DESIGN OF A MICROMETER PRECISION STAGE IN A LASER CUTTER MACHINE

摘要

Within Philips Applied Technologies research is done on the cutting of materials with lasers. As the laser-beam diameter becomes smaller (less than 20 micrometer) the limited accuracy of the roller-bearing stages become dominant. Due to stiction and friction the stage shows errors. These errors are especially visible at quadrant changes when cutting circles. Also the position noise of roller bearings during scanning gives rough edges. This requires an extra process step which reduces furthermore the contour accuracy. To be able to cut an accurate contour in one step, it's necessary to use a different technology which eliminates the stiction and friction as well as the position noise. Based on technology demonstrators developed within Philips Applied Technologies, an electro-magnetic levitated stage has been developed for the laser cutter machine. The solution consists of two stacked stages. Each stage is magnetically levitated and can move in 6 DOF, from which one is a long stroke. The bearings in the 5 short stroke directions consist of hybrid electromagnets. The long stroke is driven with electro-magnetic actuators. The total working range (XYZ) is 300 x 300 x 0.4 mm. The stage can make rotations of 0.7 mrad in all directions. The sensors consist of a mixture of encoders and inductive sensors, achieving a measurement resolution of 1 micrometer. The stage can move between speeds as slow as 1 micrometer/s and up to speeds of 120 mm/s. The non-repeatable errors are around 1 micrometer. The stage can be calibrated to a few micrometer. These results make it possible to cut smaller and more precise features. Also the smooth scanning motion eliminates the need for treatments of the edges. Several samples will be shown which were cut with the machine, showing the steps forward made with this stage.