Important trends in the plastics industry have raised the standards for plastic weld joints. The increasing use of low-viscous polymers, high-temperature formulations, functional fillers and the need for superior bonding of unlike materials have added complexity to the plastic assembly process.
Appliance designers and engineers are demanding processes that create parts with particulate-free, visible weld lines, giving them design flexibility, part integrity and manufacturing efficiency in their products.
So it is not surprising that recent advancements in technology have led to a hybrid design that incorporates the standard vibration welding technique in combination with infrared technology. This technique is called Clean Vibration Technology (CVT). In this method, the weld interfaces are precisely preheated with an infrared heat source and then vibration welded together. This technique provides all of the advantages of vibration welding, but minimizes the flash and particulate that are typically formed in standard vibration welding.
Among the benefits:
- Clean, clear weld-bead aesthetics – Welds are virtually free of the particulates and “angel hair” that can undermine aesthetics, require downstream manufacturing to remove flake-off or compromise end-product performance.
- Engineering design flexibility – With such clean optical joint welds, designers and engineers can incorporate the weld lines into their product designs, including complex 2D and 3D moldings.
- Range of tool configurations and options – A wide range of tool weights and other options include additional infrared zones, part present sensing, centering slides and bar code scanning.
- Maximum energy efficiency – The CVT process uses “wavelength matched” metal-foil IR emitters that provide optimum energy with the same absorption characteristics of typical technical polymers; this produces a faster, more efficient melt, thus saving time and energy used in the joining process.
- A range of applications: CVT is ideal for clean, precision joining of any part or product that requires a clean weld that maximizes aesthetics, integrity, or functionality.
CVT Process Overview
A ceramic fixture houses a metal-foil infrared emitter that conforms precisely to the joint lines of the two parts to be assembled. Parts to be joined are positioned above and below the emitter and brought close to it without touching.
The metal-foil emitter heats the joint planes along the weld lines, and once plasticization occurs, the emitter is removed, the two parts brought together under pressure, and vibration begins.
The vibration weld process with noncontact plasticization allows joining of molten layers of plastic with no solid-solid friction, ensuring uniform material flow while preventing particulate generation.
Once optimal weld depth is reached, vibration stops and joined parts cool into a single, clean-vibration joint, with no “angel hair” by-product and with excellent mechanical properties.
A good source of additional information on Clean Vibration Technology is a white paper from Branson Ultrasonics Corp. You can find "Selecting the Proper Assembly Process" on, www.appliancedesign.com/whitepapers.