Publikationsserver der RWTH Aachen University
Konturnahes Laserstrahlstrukturieren für Kunststoffspritzgießwerkzeuge
Abstract
dc:descriptionA comprehensive manufacturing process with which to produce flexible, large surface and precise complex structures on flat and curved surfaces was successfully developed based on near net 3D laser structuring and implemented in the form of a fully functional demonstrational machine. The single data stream running through the entire process reduces error propagation. The system is very user friendly due to a central technology database and support software applications. Different pilot applications in the fields of tool and die making, tribology, aerodynamics and bio-/medical technology verified both the technological and economic performance of the process convincingly. This highly flexible system can also produce design and surface characteristics that were previously impossible to generate. In general, the manufacturing process is designed to produce large surface components such as automobile control panel tools. The findings resulting from this work can also be applied to other forming techniques such as vacuum casting or slush molding, where structuring tools are always needed. The demonstrational machine consists of an existing 5-axis milling machine and incorporates modules for a 3-axis scanner and a laser beam source. A special profibus system and an extended NC command unit link the controls for all the system components. The strategy for the entire processing chain is based on the 3D segment process developed over the course of this work, which in turn is based on the innovative, sequential and synchronized treatment of the individual segment fields. The 3D segment process compensates for the existing technological restrictions in the field of laser-based surface structuring. Two approaches were taken in terms of structural development: reference structures generated metrologically and digital generation via CAD. The appropriate order for data preparation and processing was also developed. In comparison to the measured structures, CAD structures generate less data of a higher quality. CAD can also be used to modify the structure to suit the component while taking the technological parameters (of laser beam structuring and matching processes) into account. A uniform algorithm for tiling the structural segments – the quadrant exchange method – was developed in order to multiply the structures. Displacement mapping and u/v height map, which are virtually distortion-free, are used to digitally transfer the structures onto the surfaces. The structured surface is segmented using a universal rule that takes the boundary conditions of both the laser module and the process technology into account. The ISO-NC data for the global and the segment toolpaths can be generated with the aid of existing CAM functions. The specially developed scanner back-end converts the segment toolpath commands into commands which the laser module can understand and, at the same time, controls the laser module and communicates with the CNC/SPS in order to execute the 3D segment process. The main results of the investigations into the laser structuring process technology are twofold: defined, concrete laser parameter sets saved as ‘laser tools’ within the central process and technology database make it easier to operate the system, and comprehensive processing strategies with which to generate seamless, large structures on flat and curved surfaces true to the original structure. Extensive trials using single pulses, ablated grooves and ablated three dimensional structures were used to define the optimum processing parameters. The maximum structural resolution and minimal structuring length for NC paths is 100 µm. It is possible to reproducibly process high quality arched surfaces with a radius of curvature rmin,real of up to 60 mm. Special segment field tiling strategies were developed; which strategy is required depends on the surface and structural shape in question. The lased structures deviate on average by 2.2% from the shape of the CAD model. The plastic structures are high quality and only deviate by 1% from the original (shrinkage). Costs can vary from 0.04 to 0.11 € per mm² structure, taking from between 0.092 and 0.325 min per mm² structure, depending on the basis on which the data is gene-rated – either via a reference surface or a CAD data model. This is up to 80% faster and up to 70% cheaper than conventional etching, and is more flexible and accurate.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2007
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Kordt, Mario
- Contributors dc:contributor
-
- Klocke, Fritz
Subjects
dc:subject × 20Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger