Machine Design

Emergency lighting relies on durable insulation

Barron Lighting Group
ITW Formex

By its very nature, emergency and exit lighting must be durable and dependable, so these were key concerns for Barron Lighting Group, based in Phoenix, as part of its new design for LED exit signs and emergency lights.

Company engineers needed to keep circuit boards fully insulated, separating high and low-voltage areas. The idea was to enclose the circuit board within an insulated box, yet still have easy access to wire terminals and a 120/277-V dip switch. In addition, the box needed an interlocking mechanism that would simplify installation and display operation and warnings.

“We had a design in mind,” said Barron Lighting Group’s Mike Glaser, but admits it wasn’t in their area of expertise. “We needed a company to help us with material selection, box fabrication, and developing the interlock,” he says.

They turned to Fabrico, an experienced converter based in Kennesaw, Ga. It has an in-house lab that can test a wide range of material parameters, such as temperature resistance, shear and tensile strength, outgassing, dielectric strength, and electrical and thermal conductivity. After investigating a number of materials, company engineers recommended Formex from ITW Formex, Addison, Ill.

This flexible polypropylene electrical-insulation material is often used to protect sensitive electronic components and prevent unintended contact between circuit boards and housings, and between circuit boards themselves. Formex’s high-dielectric strength (1,460 V/mil @ 17-mil thickness), low-moisture absorption (<0.1%), and UL 94V-0 flame-class rating make it an excellent, lightweight insulating material that meets safety and environmental standards. In addition, Formex lends itself to fabrication and folding into three-dimensional shapes that retain their form. It can also be embossed or printed with product or safety information.

To meet Barron’s specifications, Fabrico die cut Formex into a box shape that included tabs for secure closure. Die cutting is held to tight tolerances with high repeatability, making it ideal for long production runs. Tolerances can range from ±0.015 in. to ±0.005 in., at speeds up to 500 fpm. Electronic web-tension control ensures precise registration. Material thicknesses can range from 0.001 to 0.015 in., with widths up to 13 in. There is no limit to the length of sheeted materials, and individual die-cut parts can be up to 22-in. long.

After die cutting, Fabrico printed the Formex boxes with warning and voltage information. Then, they were scored for easy folding during assembly, and shipped flat.

“The box has been a success,” according to Glaser. It keeps the circuit board completely insulated, yet provides ready access to the electrical connections and voltage dip switch, he notes. “And the design has proven to be easy for our production personnel to install. Keeping it simple has minimized production time and gives us a competitive advantage,” says Glaser.

© 2012 Penton Media, Inc.

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