Laser perforation of holes in panels of titanium alloys

Abstract

on the geometrical distribution of the holes: the distance between them is 0.7 mm, the distance between numbers of holes is 0.6 mm, and the distribution of rows along the length and width of the panels is kO.5 mm. Taking these requirements into account and the need to produce a very large number of holes on each panel, it was necessary to develop a standard perforation technology including the method of positioning and securing the panel, determination of the start of operation of the programs, movement ofthelaser along the co-ordinates x and y along the panel and stabilisation of the co-ordinate throughout the entire perforation time of each panel. For perforation of large panels it was necessary to develop and produce special equipment moving the laser radiation source along and across the working table. The equipment has the form of a gantry moving in the longitudinal direction above a stationary sheet to be perforated (panel). A track with an LTN-101 laser and an optical system fixed to it moves along the gantry (across the sheet). The movement of the gantry and the track is realised using a gear transmission consisting of racks and pinions. The play in the transmission is removed by pressing the teeth of the gears with springs to the teeth of the racks. The longitudinal drive includes two racks for preventing misalignment of the gantry during its movement. The position sensors are in the form of rotating transformers and the travel speed is stabilised using tachogenerators. Consequently, the accuracy of positioning is around 0.01 mm. When producing single holes of the given form, it is possible to use multipass and single-pulse treatment. In the first, each hole forms during several pulses. Multipass treatment requires usually arresting the movement of the laser in relation to the panel and greatly extends the perforation cycle. Taking into account the large volume of perforations, single-pulse perforation technology was used. In perforation of the holes in the single-pulse regime, each hole forms as a result of the effect of a short laser beam pulse during several microseconds. In this highspeed process, each hole must be produced without arresting the movement ofthe laser in relation to the panel during the treatment time, because the travel speed is considerably lower than the speed of formation of each hole. This method is more suitable for the perforations of largeareas ofplating panels with a small allowance for the