Small and tough: shop floor measuring devices

Micromanufacturers that make complex parts often need to invest in high-precision, shop-floor metrology equipment. These microscopes, measurement probes, coordinate-measuring machines and other devices must be able to withstand the effects of dust, temperature swings, light and humidity to ensure accurate measurement.

Scienscope’s XT-1000 2-D video measuring unit. Image courtesy Scienscope.

Affordable metrology equipment that can match cleanroom performance standards on the shop floor is available for micromanufacturing operations. For example, the ContourGT 3D line of optical microscopes from Bruker Nano Surfaces, Tucson, Ariz., was developed to bring 3-D microscopy to the shop environment, according to Javier Vera, product marketing manager for stylus and optical metrology.

“We design enclosed systems that minimize the effect of airborne, ambient particles, which is a key factor for use in industries such as automotive, where [these systems] perform quite well and consistently,” said Vera.

The ContourGT 3D is a new platform that is more accurate, less expensive and operates faster than previous versions of the product. The system manages shop temperature swings during operation by incorporating sealed enclosures for the components being measured.

Compared to measuring parts in a laboratory, using shop-floor metrology equipment minimizes lead time, alerts QC personnel to manufacturing errors sooner and makes machining setups easier to maintain. This leads to more-accurate parts being manufactured in less time and at higher yields, noted Vera. He added that a benchtop measuring instrument can be an entry-level platform for shops that want to perform noncontact pass/fail measurements.

One enemy of measurement is vibration, and Bruker offers a vibration-isolation feature as an option on its benchtop ContourGT microscopes. A larger, freestanding unit has an integrated air table to protect against vibration. The use of composite castings in all Contour GT microscopes helps improve vibration tolerance as well as the repeatability and reliability (R&R) capability in the shop environment, according to Vera.

ContourGT 3D microscopes measure surface topography from nanometer-scale roughness through millimeter-scale steps, with sub-nanometer resolution. Magnifications from 0.5× to 230× can be achieved, with a 10mm+ vertical range at any magnification.

The ContourGT 3D line of optical microscopes from Bruker Nano Surfaces. Image courtesy Bruker Nano Surfaces.

Smaller footprint

One factor that must be considered for shop-floor measurement is the device’s footprint. For example, Scienscope International, Chino, Calif., manufactures large, floor-stand video CMMs that can be used on the shop floor. However, these larger and heavier units take up a lot of space and are impossible to place on a workbench, as they often weigh over 800 lbs.

Dan Kelsey, general manager for Scienscope, said a better alternative is the company’s new XT-1000 VMU (video measuring unit), a 2-D system that is smaller, lighter and more mobile than comparable devices. It was designed for use by machine shops, which often require smaller-footprint devices capable of measurement accuracy comparable to lab equipment.

“We set out to shrink our floor unit into a device that would be ideal for the workbench,” said Kelsey. “We first needed to change the materials [used to manufacture] the XT-1000 to reduce the weight.” Instead of a steel frame and granite base, the machine has an aluminum-cast base and structure. The XT-1000 features a stage-load capacity of 22 lbs., repeatability of ±1µm, stage accuracy of 3µm, and X and Y measurement capabilities on a stage-travel range of 4"×8". It weighs 60 lbs. and costs less than $10,000.

“The video inspection and measurement system is designed to inspect for defects and measure features on small parts as well as small features on large parts,” Kelsey said. “We use optical scales specifically designed for the shop environment, as well as shock-absorbing, layered covers that physically protect critical components from the environmental impact of humidity, dust, dirt, oil and vibration.”

The XT-1000 has an intuitive PC touch screen and mouse, making it easy for operators to use. “Whether it’s used for each workstation, for incoming inspection or for batch inspection, the XT-1000 can be operated by shop professionals. You do not need to designate and specially train one operator; all you have to do is point, click and measure,” he said.

Technical advances

Another manufacturer made its measurement devices shop-ready by building them heavier and stronger than versions designed for the laboratory. The Kestrel Elite/SwiftDuo, a dual 2-axis optical- and video-measurement system from Vision Engineering in New Milford, Conn., provides affordable, simple and accurate measurement of precision parts, according to Jeff Bronson, Western regional manager for Vision Engineering.

“On previous models in this class, the stand and base were much lighter—[they were] primarily made of aluminum and plastic,” he said. “The stand was beefed up by using a heavier-gauge aluminum casting as opposed to an extrusion, adding about five times to the weight and strength in order to dramatically improve the stability for staging movement.” Isolation pads or granite blocks can be installed to further stabilize the unit, depending on use.

Other features make the device easy to use, according to Bronson. “By partnering with (control-maker) Heidenhain, we can offer our customers a microprocessor with a durable, robust outer casing that allows it to be used on the shop floor,” he said. “The enhanced technology makes it easy to use, as operator error is reduced and productivity increased, making it ideal for multiple users in a shop environment.”

Virtual Engineering’s Kestrel Elite/SwiftDuo, a dual 2-axis optical- and video-measurement system. Image courtesy Virtual Engineering.

The 2-axis video- and optical-measurement system provides simple and accurate measurements of precision component parts, according to Bronson. This includes even difficult-to-view samples, such as black or white parts and transparent plastics, through the use of the company’s Dynascope optical-projection technology, which removes the need for conventional microscope eyepieces. Optical projection provides a superior image of the subject than systems that feature profile projectors, according to Bronson. This technology optimizes measurements for optical image clarity, resolution and contrast on a 150mm × 100mm measuring stage, he said. The Elite costs $14,000.

“In extreme situations or areas of concern, we will do setup tests and correlation studies for customers,” Bronson said. The instruments are calibrated and certified to National Physical Laboratory standards.

“These products are designed to operate on a shop floor with a ±10º C temperature range throughout the year,” said Bronson. “Temperature is always a factor we have to consider, but our machines are calibrated at a stable midpoint for standard temperature-deviation performance.”

While a machine shop is not an ideal environment to measure parts and part features, controlling environmental effects by using ruggedized equipment can provide a way to make rapid and accurate measurements. And though laboratory measurement is still an important QC process, more shops are seeking to improve productivity and lower manufacturing costs by measuring parts at the point of processing. µ