Quality Magazine

Case Studies: Gaging Technology Helps in Testing Application

April 18, 2006
Gage-Chek delivers the accuracy, dependability and affordability crucial to the steel specimen inspection application. Source: McCue & Associates


Suzanne de Lemos-Williams, senior mechanical engineer, and her colleagues at Instron Corp. (Norwood, MA) are accustomed to challenging assignments. De Lemos-Williams and the rest of Instron's 12-person Custom Engineering (CE) department take on assignments that call for integrating the company's advanced materials testing equipment for demanding customer application requirements.

Instron's Norwood facility has more than 300 employees who manufacture products and solutions used to evaluate the properties and performance of materials, structures and components.

When a major steelmaker enlisted Instron to design and build a tensile testing application, where steel samples could be measured for thickness and width in an automated fashion, de Lemos-Williams and her colleagues geared up quickly for the demanding application, which involved designing a high precision horizontal specimen measuring device (SMD).

The system needed to be robust and reliable enough to handle hundreds of large steel specimens a day with extreme precision. It would have to function flawlessly in a steel plant, one of industry's most hostile manufacturing environments. To avoid extensive user training, it had to be easily integrated into Instron's automation software for simple use. It also had to enable 24/7 "lights-out" operations.

"Based on experience with similar type systems, we knew that by utilizing high-precision robotics, we could reduce operating costs and avoid human error, a problem brought on by the customer's old manual inspection process," says de Lemos-Williams.

The Instron CE team regularly handles major automation projects that are complex in nature, some that require considerable time. Depending on the application, it is not uncommon for a custom-engineered project to be completed over a period of months. However in this case, regardless of complexity, the customer absolutely needed a solution in just one month.

"We'd considered using several solutions that might have worked," de Lemos-Williams recalls, "But each one fell short in some way. One was awkward to operate. Another one couldn't deliver the required ±5 micron accuracy. Still another one lacked the capacity and reliability to handle hundreds of samples per day ranging from 2 to 30 millimeters in length, some of them weighing as much as four pounds."



The four-probe Gage-Chek system fit Instron's gaging, fixturing, reliability and materials handling needs. Source: McCue & Associates

Instron decided on the Gage-Chek, a gage amplifier system from Metronics Inc. (Bedford, NH) to deliver the accuracy, dependability and affordability for the success of the solution.

"The Gage-Chek truly became a key piece of the intricate puzzle this application had become," says de Lemos-Williams. "It delivered ±5 micron accuracy, real-time go/no go gaging, a flexible, intuitive user interface, and direct output for SPC.

"And the Gage-Chek gives us four probe inputs-actually half its full eight-probe capacity-enabling the system to handle four measurement probe inputs at once. The eight-probe capability could come into play in future applications, particularly if we need to combine Heidenhain Gages, LVDTs and HBTs," she adds.

Previously, the steelmaker attempted to meet its increasingly demanding production schedule using conventional hand tool gages. This method, however, failed to deliver the speed, accuracy and handling capacity required. Inspectors employed manual testing using handheld devices-a labor-intensive, time-consuming scenario where technicians had to hand-feed and measure parts plus record values, one at a time.

"They couldn't keep up with the company's accelerating inspection demands," de Lemos-Williams says.

Though the gaging station would become a single element of a highly technical, robotic tensile testing application, the CE engineers quickly recognized the unique engineering challenges this SMD presented.

The team faced multiple design decisions: How to secure and center the part to be measured? How to capture the readings and download them to a PC in an automated fashion? How to build flexibility into the solution to accommodate the breadth of specimens likely to be tested?

Initially the CE team tried using a gaging system that could handle only three-probe inputs at a time. "That device used [gages] that were compact, highly accurate and repeatable," de Lemos-Williams says. "But we were finding that the accuracies produced by the three-probe system were drifting up and down. And the parts weren't positioning properly every time.

"We knew the best solution would be to add a fourth probe to enable measuring the specimen from all four sides - width, thickness, above and below. The four probe Gage-Chek system fit our gaging, fixturing, reliability and materials handling needs," she adds.



The steel specimen in horizontal specimen measuring device (SMD) fixture is indexed, then four probes contact the part, obtaining width thickness values. Source: McCue & Associates

The Solution Close-Up

Bar coded steel specimens are held in a storage rack. A barcode reader determines the proper handling and gaging routine for each specimen, whose dimensions and fixturing requirements can differ widely.

A Fanuc LR-mate 100ib robot picks up the specimen and places it in a pneumatic workstation. The system automatically centers the specimen. Then an anodized aluminum clamp moves in to hold the part in place for measuring. The table indexes to move the specimen, and obtains three required ASTM measuring positions.

The Gage-Chek then measures two values: thickness and width. Next, it automatically computes the values and downloads them to a PC.

The piece is automatically unclamped from the table. In the next sequence the robot picks up the piece and places it in a universal testing frame, which conducts the destructive tensile testing process.

During this process, Gage-Chek functions like a microprocessor. For example, with its programmable gaging routines, six-inch graphical user interface with a choice of color-coded analog or digital displays, the instrument provides operators with instant, simplified measurement feedback. Results can be displayed numerically or graphically and archived for process studies such as statistical process control.



Three Times the Productivity

Now the entire steel inspection and tensile testing process takes about two minutes. Compare this with the steel company's former, cumbersome process of handling each part, using a digital caliper to take six measurements for width and thickness, and recording the values manually. In this scenario, the human error factor alone could seriously compromise quality control.

"Now each rack of 66 specimens can be fully tested in 120 to 130 minutes, enabling the company to gage about 300 specimens in an eight-hour shift," de Lemos-Williams says. "Previously, with the manual process, even on a good day each shift could test up to only about 100 pieces. We've helped the company achieve a 300% gain in productivity, together with greater accuracy, flexibility, and repeatability.

Peter Borsari, Instron product marketing manager, says that the capabilities of Gage-Chek have allowed Instron to enter new markets for testing larger specimens with greater speed and accuracy. "In fact, Gage-Chek will find its way into future Instron projects, such as one we began recently with another large steel manufacturer," he adds.



Metronics
(603) 622-0212
www.metronics.com
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Sidebar: Benefits

  • With its programmable gaging routines and six-inch graphical user interface, Gage-Chek provides operators with instant, simplified measurement feedback.
  • The Gage-Chek delivers ±5 micron accuracy, real-time go/no go gaging, a flexible, intuitive user interface, and direct output for SPC.
  • The entire steel inspection and tensile testing process now takes about two minutes.


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