Advanced beam steering in helical drilling

Helical laser drilling is a method for producing high quality holes with defined geometries in different materials among industries such as aerospace, medical device manufacturing and electronics. If the aspect ratio of the hole is small, drilling can be done using a fast scanner. However, a special drill head is needed for higher aspect ratio holes and improved precision. The drill head typically comprises wedges or a Dove prism to rotate the laser beam at high velocities. Using a pulsed laser, each pulse removes a portion of the material. Thermal effects and the thickness of the recast layer are significantly smaller than associated with single pulse or percussion drilling. This paper presents a new helical drill head design. The developed optical device can be used for precise drilling, as well as for creating shaped entrance holes and non-circular patterns in a one-step process. The apparatus is mounted to a galvanometric scanner and the beam rotation is arranged us ing a rotating Dove prism. Steering the beam with the galvanometric scanner enables automated coincident beam movement with the rotation, enabling the machining of special geometries such as spirals, ellipses and rhodonea curves. Such geometries can be used either for improving material removal or shaping drilled holes or hole entrances. Operating principle and sample geometries are presented, and future applications are discussed.