AAF International®, located in Louisville, KY, provides filtration products for HVAC applications, dust collection, nuclear, and biochemical products. According to Ron Unthank, manager, AF-Manufacturing Engineering for AmericanAirFilter, ultrasonic equipment is used to manufacture three of their commercial air filters.
"We had previously used both radio frequency and impulse welding to assemble our ring panel filters. The ultrasonic method proved to be faster, which helps to maintain labor costs and improves production," says Unthank. AmericanAirFilter uses Sonobond''s SeamMaster continuous bonder to bond 2 layers of filter media 2 ft sq to either side of a 23 in. sq metal frame, encasing the frame inside the filter media. The machinery creates a continuous, fused seal. The filter center is then spot welded using Sonobond''s 20 kHz SureWeld plunge welder.
Radio Frequency Assembly Can Be "Temperamental"
Ultrasonic technology is becoming widely used to assemble filter devices, replacing adhesives, stitching, and radio frequency, which is inconsistent and uses more energy than ultrasonics. "The RF process can be temperamental when working with filter media. And after upgrading our filter media recently, we discovered RF did not seal at all," says Unthank. Ultrasonic equipment provided by Sonobond helps AmericanAirFilter achieve the high-quality bonds needed for their products, while keeping production costs in check. (SeamMaster continuous bonder, above, assembles panel and cube filters, below, for AmericanAirFilter.)
How Ultrasonics Works
Sonobond''s SeamMaster continuous bonding equipment channels high-frequency vibrations to the nonwoven filter media as it passes between the horn and the rotating pattern wheel, creating a rapid heat buildup at the material contact point. According to Kyle Kimbro, Sonobond vice president, "Nonwovens are ideally suited for ultrasonic bonding because of their high synthetic content. The ultrasonic energy causes the material to melt and fuse, which creates a strong bond, without the use of consumables such as thread or adhesives." Sonobond''s SureWeld ultrasonic plunge welders, which AmericanAirFilter uses for spot welding applications, use the same technology. "We''ve found that filter manufacturers prefer ultrasonic assembly methods, because a minimal amount of material is taken up by the bond," says Kimbro. "Since the sealed area does not absorb, it''s important to minimize the size of the welded area."
In addition to ring panel filters, AmericanAirFilter uses ultrasonics to assemble commercial bag filters used for air filtration components. "The SeamMaster equipment cuts the filter pockets to size and also seals the filter on three sides," says Unthank. Before switching to ultrasonics, the company assembled the filter bags using a sewing machine process which, according to Unthank, is inferior to ultrasonics because the needle holes may compromise the weld integrity. "The ultrasonic assembly process is faster than machine stitching, and creates an uncompromised, continuous seal."
Custom Equipment Assembles Cube Filters
One of AmericanAirFilter''s newest products, the cube filter, is assembled using a custom 2-headed plunge welder, specially designed by Sonobond engineers. "We needed to bond a wire ring along the perimeter of a 5-sided cube to make the opening sturdy," says Unthank. "We had evaluated a traditional sewing method to assemble our cube filters, but it was not adopted because ultrasonics worked so well with our other filter devices. It''s a much faster process, so it''s the only method we''ve used to assemble the cubes."
Says Kimbro, "The production specifications required a specialized unit with two welding heads to accommodate the size of the cube filter. The custom SureWeld spot welder provides a one-step process that produces a high quality weld and also cuts production time."