Implant Mechanix – Design & Innovation

We have laser welding capability with our Rofin-Baasel glovebox laser welder

		Maximum capacity is 6″ x 6″ x 4″ tall..

This plastic part had a problem with localized flashing at the parting line, making it difficult to assemble to its mating part.  A tiny nick on the parting line of the mold cavity was the source of the problem. The welded repair  needed to be very delicate so it could be re-finished by hand without needing to go back into the EDM machine for re-burning.

Plastic part with flash		1. THE PLASTIC PART: This tiny flash was all it took to mess up the assembly.

The defect in the mold		2. THE DEFECT IN THE MOLD CAVITY: The cavity is P20 Hi- Hard mold steel and the ding is circled in blue and red.  Also visible laying across the penny is a bit of welding wire 0.005″ in diameter (about the thickness of a human hair).  Welding wire in this size is very difficult to handle; it’s so fine you can’t feel it with your fingers.  I have a special technique for managing wire this small: I use microsurgical needle drivers left over from my days as a dentist to hang onto it…that’s what caused the nicks you can see along its length.

The defect welded ready for finishing		3. THE REPAIRED DEFECT: The challenge with these very tiny welds is not to burn away the corners of the cavity with the welding pulse, and to place the tiny, wiggly welding wire in the proper spot without blowing it out of position with the shielding gas.  It takes a lot of practice to do this with confidence…I used up a good half of my 0.005″  wire stock just learning how to handle it, and I can’t have coffee before doing this class of repair welding.

The mold insert on the bench		4. THE INSERT ON THE BENCH READY FOR FINISHING: All that’s needed now is a couple of minutes with a ruby stone and the mold can go back together.

Shown is a titanium tee that cannot have any crevices in which bacteria can grow.  This requires both an external and an internal weld.  The external weld is completely straightforward but the internal weld is a challenge, not only to weld, but also to photograph.

		A simple freehand laser weld.  The material is Ti6Al4V and the weld is perfomed under argon coverage.  This is a fusion weld (no filler wire added) and the customer supplied the individual  parts.  Fusion welding like this requires excellent fit of the joint, typically with a gap no bigger than 0.002″

		Here is the internal weld, about a half inch down a 0.250″ diameter hole.  You can see from the photo that it’s at an awkward angle, so the hole in the upright leg of the tee was made a bit larger in diameter to provide a ledge for the beam to hit.  This weld requires no strength; its only function is to seal the crevice to prevent bacterial ingress.