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2021
Conference Paper
Titel
Position and force controlled pneumatic chuck for high precision machining
Abstract
This paper presents the development of a clamping system, including force controlled jaws, a method for position and orientation control in the XY, XZ and YZ planes, based on a visual pattern identification and a numerical compensation of the workpiece position, integrated into the machine tool control unit. Reproducible correction of workpiece position and orientation were investigated, evaluated, and combined to form the new adaptive workpiece clamping system to ensure accurate positioning and clamping repeatability. The developed system is made of an air (pneumatic) chuck with 3 clamping jaws, used for holding the workpiece with a defined clamping force, controlled by air pressure. A tilting device combined with a rotating table for inclination adjustment of the XY plane, controlled by the vision identification device, is used to measure and correct the position and orientation of the workpiece. A developed algorithm for X and Y motion of the machine tool axes as a f unction of the visually identified values enables repositioning of the workpiece after re-clamping. The clamping forces are measured by strain gauges. The design of the associated jaws is based on FEM analysis to ensure small elastic deformations, allowing for accurate clamping forces. The visual identification of the workpiece position and movement algorithm were tested with the pneumatic chuck on a high precision CNC machine tool. The developed system provided in X and Y direction a repeatability of pattern positioning within 1.1 µm, which is three times better compared to the initial chuck reclamping repeatability.