Eliminating human error

Eliminating “operator bias effects” in precision measuring of aircraft control parts has been a major priority of the Moog Inc. Aircraft Group. The company has upgraded its measuring devices to meet that goal.  “We have an ongoing EMP program—evaluate the measuring process—for all gages used in our plants,” says Bruce Fisher, senior process quality engineer who spends a major part of his time advancing the drive for the East Aurora plant near Buffalo as well as similar manufacturing plants in California, Utah, and the Phillipines. Major customers for these plants are companies such as Boeing, Lockheed Martin, Airbus, and others all over the world.

Fowler’s Z-Cal II height gage inspects an aircraft control component at Moog Inc.’s East Aurora, NY, plant.

High accuracy

Used in military and commercial aircraft controls, these components achieve accuracies as small as 0.002" true position, sometimes to millionths, for parts such as bodies, manifolds, bearings, and glands, says Fisher. Many sources of variation are connected with the measuring process itself. Gages must be able to reflect the process variation and display adequate discrimination. Moog controls its processes with statistical process control, making gage selection very important. “We like instruments that can help us attain optimum repeatability, accuracy, and ease of operation.” He comments that two such instruments that have promoted the purposes of the EMP program are a new pistol grip bore gage and an electronic height gage, both manufacturing in Europe (the UK and Switzerland) and distributed exclusively by Fred V. Fowler Co., Newton, MA.

“The Bowers Holematic Bore Gage cuts by a factor of two to four the measuring time for the tricky job of hole assessment on these components and yields a big improvement in repeatability over the height gages and indicators we formerly used and found wanting,” says Fisher. The RS232C output of this instrument “lets us input the data into SPC software without running the risk of typographical and other operator errors. Fowler has manufactured some special anvils for Moog that due to the gage’s spring tensions also help us to measure from a stark surface to locate a radius groove in cylinders.”

“Our machinists do the piece-part inspection work themselves, because we do not have inspectors at Moog. Everything is done in the shop, every part as it is produced. More companies are doing it this way. And every few weeks we have auditors check on the machinists to be sure they’re making good decisions. This is what we’ve been doing for some thirty years. We’ve never had inspection laboratories, since this new kind of equipment is literally made for shop use.”

Fowler’s Bowers Holematic Bore Gage saves measuring time for Moog Inc.

The Fowler XT Holematic Pistol Grip bore gage has a large, easy-to-read display and self-centering heads. Two preset memories for different sizes are incorporated. “Tungsten carbide measuring faces on all 3-point heads from 0.5" are desirable features,” Fisher adds, “and they have never needed replacement.” The range needed to do the job at Moog is ½" to 6". Deep measuring is done via anvil extensions up to 13" and 14".

Moog uses the Z-Cal II height gage that features Sylvac’s motorized measuring system. Fisher finds the Z-Cal II Height Gage’s motorized measuring system easy to use while providing the accuracy needed. “It directly inputs to our portable PC,” Fisher says. Probe speed is directly proportioned to the finger pressure applied. It measures heights, depths, slots, internal and external diameters, and the distance between centers, all within an accuracy of 4 or 6 grams. Its nickel-cadmium battery pack and recharger give 40 hours of operation on a single charge. 

Moog employs some 900 machinists at its US and Philipines plants, all of whom use these measuring devices. “They are proof that our Process Improvement and Measurement Evaluation Program really works,” Fisher says.

Fred V. Fowler Co. 800.788.2353