Laser-Welded Watermat
I was tasked with developing a manufacturing method for laser-welding a watertight structure within two sheets of TPE
The theoretical advantage of using laser-welding was based in the shortcomings of the more traditional method of ultrasonic welding, which led to mechanical stresses and failures from squeezing the two sheets of plastic between the metal welding fixtures.
By dialing in the power and speed of a desktop CO2 laser, I was able to create complex patterns of watertight channels in a small area, and was also able to prototype many different geometries in quick succession. Another advantage of using the laser was the ability to make relief cuts into the sheets, enabling us to test different mechanical solutions to the wrinkling effect of running water through the flat welded sheets.
Once I attempted to scale the watermat samples up to more than a couple square feet, the process became too inaccurate to make an entire part with no weld failures or leaks. The end result of this exploration was to move to a tube-based architecture, since extruded tubing has a much lower failure rate than I was getting in the lab.
Holding the two sheets down on the bed while the laser's exhasut syustem was running was a challenge. I started by using tape to hold down the stock (shown), but soon moved to a magnet-based system that was more reliable.
Weld failures between the water channels were common as well (below), leading to bulging in the watermat and incorrect flow paths.
