Coordinate measuring machines help racing cars break through the limits of quality and speed

Customers know that Pratt & Miller Engineering has quality products they can trust. Their outstanding design, flawless manufacturing and rigorous testing services are fully demonstrated through the performance of the General Motors Racing Team in the American Le Mans Series (ALMS) and the Cadillac Racing Team in the SCCA World Challenge. Although they are well-known for their racing, in fact, they are better than you think. Pratt & Miller Engineering, located in New Hudson, Michigan, provides top-notch engineering and manufacturing solutions for the motorcycle, automotive, aerospace, commercial and military industries.

They started their business in 1989 as a small racing engineering and manufacturing shop, and now the company has grown into a generalist who provides innovative solutions for multiple industries. Since 2009, Pratt & Miller has doubled its total sales to existing and new customers. With the increase of new employees, the reduction of processing time for customer orders, tighter tolerance requirements and increased customer demands, they urgently need a more advanced quality inspection solution. In

March 2011, Pratt & Miller decided to equip the quality inspection laboratory with a Zeiss CMM to meet these needs. After analyzing key factors such as component volume, target tolerance, and available space, and thoroughly evaluating the CONTURA G2 10/12/6 with VAST active scanning, it was determined that this model was the best solution for the company to meet new and growing measurement needs. At the same time, Pratt&Miller selected the VAST XT probe with a fast scanning speed to ensure that more data is collected and more detailed information is obtained.

Prior to adopting the Zeiss CMM, Pratt & Miller had been using several different sizes of portable measuring arms, as well as a variety of manual measuring tools including micrometers, bore and height gauges. However, the growing business demands required them to increase the speed, accuracy and repeatability range to meet their new tolerance requirements. Manual measurement with portable measuring arms and manual inspection instruments requires long-term consistency in measurement technology to ensure comparable data, which is almost impossible to achieve. On the other hand, the internal design tolerance of the product is required to reach 20,000ths of an inch, and some customers require tolerances of up to 5 microns in some cases. At the same time, as the company's pre-production run size continues to increase, special product types have reached hundreds and thousands, so repeatability of results is crucial.

Most of the parts that Pratt & Miller inspects are samples, such as clutch plates for electronically controlled limited-slip differentials, suspension components for military vehicles, and chassis components for racing cars. During the development process of such parts, they have to work with customers to modify these parts many times, and the closer to the final production stage, the more stringent the tolerance accuracy requirements.

The spindles used in different racing events, such as the Corvette and Cadillac race cars, are examples of complex parts designed and manufactured in-house at Pratt & Miller. These parts are often referred to as life-critical components, and because of their importance, they are required to be measured thoroughly. The three-dimensional coordinate measuring machine is responsible for the multiple measurements of the spindle. The entire inspection process is: first, the first piece inspection must be carried out, then it is sent for external processing, and then it is returned for random inspection after heat treatment is completed. After the grinding process is completed, the final inspection is repeated.

"Some of the more complex parts, such as hobs, take two months from start to finish, including the external machining process, of which the machining time and related inspection time account for more than half of the total machining time," explained Frank Wilson, quality assurance manager at Pratt & Miller. To keep these parts in the leading position for a long time, such as racing cars and other fields that Pratt & Miller has expanded into, the processing speed and repeatability of products are extremely high. They use the Zeiss CONTURA G2 to measure an average of about 12 parts a day, including the re-inspection of old parts. Depending on the machining process, the number of workpieces that can be inspected per day varies, and some days may exceed 100. The

CONTURA G2 saves Pratt & Miller a lot of inspection time. For example, after using the Zeiss three-dimensional coordinate measuring machine, the inspection time of the column was reduced from 2 hours to 20 minutes. In the past, such a manual inspection process required 10 to 20 tools, but now only one Zeiss three-dimensional coordinate measuring machine can complete the measurement of any part and size of the workpiece.

As operators have become more aware of its functions over time, they have recently used CONTURA G2 at a higher rate than expected. Pratt&Miller even set up a second fixture to prepare for other parts to be inspected. All operators are increasing their measurement speed using the CALYPSO measurement software program. Thanks to the use of CONTURA G2, Pratt&Miller's own productivity and quality have been greatly improved, thus winning more orders for products with extremely high tolerances. "Localized technical service support helps us maximize the use of the three-coordinate measuring machine." Frank said.

When Pratt&Miller's employees decided to use CONTURA G2 to measure the suspension adjusters of racing cars in order to better understand their impact on setting changes, they were shocked by the excellent performance of CONTURA G2. In order to maximize the consistency and product performance during the device setting process, these suspension devices need to be precisely measured to determine the impact of the accumulation of assembly tolerances on the accuracy of the instrument. The Zeiss three-coordinate measuring machine quickly allowed them to find areas for improvement.

One of the most helpful features of CALYPSO metrology software for Pratt&Miller is the graphical output. Now, with CALYPSO measurement software, they can visually check the roundness and locate the actual position, and rework the high tolerance points in time. "This was unimaginable before. Visual graphic output helps me quickly show my colleagues the current real-time situation without drawing sketches," said Frank. "It helps us avoid mistakes and gives us stronger control over quality. For example, sometimes a workpiece becomes a "tri-oval" due to the pressure of the chuck jaws. The accuracy of such workpieces may already be within the standard range, but there is a lot of room for improvement. The visual interface helps us communicate intuitively to express our needs." Another benefit of CALYPSO is its mirroring function, which can achieve optimal processing of the left and right parts of the car. In some cases, it can save technicians a day of programming time.

"CONTURA G2 has many advantages for us, and we are implementing more and more new ways to integrate it into our manufacturing in various application environments." Frank said, "We are still in the early stages of using this equipment. In the future, we hope to do more statistical analysis with the three-dimensional coordinate measuring machine." Sometimes, the processing quantity of some parts manufactured by Pratt & Miller can be hundreds of pieces, but most of them are small batches of about 20 pieces, and some are quite complex. For such cases, one of the biggest benefits of CONTURA G2 is that it helps Pratt & Miller monitor the processing operation process. For example, it can determine whether the bottom of the milling cutter is worn or the taper of the hole.

In order to obtain more new customers, Pratt & Miller is paying more and more attention to the different needs of various industries, especially the defense industry. The gratifying thing is that because they have always maintained the concept of building a professional workshop, they can fully adapt to the introduction of new technologies and processes required by various new requirements. Of course, in addition to providing technical support for the development of new green samples, they still expect to obtain more racing projects. If they continue to grow at the current rate, they may need to add another three-dimensional coordinate measuring machine and add an additional shift.

CONTURA G2 gives Pratt & Miller a high degree of confidence in measurement, and the introduction of graphic reports has greatly improved communication capabilities. "The CNC control system automatically measures the workpiece, so we can be completely assured of the quality of its inspection, giving us more time to complete other work," said Frank. Pratt & Miller customers often bring orders that require expedited production. Thanks to the extremely high measurement efficiency of CONTURA G2, there is no need to rush to complete the measurement, which will not lead to the mistakes made in the past. "When you see that the Zeiss three-coordinate measuring machine can improve measurement accuracy and repeatability to such a large extent, you will think it is completely priceless. It adds another layer of confidence to our daily work." (end)