Non-contact CNC Shaft Measuring System: An Alternative to Conventional Methods

Combining length and roundness measurement with a digital image projector, the new optical CNC shaft gaging systems from Detroit Precision Tool Co. (Detroit, MI) can inspect up to 150 different features in less than a minute.

Contour, diameters, length, roundness, concentricity, cones, angles, flatness, parallelism, eccentricity, stroke, threads, and more, in submicron detail, can be recorded during a single pass of the optical measuring head. The gages, driven by Windows NT measuring software, can be used as an alternative to conventional shaft measuring techniques that is faster, more accurate, and more complete.

"With no practical limit to the number or the size of features that can be measured, our systems offer shaft manufacturers a highly flexible, cost-effective, high accuracy, and high-speed measurement tool that can confirm production quality instantly," said John Sattmann, Detroit Precision Tool vice president.

For use in production lines or cells, the gaging systems can help reduce machine qualification times while providing the ability to ensure 100% quality control within the machining cycle. Already at work in Europe, the gages are widely used in the automotive industry. In fact, in one application, the gages are checking 32 valve features in one second.

Two models, the AMV and WMS CNC measuring systems, are available. Both are adaptable to manual, semiautomatic, fully automatic gaging, horizontal, or vertical installations. The narrow-profile AMV is more suited to integration within the manufacturing process, while the WMS is tailored for stand-alone operation and universal measuring.

The fully flexible shaft gaging systems accommodate shaft sizes from 0.2–270 mm diameter, 1–1,500 mm long with measuring accuracies to ±1 micron. Filters are used to ensure highly reliable measuring results, and to eliminate sources of error including dirt and swarf.

According to the company, the CNC eliminates changeover time from one part to another, and measuring times can typically be matched to production rates. Manufacturing checks, automatic tool correction, initial sample measurement, and machine setup, are typical applications.

"The measurement and analysis software, consisting of about 150 measurement modules for a range of measuring functions, is simple to program," said Sattmann. "A measuring program can be assembled from function macros, so repeated measuring tasks can be accomplished very quickly. And the flexible design of the measurement modules, the consistent use of common standards, the measurement technology, and the use of standard-operating systems makes it possible to create the optimum solution for each application," he added.

The workpiece is clamped into the gage between centers. A rotary drive with integral angular encoder is located in the headstock, A measuring slide, consisting of a camera with CCD diode lines opposite a high-power LED, travels axially along the shaft, registering digitally up to 2,000 measurements per second. Profiles of the workpiece are reflected onto the diode lines, and an image-processing system analyzes longitudinal and rotational measurement data. This information is converted to X-Y measurements, the angle of rotation is included to assess deviations in shape, and measurement results are then documented or used to instantly correct the manufacturing process.

Once the workpiece has been scanned, a part profile is displayed on the large CRT, at which point the part may be analyzed, documentation can be output, data can be stored and graphed for later reference, or transferred.

For more information, contact Detroit Precision Tool Co., 1505 Hamlin Rd., Rochester Hills, MI 48309. Tel. 248-853-5888; Fax: 248-853-1505.