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by Dirk Dusharme

 

Make it smaller, faster, cheaper, easier and more accurate. That's what today's (and yesterday's and tomorrow's) metrology customers demand. Everyone knows that semiconductor devices continue to get smaller and faster, with more computing power in less expensive packages. What many consumers may not consider is that, pushed by shrinking computer chips, mechanical devices also continue to shrink: Computer-aided fuel injection allows more precise control over fuel flow, which in turn creates a need for more precisely machined fuel injectors; pacemakers, once cigarette packet-sized boxes carried outside the body, are now so small they're embedded in the body.

The Softer Side of Metrology

To review recent advancements in metrology software would take a book rather than a few paragraphs. But there's one key driver for all the advancements: "With the economy fluctuating, it's difficult to keep operators up to speed," explains Dave Genest, director of marketing and communications at Brown & Sharpe. "You're always training. The software has to be simple. It's even more important than the [hardware] technology."

Enterprise Metrology Solutions from Hexagon Metrology, Brown & Sharpe's parent company, is a suite of advanced software tools available with PC-DMIS. Depending on installed options, EMS allows PC-DMIS to create inspection programs directly from native CAD languages for CMM, vision and even probe-fitted NC machine tools. PC-DMIS will control and take measurements from equipment across the enterprise and provide reports via the Web.

With outsourcing becoming more prevalent, maintaining supplier quality is critical. Origin International Inc. gives its customers the means to monitor part quality across all of its suppliers. To do this, Origin installs CheckMate software on the CMMs of its client's suppliers. SoftFit software provides root cause and GD&T analysis to deal with out-of-specification dimensional issues on supplier- or manufacturer-made parts.

Once implemented and personnel trained, the Origin software allows CAD-based CMM dimensional data to flow to and from all participants over the Internet or dedicated networks. The manufacturer can control/standardize the data required, decide what gets measured and how, and provide the supplier with CMM programs that will run on any DCC CMM. Some of the benefits are accurate and consistent supplier dimensional data from all participating suppliers at all stages, from part design to manufacturing or assembly; reduced timeframes to determine and fix out-of-spec parts; and instantaneous communication of dimensional data.

Partly in response to the new ISO 9001:2000 standard that requires determination of measurement uncertainty, Carl Zeiss Industrial Measuring Technology has introduced Offline Virtual Coordinate Measuring Machine, a new option for its Calypso CAD-based software. Previously, all accuracy specifications of coordinate measuring machines consisted exclusively of data obtained on comparison standards. OVCMM allows operators to determine the measurement uncertainty for every measured feature--a central requirement of the ISO 9001:2000 standard. Each record indicates the captured measurement uncertainty next to the actual value. The main uncertainty factors of the CMM, the probe, the workpiece, the measuring strategy and the environment are all included in the OVCMM measurement.

Zeiss is also addressing automation with its new Flexible Automation and Control System, and Application Automation Interface. These products supervise all the devices in the process flow. For instance, it can control a robot loader to place parts on the CMM, tell the CMM to measure the part and then tell the loader to unload the part.

"Even people with medium-sized companies are using it for cost savings," says Jose Torres of Zeiss. "They can use half the staff with a simple pallet loader and can save money."


To keep technology and innovation rolling, metrology equipment manufacturers must continuously develop the means of measuring our shrinking universe. But higher measurement resolution and accuracy aren't the only issues. Pressure from low-cost foreign manufacturers means that measurement equipment must not only measure increasingly smaller parts, but it must also do it faster and with fewer people involved in the process. Moreover, faced with high employee turnover, today's metrology customers demand operator interfaces that are easy to learn.

Following is a look at some of this year's new metrology products, chosen because they typify metrology equipment makers' response to customer demands. This is by no means a comprehensive list; there are literally hundreds of cutting-edge products from dozens of leading metrology companies released each year. Use the following information as a brain tickler for the current state of measurement technology and what it can do for you.

Pushing the micron

Many industries--particularly electronics and medical device--are driving the need for high-accuracy large-envelope vision measurement. Both require micron and even submicron measurement accuracies at ever-escalating production speeds.

"Customers are pushing for yield," explains Mike Metzger, measuring department manager at Nikon Instruments Inc. "For example, medical device manufacturers are building stents at a remarkable rate. Production capabilities are higher than they've ever been. The ability to build things accurately and repeatably is higher than it's ever been. Metrology has to keep up."

Nikon has addressed the need for large-envelope high-accuracy measurement with the VMR-H3030 CNC video measuring system. Equipped with a maximum magnification module, the product features a final magnification range of from 36X to 4,320X when displayed on a 17-inch high-resolution monitor, a field of view of 4.7 by 3.5 mm at 36X to 0.04 by 0.03 mm at 4,320X, stage scale resolution of 10 nm (0.01 mm), accuracies from 0.6 mm and a working distance of from 32 to 9.8 mm, depending on magnification. The product also features a through-the-lens laser focusing system that allows the instrument to scan parts at 1,000 points per second, greatly increasing inspection throughput when measuring profiles of 3-D precision parts.

Submicron accuracy and repeatability has been around for a while, but stage-accuracy and other mechanical issues have limited submicron accuracies to workpieces of less than about 10 X 10 in. As the need grows for precision measurement of large-envelope parts such as printed circuit boards and flat panel displays, look for vision-based machines to provide submicron accuracies over distances of 30 inches or more.

Stay focused

To increase throughput in 2-D measurements, vision-based-equipment manufacturers continuously push the envelope on depth of field--the maximum distance from top to bottom that a device can remain accurately focused.

"For a long time, customers have been wishing for something that's going to provide much quicker and easier measurement of parts that exhibit depth and different types of features that need to be verified with a single parts program," explains Frank Demski, Mitutoyo America Corp.'s vision products manager.

Because high accuracy once meant higher magnification and lower depth of field, it also meant focusing on a feature at one height, performing a measurement and then changing Z-axis position and focus to measure a feature at another height. "That took time," says Demski. "Now we've just come out with a special telecentric lens that allows us to develop a vision machine that has both wide field of view and long depth of focus. With Quick Image, a workpiece up to about 1 X 1 in. is entirely visible in the field of view. And, the part can be up to 0.9 in. in depth."

Quick Image is basically a manually focused 0.2X fixed-magnification device that provides a field of view of 29.5 by 22.2 mm. The user has control over measurement resolution and therefore depth of field. At the maximum 22 mm depth of field, the Quick Image can measure an object with a height variation of about 0.9 in. and a minimum feature width of 300 mm with an accuracy of 8 mm. Measurements of 5 mm accuracy are possible if the depth of field is reduced to 1.2 mm.

"Once you create a measurement program for a specific workpiece, the operator can grab a sample from the production line, place it on the Quick Image stage and instantly measure 100 percent of the part features and get a report, all without any stage movement or focusing," says Demski.

Small probes for small dimensions

Customer requirements for measuring small or fragile parts are pushing traditional touch-probe equipment to the limit.

To measure fragile parts with critical surface boundaries, Optical Gaging Products Inc. has developed the Feather Probe, a 100 mm diameter stylus that uses proprietary technology to determine when the probe has contacted a surface. The probe requires less than one milligram of force to acquire a data point and is ideal for measuring microminiature components and parts that can be deformed by traditional touch probes (e.g., rubber parts or solder paste). The Feather Probe is a specialty probe that can be used on any OGP measurement system that accepts traditional touch probes.

Mitutoyo's UMAP is another product to measure microfeatures, in particular, microholes. The product was developed to measure the orifices of fuel injectors but can be used for any small feature, such as optical ferrules or medical device parts.

UMAP consists of a vision system with an accuracy of 1.4 mm and resolution of 10 nm. The vision system positions UMAP's touch probe over the microfeature to be measured. The touch probe is a 2 mm or 12 mm long stylus with a 30 mm tip. The system uses piezoelectronics to excite the probe at an ultrasonic frequency and then detect a change in the signal frequency and amplitude, indicating that the probe has contacted the workpiece's surface. With a contact force measured in micronewtons (1 micronewton is about 0.1 mg force), the system can also be used when ultralow contact force is required. Of course, the vision portion of UMAP can be used as a traditional stand-alone vision system.

Until a technology comes along that replaces touch probes for accurate measurement in hard-to-reach places, look for touch-probe technology to continue evolving toward smaller and smaller probes.

Behind the scenes

One key feature of most high-precision stage products is a 10 nm resolution specification. For measuring machines that have a moveable stage, this specification defines the ability to accurately identify the location of the stage in the X, Y and Z axes. This is dependent upon stage construction and the linear scales attached to the stages.

Heidenhain is a leading international manufacturer of precision measurement, and its scales are used in a variety of dimensional measurement equipment. Heidenhain recently announced the release of a linear scale, the LIF 400 series. Although the scale's 8 mm line spacing and 10 nm resolution aren't unique in the industry, several other features address customer needs in linear scales.

One problem with scales is that, on startup, the stage electronics don't recognize where the stage is located and must traverse the entire length of the scale in order to find the stage's home or index position. A special homing track on the LIF 400 series tells the machine which direction to move the stage in order to most quickly reach the index. The product also features optical limit switches instead of magnetic switches. Linear motors used with most measuring machines interfere with magnetic switches if the two get too close together. On the LIF 400, optical switches allow the scales and motors to be right next to each other, facilitating the construction of smaller machines. Finally, a unique scale construction eliminates the peaks and valleys between a scale's lines that can fill with dirt. The result is improved accuracy and reduced maintenance.

As the requirement for even higher precision stages at reasonable costs pushes the market, look for higher precision scales to become more mainstream.

Multisensor measuring devices

There was once a definite line between vision-based systems and traditional probe-based CMMs, usually a tradeoff between speed and accuracy. Customer demand has caused the line to blur considerably.

One type of product hyped at this year's Quality Expo was the multisensor vision system. In addition to their vision capabilities, these products generally also include touch probes, laser scanners or other probe types, allowing the machine to quickly measure large features, while providing high-accuracy measurement of critical dimensions. A multisensor machine swaps one probe for another as measurement requirements change on a particular workpiece.

The intent is to meet the customer's need to balance inspection throughput requirements with accuracy requirements for workpieces of most any size, says R. Stephen Flynn, senior vice president of marketing and sales for Quality Vision International, the parent company of OGP, RAM Optical and View Engineering.

"Multisensing is a real value," says Flynn. "You can completely measure a part without having to restage it on a number of different machines. And, a single setup improves accuracy."

SmartScope Quest 650 Multi-Sensor Metrology System is the latest multisensor system from OGP. It has a measuring envelope up to 24 by 26 by 16 in., 10 nm resolution, 1.0 + 4L/1,000 mm accuracy and can utilize video, laser, touch probe, continuous contact probing and other probing technologies.

Of course, large volume for a vision system is tiny compared to a large CMM such as those from Brown & Sharpe, Mitutoyo or Zeiss. But companies that measure very large parts on such CMMs can also benefit from multisensor technology. Although not necessarily called "multisensor," most large-envelope CMM manufacturers are incorporating noncontact measuring probes such as cameras or lasers in addition to touch or scanning probes.

The advantage is obvious when measuring large structural components that also contain critical dimensions, says David Genest, director of marketing and communications at Brown & Sharpe, which provides various noncontact sensors for its large CMMs, such as its Global series. "The advantage is that you can match the right type of probe with the right application," he explains. "For big parts, like an aircraft structural component, you could zoom over the top with a noncontact probe and then, if you need precision measurement of prismatic features, you could use a touch probe."

The Global series CMMs can measure parts up to about 78 by 157 by 59 in. and with accuracies starting from 4.5L/200 mm.

Each year, the line between CMM and vision systems gets blurrier. Look for these two to eventually merge into one integrated technology.

Form measurement

Advancements have also been made in form and surface measurement equipment. Driven in part by the automotive industry, Corning Tropel has announced two new products that provide greater speed and accuracy in this area.

The ThetaForm was developed to meet the need for high production volume, high-accuracy measurements on rotationally symmetric forms (e.g., valves, pistons, etc.), according to John Bruning, president of Corning Tropel. "As next-generation technologies are implemented on manufacturing floors, sealing and bearing surfaces will undoubtedly require lower form tolerances," says Bruning. "Conventional measurement technologies no longer have the accuracy and speed necessary to control a high-volume production process."

Although accurate, traditional touch-probe form measurement devices are slow. The ThetaForm uses dual interferometers to perform noncontact measurements with accuracy in the submicron range. A part that might take 20 minutes to measure on a touch-probe device takes about two minutes on the ThetaForm. In addition, it collects about 100 times more data than a touch-probe system, meaning a more accurate representation of the form.

Another product, Tropel's Lasercheck, was designed for in-process surface roughness measurements. Although the Lasercheck's technology isn't new, advancements in product packaging allow the device to be used for inline process control, says Andrew Kulawiec, director of metrology operations. "There's nothing else that does 100-percent inspection of parts while moving by on a conveyor," claims Kulawiec, "The Lasercheck takes 10 individual roughness measurements per second. You can integrate this into the control system to provide process feedback or pass/fail."

Nondestructive technologies

Along with advancements in dimensional measurement, much has been done to increase throughput and accuracy in noncontact, nondestructive technologies.

Ultrasonic evaluation is usually associated with one-sided thickness measurement, particle size measurement or subsurface fault detection, but this technology continues to grow as its uses widen, particularly in the area of real-time inline process control.

The Ultrasonic Process Analyzer by UTEX Scientific Instruments Inc. allows users to make inline measurements of the physical properties of polymers and food products. Using a patented ultrasonic technique, the UPA can measure such properties as the blend ratios of two or more polymers, cooking cycle measurements for food processing, cure rates of polymers like those used in contact lenses, and physical properties such as viscosity, molecular weight and particle size.

Before this, such measurements were taken offline, says Matthew Oleskiw, marketing manager at UTEX. "You would take a sample from the process, run it to the lab--of course it's curing all the while--and then put it into the lab equipment to measure."

Inline monitoring of a production process using the UPA system means real-time information can be used to adjust process controls faster. This reduction in testing time, and improvement of the accuracy of the measurements, means that product quality improves while costs due to production waste go down.

UTEX and other nondestructive equipment manufacturers believe that many companies don't think of nondestructive methodologies like ultrasonics when considering measurement equipment. For instance, noncontact form and density measurements can be taken on contact lenses while they're curing.

"There's a lot that we can offer," says Oleskiw. "We need to open the realm of how NDT and metrology fit together."

More choices

The demand for tighter tolerances and networkability has driven metrology companies to design equipment that measures faster with ever-increasing accuracy and communicates more easily with the manufacturing environment. As traditional technologies like touch probes continue to evolve and newer technologies such as ultrasound, interferometry, laser, radar and vision become faster and more accurate, the applicability of these technologies increasingly overlap, giving users more options when selecting metrology equipment. Now more than ever, users can select from among several technologies to find measuring equipment that meets their specific needs of accuracy, throughput and cost.

About the author

Dirk Dusharme is Quality Digest's technology editor. Letters to the editor regarding this article can be sent to letters@qualitydigest.com.