1、 Question: how to divide the process?
Answer: generally, the division of NC machining process can be carried out according to the following methods:
(1) Tool centralized sorting method is to divide the process according to the tool used, and use the same tool to process all the parts that can be completed. Use a second knife, a third knife to do whatever else they can. In this way, the number of tool changes can be reduced, the idle travel time can be compressed, and the unnecessary positioning error can be reduced.
(2) According to the structural characteristics of the parts, the processing parts can be divided into several parts, such as inner shape, shape, surface or plane. Generally, the plane and positioning surface are processed first, and then the hole; the simple geometric shape is processed first, and then the complex geometric shape; the parts with low precision are processed first, and then the parts with high precision requirements are processed.
(3) According to the method of rough and finish machining, the parts which are easy to deform need to be adjusted because of the possible deformation after rough machining, so generally speaking, the working procedure should be separated for rough and finish machining.
To sum up, in the division of working procedures, it is necessary to flexibly master the structure and technology of parts, the function of machine tools, the number of NC machining contents of parts, installation times and the production organization of the unit. In addition, it is suggested that the principle of process centralization or process decentralization should be adopted according to the actual situation, but it must be reasonable.
2、 Q: what principles should be followed in the arrangement of processing sequence?
Answer: the arrangement of processing sequence should be considered according to the structure and blank condition of parts, as well as the need of positioning and clamping. The key point is that the rigidity of the workpiece will not be damaged. Generally, the sequence should be carried out according to the following principles:
(1) The processing of the previous process cannot affect the positioning and clamping of the next process, and the machining process of general machine tool should be considered comprehensively.
(2) The inner shape and inner cavity processing sequence is carried out first, and then the contour processing process is carried out.
(3) In order to reduce the times of repeated positioning, tool changing and pressing plate moving, the same positioning and clamping methods or the same tool processing process should be well connected.
(4) For multiple procedures in the same installation, the process with less damage to the rigidity of the workpiece should be arranged first.
3、 Question: which aspects should be paid attention to in determining the clamping mode of workpiece?
A: in determining the positioning reference and clamping scheme, the following three points should be noted:
(1) Strive to design, process, and programming calculation of the benchmark unity.
(2) The clamping times should be reduced as much as possible, and all the surfaces to be machined can be processed after one positioning.
(3) Avoid using manual adjustment plan.
(4) The fixture shall be open, and its positioning and clamping mechanism shall not affect the tool feeding during processing (such as collision). In case of such situation, the vise or bottom plate drawing screw can be used for clamping.
4、 Question: how to determine the tool setting point is reasonable? What is the relationship between workpiece coordinate system and programming coordinate system?
1. The tool setting point can be set on the part to be processed, but pay attention to that the tool setting point must be the reference position or the position that has been finished. Sometimes, the tool setting point will be damaged after the × * * process, which will make the second process and the subsequent tool setting point impossible to find. Therefore, when setting the tool in the × * * process, it is necessary to set up a relative tool setting where there is a relatively fixed dimension relationship with the positioning reference In this way, the original tool setting point can be retrieved according to the relative position relationship between them. This relative tool setting position is usually set on the machine tool table or fixture. The selection principles are as follows:
1) It’s easy to find the right one.
2) Programming is convenient.
3) The tool setting error is small.
4) It is convenient to check during processing.
2. The origin position of the workpiece coordinate system is set by the operator himself. After the workpiece is clamped, it is determined by tool setting. It reflects the distance position relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is fixed, it is generally not changed. The workpiece coordinate system and the programming coordinate system must be unified, that is, during machining, the workpiece coordinate system and the programming coordinate system are consistent.
5、 Question: how to choose the cutting route?
Tool path refers to the path and direction of the tool relative to the workpiece in the process of NC machining. The reasonable choice of machining route is very important because it is closely related to the machining accuracy and surface quality of parts. The following points are mainly considered in determining the tool path:
1) Ensure the machining accuracy of parts.
2) It is convenient for numerical calculation and reduces the workload of programming.
3) To find a short processing route, reduce the idle time to improve processing efficiency.
4) Minimize the number of program segments.
5) To ensure the surface roughness of workpiece contour after machining, the final contour should be processed continuously by the next tool feed.
6) The tool’s advance and retreat (cut in and cut out) routes should also be carefully considered, so as to minimize tool marks caused by tool stopping (elastic deformation caused by sudden change of cutting force) at the contour, and to avoid scratching the workpiece due to vertical cutting on the contour surface.
6、 Q: how to monitor and adjust during machining?
After the alignment and program debugging are completed, the workpiece can enter the automatic processing stage. In the process of automatic machining, the operator should monitor the process of cutting to prevent the quality problems and other accidents caused by abnormal cutting.
On the cutting process
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