This part is used by a well-known German motorcycle manufacturer. The process sees ball bearings, all of a set size, ground with a flat. They are then measured and laser marking used to place the size onto the part for identification, and grading purposes around the circumference to two decimal places.
Due to the nature of the component, the surface finish had to be smooth with no raisures to the mark area. The laser marking process used an Nd:YAG laser run in CW mode (continuous mode) to give us the black mark. Tooling was designed to magnetically hold the ball bearing with the flat face vertical giving us access to the mark area. While the mark time was very short, we were able to load the tooling with multiple units providing a higher throughput and lower cost for our customer. The operator had two jigs for speed of loading. The customer was tasked with de-magnetising the parts after their return.
The application did not require the part to be rotated during the process, due to the mark data being contained within an acceptable area for the laser. There are a series of guidelines (rules) to follow when marking on curved surfaces. If the mark data can be contained within a 20 – 25 degree segment on the circumference, then the mark distortion can be contained.
Distortion is caused by the focal position of the laser beam changing when it travels across a curved surface. If the focal position changes, then in theory the spot size increases and the energy density is lower. If the laser is travelling over an outer diameter, then as it approaches the outer limits of the 20 -25 degrees, the beam will start to deflect off the edge, introducing character definition changes. To combat this effect, we try to place the starting focal position in the middle of the highest and lowest point. This provides the minimum amount of focal shift across any radial surface.
If you would like further information on this laser marking application, or any other application, please request a call back, or talk to one of our laser marking specialists on 01737 826902.
