Technical releases white-light welding machines

Technical Radiance has announced the availability of advanced plastics welding machines based on white-light spectrum energy.

According to the company, the welding of modern plastics and laminates with hot-air or extrusion systems becomes increasingly problematic as line speeds increase.

Hot air is an inefficient source of heat, with most of the heat simply blowing away.

Extrudate systems have a limited output speed as they have to melt the entire material used to form a weld.

Both these systems have difficulties with typical production processes that must stop, start and change speed.

Infrared welding has been proposed as a solution but fails to compete with the high power density available with lasers.

Even lasers, known for their very concentrated beam intensity, do not achieve much when this beam power is spread out over a large area with the goal of melting a reasonable thickness for optimal welding.

In 1996, Technical Radiance first went beyond infrared into the white-light spectrum to achieve a power output of up to 12kW emitted from a 90mm x 90mm opening (more than 1MW/m2).

These powerful sources can selectively target buried layers with laminated structures to facilitate rapid welding with reasonable quantities of hot-melt material.

Coupled to opto-mechanical tape applicators, these advanced forced-air cooled systems have been in production use in Denmark for more than 10 years, but the technology is only now available on the open market.

Both continuous-strip welders and pressure-patch welders are available.

A two-layer co-extruded tape (one clear layer and one absorbing layer) is another key ingredient of the patented system.

Only the thinner pigmented layer melts because the light passes straight through the transparent layer, giving a controlled melt flow in the pigmented plastic layer.

The process is mess free as the bulk of the tape remains solid.

The weld is suitable with a combination of simultaneous heat and significant pressure at a buried air-free interface region.

The controlled pool of molten weld material is sufficient to give encapsulation on composite structures, such as those with polyester reinforcement or stitching.

The joint is ready to handle within a few seconds as heat from the molten welding layer quickly dissipates into the surrounding plastic without causing overall melting.

A standard unit can weld a 65mm-wide strip of 1mm-thick tape (plain or reinforced) at speeds of up to 40m/min.

Widths can be extended indefinitely, with custom-designed variants at moderate NRE costs.

A universal power controller is available to match the output to the typical start/stop and process speeds encountered on a production line.

Units with up to 40kW are available and can be cascaded for higher-output powers.

Redundant-element operation is standard, so if a lamp fails, a standby lamp takes over within milliseconds and production is uninterrupted.

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