Research on the creation process of CNC machining process planning

Due to the relatively concentrated, high-efficiency, high-flexibility, high precision and good consistency of CNC machine tools, one-time clamping can complete milling, drilling, boring, comparison, tapping and other processes. The same processing method carried out in one setup is defined as a generalized process, then the creation and design of the CNC machining process is different from the design of the ordinary machine sheet processing technology, and the group technology (GroupTechnolgy) is supported. A part of the CNC production system has its important mission. To fully utilize the characteristics of CNC machine tools, scientific and rational design of the process is the key. Reasonable and scientific process planning and design will greatly increase productivity, shorten production cycle and reduce overall production costs. The following is a discussion of the guidelines for the creation of CNC machining processes.

1 The characteristics of CNC machining technology The CNC machining process has the following characteristics: high machining accuracy. On a CNC machine tool, the machining accuracy can be achieved by one-time machining, without the need for coarse and fine machining.

Once the workpiece is clamped, it can complete the processing of multiple parts and profiles, and even complete the processing of the workpiece, especially the CNC machine with multiple power heads and more than four axes.

Since the tools required for each machining are pre-loaded on the tool magazine, the tool configuration, installation and use do not interrupt the machining process when machining the workpiece on the CNC machine, so that the machining process is continuous.

Since the machining process is described by a generalized process when machining a workpiece on a CNC machine tool, the clamping of the workpiece, the arrangement of the tool, the use of the tool, and the determination of the machining route are different from those of the ordinary machine tool.

Due to the relatively concentrated process in the CNC machining process, the process content in the process creation process (such as the path of the tool, the cutting route, the cutting parameters, the processing sequence, the configuration of the tool and the order of use, etc.) require detailed formulation, and Once developed, it cannot be easily changed.

2 The decision rule of CNC machining process The creation of CNC technology has become the necessary process information for the generation of CNC machining program, and the numerical control process decision rule is the principle and mechanism of CNC machining creation, which is the basis for characterizing CNC machining process CAPP system. Due to the characteristics of the above-mentioned CNC machining process, it is decided that in the CAPP system, the CNC process decision is different from the machining process decision of the ordinary machine tool. The decision process of the CNC machining process in the CAPP system can be summarized as follows: The processing of the machining surface and the position with the precision required on the workpiece is completed. Therefore, the processing method chain for establishing the workpiece profile and position is different from that of the ordinary machine tool. Taking milling as an example, if a certain feature, its profile and bit processing method chain should be divided into semi-finished milling and finishing in the ordinary process decision-making, and in the numerical control machining process decision, the generalized calibration is CNC milling. Just take a few passes or replace different tools and cut the same amount in the design of the CNC program.

If the CNC machine tool has multiple power heads or more than four axes 0 inches, the workpiece can be loaded in one time to complete the machining tasks that can be completed by the ordinary machine tool. Therefore, in the NC process decision, the content of a process can be determined according to the processing tasks that can be completed in one setup.

Since the configuration, installation and use of the tool during CNC machining are different from those of ordinary machine tools, the step of grading in the process decision should follow the configuration, use sequence and tool change of the NC machining, which cannot be merged into the same machine. The content of the step can be merged into the same step on the CNC machine.

The ordering of the processes in the machining process decision of CNC machine tools should be consistent with the characteristics of CNC machine tool workpiece clamping and tool configuration, tool change, and order of use. This is especially true for CNC machines with multiple power heads and more than four axes.

The content of the numerical control process needs to be described in detail. In the process decision-making, the detailed rules of the process and the work step should be followed, that is, the rules for the machine tool, the cutting tool, the cutting parameters, the automatic route selection and the matching in the process decision making are made in detail, so that the process after the decision is made. The content is simple and detailed.

It can be seen from the above that the difference between the decision rules of CNC machining process and the decision rules of ordinary machine tool processing is mainly reflected in: a) the decision rules of the process stage division are different;) the process, the step concentration and the decentralized decision rules are different; The decision rules of merging and sorting are different; d) the details of the process and the step are different from the simple requirements; the decision rules of the tool, cutting parameters and the route are different.

3 machining process creation model CNC machining process creation model (, 2) is established: create a task acceptor that can fully describe and store the characteristics of the processed object, let the system know the target condition of the product parts (such as material, geometry) Dimensions, geometric tolerances, relative position and accuracy requirements, etc.).

Design a knowledge base of parts on how to distinguish and understand the various parts to be processed.

Create a process knowledge base for the constraints that need to be met when designing a part process.

Design a receiving editor that continuously captures and updates the contents of the part knowledge base and process knowledge base.

The numerical control machining method based on the feature surface of the part is used to establish the CNC machining element CNC-ME. The element is the entity of the NC machining information related to the feature of the part. It is the basic instruction of the NC machining process and is processed by the CNC machining process. The NC machining method, the process parameters and the corresponding features of the parts are matched in the rules. After the parts are determined, the corresponding knowledge bases (such as shape, precision, materials, etc.) of the parts are searched for the corresponding knowledge base to obtain the best processing scheme.

4 CNC machining process creation process CNC process creation process (such as, 4, 5, 6) is divided into three stages: “positive discrete”, “reverse concentration” and “process route generation”.

The forward discrete process is the stage of decomposing the parts into various feature elements. By scanning the part feature information database, judging the feature type, reading the feature parameters, and matching and optimizing the NC machining methods of each feature in the NC process rules to determine each The characteristic NC machining method (CNC-ME) reverse concentration is the step of forming the CNC machining process by the steps and processes of the CNC machining elements CNC-ME according to the characteristics of data processing. After the NC machining method of each feature is determined, according to the machining accuracy, clamping method, machining sequence, and knife pattern parameters of the CNC machine tool, the number of the L-number of the machine is returned to the sequence of the step-by-step sequence.