Laser Welding

How does laser welding of plastics work?

The common industrial form is through-transmission welding. One part is transmissive at the laser wavelength and the other absorbs, so the beam passes through the upper part and deposits its energy at the interface. The absorbing surface melts, heat conducts into the transmissive part, and the two fuse under clamping pressure. The heat is generated at the joint rather than applied from outside, which is why the process leaves the outer surfaces untouched.

Why does carbon black selection matter so much?

Carbon black is the usual absorber, but not all carbon blacks behave the same at laser wavelengths, and the grade and loading that give the colour a designer wants may not give the absorption the weld needs. Selecting carbon black for successful through-transmission welding is a materials decision made before tooling is cut, and getting it wrong is one of the more expensive ways for a laser welding program to fail.

Can two black parts be laser welded together?

Only if the transmissive part is black by a means other than laser-absorbing carbon black. Colourants exist that appear black to the eye while transmitting at the laser wavelength, which is what makes a black-to-black weld possible. This is a formulation problem rather than a laser problem, and it is resolved at the resin and pigment stage.

What has to be designed into the part for laser welding?

Joint design, wall thickness and the transmission characteristics of the resin all have to be established up front, together with clamping that holds intimate contact across the joint line -- the beam cannot bridge a gap. Transmission and absorption testing on the actual production resin and colour is the step that converts an assumption into a specification.

Which industries use laser plastic welding?

It is used where a clean, particulate-free, hermetic joint matters and where vibration or ultrasonic welding would damage internal components. Documented applications include automotive interior levers, capless fuel fillers, RFID employee smart badges, and medical tubing and devices manufactured to FDA compliance requirements.