Multiresolution analysis as an approach for tool path planning in NC machining

Wavelets permit multiresolution analysis of curves and surfaces. A complex curve can be decomposed using wavelet theory into lower resolution curves. The low-resolution (coarse) curves are similar to rough-cuts and high-resolution (fine) curves to finish-cuts in numerical controlled (NC) machining.;In this project, we investigate the applicability of multiresolution analysis using B-spline wavelets to NC machining of contoured 2D objects. High-resolution curves are used close to the object boundary similar to conventional offsetting, while lower resolution curves, straight lines and circular arcs are used farther away from the object boundary.;Experimental results indicate that wavelet-based multiresolution tool path planning improves machining efficiency. Tool path length is reduced, sharp corners are smoothed out thereby reducing uncut areas and larger tools can be selected for rough-cuts

Computing offsets and tool paths with Voronoi diagrams

Journal ArticleIn this paper we describe the use of Voronoi diagrams to generate offsets for planar regions bounded by circular arcs and line segments, and then use the generated offsets as tool paths for NC machining. Two methods are presented, each producing a different type of offset. One of them generates the offsets of the region; the other divides the region into subpockets first, then offsets of the subpockets boundaries are used for tool paths. We show that a set of m offsets can be computed in 0(c\n log n + C2mn) time , where n is the numberof sides of the region, using either method

NURBS output based tool path generation for freeform pockets

A robust method is proposed to generate tool paths for NURBS-based machining of arbitrarily shaped freeform pockets with islands. Although the input and output are all of higher-degree NURBS curves, only one simple category of geometric entities, i.e., line segments, is required for initial offsetting and for detecting and removing self-intersecting loops. Furthermore, using those linear non-self-intersecting offsets as the legs of NURBS control polygons, NURBS-format tool paths can be smoothly reconstructed with G(1)-continuity, no overcutting, no cusps, and global error control. Since all operations involved in computing tool path curves are linear geometric calculations, the method is robust and simple. Examples with integrated rough and finish cutting tool paths of pockets demonstrate the usefulness and effectiveness of this method

Pengoptimuman jarak laluan mata alat menggunakan algoritma koloni semut untuk proses pengisaran poket

Pada masa kini, proses pemesinan kisar poket menggunakan mesin Kawalan Komputer Berangka (CNC) banyak digunakan dalam pemotongan logam. Terdapat dua langkah pemesinan di dalam proses pengisaran poket iaitu pemesinan kasar dan kemasan. Pemesinan kasar mengambil masa lebih 50 % dari keseluruhan masa pemotongan kerana sejumlah besar bahan kerja dipotong sehingga hampir menyerupai bentuk yang dikehendaki. Oleh itu, adalah penting untuk mempercepatkan masa pemesinan kasar. Pemesinan kontur selari dapat menghasilkan masa pemesinan kasar yang lebih rendah berbanding zigzag dan satu hala. Walau bagaimanapun, terdapat satu masalah di dalam pemesinan kontur iaitu berlaku bahagian lebihan tidak terpotong pada bahagian bucu dan tengah. Kawasan lebihan tidak terpotong ini berlaku kerana penetapan nilai selang antara kontur (ω) yang melebihi jejari mata alat (r). Salah satu cara untuk memotong kawasan lebihan ini adalah dengan menambahkan satu laluan mata alat tambahan (Llt) ke atas laluan asal, iaitu laluan kontur selari. Kaedah penghasilan laluan mata alat tambahan yang diperkenalkan kajian terdahulu berjaya untuk memotong keseluruhan kawasan lebihan ini. Namun, laluan yang dihasilkan oleh kajian sebelum ini tidak mempertimbangkan pergerakan mata alat yang menyumbang kepada peningkatan jarak laluan mata alat dan masa pemesinan kasar. Oleh itu, objektif kajian ini adalah untuk mengoptimumkan laluan mata alat bagi menentukan jarak laluan mata alat yang minimum di dalam proses pengisaran poket berdasarkan pemesinan kontur selari menggunakan kaedah cerdik buatan (AI). Algoritma kontur selari (Algo-KS) dibina bagi menghasilkan laluan mata alat secara kontur selari dan untuk menentukan kawasan lebihan tidak dipotong. Algoritma Koloni Semut berdasarkan aturan peralihan baru (ACO-PB) telah diperkenalkan untuk menentukan pergerakan mata alat bagi memotong kawasan lebihan berdasarkan aturan peralihan dan jarak minimum di antara dua kawasan lebihan. ACO-PB telah diuji keberkesanannya ke atas dua model iaitu model pertama dan model kedua bagi menentukan masa pemesinan kasar (Tmk). Seterusnya, Tmk yang diperoleh ini disahkan keputusannya menggunakan proses uji kaji pemesinan. Uji kaji dilakukan dengan mempraktikkan laluan mata alat yang dihasilkan berdasarkan ACO-PB ke dalam mesin kisar CNC tiga-paksi. Bahan kerja Aluminium 6061 dan mata alat jenis keluli laju tinggi (HSS) hujung rata yang bersalut Titanium Nitrida digunakan sepanjang proses pemesinan kasar. Hasil kajian mendapati terdapat perbezaan Tmk sebanyak 7.2 % di antara Tmk ACO-PB dan uji kaji. Keputusan ini telah mengesahkan bahawa ACO-PB yang dibangunkan berupaya untuk meminimumkan jarak laluan mata alat dan dapat dipraktikkan di dalam proses pemesinan sebenar. Llt dan Tmk yang dihasilkan ACO-PB juga telah dibandingkan dengan Llt dan Tmk yang diperoleh berdasarkan kajian terdahulu. Keputusan simulasi menunjukkan ACO-PB telah menghasilkan laluan mata alat yang lebih pendek sebanyak 23.7 % dan pengurangan Tmk sebanyak 4.95 % berbanding kajian terdahulu. Kajian ini juga telah membandingkan Tmk yang diperoleh menggunakan ACO-PB dan Mastercam dan mendapati ACO-PB berjaya mengurangkan Tmk sebanyak 46.5 %. Sebagai kesimpulan, kajian ini telah berjaya membangunkan algoritma ACO-PB yang berupaya untuk meminimumkan jarak laluan mata alat di dalam pemesinan kontur selari dan mengurangkan masa pemotongan bagi proses pemesinan kasar

Mold Feature Recognition using Accessibility Analysis for Automated Design of Core, Cavity, and Side-Cores and Tool-Path Generation of Mold Segments

Injection molding is widely used to manufacture plastic parts with good surface finish, dimensional stability and low cost. The common examples of parts manufactured by injection molding include toys, utensils, and casings of various electronic products. The process of mold design to generate these complex shapes is iterative and time consuming, and requires great expertise in the field. As a result, a significant amount of the final product cost can be attributed to the expenses incurred during the product’s design. After designing the mold segments, it is necessary to machine these segments with minimum cost using an efficient tool-path. The tool-path planning process also adds to the overall mold cost. The process of injection molding can be simplified and made to be more cost effective if the processes of mold design and tool-path generation can be automated. This work focuses on the automation of mold design from a given part design and the automation of tool-path generation for manufacturing mold segments. The hypothesis examined in this thesis is that the automatic identification of mold features can reduce the human efforts required to design molds. It is further hypothesised that the human effort required in many downstream processes such as mold component machining can also be reduced with algorithmic automation of otherwise time consuming decisions. Automatic design of dies and molds begins with the part design being provided as a solid model. The solid model of a part is a database of its geometry and topology. The automatic mold design process uses this database to identify an undercut-free parting direction, for recognition of mold features and identification of parting lines for a given parting direction, and for generation of entities such as parting surfaces, core, cavity and side-cores. The methods presented in this work are analytical in nature and work with the extended set of part topologies and geometries unlike those found in the literature. Moreover, the methods do not require discretizing the part geometry to design its mold segments, unlike those found in the literature that result in losing the part definition. Once the mold features are recognized and parting lines are defined, core, cavity and side-cores are generated. This work presents algorithms that recognize the entities in the part solid model that contribute to the design of the core, cavity and side-cores, extract the entities, and use them in the design of these elements. The developed algorithms are demonstrated on a variety of parts that cover a wide range of features. The work also presents a method for automatic tool-path generation that takes the designed core/cavity and produces a multi-stage tool-path to machine it from raw stock. The tool-path generation process begins by determining tool-path profiles and tool positions for the rough machining of the part in layers. Typically roughing is done with large aggressive tools to reduce the machining time; and roughing leaves uncut material. After generating a roughing tool-path for each layer, the machining is simulated and the areas left uncut are identified to generate a clean-up tool-path for smaller sized tools. The tool-path planning is demonstrated using a part having obstacles within the machining region. The simulated machining is presented in this work. This work extends the accessibility analysis by retaining the topology information and using it to recognize a larger domain of features including intersecting features, filling a void in the literature regarding a method that could recognize complex intersecting features during an automated mold design process. Using this information, a larger variety of new mold intersecting features are classified and recognized in this approach. The second major contribution of the work was to demonstrate that the downstream operations can also benefit from algorithmic decision making. This is shown by automatically generating roughing and clean-up tool-paths, while reducing the machining time by machining only those areas that have uncut material. The algorithm can handle cavities with obstacles in them. The methodology has been tested on a number of parts

Pengoptimuman jarak laluan mata alat menggunakan algoritma koloni semut untuk proses pengisaran poket

Pada masa kini, proses pemesinan kisar poket menggunakan mesin Kawalan Komputer Berangka (CNC) banyak digunakan dalam pemotongan logam. Terdapat dua langkah pemesinan di dalam proses pengisaran poket iaitu pemesinan kasar dan kemasan. Pemesinan kasar mengambil masa lebih 50 % dari keseluruhan masa pemotongan kerana sejumlah besar bahan kerja dipotong sehingga hampir menyerupai bentuk yang dikehendaki. Oleh itu, adalah penting untuk mempercepatkan masa pemesinan kasar. Pemesinan kontur selari dapat menghasilkan masa pemesinan kasar yang lebih rendah berbanding zigzag dan satu hala. Walau bagaimanapun, terdapat satu masalah di dalam pemesinan kontur iaitu berlaku bahagian lebihan tidak terpotong pada bahagian bucu dan tengah. Kawasan lebihan tidak terpotong ini berlaku kerana penetapan nilai selang antara kontur (ω) yang melebihi jejari mata alat (r). Salah satu cara untuk memotong kawasan lebihan ini adalah dengan menambahkan satu laluan mata alat tambahan (Llt) ke atas laluan asal, iaitu laluan kontur selari. Kaedah penghasilan laluan mata alat tambahan yang diperkenalkan kajian terdahulu berjaya untuk memotong keseluruhan kawasan lebihan ini. Namun, laluan yang dihasilkan oleh kajian sebelum ini tidak mempertimbangkan pergerakan mata alat yang menyumbang kepada peningkatan jarak laluan mata alat dan masa pemesinan kasar. Oleh itu, objektif kajian ini adalah untuk mengoptimumkan laluan mata alat bagi menentukan jarak laluan mata alat yang minimum di dalam proses pengisaran poket berdasarkan pemesinan kontur selari menggunakan kaedah cerdik buatan (AI). Algoritma kontur selari (Algo-KS) dibina bagi menghasilkan laluan mata alat secara kontur selari dan untuk menentukan kawasan lebihan tidak dipotong. Algoritma Koloni Semut berdasarkan aturan peralihan baru (ACO-PB) telah diperkenalkan untuk menentukan pergerakan mata alat bagi memotong kawasan lebihan berdasarkan aturan peralihan dan jarak minimum di antara dua kawasan lebihan. ACO-PB telah diuji keberkesanannya ke atas dua model iaitu model pertama dan model kedua bagi menentukan masa pemesinan kasar (Tmk). Seterusnya, Tmk yang diperoleh ini disahkan keputusannya menggunakan proses uji kaji pemesinan. Uji kaji dilakukan dengan mempraktikkan laluan mata alat yang dihasilkan berdasarkan ACOPB ke dalam mesin kisar CNC tiga-paksi. Bahan kerja Aluminium 6061 dan mata alat jenis keluli laju tinggi (HSS) hujung rata yang bersalut Titanium Nitrida digunakan sepanjang proses pemesinan kasar. Hasil kajian mendapati terdapat perbezaan Tmk sebanyak 7.2 % di antara Tmk ACO-PB dan uji kaji. Keputusan ini telah mengesahkan bahawa ACO-PB yang dibangunkan berupaya untuk meminimumkan jarak laluan mata alat dan dapat dipraktikkan di dalam proses pemesinan sebenar. Llt dan Tmk yang dihasilkan ACO-PB juga telah dibandingkan dengan Llt dan Tmk yang diperoleh berdasarkan kajian terdahulu. Keputusan simulasi menunjukkan ACO-PB telah menghasilkan laluan mata alat yang lebih pendek sebanyak 23.7 % dan pengurangan Tmk sebanyak 4.95 % berbanding kajian terdahulu. Kajian ini juga telah membandingkan Tmk yang diperoleh menggunakan ACO-PB dan Mastercam dan mendapati ACO-PB berjaya mengurangkan Tmk sebanyak 46.5 %. Sebagai kesimpulan, kajian ini telah berjaya membangunkan algoritma ACO-PB yang berupaya untuk meminimumkan jarak laluan mata alat di dalam pemesinan kontur selari dan mengurangkan masa pemotongan bagi proses pemesinan kasar

2-D path planning for direct laser deposition process

The zigzag and offset path have been the two most popular path patterns for tool movement in machining process. Different from the traditional machining processes, the quality of parts produced by the metal deposition process is much more dependent upon the choice of deposition paths. Due to the nature of the metal deposition processes, various tool path patterns not only change the efficiency but also affect the deposition height, a critical quality for metal deposition process. This thesis presents the research conducted on calculating zigzag pattern to improve efficiency by minimizing the idle path. The deposition height is highly dependent on the laser scanning speed. The thesis also discussed the deposition offset pattern calculation to reduce the height variation by adjusting the tool-path to achieve a constant scanning speed. The results show the improvement on both efficiency and height --Abstract, page iii

2-D PATH PLANNING FOR DIRECT LASER DEPOSITION PROCESS

ABSTRACT The zigzag and offset path have been the two most popular path patterns for tool movement in machining process. Different from the traditional machining processes, the quality of parts produced by the metal deposition process is much more dependent upon the choice of deposition paths. Due to the nature of the metal deposition processes, various tool path patterns not only change the efficiency but also affect the deposition height, a critical quality for metal deposition process. This paper presents the research conducted on calculating zigzag pattern to improve efficiency by minimizing the idle path. The deposition height is highly dependent on the laser scanning speed. The paper also discussed the deposition offset pattern calculation to reduce the height variation by adjusting the tool-path to achieve a constant scanning speed. The results show the improvement on both efficiency and height

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