Computer aided process planning for rapid prototyping using a genetic algorithm

This thesis presents a new method for Computer Aided Process Planning (CAPP) for a subtractive Rapid Prototyping (RP) process. The CNC-RP process uses a 4-axis CNC machining center to create parts with flat end-mills. The objective is to determine the optimal system parameters for the RP process - those that enable parts to be created in a shorter amount of time. Two main contributions make this possible. First, a method of generating different machining orientation sets enables the part to be created with the same level of safety and quality available with the current system. Second, machining time is related to tool selection. These two contributions are combined into a single objective function. A Genetic Algorithm technique is implemented to determine the best machining tool sizes and machining orientations. The results show that a Genetic Algorithm can be applied to a RP process plan to reduce the total processing time

Synergy in Additive Manufacturing and Machining of Complex Design Topologies

Additive manufacturing (AM) enables freedom of design, part complexity and customization with minimal added cost, light weighting, design for function, and part consolidation. It is gaining increasing interests in the fields of biomedical, aerospace, automotive, tooling, and heat exchange systems where small batch productions of customized parts with high value are usually in demand. AM, in general, is considered to have great potential in complementing conventional manufacturing methods. Functional parts with high strength to weight ratio generated using structural topology optimization can be eventually realized by AM. Limitations of AM parts related to surface finish and dimensional accuracy are likely to be overcome by post-machining of critical features and surfaces in order to achieve specific tolerance and surface quality. To minimize trial and error efforts, AM and post-machining simulations are essential for effective planning of the synergized processes. The goal of this study is to propose a process workflow which can be used as a guideline for successful production of complex parts manufactured via AM, particularly laser powder bed fusion (LPBF), and post-processed via CNC (computer numerical control) machining. The workflow is deployed and iterated through a case study of manufacturing a surgical navigation tracker, where the holistic manufacturing process involves digital design utilizing structural topology optimization, AM simulation, machining planning, fabrication, and validation

Advanced Process Planning for Subtractive Rapid Prototyping

This paper presents process planning methods for Subtractive Rapid Prototyping, which deals with multiple setup operations and the related issues of stock material management. Subtractive Rapid Prototyping (SRP) borrows from additive rapid prototyping technologies by using 2½D layer based toolpath processing; however, it is limited by tool accessibility. To counter the accessibility problem, SRP systems (such as desktop milling machines) employ a rotary fourth axis to provide more complete surface coverage. However, layer-based removal processing from different rotary positions can be inefficient due to double-coverage of certain volumes. This paper presents a method that employs STL models of the in-process stock material generated from slices of the part along the rotation axis. The developed algorithms intend to improve the efficiency and reliability of these multiple layer-based removal steps for rapid manufacturing.Mechanical Engineerin

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

Automated Process Planning for Five-Axis Point Milling of Sculptured Surfaces

Ph.DDOCTOR OF PHILOSOPH