On construction jobsites throughout the world, contractors rely on the spirit level to make sure surfaces are truly flat (horizontal) or plumb (vertical). This type of level—so named because it contains a vial of alcohol (spirit) with a bubble in it—has been used for centuries and remains very popular.

Since 1919, Mukwonago, WI-based EMPIRE Level has been producing all types of spirit levels, including those with a digital readout. The company also manufactures squares (framing, T, T-bevel), marking and layout products, safety and utility tape, and measuring devices like calipers.

EMPIRE introduced its TRUE BLUE line of I-beam levels in 2004. It has expanded and improved the line several times since then, most recently in 2016 with the E55 series. This series includes 24-, 48-, 72- and 78-inch-long levels with all-metal construction (magnetic or nonmagnetic), acrylic vials (accurate to within 0.0005 inch) and blue bands that optimize bubble visibility.

However, welding the levels during their initial mass production was challenging. According to Walter Ziller, manufacturing engineer at EMPIRE, the company’s welding system at the time failed to produce strong-enough weld joints.

This problem led to multiple quality checks on the automated assembly line and inefficient production. It also convinced EMPIRE management to meet with Herrmann Ultrasonics Inc., which, several years before, had done work on the prototype of EMPIRE’s Mono Vial system.

To increase production efficiency and assembly line flexibility, Herrmann designed a replacement ultrasonic welding system that features four VE Slimline 20-kilohertz weld heads with a long horn (sonitrode) and two Solid SDM generators. High-frequency switching enables EMPIRE to save money by controlling the four heads with only two generators.

Two heads are mounted next to each other on both sides of a gantry, which moves to specific locations on the level. At each location, one head applies a weld to attach a molded ABS plastic component to the level frame. To ensure that the weld leaves no surface mark, the horn face and the part are kept perfectly parallel during welding.

Some TRUE BLUE level series, such as the E55, require only three welds. In these applications, only three heads perform welding. Ziller says the three welds provide strength equivalent to eight shear welds and multiple energy directors. An energy director is a contact point on the plastic part that concentrates energy to rapidly initiate material softening and melting, and enhance the weld joint.

VE Slimline heads come in frequencies of 20, 30 and 35 kilohertz, and feature guiding systems that ensure accurate, repeatable welds. Additional-distance modes in SDM generators allow for constant monitoring of the welding process.

Ziller says the new welding system has enabled EMPIRE to increase its annual production of I-beam levels to about 1 million. Most of the levels are sold at Home Depot, and most users of the E55 series are do-it-yourselfers.

“Ultrasonic technology has allowed us to eliminate failure modes,” concludes Ziller. “We now have confidence that each part coming off the line is within conforming standards at a Six Sigma level.”

For more information on ultrasonic welding, call 630-626-1626 or visit www.herrmannultrasonics.com.