The benchtop optical system has cut inspection times from 11-1/2 to 7 minutes. Photo: Rexnord Bearing Co.

Manual inspections of precision bearings took 45 minutes to inspect and 45 minutes to set up two years ago. Today, with a multisensor optical coordinate measuring machine (CMM), the same job can be done in less than seven minutes.

Rexnord Bearing Corp. (Downers Grove, IL) previously used manual gages and custom fixture gages. One of Rexnord Bearing's specialties is the manufacture of precision bearing components for the aerospace industry. Because of the critical nature of these parts, Rexnord had to do 100% inspection. This process was time consuming and had become a major bottleneck in their manufacturing process.

Rexnord went to OKM/esco North America (Kenosha, WI) to provide them with a solution that would capture better data and solve their throughput issues. OKM recommended an Uni-Vis 250T optical CMM. "We chose OKM based on their specialty in the measurement of precision cylindrical parts and for their ability to customize a solution to our needs," says Don Klein, quality engineer at Rexnord.

The Uni-Vis 250T is a fully automatic optical measuring system. It also has the capability of incorporating several other sensing methods including touch probe and laser sensors.

Rexnord makes a large family of parts that have a threaded end on the bearings with unique measurement requirements. OKM in partnership with esco, a software company, customized a solution to measure

thread profiles.

Upon installation of the Uni-Vis 250T, Rexnord conducted a gage repeatability and reproducibility (GR&R) analysis and found that it had less than a 7% gage error with 43 categories of distinction. This was especially impressive considering that many of Rexnord's tolerances were 0.0002 inch and less.

Programming time was a big issue for Rexnord. They have many different part families, each with many parts. OKM provided them with the option to import a CAD drawing and programming from that the drawing. This process required only a fraction of the time that is involved with manual programming. When manual programming is used, the system makes it simple because it records instructions as the first part is measured and then saves the program for future use.

After the inspection process was developed and proven, a second Uni-Vis 250T was purchased. A Renishaw (Hoffman Estates, IL) touch probe and a computer numeric controlled-rotary axis option were added to the second machine to increase its measuring capability.

According to Don Klein, "Rexnord has benefited in several ways as a result of the OKM machines. Not only have we been able to reduce the labor required to inspect our bearings by approximately 95%, but the Uni-Vis surpassed our expectations for the number of features we were able to measure." In addition, as a result of the increased quality of measurements and data they were able to provide to their customer, the sampling rate decreased, further reducing the inspection costs.


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