Benefits of the hottest mechanical accuracy

2022-08-08
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Benefits of mechanical accuracy

traditionally, manufacturers rely on measuring equipment and the physical properties of coordinate measuring machines (CMM) to maintain a qualified quality level

for CMM, the most important criterion of accuracy is the toughness and stability of component materials and structures. Recently, however, due to the extensive use of error mapping techniques to compensate for mechanical deviations, the center of gravity has shifted from these physical parameters

since the early 1980s, the development of CMM integrating "virtual accuracy" has had a significant impact on users. At the beginning, error mapping involves software used to assist in the calibration of the linear accuracy of the coordinate axis of machine tools. Using this method, CMM software measuring ruler is adjusted by measuring ruler tensioning device. Because this can make the accuracy of the measuring ruler equal to the reading accuracy of the laser interferometer, it improves the accuracy of CMM without losing its mechanical quality

but not long after it came out, CMM manufacturers began to use error mapping technology to compensate mechanical errors more thoroughly. In this way, manufacturers can reduce costs by designing machine tools with greatly reduced accuracy. Error mapping also requires OEM to intervene more frequently to maintain the accuracy of "locked" CMM images that cannot be accessed by third parties. This may cause high uncertainty and inconvenience to users

Otto Geiseman, President of Wenzel USA (Wixom, Michigan), said, "updating image parameters requires a lot of time in the calibration process because it frequently needs to verify other relevant parameters." In addition, the previous calibration of a mapped CMM may not be as complete as the user expected for the high purchase cost. Mr. Geiseman said, "because the mapping process requires a lot of labor, it is often found that the remaining image files are not related to the calibration data." Therefore, in some cases, it may take twice as long to update a mapped CMM as to calibrate a (mechanically accurate) CMM

Wenzel adopts a "contemporary" approach to traditional quality issues. The company has launched a series of CMM, emphasizing the use of high-precision mechanical components as an alternative to the error mapping system. Instead of computer algorithms, these CMMS are constructed of stable materials that are well suited for metrological applications. For example, in order to achieve high accuracy, CMM guide rail is precision ground, and manual grinding is carried out by process technicians with autocollimator to monitor many of their production lines called 1 manual factory. Combined with high-precision bearings, this process produces a very accurate machine tool

Mr. Geiseman said that the materials commonly used in the components used to manufacture the mapped CMM may not be ideal. "Nowadays, most CMM guide rails are made of composite materials, most of which are aluminum. Although aluminum does have some advantages in the manufacturing process, it is a soft material, which is easy to creep and deform. It may not be stable enough for metrological applications," he said In addition to the low stability in weight, the expansion coefficient of aluminum is almost 4 times higher than that of graphite

another important factor is that CMM mapping blurs the mechanical parameters of a specific measuring machine. Mr. Geiseman said, "in the mapping process, although the original inaccuracy was measured, it was never reflected to the user." Since there is no regulatory body to approve the measurement standard of the design and the accuracy of error mapping, users face great uncertainty after changing the image

these factors make people advocate more traditional measurement methods based on more accurate hardware design than software. Wenzel believes that high-precision machine tools are still a very important part to ensure the measurement quality - brake pads largely determine the best means of braking energy of cars. Mr. Geiseman said, "unlike the mapped CMM, the mechanically accurate CMM has nothing to hide. Users have the right to know whether a CMM has zero compensation or is 10, 20, 30 times more inaccurate than the value declared by the OEM."

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