Common Joint Designs

Laser welding uses a precise IR laser beam that is directed through a transmissive material and penetrated into an absorptive material. As with all plastic joining technologies, a properly designed weld joint is critical to achieving the desired weld strength and appearance.

General Guidelines

• The transmissive part must be transparent/translucent to IR, but does not have to look transparent to the human eye.
• The transmissive part should be approximately 3 mm thick or less for semi-crystalline materials and can be much thicker for amorphous materials as long as they are transparent.
• If the transmissive part has glass filler, as the percentage increases, the maximum thickness decreases due to scattering of the laser energy.
• Typically weld ribs are 2 mm wide, but narrower or wider is feasible and depends on customer requirements.
• Typically plan for 0.2 – 0.4 mm interference (displacement) in the weld joint unless it is a simple lap joint or an inline lap joint that doesn’t allow for displacement.
• Make gaps twice as tall as displacement depth to account for flash.

Lap Joint Designs

T Joint Designs

Radial Welding Joint Design

• Interference is required between the two components.
• Typically plan for 0.1 – 0.4% of part diameter interference.
• The angle of interference depends on overall part geometry, aesthetics, and strength. The angle should be between 45 and 85 degrees.