Due to the complexity of CNC machining (such as different machine tools, different materials, different cutting tools, different cutting methods, different parameter settings, etc.), it is determined that CNC machining (whether machining or programming) must be practical in the long-term The production process continues to accumulate experience.
What principles should be followed in the arrangement of the processing sequence?
The arrangement of the processing sequence should be considered according to the structure of the part and the condition of the blank, as well as the need for positioning and clamping. The important point is that the rigidity of the workpiece is not destroyed. The order should generally 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 general machine tool processing processes should also be considered comprehensively.
(2) The inner cavity is added first, and then the outer shape is processed.
(3) It is best to connect the same positioning, clamping method or the same tool processing process to reduce the number of repeated positioning, tool change times and the number of times of moving the platen.
(4) For the multiple processes carried out in the same installation, the process should first be arranged with less rigid damage to the workpiece.
Which aspects should be paid attention to when determining the clamping method of the workpiece?
Attention should be paid when determining the positioning datum and clamping plan:
(1) Strive to unify the design, technology, and programming calculation benchmarks.
(2) Try to reduce the number of clamping times, and try to achieve all the surfaces to be processed after one positioning.
(3) Avoid using manual adjustment schemes.
(4) The fixture should be opened smoothly, and its positioning and clamping mechanism should not affect the cutting during processing (such as collision). When encountering such a situation, it can be clamped by using a vise or adding a base plate to draw a screw.
How to determine the tool setting point is more reasonable? What is the relationship between the workpiece coordinate system and the programming coordinate system?
1. The tool setting point can be set on the part to be processed, but note that the tool setting point must be a reference position or a part that has been finished. Sometimes the tool setting point is destroyed after the first process, which will cause the second process It is impossible to find the process and subsequent tool setting points, so when setting the tool in the first process, pay attention to setting up a relative tool setting position where there is a relatively fixed size relationship with the positioning datum, so that you can find it according to the relative position relationship between them. Back to the original tool setting point. This relative tool setting position is usually set on the machine tool table or fixture. The selection principles are as follows:
1) Easy to find
2) Easy to program
3) Small tool setting error
4) Easy to check during processing
2. The origin position of the workpiece coordinate system is set by the operator. It is determined by tool setting after the workpiece is clamped. It reflects the distance position relationship between the workpiece and the machine zero point. 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 processing, the workpiece coordinate system and the programming coordinate system are the same.
How to choose the knife route?
The path of the tool is the path and direction of the tool relative to the workpiece in the index control process. The reasonable choice of the processing route is very important, because it is closely related to the processing accuracy and surface quality of the parts. The following points are mainly considered when determining the path of the knife:
1) Ensure the machining accuracy requirements of the parts.
2) Convenient numerical calculation and reduce programming workload.
3) Seek the shortest processing route, reduce the empty tool time to improve processing efficiency.
4) Try to reduce the number of blocks.
5) To ensure the roughness requirements of the workpiece contour surface after machining, the final contour should be processed continuously in the last pass.
6) The advance and retreat (cut-in and cut-out) route of the tool should also be carefully considered to minimize the tool stop at the contour (a sudden change in cutting force causes elastic deformation) and leave tool marks, and avoid vertical downward on the contour surface Knife and scratch the workpiece.
How to monitor and adjust during processing?
After the workpiece is aligned and the program is debugged, it can enter the automatic processing stage. In the automatic machining process, the operator should monitor the cutting process to prevent abnormal cutting from causing workpiece quality problems and other accidents.
The monitoring of the cutting process mainly considers the following aspects:
1. Machining process monitoring The main consideration for rough machining is the rapid removal of excess margin on the surface of the workpiece. In the automatic machining process of the machine tool, according to the set cutting amount, the tool automatically cuts according to the predetermined cutting path. At this time, the operator should pay attention to observe the cutting load changes in the automatic machining process through the cutting load table, and adjust the cutting amount according to the bearing capacity of the tool to maximize the efficiency of the machine tool.
2. Monitoring of cutting sound during cutting In the automatic cutting process, when cutting is generally started, the sound of the tool cutting the workpiece is stable, continuous, and brisk. At this time, the movement of the machine tool is stable. As the cutting process progresses, when there are hard spots on the workpiece, tool wear, or tool clamping, the cutting process becomes unstable. The unstable performance is that the cutting sound changes and the tool and the workpiece collide with each other. Sound, the machine tool will vibrate. At this time, the cutting amount and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended to check the condition of the tool and workpiece.
3. Finishing process monitoring Finishing, mainly to ensure the processing size and surface quality of the workpiece, the cutting speed is high, and the feed rate is large. At this time, attention should be paid to the impact of built-up edge on the machined surface. For cavity machining, attention should also be paid to over-cutting and cutting at corners. To solve the above problems, one is to pay attention to adjusting the spray position of the cutting fluid, so that the machined surface is always in the best cooling condition; the second is to pay attention to the quality of the machined surface of the workpiece, and adjust the cutting amount to avoid as much as possible Changes in quality. If the adjustment still has no obvious effect, the machine should be shut down to check whether the original program is reasonable.
Special attention is to pay attention to the position of the tool when the inspection is suspended or stopped. If the tool stops during the cutting process, a sudden stop of the spindle will cause tool marks on the surface of the workpiece. Generally, consider stopping the tool when it leaves the cutting state.
4. Tool monitoring The quality of the tool largely determines the processing quality of the workpiece. In the automatic machining and cutting process, it is necessary to judge the normal wear condition and abnormal damage condition of the tool through methods such as sound monitoring, cutting time control, pause inspection during cutting, and workpiece surface analysis. According to the processing requirements, the tools should be handled in time to prevent the occurrence of failure by the tools.