Punching out micromechanical parts by progressive tools is primarily a hydraulic or mechanical process. The motorisation of axes and their control by a CNC brings this technology into the Industry 4.0 era. Greub, a Swiss machine tool designer and refurbisher has demonstrated its awareness of the potential by calling in the world leader in CNC technology.
Watchmaking, micromechanics, mechatronics and many electrical and electronic manufacturers need small, thin components in small, medium and large production runs. These pieces are punched out at extremely high speeds (up to 300 cuts/min) from steel rolls with thicknesses of less than 1mm. Heir to a long family tradition of expertise in the reconstruction of machine tools, François Maxime Greub, the proprietor of Greub Machines SA founded by his grandfather (Jean), has shown an early appreciation the potential for digitisation of such operations, by motorising and adapting small 3 tonne presses to the digital age a few years ago with his partner FANUC. This perfect integration opens the way to implementation of Industry 4.0, the 4th industrial revolution.
Absolute control of operations
A progressive press must work within several key parameters: the descent of the slider, with a given length and possible adjustment of the top dead centre (TDC) and bottom dead centre (BDC); the striking rate in strokes/minute; the speed and feed rate of the steel roll feed. Scrap and/or the workpiece can be ejected by means of the die, or can be reintroduced into the feed line, for example for a rework operation or for subsequent overmoulding. The accuracy of positioning between punches and dies depends on the tool die set and on final recentering of the strip. All these factors depend on the quality of the tool, the adjustment of the press power to the material strength and the perimeter to be cut or the surface to be punched. François Maxime Greub and Thierry Maître, an independent FANUC integrator, had the ingenious idea of interactively motorising, numerically controlling and monitoring all the functions of the press, thereby taking the specific mechanical features of the press completely into account. Accordingly, the slider is lowered and its TDC/BDC are monitored by a FANUC DiS torque motor and its encoder, actuating a ball screw with a 3 tonne pressing force in a controlled manner. Meanwhile the steel strip feed is controlled by a linear motor. The strip is unrolled by two motorised winders on each side of the machine, whereby the feed rate is monitored optoelectronically. With six FANUC absolute motors, the protective door can also be numerically controlled. The drive system is programmed and controlled by a FANUC Power Motion i-A
CNC. "The FANUC man-machine interface of the CNC means that everything is under control and easily programmable," explains Thierry Maître.