issue: November 2003 APPLIANCE Magazine
Plastics Buyers' Guide
Advantages of Ultrasonic Plastic Welding for Appliances
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Ultrasonic plastic welding has unique benefits as an assembly method. It uses no consumables and is easily automated and monitored for quality control.
Plastics are finding more applications in the appliance and other industries including the automotive, medical, packaging, computer, data and telecommunications, and toy industries. Many of these applications require the ability to weld small plastic parts, make internal welds, or weld thermoplastic fabrics and films.
The Stapla K1
is an ultrasonic plastic welding system with a vertical sonotrode and a
controller for one-button operation.
When ultrasonically welding plastics, a thermal rise in the bonding area is produced by mechanical vibration, producing frictional heat that causes the material to plasticize, forging an insoluble connection between the parts.
Unlike metal welding, where the parts are vibrated horizontally, ultrasonic plastic welding utilizes a welding tool (the sonotrode) that is oriented to apply vibrations vertically rather than horizontally. A prerequisite for welding plastics is that both working pieces have a near equivalent melting point. Joint quality is very uniform because the energy transfer and the released internal heat remain constant and are limited to the joining area.
Hermetic sealing with interlocking intersection points is readily accomplished. Ultrasonic plastic welding systems also support far-field welding, where the sonotrode may be inches away from the joining area without compromising results.
Today's ultrasonic plastic welding systems can be pre-calibrated to automatically maintain consistent welding parameters and compensate for differences in part size to maintain pre-set welding depths. This provides excellent control over the aesthetics of the joining area to produce welds without the loosely controlled deformation that is typically exhibited in hot-melt joints.
Plastic welding and bonding systems have to be evaluated on an application-by-application basis, taking into account investment costs, energy requirements, process time, part size and material, and weld quality, among other factors.
Because ultrasonic welding systems have very low energy requirements, use no consumables, require no cooling water, and have modest space requirements, they provide cost-effective, environmentally friendly solutions in many application areas.
Ultrasonic plastic welding is ideal for sealing plastic tubes, welding metal conductors to plastic parts, joining plastic parts in the manufacture of appliances, and fabricating cases and enclosures for cell phones, garage door openers, and other electronic and electrical appliances. Advances in plastic welding machine technology make their use advantageous for high-volume manufacturing with a fast and highly repeatable process, as well as data reporting for yield tracking.
This information is provided by Tony DiFinizio of Stapla Ultrasonics (Wilmington, MA, U.S.).