Software turns digitizing arm into instant inspection station

May 22, 2003
Portable FaroArms are coordinate-measuring machines (CMMs) used in our facility to improve the fabrication of parts and weldments. Using the arm captures coordinates that can be turned into accurate dimensions and then compared to a print.

A screen from CAM2 shows measuring guides for a complex fixture. Purple cylinders are locator pins. Four pins describe the corners of the large grid that holds a zero point or common coordinate origin. A direction is set through two of the pins across from one another, with the origin being their midpoint. This produces a 3-2-1 (plane-line-point) alignment. Smaller "floating" grids are planar surfaces of pin locators. The X through the grids are points constructed at the intersection of the pin and its corresponding plane. These points set the fixture for position, while the cylinders of the measured pins indicate how well locators are aligned.


An inspector takes coordinates off a just-completed part. Should the inspection turn up errant dimensions, the information generated by CAM2 is handed to a machine operator who makes adjustments that bring the next part into spec.


But the measuring arm is just one part of the inspection equation. The CAM2 Measure program guides inspectors and turns measured coordinates into useful information. For instance, parts can be inspected right off a press brake. In minutes, data from the inspection guides toolmakers and the press-brake operator to adjust tooling and gaging that produces parts to print with a minimum of scrap.

The software also lets us write programs that show others what measurement locations on a part will capture enough coordinate information for a complete inspection. Writing and debugging such programs can usually be done in a single shift.

Software output also lets us resolves fit-up issues in assemblies. In one instance, a large rotating weldment was possibly twisted a bit by interference with another part, pushing a locating feature a few millimeters off position. But in less than an hour, we verified the fixture was undamaged and holding the original positions despite interference incident.

The software works like this: An operator calls up the CAM2 measuring program for a particular part, and using the FaroArm, follows step-by-step instructions for digitizing the required features. For some parts, a wire-frame image may show where to pick points that will align and position critical features and details. The program performs a part alignment, relating features to a coordinate system based on the part's drawing. Alignment calculations take only seconds, so operators need not pause when taking measurements. When finished, measured data can be transmitted to those who need it.

A few characteristics in the software stand out. For one, the program-measuring feature lets layout inspectors and me take a simple part, write a program, edit and proof it, and inspect a set of 10 to 20 parts in a few hours. It also lets us take a newly formed part from a gage or forming setup to production-ready in one shift. Larger, more complex parts can take up to two days, which is still faster than other inspection methods.

The software trims time from projects by letting us measure parts quickly, sometimes as fast as they can be brought to the measuring arm. In a matter of minutes, we can analyze the data for a part and adjust its gaging or fixtures. Cost reductions come from keeping scrap to a minimum.

The software is user friendly for both programmers and arm operators. A few days training is enough to provide a basic understanding and let operators run programs. The software is well organized, easy to edit, and structurally well defined. It is also well supported by tutorials and a reference library. Documentation is easy to read and understand.

Fixture verification often takes less than an hour, including arm setup, measurement review, and turnover to production. Without the software, large and complex hydraulic fixtures would have to be disassembled, sent to the machine shop for verification, and then checked for detail. This would take several people at least half a work shift.

The only change I would make is to reinstall the Average Point function found in older versions. I often used it to dial in an accurate Move Device Position. Improving the probe position for each point taken reduces the movement error per point. The feature also lets users quickly set points without identifying a second part feature.

Cam2 Measure and the digitizing arms come from Faro Technologies Inc., 125 Technology Park, Lake Mary, FL 32746, (800) 736-0234, (

-- Rex A. Mericle

Rex Mericle ([email protected]) is a quality-engineering analyst at the Skid Steer Fabrication of the John Deere Dubuque Works in Iowa. The facility manufactures five models of skid-steer loaders for lawn, grounds, and turf care.

About the Author

Paul Dvorak

Paul Dvorak - Senior Editor
21 years of service. BS Mechanical Engineering, BS Secondary Education, Cleveland State University. Work experience: Highschool mathematics and physics teacher; design engineer, Primary editor for CAD/CAM technology. He isno longer with Machine Design.

Email: [email protected]


Paul Dvorak - Senior Editor
21 years of service. BS Mechanical Engineering, BS Secondary Education, Cleveland State University. Work experience: Highschool mathematics and physics teacher; design engineer, U.S. Air Force. Primary editor for CAD/CAM technology. He isno longer with Machine Design.


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