Common problems and answers in CNC machining
1. How to divide the machining process?
A: dividing CNC machining step according to the following general methods, specific examples are:
(1) Tool sequence method
It is the process of dividing the tool used, and the same tool is used to machine all the parts that can be completed on the part. Use the second knife and the third handle to complete other parts that they can complete. This reduces the number of tool changes, compresses the dead time, and reduces unnecessary positioning errors.
(2) Sorting method for processing different parts positions
For parts with a lot of processing content, the machining part can be divided into several parts according to its structural characteristics, such as inner shape, shape, curved surface or plane. Generally, the plane, the positioning surface, and the rear processing hole are processed first; First process simple geometric shapes and then process complex geometric shapes; First, the part with lower precision is processed, and the part with higher precision is required.
(3) The method of roughing and finishing is used for parts that are prone to deformation. Since the deformation may occur due to deformation that may occur after roughing, it is generally necessary to separate the processes for roughing and finishing. Therefore, when dividing the process, it must be based on the structure and processability of the part, the function of the machine tool, the amount of CNC machining content of the part, the number of installations and the production organization of the unit. It is also recommended to adopt the principle of process concentration or the principle of process dispersion, which should be determined according to the actual situation, but it must be reasonable.
2. What principles should be followed for the arrangement of the machining sequence?
A: The processing sequence should be based on the structure of the part and the condition of the blank, as well as the need for positioning and clamping. The point is that the rigidity of the workpiece is not destroyed. The order should generally be based on the following principles:
(1) The processing of the previous process cannot affect the positioning and clamping of the next process, and the intermediate machining process must be considered in the middle.
(2) First, the inner cavity is added, and then the outer shape processing step is performed.
(3) It is best to connect the same positioning, clamping method or the same tool to reduce the number of repeated positioning, the number of tool changes and the number of moving plates.
(4) In the multiple processes carried out in the same installation, the process of reducing the rigidity of the workpiece should be arranged first.
3. What aspects should be paid attention to when determining the clamping method of the workpiece?
A: The following four points should be noted when determining the positioning reference and clamping scheme:
(1) Strive to unify the benchmarks of design, process, and programming calculations.
(2) Minimize the number of clamping operations, and as far as possible, can process all the surfaces to be processed after one positioning.
(3) Avoid the use of mechanical manual adjustment programs.
4. How to choose the knife route?
The path of the tool is the trajectory and direction of the tool relative to the workpiece during the index control process. A reasonable choice of the machining route is very important because it is closely related to the machining accuracy and surface quality of the part. The following points are mainly considered in determining the route:
(1) Guarantee the processing accuracy requirements of parts.
(2) Convenient numerical calculation and reduced programming workload.
(3) Seek the shortest processing route and reduce the emptying time to improve the processing efficiency.
(4) Minimize the number of blocks.
(5) To ensure the roughness of the contour surface of the workpiece after processing, the final contour should be arranged for the last pass to be continuously processed.
(6) The path of the tool's advance and retraction (cut-in and cut-out) should also be carefully considered to minimize the loss of the knife at the contour (the sudden change of the cutting force causes elastic deformation). Also avoid scratching the workpiece by cutting it vertically on the contour.