest in the industry.

Nordson’ diameter gauges support a wide range of communication protocols for easy integration into the process and can be equipped with one of our process controllers for added quality assurance. In addition, you’ll benefit from easy-to-use features for simple setup and operation.

To learn more about diameter measurements and the gauging options available to you, browse our Measurements and Industry Solutions pages. We offer a number of great resources at your fingertips. If you need help, we’re just a phone call or email away.