Suppliers of metrology equipment are working towards making measurements easier, allowing greater use throughout the manufacturing process.
The ultimate goal in metrology is easy, effortless measurements—operators walk up, load a part, push a button and get an answer.
“A few years ago, we [investigated] how to create a better walk-up environment,” said Tom Groff, vice president, North American sales for Quality Vision International Inc. (QVI), Rochester, N.Y. They first tried to define it—and got a surprising number of answers. “We discovered it is a broad topic, actually, and the answer depends on who you ask and what their environment is,” he said.
As always, achieving simplicity is complicated.
Groff and his team knew it would include a combination of hardware and software programming. It could range from a single sensor with no programming to multisensor machines that require a program to measure complex GD&T call-outs. “We broke it up into machines vs. software. We developed a few machines dedicated to walk-up, and then some software tools [that expanded their capabilities],” he explained.
“Sometimes, you need both, and sometimes you just need one or the other,” he said. Groff and QVI concluded there are four scenarios that could be called walk-up metrology.
The simplest scenario is measuring a 2D part using a large field-of-view (FOV) camera, such as the QVI SNAP with its maximum 100 mm FOV. “Given the part fits, you put it on the SNAP, hit a button, and you get results without any programming,” he said. The trick in this scenario is the user must select which results are relevant, which requires an easy user interface on the machine.
“The next, or second, level is if you do select a set of features, and the user can store that memory away in the software—program it on the fly. Then, the next time it is even easier because now you will get only the measurements you want,” he said.
But what if the part is prismatic or you need to scan 3D features? What about measuring surface form or taper on a cylinder? “For that third scenario we developed our [programmable] multisensor Fusion that combines a large field-of-view camera with other sensors to get more than 2D,” he said. This more capable system can solve the 2D walk-up case without programming, but it does require programming for the more complex features. That could be done ahead of time or, again, on the fly by the user, with automatic path generation. This does require a user with some programming skills, but with much less time and knowledge required. After that, it becomes walk-up.
The fourth scenario is having a part whose CAD model has full product manufacturing information, or PMI, associated with it. With PMI properly specified and a software program that can make use of it, such as QVI’s ZONE3, an inspection program is automatically programmed. The user walks up at the point of use, identifies the part, a parts program is loaded and measurements are made. The end user needs to know little about programming—he just walks up and uses it.
Until that scenario becomes universal—attaching PMI to CAD models is not widespread as of yet—it is worth taking a deeper look at walk-up scenarios and use cases.
Simple When Needed
Small and medium-sized machine shops certainly need a versatile metrology device shareable among a group of professionals with diverse metrology skills. “With our XM machine, we give machinists a way to measure 3D and GD&T geometry quickly and easily without any of the programming complexity of a traditional CMM,” said Steve Chirichella, regional product sales director for Keyence Corporation of America, Itasca, Illinois. “This kind of a walk-up-and-use metrology system is one of the fastest growing market segments right now for Keyence,” he said.
If an operator can move a part to the system, he simply fixtures it with a couple of clamps, establishes the frame of reference, and uses a probe to make measurements. Said to be as easy to use as calipers, the system was designed to fill a gap between simple hand tools (with their limitations) and the complexity of programmable, high-end CMMs.
“Our latest release can compare product profile measurements and free-form surfaces against a 3D CAD model,” he said. It is also small and light enough to be portable throughout the shop. Chirichella said most operators put the device on a cart and wheel it to where they want. “Our XM device fits more in machine shops that are lower volume with a higher mix of parts. They typically concentrate on milling or casting.”
Keyence also offers its IM series of image dimension measurement systems, what Chirichella describes as an automated optical comparator. “The IM is a 2D inspection system. We see it used with Swiss machining, turning, stamping or wire forming—higher accuracy, smaller parts that need to be inspected,” he said. Customers are always asking for larger inspection volumes, and Keyence responded with its latest IM 7000 that measures up to 8″ x 12″ (203.2 x 304.8 mm).
Mark Arenal, general manager for Starrett Kinemetric Engineering, Laguna Hills, Calif., agreed that the concept of walk-up metrology might encompass a wide range of meanings. “It could include a single instrument that makes both simple or complex measurements, depending on how it’s used,” he said. One full-featured instrument equipped with full-featured software may well be used both for spot checking or for complex checking of hundreds of production parts. “To do that, the software has to have discoverable features, so that someone can easily make a few measurements, or a quality control professional can program it to do much more,” he said.
In either case—spot checking or in-process quality control—he sees the concept of walk-up metrology as empowering shop floor personnel. It avoids the bottleneck that frequently occurs when parts must be sent to a separate quality room.
“A good example of this is using our HVR100-FLIP digital video system, with its wide-FOV camera and a stored program,” he said. “The software on that machine will auto-recognize a part or multiple parts and automatically measure all of the features or those specifically selected.”
He is also quick to point out that putting metrology equipment on the shop floor still demands a suitable environment for metrology. Today’s metrology equipment is more robust than ever, but limits remain. “Be wary of temperature swings and shop floor contaminants,” he said. Fortunately, precision machining is now requiring cleaner, more controlled environments as well, making it easier to use metrology equipment in the same space. He also stressed the need for tooling and fixtures that enable the part inspection routine to be easily launched by the machine operator.
Another important element is connecting the QC and metrology processes with the manufacturing system, according to Arenal. “We need to think on the shop floor as we do in an inspection lab,” he said. In this vein, training is important, especially when shop-floor people are deciding what to measure rather than executing a comprehensive, pre-loaded program. It does not need to be a two-year certificate program. “We are talking two days to two weeks of training, at most, depending on the individual’s skill set,” he said.
Walk the Part or The Device
The idea of metrology being easy to use and accessible in a walk-up situation is not new—it is now becoming expected, according to Zvonimir Kotnik, business unit manager, portable solutions for Hexagon Manufacturing Intelligence, North Kingstown, R.I. He agreed that manufacturers are moving away from sending parts to controlled quality labs. He sees this trend as accelerating of late as manufacturers are driven to streamline their processes. “In-situ metrology is helping manufacturers create a better process that produces better parts for less cost,” he said.
Like others, Kotnik is seeing a demand for instruments that can take a wide range of measurements and are easily adaptable. There are various use cases, ranging from a single device for use by an entire machine shop to one dedicated to a manufacturing cell to ensure first parts are correct and perform routine in-process measurements. “In either case, it needs to support different absolute measurements,” he said. Manufacturers need a device that in a dedicated work cell can measure both a roughing operation or critical features for adjusting machine offsets, or support a worker wanting to make a few one-off measurements.
He offers an important twist on what exactly is being moved, the part to the device or the device to the part. “In many cases, you do not want to take a part out of the fixture in a machine to check it after a critical operation but before it is complete,” he said. “If you walk the metrology device to the part, while it is still on the machining center, it will ensure greater consistency and you have the added bonus of not having to refixture the part.”
Devices ideal for this walk-to-the-part scenario include Hexagon’s line of portable arm CMMs, laser trackers, and portable 3D optical scanners. “Each can work as either ‘walk the part’ or ‘walk the device’,” he explained.
Quality control is more than dimensional geometry. It also means checking for surface blemishes, burrs, inclusions, and other defects, especially in bores, channels, and holes. That is where borescopes such as those from Gradient Lens Corp., Rochester, N.Y., enter the picture. These also can be walked to the part. The company’s markets include machining and casting for the automotive, aerospace, and medical industries.
“Typically, applications are for checking parts associated with fluid flow of some kind. Hydraulic components, for instance, fuel systems, and engine blocks where they’re checking the coolant passages or oil passages. Those passages are critical,” said Doug Kindred, president and CTO for Gradient Lens.
A wide variety of applications led Gradient to develop more than 80 different models of borescopes, checking holes from 0.5 to 8 mm, with the most popular in the 4 mm range. Some passages they check are as tiny as the fuel injector nozzles used in engines.
“We employ three different core technologies to satisfy all of these applications,” explained Kindred. They include rigid borescopes, flexible borescopes, and video borescopes. Rigid borescopes produce images with resolutions up to 300,000 pixels but are limited to straight, accessible bores. Flexible scopes using optical glass fibers are limited to about 18,000 pixels but can reach inaccessible bores and hydraulic or fluid channels.
“Videoscopes are the more modern approach, putting a camera at the tip of the scope and sending an image electronically rather than optically to a video screen,” explained Kindred. “These can produce up to 400,000-pixel images,” he said. Which to choose? It’s a question of applications and value, with the rigid scopes the least costly and video the most capable (for a higher price). Videoscopes are especially useful in aircraft maintenance—perhaps the ultimate walk-the-device-to-the-part scenario.
The Future is PMI
“When my customers describe the metrology machine they want, they want one that operates like a microwave—put in any part, push a button, and measure the entire part,” said Dylan Coutelle, technical sales engineer for Carl Zeiss Industrial Metrology LLC, Brighton, Mich. Maybe the concept today is not feasible for any part for any measurement, but he agreed the industry is inching closer. Coutelle’s customers, like others, measure 2D parts on vision systems, such as the company’s O-SELECT device, that are essentially place-and-measure.
Slightly more complicated measurements can still be performed by shop-floor personnel with a minimum of training, using more capable machines like the O-INSPECT that combines vision with tactile measurements.
“Many companies have a small O-INSPECT on the shop floor, where operators with a little bit of training can use the camera to measure a diameter or other simple feature very quickly,” he said. Other shop floor machines that could be used in the same fashion, even if dedicated to in-process measurement, include the company’s GageMax and DuraMax.
But according to Coutelle, the ultimate in walk-up under any circumstances—creating the “metrology microwave”—requires off-line programming. And that means automated programming using PMI attached to a CAD model. Like others in the industry, Zeiss is anticipating a wider practice of attaching PMI to CAD models. Its CALYPSO metrology programming software—like many others—can now automatically create measuring programs with its Autorun capability.
“Autorun allows the operator to select a program and hit run, minimizing the amount of programming work that’s done on the shop floor,” he said. “This keeps the shop floor as a walkup metrology process.”
Compact Display Unit Designed for Shop Floor Gaging
The duo premium compact electronic display unit from Marposs, about the size of a smartphone, is designed for shop floor measurement. It has a 4.3” touch screen unit for display and storage of measuring data acquired through one or two sensors. The device is designed for manual applications when a few measurements are needed on the shop floor. With two sensor input channels, it displays two measurements at once in either analog of digital.
According to Marposs, the system is portable, easy to configure and visualizes measurement status. Duo works with Marposs LVDT/HVT manual gages, such as bore gages M1 and M1 Star, snap gages M3 Star, ring gages M4 and M4 Star, and Red Crown/Red Crown2 displacement sensors with a measuring range up to ±5 mm. Data collected can be exported through the USB port or an optional Fieldbus port.