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Metrology, Fundamentals and the Future

Bruce Morey
By Bruce Morey Senior Technical Editor, SME Media

The very nature of manufacturing is changing. Future factories will be highly automated, distributed geographically, yet tied to a central information net, with fewer but highly productive workers. They will produce more, for less, delivering goods efficiently worldwide. As manufacturing changes, so should the methods used to ensure quality products are produced. “Metrology underpins this vision of modern manufacturing,” said Dan Skulan, general manager for industrial technology at Renishaw Inc. (West Dundee, IL). The company certainly is pushing the technology of metrology, providing new products adapted for this new world.

However, to enable a journey to the future, many manufacturers need to get a handle on the present, according to Skulan. It is all about control and process. “There is a tendency for manufacturers to focus on a couple of areas, what we call process setting and post-process monitoring, while neglecting others that are just as important,” he explained. To put this in context, about a decade ago Renishaw developed a conceptual framework it calls the “productive process pyramid.” The pyramid consists of four basic process steps: a) process foundation, b) process setting c) in-process control and d) post-process monitoring. Each step sets the stage for success in the next. Neglecting any reduces efficiency. For example, ignoring the first step, process foundation, means ignoring preventative controls in advance of an operation, such as calibrating machine tools for volumetric compensation.

Skulan also noted that while the second step, process setting (measuring the process just before an operation) is commonly done, the third step, in-process control, is not. Examples of this third step include on-machine probes that control cutting action during the process of making a part. Adaptive machining is the ultimate in-process control step. The final step, checking a part prior to delivery, is perhaps the most common.

But future manufacturing is not just about quality. It is about process yield at that quality. “Practically every manufacturer ships 100% quality parts. The question is do they produce them at a process yield of 100%?” he asked rhetorically. The first step in increasing process yield is to have a steady flow of “actionable” information throughout the manufacturing process. That means including tools and methods to produce information at all four steps. The commonly ignored steps, process foundation and in-process control, contribute directly to increasing process yield.

Towards that end, Renishaw offers tools like ball-bar testing as well as its XM-60 laser measurement system for volumetric compensation, the first step of process foundation. According to a company spokesman, it can measure a CNC machine tool in six degrees of freedom in a single setup, within a few minutes. On machine probes, like Renishaw’s OSP 60 with its latest capability to measure surface waviness, provide that vital third step, in-process control. The company’s latest Equator Gage, a larger size that can measure parts up to 500 mm in length, contributes to in-process control on larger parts, as well.

Skulan stressed the need to mentally, perhaps emotionally, prepare for change. “You need to stay current, using knowledgeable partners, and stay flexible by using equipment and technologies that can adapt as you change,” he said.

What might this future of manufacturing look like? “Think of individual factories as production cells, modular in concept and operation,” said Skulan. The key is consistency—of inputs, outputs, and the process in-between. Each production cell must produce its parts consistently, with both the same accuracy and the same process yield, for it to make sense. “The key to get that is to balance all four of those process elements,” he said.

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