F.A.Q about NC processing procedures


1Q: How to divide processing operations?

Answer: NC processing procedures can be divided according to the following methods:

(1) The centralized tool sorting method is to divide the working procedure according to the tool used, and use the same tool to process all the parts that can be completed on the part. Use the second knife and the third knife to complete other parts that they can complete. This can reduce the number of tool changes, compress the idle time and reduce unnecessary positioning errors.

(2) For parts with a lot of processing content, the processing part can be divided into several parts according to its structural characteristics, such as internal shape, shape, curved surface or plane. Generally, the plane and positioning surface are processed first, and then the hole is processed; First process simple geometric shapes, then process complex geometric shapes; The parts with lower accuracy shall be processed first, and then the parts with higher accuracy requirements shall be processed.

(3) For the parts that are easy to be deformed by rough and finish machining in sequence, due to the deformation that may occur after rough machining, it is necessary to calibrate, so generally speaking, all processes that need to be rough and finish machined should be separated.

To sum up, when dividing processes, it is necessary to flexibly master the structure and process ability of parts, the function of machine tools, the number of NC machining contents of parts, the number of installation times and the production organization of the unit. In addition, it is suggested to adopt the principle of process centralization or process decentralization, which should be determined according to the actual situation, but must be reasonable.

2Q: What principles should be followed in arranging the processing sequence?

Answer: The processing sequence should be arranged according to the structure of the part and the blank condition, as well as the need for positioning and clamping. The key is that the rigidity of the workpiece will not be damaged. The sequence shall generally follow the following principles:

(1) The processing of the previous process shall not affect the positioning and clamping of the next process, and the processing of general machine tools interspersed between them shall also be considered comprehensively.

(2) The internal cavity processing sequence is carried out first, and then the contour processing sequence is carried out.

(3) It is better to connect the processes of the same positioning, clamping method or the same knife processing to reduce the times of repeated positioning, tool change and moving the pressing plate.

(4) For multiple processes in the same installation, the process with small rigid damage to the workpiece shall be arranged first.

3Question: What aspects should be paid attention to when determining the clamping mode of the workpiece?

Answer: Pay attention to the following three points when determining the positioning datum and clamping scheme:

(1) Strive to unify the design, process and programming calculation.

(2) The clamping times shall be reduced as far as possible, and all surfaces to be machined can be machined after one positioning.

(3) Avoid using manual adjustment scheme for machine occupation.

(4) The fixture shall be open smoothly, and its positioning and clamping mechanism shall not affect the tool path during processing (such as collision). In such cases, it can be clamped with a vise or by adding a base plate to draw screws.

4Q: How to determine a reasonable tool setting point? 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 machined, but it should be noted that the tool setting point must be the reference position or the part that has been finished. Sometimes the tool setting point is destroyed after the first process, which will lead to no way to find the tool setting point in the second process and the subsequent process. Therefore, when aligning the tool in the first process, it should be noted that a relative tool setting position should be set where there is a relatively fixed dimension relationship with the positioning reference, In this way, the original tool setting point can be found according to the relative position relationship between them. This relative tool setting position is usually set on the machine tool workbench or fixture. The selection principles are as follows:

1) It's easy to find it.

2) Easy programming.

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. 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 unchanged. 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 consistent.