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Adaptive workpiece clamping and adjustment system

To define solutions to arrange precision clamping and position and angle adjustment of a micro- or thin-walled workpiece near the working area directly in a new type of adaptive workpiece holder with clamping force control and pattern recognition for higher repeatability.

A key-problem in micro-manufacturing (e.g. micromilling, ECM, EDM) is the accurate position assignment between micro-tool and workpiece surface or geometry outline and the repeatable and reliable clamping, especially of micro-workpieces and difficult-to-clamp workpieces (e.g. thin-walled workpieces). The processing of complex geometries with high level accuracy or within multiple setups has not been sufficiently solved for today. This is not a priority question of machine accuracy and measurement but of process setup, alignment and additional precise calibration equipment. Dominating errors, especially from the workpiece clamping device, spindle-system, tool-holder, micro- tool geometry and tool deflection are in a greater magnitude than the machine axis error and are currently not compensable. Errors in deflection, positioning and clamping errors remain at these mechanical interfaces. Methods of external workpiece measurement, relative determination of tool position and workpiece with testing probes and numerical control error compensation to the Tool- Center-Point reach their limits. The network’s main topic is to define ideas to arrange precision clamping and position and angle adjustment of a micro- or thin-walled workpiece near the working area directly in a new type of adaptive workpiece holder. Project idea: Implementation of smart material actuators in connection with adapted form elements and clamping elements for the initiation of clamping forces. Optical and/or tactile measuring systems are used for monitoring of workpiece deformation during clamping. Combination of these options should be developed into a visual system. Thus information can be used for adaptive force control application (e.g. stress, force direction, points of contact). In addition, the used visual systems can also be used to control the workpiece adjustment and orientation during manufacturing. Internal stresses in the material can affect delays during the machining process which also could be controlled by adjusting the chucking devices. External affected stresses (deflection, heating) resulting from the machining process could also be compensated with the smart clamping system. The principal project tasks of smart clamping systems for repeatable and reliable clamping force and local position assignment are as following: 1. Investigation of general possibilities to increase the position assignment between micro-tool and workpiece with a position correction system and to determine the interactive relations between structural machine components and the local position assignment in a motion range of up to +/- 500 m or +/-3°. 2. Analysis and experimental trials to combine the structural machine design with local workpiece clamping device correction as a smart system for cylindrical and prismatic, freeform and thin-walled workpieces. 3. Testing working principles for local error detection under 0.2 m or 5 arcsec deviation of clamped workpieces and repeatable adjustment of the micro-workpiece position and orientation. Technical demand: Especially in the field of precision and micro-manufacturing, small microparts and filigree components and semifinished parts have to be clamped. Commercially available devices and chucks for clamping are inadequate in many cases. Due to introduced clamping forces unrequested pushing and deformation of the parts can lead to substantial deviations regarding the manufacturing accuracy in high-precision applications. Furthermore, the high-precision orientation of difficult to clamp workpieces in the machine tool is problematic in many applications.
Acronym: 
SMARTCLAMP
Project ID: 
11 228
Start date: 
01-04-2017
Project Duration: 
24months
Project costs: 
900 000.00€
Technological Area: 
Machine Tools technology
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.