Modeling of deformed swept volumes with SDE and its applications to NC simulation and verification

Representation of swept volumes has important applications in NC simulation and verification as well as robot-motion planning. Most research on .the representation of swept volumes has been limited to rigid objects. In this study, a sweep deferential equation (SDE) approach is presented for the representation of deformed swept volumes generated by flexible objects. The deformed swept volume analysis is integrated with machining physics to account for tool deformation/deflection for the NC simulation. End milling is modeled and analyzed and the tool deformations are calculated and integrated with the SDE program. A program is developed in C++ for the generation of deformed swept volumes. Using Boolean subtraction, the deformed swept volume of the tool is cut from the workpiece to simulate the machined part. It is shown that this representation approach constitutes an efficient and accurate NC simulation technique for collision detection, geometric verification as well as surface error prediction

Automatic polishing process of plastic injection molds on a 5-axis milling center

The plastic injection mold manufacturing process includes polishing operations when surface roughness is critical or mirror effect is required to produce transparent parts. This polishing operation is mainly carried out manually by skilled workers of subcontractor companies. In this paper, we propose an automatic polishing technique on a 5-axis milling center in order to use the same means of production from machining to polishing and reduce the costs. We develop special algorithms to compute 5-axis cutter locations on free-form cavities in order to imitate the skills of the workers. These are based on both filling curves and trochoidal curves. The polishing force is ensured by the compliance of the passive tool itself and set-up by calibration between displacement and force based on a force sensor. The compliance of the tool helps to avoid kinematical error effects on the part during 5-axis tool movements. The effectiveness of the method in terms of the surface roughness quality and the simplicity of implementation is shown through experiments on a 5-axis machining center with a rotary and tilt table

Manufacturability analysis for non-feature-based objects

This dissertation presents a general methodology for evaluating key manufacturability indicators using an approach that does not require feature recognition, or feature-based design input. The contributions involve methods for computing three manufacturability indicators that can be applied in a hierarchical manner. The analysis begins with the computation of visibility, which determines the potential manufacturability of a part using material removal processes such as CNC machining. This manufacturability indicator is purely based on accessibility, without considering the actual machine setup and tooling. Then, the analysis becomes more specific by analyzing the complexity in setup planning for the part; i.e. how the part geometry can be oriented to a cutting tool in an accessible manner. This indicator establishes if the part geometry is accessible about an axis of rotation, namely, whether it can be manufactured on a 4th-axis indexed machining system. The third indicator is geometric machinability, which is computed for each machining operation to indicate the actual manufacturability when employing a cutting tool with specific shape and size. The three manufacturability indicators presented in this dissertation are usable as steps in a process; however they can be executed alone or hierarchically in order to render manufacturability information. At the end of this dissertation, a Multi-Layered Visibility Map is proposed, which would serve as a re-design mechanism that can guide a part design toward increased manufacturability

Point-based mathematics for computer-aided manufacture

This thesis demonstrates the feasibility of machining high quality sculptured surfaces directly from a point-based definition. The work is founded on the strategy of using a sparse set of points to characterise shape although it is assumed that an appropriately dense definition can be generated by the use of some unspecified high quality interpolation algorithm. This is in contrast to the conventional CAD/CAM approach where explicit parametric expressions are used to describe the part. The research is founded on the Inverse Offset Method (IOM) proposed by Kishinami; the algorithm is chosen because it possesses a number of desirable properties, most notably its versatility and robustness. The first fundamental contribution is an error analysis of the IOM that has not been published before, the analysis is dependent on the surface and cutter path point spacing, the tool radius and the local surface curvature. The accuracy of the error analysis is corroborated by the machining and measuring of a physical part. Furthermore it is established that the quality of the finished part produced by the IOM compares favourably with that produced by a commercial package for similar tolerances. The principal research achievement is the optimisation of the IOM to exploit the coherence of data ordered into sections. This results in the IOM generating cutter paths in a time period comparable to that of the commercial package without a reduction in the quality of the finished part. The last contribution made in this thesis is a report on the issues concerning the machining of point definitions derived from multi-surfaces. The work presented in this thesis offers an alternative strategy to the design and manufacture of free-form surfaces. The main benefits of adopting this strategy are gained because it removes the need to generate a parametric surface definition

Integrated process planning for a hybrid manufacturing system

A hybrid manufacturing system integrated CNC machining and laser-aided layered deposition and achieves the benefits of both processes. In this dissertation, an integrated process planning framework which aims to automate the hybrid manufacturing process is investigated. Critical components of the process planning, including 3D spatial decomposition of the CAD model, improvement of the toolpath generation pattern, repairing strategies using a hybrid manufacturing system, etc., are discussed --Abstract, page iv

Repair of metallic components using hybrid manufacturing

Many high-performance metal parts users extend the service of these damaged parts by employing repair technology. Hybrid manufacturing, which includes additive manufacturing (AM) and subtractive manufacturing, provides greater build capability, better accuracy, and surface finish for component repair. However, most repair processes still rely on manual operations, which are not satisfactory in terms of time, cost, reliability, and accuracy. This dissertation aims to improve the application of hybrid manufacturing for repairing metallic components by addressing the following three research topics. The first research topic is to investigate and develop an efficient best-fit and shape adaption algorithm for automating 3D models\u27 the alignment and defect reconstruction. A multi-feature fitting algorithm and cross-section comparison method are developed. The second research topic is to develop a smooth toolpath generation method for laser metal deposition to improve the deposition quality for metallic component fabrication and repair. Smooth connections or transitions in toolpath planning are achieved to provide a constant feedrate and controllable deposition idle time for each single deposition pass. The third research topic is to develop an automated repair process could efficiently obtain the spatial information of a worn component for defect detection, alignment, and 3D scanning with the integration of stereo vision and laser displacement sensor. This dissertation investigated and developed key technologies to improve the efficiency, repair quality, precision, and automation for the repair of metallic components using hybrid manufacturing. Moreover, the research results of this dissertation can benefit a wide range of industries, such as additive manufacturing, manufacturing and measurement automation, and part inspection --Abstract, page iv

Compensation of part distortion in process design for re-contouring processes

The repair of compressor blades requires a precise coordination of the material deposit and the subsequent re-contouring process. Since re-contouring is the last step in the process chain, it is a crucial stage for the final part quality and shape. Therefore, machining-induced part distortions must be considered in process design. This paper introduces a method for the simulation-based compensation of part distortions. The method combines process planning and evaluation by means of a geometric simulation. In order to validate the approach, milling experiments are carried out. A subsequent measurement of the part geometry shows that the part distortion can be reduced by up to 21% using the presented approach. © 2019 The Authors. Published by Elsevier Ltd

Recent progress in turbine blade and compressor blisk regeneration

The regeneration process of jet engines is a highly complex, expensive and time-consuming. Especially the regeneration of high pressure turbine blades and compressor blisks are at the border of what is technically feasible. These components are highly loaded and thus substantial wear occurs. The blades and blisks must be overhauled or replaced regularly. The existing repair methods for these parts are inflexible and cannot be applied in many cases, resulting in a large number of scrapped parts. Therefore a new turbine blade regeneration process is presented. The goal of the improved process is to reduce the scrap rate and cost. This process includes an early evaluation of the condition of the hot-gas path components before disassembly, new detection methods for defects on the turbine blades surfaces, and more flexible manufacturing processes. The process is supported by production process simulations and functional simulations to predict the optimal regeneration path depending on the blade condition and the business model of the customer. The paper also presents a new approach for compressor blisk regeneration. This process will be developed and validated in the next years. New challenges in structural mechanics, aerodynamics, and manufacturing must be addressed due to the complexity of blisks. As part of the ongoing research, three new blisks will be designed and subjected to the complete regeneration path, which is also supported by simulations. In order to validate the simulations, their results will be compared to experimental results of the regenerated components on a compressor test rig.DFG/SFB/87

System benchmark of CAD-CAM in the area of tool making

In the following thesis a benchmark for CAD/CAM systems in the area of tool making is explained. This benchmark is adapted to the specific requirements existing in a hot-forging company located in the region of Styria (Austria). The mid-sized company demands an improvement of the current software situation to enhance the efficiency of the CAD/CAM processes and its landscape towards future digitalization processes. Due to the broad spectrum of CAD/CAM software systems existing in today’s market, it might be challenging to choose one software system that really fits to the requirements. In order to solve this situation, a benchmark is done. Out of this benchmark, two CAD/CAM software systems were considered as future potential alternatives based on the requirements existing at the company. Then, a decision-making procedure made of five different scenarios and based on certain criteria is proposed. These five different scenarios are the combination of the current software systems existing at the Styrian forging company and the alternative software systems.<br /