The Research On The NC Machining Planning Creation Process
Due to the relative concentration, high efficiency, high flexibility, high precision, and good consistency of the CNC machine tool processing procedures, one clamping can complete the milling, drilling, boring, comparison, tapping and other procedures and the processing of multiple parts;
Defining the same machining method in a clamping as a generalized process, then the creation and design of the CNC machining process is different from the design of the ordinary machine bed sheet processing technology. GroupTechnolgy is one of the supporting CNC production systems. Ring, has its important mission, to give full play to the characteristics of CNC machine tools, scientific and reasonable design process is the key. Reasonable and scientific process planning and design will greatly increase productivity, shorten production cycles, and reduce overall production costs. The following is a discussion on the principles of CNC machining technology creation.
1 Features of CNC machining technology
CNC machining technology has the following characteristics: high machining accuracy. Generally, the accuracy of the processed part can be achieved by one-time processing on a CNC machine tool, without the need for rough and fine processing.
One-time clamping of the workpiece can complete the processing of multiple parts and profiles, and even complete the entire processing content of the workpiece, especially for CNC machine tools with multiple power heads and more than four axes.
Because the tools required for each machining are pre-installed on the tool magazine, therefore, the tool configuration, installation and use do not need to interrupt the machining process when machining the workpiece on the CNC machine tool, so that the machining process is continuous.
Because the machining process is described in generalized procedures when machining workpieces on CNC machine tools, the clamping of workpieces, the equipment and use of tools, and the determination of processing routes are different from those of ordinary machine tools.
Due to the relative concentration of processes in the CNC machining process, the process content (such as tool path, cutting route, cutting parameters, processing sequence, tool configuration and use sequence, etc.) in the process creation rules of its processing technology requires detailed formulation, and Once established, it cannot be easily changed.
2 Decision Rules of CNC Machining Process
The creation of CNC technology prepares the necessary process information for the generation of CNC machining programs, and the CNC process decision rule is the principle and mechanism of CNC process creation, and it is the basis of the CAPP system that characterizes the CNC machining process. Due to the characteristics of the above-mentioned numerical control processing technology, it is determined that in the generative CAPP system, the numerical control process decision is different from the processing process decision of the ordinary machine tool. The decision rule of the numerical control processing technology in the generative CAPP system can be summarized as follows: CNC machine tools can be used once Finish the machining of the machining profile and position on the workpiece with precision requirements. Therefore, the establishment of the machining method chain related to the workpiece profile and position is different from that of ordinary machine tools. Take milling as an example. For example, for a certain feature, its profile and position processing method chain should be divided into margin removal semi-finish milling* fine milling in the general process decision-making, while in the CNC machining process decision-making, it is broadly calibrated as CNC milling. It’s just that in the design of the CNC program, the tool is divided into several passes or replaced with different tools and cuts the same amount.
If the CNC machine tool has multiple power heads or more than four coordinate axes of 0 inches, the workpiece can be clamped once to complete the processing tasks that can be completed by ordinary machine tools for multiple clamping. Therefore, in the numerical control process decision-making, the content of a process can be determined according to the processing tasks that can be completed in one clamping.
Since the configuration, installation and use of tools in CNC machining are different from those of ordinary machine tools, the process decision-making process should follow the tool configuration, use sequence and tool change conditions during the process decision. It cannot be combined into the same on ordinary machine tools. The content of the process steps can be combined into the same process step on the CNC machine tool.
The sequence of procedures in the decision-making process of CNC machine tools should conform to the characteristics of CNC machine tool workpiece clamping and the characteristics of tool configuration, tool change, and order of use. This is especially true for CNC machine tools with multiple power heads and more than four axes.
The content of the numerical control process needs to be described in detail. The process decision should follow the detailed rules of the process and the step content, that is, the automatic selection and matching of machine tools, tools, cutting parameters, and tool routing in the process decision, so that the process after the decision The content is concise and detailed.
It can be seen from the above that the difference between the decision rules of CNC machining process and the process decision rules of ordinary machine tools is mainly reflected in: a) The decision rules for the division of processing stages are different; the decision rules for process and process steps are different from the decentralized decision rules;) process and process steps The decision rules for merging and sorting are different; d) The detailed and brief requirements of the procedures and steps are different; the decision rules for cutting tools, cutting parameters, and cutting routes are different.
3 Machining process creation model
The establishment of CNC machining process creation model (2) includes: creating a task acceptor that can completely describe and store the characteristics of the processed object, and let the system know the target situation of the product part (such as material, geometry) Dimensions, shape and position tolerances, relative position and accuracy requirements, etc.).
Design a parts knowledge base on how to distinguish and understand the various parts to be processed.
Create a process knowledge base of the constraints that need to be met when designing parts processing technology.
Design a receiving editor that can continuously obtain and update the content in the parts knowledge base and the process knowledge base.
The numerical control machining method based on the feature profile of the part is used to establish the numerical control machining primitive CNC-ME. The primitive is the entity of the characteristic numerical control machining information with the part feature as the core. It is the basic instruction of the CNC machining process and is through the CNC machining process It is formed by matching the corresponding relationship between the CNC machining method, process parameters and part features in the rules. When the part is determined, use each characteristic element (such as shape, precision, material, etc.) of the component as a keyword to search the corresponding knowledge base to obtain the best processing technology plan.
4 CNC machining process creation process
The CNC process creation process (such as 4, 5, 6) is divided into three stages: “forward discrete”, “reverse concentrated”, and “process route generation”.
The forward discrete process is the stage of decomposing the part into each feature element. By scanning the part feature information database, judging the feature type, reading the feature parameters, and matching and optimizing the NC machining method of each feature in the NC process rule, each is determined. The characteristic numerical control machining method (CNC-ME) reverse concentration is the process steps and procedures formed by the merging of various numerical control processing primitives CNC-ME according to the characteristics of data processing until the generation of the numerical control processing process. After the numerical control processing method of each feature is determined, according to the processing precision, clamping method, processing sequence, and knife graphic parameters of the numerical control machine tool 1-Lf number, screw control process step, sort order, merge number.
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