This technical information has been contributed by
Futek Advanced Sensor Technology, Inc.

Inspection with Sensor Film Leads to Redesign of Clamp

Control and Measurement Electronics

MADISON, N.J.--Futek, Inc., an Irvine, California-based manufacturer and supplier of load cells, as well as torque and pressure sensors that incorporate metal-foil strain gauge technology, recently experienced difficulty assembling some of its load cells to specifications. By performing several tests and controlling for different variables, the company found fluctuations in clamping pressure to be a significant factor.

To bond the gauges to the sensors, Futek uses an adhesive that requires a clamping pressure of 50-75 psi. But by using Pressurex®, a thin flexible film from Sensor Products Inc., James Meiselbach, a mechanical engineer at Futek, was able to see that the pressure fluctuated from 50 psi to upwards of 200 psi in some of the production runs. This discovery led Futek to use Pressurex® to help redesign several of its clamps, incorporating silicone die springs to regulate the pressure more precisely. "A sample pack of Pressurex® with film that revealed different surface pressure ranges allowed our production to continue," said Meiselbach.

According to Sensor Products, Pressurex® is a versatile non-destructive testing (NDT) tool for quality control and machine component inspection. Its ability to easily and rapidly show inconsistencies in surface pressure between mating or contacting surfaces has lowered scrap rate and assisted in the design and manufacture of many industrial and electronic products, the company says. Pressurex® reveals surface pressure from 2 psi to 43,200 psi (0.14 - 3,000 kg/cm2), and can be used to assess surface contact inconsistencies in "virtually any industrial or electronic application," according to the company. These include gaskets, clamps, bolted joints, and connectors. Additional applications are said to include heat sinks, heat sealing elements, welding heads, and plastic and composite manufacturing, among others.

To measure the surface pressure of a clamp around the outside of a load cell, Meiselbach cut Pressurex® in the configuration of the clamp surface area, placed it in between the clamp and the load cell, and applied force. He then unclamped it, removed the Pressurex®, and compared the film, which changes color depending on how much pressure is exerted, to an accompanying color calibration chart.

Meiselbach became aware of Pressurex® when he previously worked for an aerospace company. "We were having a problem with the main rotor blade of a helicopter," he commented. "Interference was causing a fatigue crack in one of the inner spar tubes of the rotor blade. We put a large sheet of Pressurex® in the bonding tool, bagged it up, and pressurized it in the autoclave. When we removed the film, we were able to identify the exact amount of pressure causing the crack."

For more information on Pressurex®, visit

This technical information has been contributed by
Futek Advanced Sensor Technology, Inc.

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