By: Marek Mamczur – Dynamic Laser Solutions and Jack Gabzdyl – SPI Lasers

Today’s high speed production drills in PCB board manufacture operate at speeds in excess of 250,000rpm. The spindle shafts in these devices need to be individually balanced by very selective removal of material to ensure that, in operation, they run true. Any eccentricity in rotation can cause drill bit wobble, resulting in breakage and down time. Current manufacturing methods are manual and time consuming, requiring skilled labour.

Using DLS proprietary software in conjunction with an SPI 40W pulsed fiber laser, an automated laser balancing system has been created. The system identifies the amount of material for removal and then accurately removes through a laser milling process while the spindle is still rotating.

The spindles are loaded into a rotating jig that analyses the rotation and separates the complex motion into its static and couple components. The software then automatically calculates the amount and location of material that needs removal. The pulsed laser is then used in-conjunction with a scanner to locally machine the spindle while it’s still rotating. The material is removed from a small arc on the circumference of the spindle (photo 1).

The process has had a dramatic effect on throughput and efficiency, resulting in a 80% reduction in balancing time and a 20% increase in yield. Quality is also significantly improved, in that balance accuracy is down to 100’s of micro grams and shaft runout (TIR) can be reduced to less than 500nm.