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JUL/AUG 2013  

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News/Features: Measurement Matters

They may be compact, but the latest tabletop measuring machines come up big where it counts. Sporting an array of features, these systems have what it takes to meet many of the inspection needs of small-part manufacturers. In many cases, moreover, these capabilities come at a price that should please cost-conscious buyers.

While not everyone agrees that digital technology is better than analog, digital is the way most technology is trending—and optical comparators are no exception.

Though they may not be throwing away their conventional probing tools in droves, micromanufacturers are showing increased interest in an inspection alternative that yields large amounts of data and goes easy on small, fragile parts.

Inspecting parts is an important element of the manufacturing process, but equally important is calibrating the metrology equipment performing that work. Parts makers and metrology labs need to ensure the devices they’re using to measure parts are as accurate as possible.

Inspecting microparts is an important part of the manufacturing process, but not all shops can handle this role themselves. So they send their parts to a parts-inspection service provider. But, would they be better off doing it themselves?

If a manufacturer is unable to accurately measure its parts, it can’t guarantee they will perform to specifications. The challenges to achieving accuracy are amplified when determining microscale dimensions with a coordinate-measuring machine that has a probe too large to access tiny geometrical features.

Part measurement methods include physically touching the part with a probe or a micrometer, or using a noncontact approach, such as an optical comparator or vision system. With macroscale parts, touching a part is often acceptable since the part is not affected by the measurement. But with microparts, touch is sometimes not an option, since the measurement process moves or otherwise affects the part.

Making microstructures such as microfluidic, MEMS and biomedical devices is a challenge. So is accurately measuring fluid flow through these devices, which often incorporate channels measured in microns.

That’s where particle image velocimetry (PIV) comes in. The technology measures flow velocity in a range of applications—including microscale ones.

Error budgeting, also called uncertainty budgeting or uncertainty analysis, is a simple tool used for processes having tolerances that are difficult to achieve. It originally was developed for diamond turning—operations in which parts are turned with single-point-diamond tools—but is widely used in metrology, optics and other high-precision applications.

Scanning white light interferometry (SWLI) is a versatile technology that provides a noncontact, 3-D method of measuring surface roughness. The interference microscopy technology combines an interferometer and microscope into one instrument.