Generation of toolpath with selection of proper tools for rough cutting process

doi:10.1016/0010-4485(94)90096-5

Computer-Aided Design

Volume 26, Issue 11, November 1994, Pages 822-831

https://doi.org/10.1016/0010-4485(94)90096-5 Get rights and content

Abstract

The rough cutting process constitutes a major portion of the machining operation by an NC milling machine in terms of the machining volume that must be removed by the process. In particular, a fair amount of the machining time may be spent in this process when a large portion of the raw material has to be removed, e.g. when parts such as moulds and dies are machined. Therefore, an efficient algorithm for generating the toolpath for rough cutting is suggested in the paper. The first step of the procedure is the generation of the volume to be machined by applying a Boolean operation to the finished model and the workpiece, both of which have been modelled by a solid modelling system. The assumption in determining an efficient machining procedure is that a large tool should be used for the portion with a simple shape while a small tool should be used for the complex portion. This is realized by representing the volume to be machined by an octree, which is basically a set of hexahedra of different sizes, and matching the proper tools with the given octants. When the tools are matched with the octants, the toolpath can be derived at the same time.

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Cited by (53)

Recent development in CNC machining of freeform surfaces: A state-of-the-art review
2010, CAD Computer Aided Design
Citation Excerpt :
Octree volume decomposition has been used to divide each layer into areas with simple and complex geometries [118,121]. In the method developed by Lee et al. [118], simpler portions (full octants) in all layers are cut by larger cutters first, and then the complex portions (partial octants) of the layer boundaries are removed by subdivision and matching with smaller tools. Evaluation of the machining time improvement compared to hunting–merging methods was not provided in this paper.
Freeform surfaces, also called sculptured surfaces, have been widely used in various engineering applications. Freeform surfaces are primarily manufactured by CNC machining, especially 5-axis CNC machining. Various methodologies and computer tools have been developed in the past to improve efficiency and quality of freeform surface machining. This paper aims at providing a state-of-the-art review on recent research development in CNC machining of freeform surfaces. This review primarily focuses on three aspects in freeform surface machining: tool path generation, tool orientation identification, and tool geometry selection. For each aspect, first concepts, requirements and fundamental research methods are briefly introduced. The major research methodologies developed in the past decade in each aspect are presented with details. Problems and future research directions are also discussed.
Pocketing toolpath optimization for sharp corners
2007, Journal of Materials Processing Technology
In pocket milling, there may be residual material left at sharp corners when stepover is inappropriately large in contour-parallel tool paths. According to this problem, the paper proposes an improved NC toolpath generation strategy in order to optimize NC machining processes for pocket milling. By inserting two types of biarc transition segments in contour-parallel toolpaths, the new method can remove the residual material completely without cutter compensation, produce second order continuous toolpath, and allow the stepover to be as wide as possible to reduce the machining time. A machining experiment has been implemented to validate the efficiency of the method.
On setup level tool sequence selection for 2.5-D pocket machining
2006, Robotics and Computer-Integrated Manufacturing
This paper describes algorithms for efficiently machining an entire setup. Previously, the author developed a graph based algorithm to find the optimal tool sequence for machining a single 2.5-axis pocket. This paper extends this algorithm for finding an efficient tool sequence to machine an entire setup. A setup consists of a set of features with precedence constraints, that are machined when the stock is clamped in a particular orientation. The precedence constraints between the features primarily result from nesting of some features within others. Four extensions to the basic graph algorithm are investigated in this research. The first method finds optimal tool sequences on a feature by feature basis. This is a local optimization method that does not consider inter feature tool-path interactions. The second method uses a composite graph for finding an efficient tool sequence for the entire setup. The constrained graph and subgraph approaches have been developed for situations where different features in the setup have distinct critical tools. It is found that the first two methods can produce erroneous results which can lead to machine crashes and incomplete machining. Illustrative examples have been generated for each method.
Methodology of machining costs evaluation for die and mould manufacturing
2004, Journal of Materials Processing Technology
In this paper we propose a procedure for evaluating machining costs of dies produced on CNC machines. Our survey is interested in companies manufacturing plastic blowing moulds, and it is limited to the unit parts, with a gross estimation. To do this, we developed a process using techniques of the semi-analytical method based on:
- •
  The decomposition of the shape to manufacture in cavities, each cavity is decomposed in its turn to machining features. When using feature modelling, a designed part is represented by its geometrical shape and other informations such as technological characteristics. Moreover, this modelling technique favours the bind of CAD application with the information required for the applications such as the process planning.
- •
  The generation of machining process and consequently the machining time equation, the volume to remove and the produced surface.
Automated tool sequence selection for 3-axis machining of free-form pockets
2004, CAD Computer Aided Design
This paper describes an efficient method to find the lowest cost tool sequence for rough machining free-form pockets on a 3-axis milling machine. The free-form pocket is approximated to within a predefined tolerance of the desired surface using series of 2.5-D layers of varying thicknesses that can be efficiently removed with flat-end milling cutters. A graph-based method finds an optimal sequence of tools for rough machining the approximated pocket. The algorithm used here can be tuned to suit any available tool set and preferred cost models. The tool sequence that is obtained is near optimal, and may take into account tool wear, as well as various overhead costs of the machine shop.
Algorithms for selecting cutters in multi-part milling problems
2003, CAD Computer Aided Design
This paper describes geometric algorithms for automatically selecting an optimal sequence of cutters for machining a set of 2.5-D parts. In milling operations, cutter size affects the machining time significantly. Meanwhile, if the batch size is small, it is also important to shorten the time spent on loading tools into the tool magazine and establishing z-length compensation values. Therefore, in small-batch manufacturing, if we can select a set of milling tools that will produce good machining time on more than one type of parts, then several unnecessary machine-tool reconfiguration operations can be eliminated. In selecting milling cutters we consider both the tool loading time and the machining time and generate solutions that allow us to minimize the total machining time. In this paper we first present algorithms for finding the area that can be cut by a given cutter. Then we describe a graph search formulation for the tool selection problem. Finally, the optimal sequence of cutters is selected by using Dijkstra's shortest path planning algorithm.

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^∗: Kunwoo Lee received a BS in mechanical engineering from Seoul National University, Korea, in 1978, where he is now an associated professor, and an MSc and a PhD in the Department of Mechanical Engineering, Massachusetts Institute of Technology, USA, in 1981 and 1984. His current research interests include computer-aided geometric design, NC toolpath generation and verification, cad systems for styling car bodies, and the application of solid-modelling systems for realizing design-automation systems such as mould-testing systems.

^∗∗: Tae Ju Kim received a BS and an MS in mechanical engineering from Seoul National University, Korea, in 1993. He is currently a researcher at Daewoo Heavy Industries in Korea. His research interests include computer-aided manufacturing and the kinematic design of robots.

^∗∗∗: Sung Eui Hong received a BS in mechanical engineering from Korea University in 1992, and an MS from Seoul National University, Korea, in 1994. He was a researcher at the Automation and System Research Institute in Seoul National University from 1992 to 1993, and he is currently a researcher at Samsung Aerospace Industry in Korea. His current research interests include computer-aided geometric design, computer-aided manufacturing, and computer-aided analysis.

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Generation of toolpath with selection of proper tools for rough cutting process

Abstract

Comput.-Aided Des.

Ann. CIRP

Comput. Indust.

Comput.-Aided Des.

Ann. CIRP

NC milling tool path generation for arbitrary pockets defined by sculptured surfaces

Comput.-Aided Des.

A study on development of NC milling machining system

Methods for detecting errors in numerically controlled machining sculptured surface

IEEE Comput. Graph. & Appl.