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Quality Scan: Metrology for Job Shops?

Ken Woodbine




A new, small-arm-type 3D CMM is so portable you can hand-carry it anywhere in your shop and put it on a surface plate, or even the table of your machine tool. A machine operator, with very little training, can accurately inspect parts on the spot, and then send the results back to the shop's measurement database using built-in WiFi networking. This one product can do the work of all sorts of measurement tools. My company, I'm proud to say, developed its underlying software.

Is this piece of measurement technology right for a particular job shop? I haven't got the slightest idea. That's right. I couldn't possibly advise anyone on the type of measurement equipment to buy (even if it is made by a sister company), unless I knew a lot more about the shop's manufacturing capabilities, the types of parts it manufactures, the industries it serves—in other words, the Big Picture. What I can say with a high level of certainty is that, for the vast majority of shops today, the big picture favors the use of electronically integrated measurement systems.

No matter the size of a shop or its customer base, the measurement data collected there are increasingly important, not only for keeping the shop's manufacturing processes on target, but for providing its customers with a better understanding of how the parts it delivers relate to the manufacturability and ultimate performance of the end product. So the trend is for customers to ask their suppliers to provide them with more and better measurement data as quickly as possible.

Adding to this demand is the trend to outsource more short-run projects with high requirements for inspection data. This translates into more inspections, inspection-system programming, analysis and report generation and communications—all of this with fewer parts per project against which to amortize the increased inspection requirements.

Unfortunately, job shops generally get paid for making parts, not measuring them. Consequently, most shops will have to rely on automation to keep pace with increased metrology expectations. Electronically integrated measurement can provide a means for manufacturers to measure parts without driving up labor content or slowing down operations. In choosing measurement systems or software products to meet this requirement, there are six primary considerations:

  • Concerning design intent, what should you measure and to what tolerances? These criteria have traditionally been denoted on marked-up drawings. Using the design-intent features available within some CAD systems or standalone software is less ambiguous, however, and eliminates vast amounts of measurement-device programming.

  • Control and operation issues arise. Does the software controlling your various measurement systems have a common look and feel? If it does, it reduces training requirements and allows operators to become more proficient at their jobs, because they don't have to learn a lot of different software products. Just as you can use good CAM software to write programs for many CNC machines, you can use cross-platform metrology software to control many brands and types of measuring systems.

  • As for programming, if you can't avoid part programming, then it should be highly automated. If you use a software solution that captures design intent (see above) in the CAD model, it can automatically do as much as 80% of the programming job.

  • Having a robust database to store all of your raw data, measurement results, and reports should be part of an ongoing big-picture metrology strategy.

  • A shop's metrology system must be able to produce actionable information in the reporting format most useful to its intended audience.

  • Finally, the system must be able to get the requisite information published where it needs to be published, in the fastest way possible.

Here's a small but illuminating example:The Jet Propulsion Lab (JPL) uses more than 200 job shops to make parts for the Mars Science Laboratory. Because they've worked with their suppliers in putting together a variation of the big picture metrology system outlined above, they no longer have to travel for on-site source inspections. Rather, their suppliers measure critical parts using compatible software, and send the inspection programs and data in by e-mail. This approach streamlines the entire process, and substantially reduces cost.

Getting back to my original question: "Is this new portable CMM right for a job shop?" It all depends on where it fits into the shop's metrology big picture. Shops without a big picture are at a competitive disadvantage, and should begin working with their customers and vendors to formulate one.


This article was first published in the February 2009 edition of Manufacturing Engineering magazine. 

Published Date : 2/1/2009

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