The emergence of CNC machine tools is a manifestation of a great progress in the industry. It can better solve complex, precise, small batch, and changeable parts processing problems. It is a flexible and efficient automatic machine tool. When the programmers of Dongguan CNC processing plant use CNC machine tools for processing, they must first perform process analysis. According to the material, contour shape and machining accuracy of the workpiece to be processed, the appropriate machine tool is selected, the processing plan is formulated, the processing sequence of the parts is determined, the tools used in each process, the fixture and the cutting amount, etc.
1. Reasonable selection of machine tools
When Dongguan CNC processing plants process parts on machine tools, there are generally two situations.
The first case: there is a part pattern and a blank, and a CNC machine tool suitable for processing the part should be selected.
The second situation: There is already a CNC machine tool, and it is necessary to select parts suitable for processing on the machine tool.
In either case, the main factors to be considered are the material and type of the blank, the complexity of the contour shape of the part, the size, the processing accuracy, the number of parts, and the heat treatment requirements. In summary, there are three points:
① It is necessary to ensure the technical requirements of the processed parts and process qualified products.
② Conducive to improving productivity.
③ Reduce production costs (processing costs) as much as possible.
2. Process analysis of CNC machining parts
The process analysis of CNC machining involves a wide range of aspects, so we only analyze the possibility and convenience of CNC machining here.
(1) The size data on the part drawing should conform to the principle of programming convenience
1. The dimensioning method on the part drawing should adapt to the characteristics of CNC machining
The Dongguan CNC processing plant shall cite the dimensions with the same reference or directly provide the coordinate dimensions on the processed parts drawings. This marking method is not only convenient for programming, but also convenient for mutual coordination between dimensions, and brings great convenience in maintaining the consistency of design benchmarks, process benchmarks, inspection benchmarks and programming origin settings. Because part designers generally consider assembly and other use characteristics in dimensioning, they have to adopt a partially dispersed marking method, which will bring a lot of inconvenience to process arrangement and CNC machining. Because the precision of CNC machining and repeated positioning are very high, and the use characteristics will not be damaged due to large accumulated errors, so the local scattered labeling method can be changed to the same reference citation size or the labeling method that directly gives the coordinate size .
2. The conditions of the geometric elements constituting the contour of the part should be sufficient
The Dongguan CNC processing plant must calculate the base point or node coordinates during manual programming. During automatic programming, all geometric elements constituting the contour of the part must be defined. Therefore, when analyzing the part drawing, it is necessary to analyze whether the given conditions of the geometric elements are sufficient. For example, the arc and the straight line, the arc and the arc are tangent on the drawing, but according to the size given on the drawing, when calculating the tangent condition, it becomes the intersecting or separating state. Due to inadequate conditions of the geometric elements of the components, it is impossible to start programming. When encountering such a situation, it should be resolved through consultation with the part designer.
(2) The structure and craftsmanship of each processing part of the part should conform to the characteristics of CNC machining
1) It is better to adopt uniform geometric types and dimensions for the cavity and shape of parts. In this way, the tool specifications and the number of tool changes can be reduced, the programming is convenient, and the production efficiency is improved.
2) The fillet size of the inner groove determines the size of the tool diameter, so the fillet radius of the inner groove should not be too small. The manufacturability of the parts is related to the height of the processed contour and the size of the transition arc radius. 3) When the part is milling the bottom plane, the groove bottom fillet radius r should not be too large.
4) A unified reference positioning should be used. In CNC machining, if there is no unified reference positioning, the contour position and size of the two faces after machining will be inconsistent due to the reinstallation of the workpiece. Therefore, to avoid the above problems and ensure the accuracy of the relative position after the two clamping processes, a unified reference positioning should be adopted.
It is better to have suitable holes on the parts as the positioning reference holes. If not, set the process holes as the positioning reference holes (such as adding process lugs on the blank or setting process holes on the margin to be milled in the subsequent process). If the Dongguan CNC processing plant cannot produce craft holes, at least the finished surface should be used as a unified reference to reduce the error caused by the two clamping. In addition, it is necessary to analyze whether the required machining accuracy and dimensional tolerances of the parts can be guaranteed, whether there are redundant dimensions that cause contradictions or closed dimensions that affect the process arrangement.