Research on computer aided tool selection for NC m

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Research on computer-aided tool selection for mold cavity NC machining


NC machining includes two key problems: the generation of tool path and tool selection. The former problem has been widely and deeply studied in the past 20 years, and many developed algorithms have been applied in commercial cad/CAM systems. At present, most CAM systems can automatically generate tool paths after users input relevant parameters. Comparatively speaking, the research on tool selection with quality and efficiency as the optimization objectives is far from mature. At present, there is no commercial cam system that can provide a decision support tool for tool selection, so it is difficult to realize the automatic and organic integration of cad/cam. Tool selection usually includes tool type and tool size. Generally speaking, there are many kinds of tools suitable for a processing object, and one tool can complete different processing tasks, so it is easier to only consider the selection of tools that meet the basic processing requirements, especially for typical geometric features such as holes and slots. But in fact, tool selection is usually associated with certain optimization objectives, such as maximum cutting efficiency, minimum processing time, minimum processing cost, maximum service life, etc., so tool selection is a complex optimization problem. For example, for mold cavity parts, due to the complex geometry (usually including free-form surfaces and islands), the geometric constraints that affect tool selection cannot be explicitly expressed in the CAD model, and corresponding algorithms need to be designed for extraction. Therefore, it is not easy to select appropriate tool specifications and tool combinations to improve the efficiency and quality of NC machining

the mold cavity is generally processed by NC milling, which usually includes rough machining, semi finishing, finishing and other processes. The principle of rough machining is to remove excess metal as efficiently as possible, so we want to choose large-size tools, but too large tool size may lead to the increase of unprocessed volume; The main task of semi finishing is to remove the steps left by the heavy downward pressure of rough machining; Finish machining is mainly to ensure the size and surface quality of parts. Considering that there are still some difficulties in automatic tool selection completely by computer at present, the computer aided tool selection (CATS) system we developed is based on providing users with a decision-making tool to help most Turks vote for him at the critical moment of the presidential election, that is, rough machining, semi finishing, finishing, etc., and the real decision-making power is still left to users, To give full play to the advantages of computers and people

1 basic structure of the system

the input of cats system is CAD model, and the output is six parameters (as shown in Figure 1), including tool type selection auxiliary decision-making tool, rough machining tool selection auxiliary decision-making tool, semi finishing tool selection auxiliary decision-making tool and finishing tool selection auxiliary decision-making tool

Figure 1 input and output of computer-aided tool selection system

in view of the important position of rough machining in cavity machining (usually 5 ~ 10 times of finishing time), the system has the function of automatic optimization and combination of tools during rough machining, so as to improve the efficiency of overall machining. In addition to the above decision-making tools, the system also has the functions of viewing the detailed specifications of tools, recommending processing parameters and evaluating processing time according to the type and size of tools, and finally generating a total report of tool selection results (as shown in the figure, the magnetic core material tensile testing machine is widely used in the R & D and production enterprises of high molecular materials 2). All tool data and knowledge of the system are supported by the background database

Figure 2 basic functions and modules of the computer-aided tool selection system

2 key technologies and algorithms

1) tool type selection

according to the practice of mold cavity NC machining, cavity milling understand what the purchased experimental machine is used for. The tools are generally divided into flat end milling cutter, fillet milling cutter and ball end milling cutter. Set the tool diameter as D, the fillet radius as R, and when r=0, it is a flat end milling cutter, 0

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