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by Jack Anderson

Smaller precision-manufactured parts, tighter tolerances, and the need to measure and verify parts faster, more accurately, and with greater repeatability are driving developments in metrology systems and equipment. How to manufacture and measure these cost-effectively is a challenge for both machine tool and metrology equipment manufacturers.

Faster inspection cycle time, improved throughput, and the ability to gather and quickly analyze large amounts of dimensional data can have a significant influence on manufacturers’ abilities to reduce overall production costs. In the global economy of the 21st century, lower production costs equate to improved competitiveness.

What does the future of metrology hold? To meet the anticipated industry needs, equipment manufacturers are looking for ways to optimize the functionality of measurement and inspection equipment--to measure all things in all ways--using a wide range of sensor and mechanical technologies to reduce inspection time and costs.

Multisensor technology
Smaller and varying feature sizes and tighter tolerances are good incentives for manufacturers to investigate multisensor data-gathering systems that incorporate tactile, vision, and laser-scanner systems. Multisensor technology offers the benefits of a single setup, reducing time and saving money on fixtures.

“Multisensor technology offers the accuracy, speed, and throughput, plus the ability to measure forms and features, that may be impossible for a single-sensor machine,” says Steve Flynn, president of Optical Gaging Products Inc. “Multisensor systems also provide a high level of flexibility in measurement and inspection operations, allowing users to measure a variety of parts and part families on a single machine.”

OGP is continuing its development of unique data-gathering sensors, including the Feather Probe, which provides access to small features that are inaccessible to optical measurement or conventional touch probes. The Feather Probe uses a 1-mm diameter or smaller stylus with a measurement force of less than 1 mg, and minimal approach and back-off distances compared to traditional touch-probe technologies.

“Manufacturers today have wide-ranging requirements and different levels of sophistication in their measurement and inspection operations,” Flynn says. “We help customers solve their metrology problems by adapting our level of support and our solution to fit their particular needs.”

Mark Arenal, managing director of The Starrett Co.’s kinemetric measurement and inspection division, agrees that there will be a continuing emphasis on providing users with equipment and technology that are appropriate to the application while not being dedicated to a single part or part family.

“That approach includes simple, flexible, multisensor systems,” says Arenal. “Metrology equipment manufacturers are looking to offer one piece of equipment that will handle many different applications and will measure a variety of features quickly and easily.”

He also sees in-process inspection systems continuing to be designed for less operator intervention, with the resulting improved throughput and greater accuracy.

“Looking down the road, we’re seeing software and hardware that is easier to use with systems that offer application flexibility, such as Starrett Co.’s Galileo CNC Vision System, that, in addition to its video measuring capabilities, can be fitted with a touch probe and a laser scanner,”

Arenal adds, “A major focus of development efforts is in the area of accuracy, particularly in the areas of micro and nanomanufacturing. “Metrology systems designed to inspect parts produced using these micromachining technologies will require higher power optics and advanced illumination techniques to assure the accuracy and repeatability of measurement results,” says Arenal.

Measuring system flexibility with reduced changeover time and shorter lead times is another key to the future of metrology. “We have to think like machine-tool builders and design our measuring systems to provide the level of dedication necessary for a part or part family, but be easily adaptable to changeover,” explains Dick Mierzejewski, vice president of sales and service at Edmunds Gages.

For example, Edmunds Gages has integrated small, tabletop selective compliant assembly robot arm (SCARA) robots and six-axis robots with some of their gauging systems, programmed to handle a family of parts or different parts. Modular tooling has also been incorporated into measuring systems, as have automated contact adjustments using servo drives.

“All of these features facilitate gauge changeover, allowing users to essentially retool existing equipment by adapting materials handling and fixturing rather than investing in a new system,” Mierzejewski says. “Changeover becomes a programming issue rather than rebuilding issue, and that saves time and money.”

Mierzejewski also says that the company is considering vision systems more than in the past. “Vision systems are an efficient way to measure small, micro-machined parts, and certainly allow easier, faster changeovers. In addition, they offer higher speeds for improved throughput, plus they can see part features that are impossible for other types of data-gathering sensors to reach.”

The use of optical sensors fitted to stationary and portable coordinate measuring machines is a trend as measurement and inspection operations begin to encompass more than simply feature size and location, but form and fit as well.

“We’re seeing a major improvement in camera technology with the move from analog to digital technology that allows the camera to operate on a pixel-by-pixel basis,” says Jim Clark, vice president of business development and marketing at Metris USA Inc. “This means that the camera is less influenced by the color or reflectivity of the workpiece, opening up a wide range of applications for this technology.”

Users and equipment manufacturers can no longer consider scanning and CMM control technologies to be separate and distinct. “Integrated software that controls both the data-gathering operation and the CMM operation is necessary in order to realize the full potential of gathering large amounts of data,” says Clark.

Software
Another trend is the reuse of existing equipment through the application of new, easier-to-use software and retrofitting CMMs with advanced sensors. “Retrofitting CMMs with new sensor technology, such as Renishaw’s Revo five-axis measuring head and probe system, and laser scanners, will significantly help manufacturers improve throughput with the degree of accuracy necessary to provide users with meaningful dimensional data,” Clark says.

Large-scale metrology, too, will get a boost as indoor GPS technology is applied to more applications. “Its strength is in multiple tracking of items, allowing all parts to come together at once, in their proper positions, for fail-safe assembly,” Clark says. Laser radar will be used more frequently as well, he adds.

Of growing interest in the metrology equipment industry is the use of X-ray and computer tomography (CT) inspection systems, particularly as applied to small components.

Metris recently acquired X-Tek, a British manufacturer of X-ray and CT inspection systems, to offer customers this type of system to inspect printed circuit boards and whole-part inspection of consumer electronics housings and other small, micromachined parts.

CT metrology is also among the developments at Carl Zeiss Industrial Metrology. The Metrotom 1500 is a CT system that provides access to the interior of workpieces that are inaccessible by optical and contact sensors.

“CT metrology can be combined with other types of dimensional measurement and integrated into the production process. Today CT metrology pays large dividends in the process--development phase,” says Chris Grow, vice president of marketing for Carl Zeiss.

Along with more flexibility in the data-gathering process comes the need to effectively compute and report dimensional information to get value from the information on parts.

“Software will become more robust to more effectively handle large amounts of data, while at the same time becoming easier for nonmetrologists to use,” Grow says. “The trend in software development coincides with the continuing trend to move metrology operations to the shop floor and to more fully integrate metrology systems in the production line. To help facilitate the move to the shop floor, metrology equipment manufacturers are looking at improved designs and construction materials that will effectively resist changes in ambient temperature for greater in-process accuracy.”

There will be even more focus on micro and nanomanufacturing technologies in the future, and Carl Zeiss offers a highly accurate multisensor measuring machine, the F25 CMM, that specifically addresses the needs of this market. It features ultra-precise kinematics with very accurate touch and optical sensors--the combination offering precision measurement capability with improved throughput.

To meet the demands of the micro-machining market, Hexagon Metrology has recently introduced the Brown & Sharpe Optiv product line, which combines video-based measurement with other 3-D measuring tools such as laser, white light, and touch probe in a single system. Certain configurations of these systems are capable of inspecting micromachined parts.

“The real benefit comes with the PC-DMIS Vision software module, which incorporates 3-D CAD programming capability that allows manufacturers of micromachined parts to reference directly from the original design intent,” says William Fetter, director of marketing and communications at Hexagon Metrology. “PC-DMIS software has modules that reference the actual CAD database itself, so that there is no translation of the CAD data in any way. This is very important in certain industries, such as aerospace and medical-devices manufacturing.”

The worldwide acceptance of 3-D CAD as a design tool will also continue to benefit inspection operations. “The CAD model can be used to communicate the design intent perfectly to subsuppliers so that intent is clear in design and inspection,” says Fetter. “Using 3-D inspection software, manufacturers can actually create virtual part-mating simulations, so a model of inspected parts produced halfway around the world can be virtually assembled with models from another supplier.”

Marc Soucy, president of InnovMetric Software Inc., developers of PolyWorks point-cloud software, sees a continuing growth in the use of point-cloud data in what he calls the engineering phase of product and process development. “The engineering phase occurs after design, but before production. For example, using a portable CMM equipped with a laser-scanning sensor and combined with point-cloud software, design engineers can significantly reduce the number of iterations necessary to create final production tools for processes such as stamping and casting,” he says. “What is important in the final analysis is that the part functions as it is designed to function in the final assembly and that the functionality be reached as quickly as possible.”

Point-cloud software combined with multisensor measuring systems is an area of interest and synergy, according to Soucy. “We in the industry must integrate our systems with the customers’ processes to provide them with the data-gathering and computational power that allows them to optimize the value of dimensional data to specifically solve their unique production problems.”

At Mitutoyo, vision products specialist Allen Cius sees increased measuring speed, improved throughput, and accuracy as the keys to meeting user requirements for small-parts inspection. The company’s Quick Vision (QV) series of vision-inspection systems are designed to offer high throughput and accuracy.

“Vision inspection systems were developed in Japan for the semiconductor market,” Cius says. “We’ve found that anything can be measured if it can be seen by the camera. That opens up opportunities for these types of systems.”

Typically, vision machines traverse the camera to a location, stop, pause for vibration, digitize an image, and then perform the measurement. Mitutoyo’s QV Stream vision-measuring system uses stroboscopic illumination with a progressively scanning camera to obtain many images while moving across the workpiece in an uninterrupted motion, increasing inspection throughput. The QV Stream’s camera moves continuously across the part, fires the strobe lighting, and stores the captured image. Once the images are captured they are analyzed for dimensional information.

“For example, we were able to measure the size and position of 30,000 diameters in approximately 45 minutes. On standard vision equipment this would take up to eight hours,” says Cius.

There are also improvements in LED lighting used in vision systems. Newer systems allow users to change the color of LED lighting to facilitate measuring edges that were difficult in the past because of contrast or texture issues.

In the area of form measurement, the focus is on improved throughput so that the inspection process can keep pace with manufacturing operations. “Reducing setup time is important. We want to be able to put the part in place and start the program as quickly as possible,” says Mitutoyo’s form products specialist Chris Lee.

An approach to this is the use of six-axis CNC technology to quickly position the data-gathering sensor. Mitutoyo offers some form-measuring systems that position the probe at 300 mm/sec.

“More flexibility in form measurement is also a goal--for example, combining contour and surface measurements in one pass to perform several analyses using one machine,” says Lee.

Measurement and inspection technology in the future will be largely dependent on the form and size of parts to come. As production technology evolves, so too will the capabilities of metrology equipment to provide manufacturers with not only a means of inspection, but also valuable insights into the production process that will lead to higher quality at lower cost.

About the author
Jack Anderson is a writer and public relations professional specializing in business-to-business communications. He has written articles for major trade publications in the quality, manufacturing, and engineering markets, and provides marketing communications consulting services and writing assistance for companies in a wide range of industries, in the United States and abroad.