AUG 2018

Techspex provides metalworkers free research and analysis tools to help them find the right machine for their job.

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W H A T T O C O N S I D E R W H E N P U R C H A S I N G A C M M 4 Coordinate measuring machines (CMMs) have been around since the 1960s. In most precision manufacturing facilities, the CMM is the company's chief dimensional measurement device that is traceable to the standards maintained by National Institute of Standards & Technology (NIST). Most CMMs are used to verify dimensional accuracy for quality control and first-article inspection, the function of checking the first part produced by a manufacturing process to verify that it is meeting tolerance requirements. Inspection with a CMM provides data for in-process measurements to ensure dimensional integrity from operation to operation and to satisfy traceability requirements. CMMs are also used to perform gage repeatability and reproducibility (R&R) studies, 2D and 3D scanning, part sorting, reverse engineering, and a host of other tasks. By some estimates, the global installed base of CMMs is around 150,000 units. Because of the typical air-bearing design of many CMMs, the structure of these devices seldom wears out. Therefore, the lifespan of a CMM may exceed 30 years. Many 30-year-old CMMs are used daily throughout the precision manufacturing world. Older CMMs can easily be upgraded with new electronics, drives and the latest software, adding an extra 10 years to a machine's usable life. In fact, a CMM can be retrofitted multiple times to extend its life even further. During the past several decades, CMMs have become faster, more accurate, and more affordable. While there has been much speculation that CMMs are becoming obsolete, the opposite is true. Today, CMMs are more versatile and functional than ever before. Multi-Sensor Technology and Software Advances in sensor technology are leading to improvements in metrology, thus enhancing quality control and inspection methods and resulting in more precise manufacturing processes. CMMs are becoming more flexible with multi-sensor technology, which combines 3D non-contact laser scanners, five-axis scanning with a touch probe, optical systems and surface finish measurement. Tool racks enable sensors to be changed automatically to continue measuring the same part. Currently, customers often dedicate machines exclusively to touch-trigger or scanning measurement processes. While one CMM operator may specialize in touch-trigger scanning, another operator may specialize in laser scanning and yet another in optical or five-axis scanning. Different metrology techniques may require specific software to drive the data collection routine, while additional software may be required to analyze the data. Software may also be tailored for the application and the types of parts being measured, such as plastic, sheet metal, aerospace or automotive. Software enabling the full capability of the sensor type is essential. It's also important for sensors to be fully integrated with metrology software across multiple platforms. Programming a CMM should be intuitive and operator-friendly. For example, programming a scanning probe to sweep each blade of a What to Consider When Purchasing a CMM By Barry Rogers

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