Featured part: Ametek, Inc.

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By Steve Baker | Jan 17, 2017
Instrument device overlay

GMN has been working with Ametek, Inc., an electronic instruments and electromechanical device manufacturer, for years. Ametek’s Crystal Digital Test Gauge is used for testing pressure vessels and piping systems in critical industries such as the oil, gas, nuclear, and power generation.

The device requires a corrosion resistant user interface that will be able to withstand harsh environments. To meet these requirements GMN strategically developed the stack up of the overlay, adhesive, and membrane to act as a sealant from moisture and fluids. Usually, the tail end of a membrane exits the membrane circuit at the border of the part. Instead, GMN positioned the membrane tail to exit the membrane circuit at the center of the part, near the window. This allows the part to have a firm edge on the border, preventing any moisture from passing through the part.

Under these tough environmental conditions, the graphic on the overlay also must be preserved. GMN printed the graphic on the backside of the overlay material to prevent the design from eroding. This technique is common for electronic instruments.

When a device requires a membrane with tactile switch technology, GMN often uses polyester (PET) film. This is to ensure the membrane switch overlay is durable enough not to crack. Additionally, PET film is scratch and chemical resistant, which contributes to the components that prevent this device from corroding.

The overlay features seven colors, one texture, and a window for the display screen. The window is an added challenge to the part because it must be rigid and durable without disturbing the thickness of the overlay material or the dimensions of the membrane switch. GMN solved this issue with a window stiffener layer that secures this component to the back of the overlay.

As a 3M preferred converter, GMN used a high performance acrylic adhesive for this overlay. The easily die-cut adhesive is moisture and solvent resistant. Once all the components are assembled together, the part can withstand maximum operating temperature of 185 degrees Fahrenheit and minimum operating temperature of -22 degrees Fahrenheit.