We all know the complexity of NC machining centers (such as different NC machine tools (including line rail machining centers, hard rail machining centers, die machining centers, gantry machining centers, etc.) These machines are not exactly the same, and three of them use different materials and have different cutting tools. For example, our drilling and tooth tapping machine is 16 knives, and the line and rail machining centers are generally equipped with 24 knives. In addition, machining centers also have different cutting methods, different parameter settings, etc.), which determines that it must go through a relatively long period of time from engaging in NC machining (whether in addition or programming) to reaching a certain level. This manual is a collection of experiences of engineers in Xiangyu precision machine laboratory in the long-term actual production process, including NC machining technology, working procedure, selection of parameters of common force tools, monitoring and control of machining process, etc. For your reference
I.Q: how are the processing procedures divided?
Answer: the division of NC machining process can be carried out according to the following methods:
(1) tool concentration sequence method: according to the cutting tools used, all parts of the parts that can be finished are processed with the same cutting tool, and the other parts that can be completed by the second knife and the third tool are finished by the same tool. This can reduce the number of times of tool change, compress the space time, and reduce the unnecessary positioning error.
(2) the machining part can be divided into several parts according to its structural characteristics, such as inner shape, curved surface or plane. Machining simple geometric shapes first, then complex geometric shapes: the parts with lower accuracy first and those with higher precision requirements
(3) for the parts which are easy to be deformed by roughing and finishing, it is necessary to calibrate the parts because of the possible deformation after rough machining. Therefore, it is generally said that the working procedures should be separated from each other in order to carry out roughing and finishing.
To sum up, in the division of working procedures, we must depend on the structure and workmanship of the parts, the function of the NC machining center, the number of NC machining contents of the parts, the number of installation tables and the flexible grip of the production organization of the unit. In addition, it is suggested that the principle of centralization of working procedures or the principle of separation of processes should be determined according to the actual situation, but must strive to be reasonable.
II. Q: what principles should be followed in the arrangement of processing order?
Answer: the arrangement of processing order should consider according to the structure of the part and the condition of the blank, as well as the need of positioning clamping, the emphasis is the rigidity of the workpiece not to the slope damage, The sequence should generally be based on the following principles
(1) the processing of the upper process can not affect the positioning and clamping of the next working procedure, and if there is a general machine tool in the middle of the process, it should also be considered synthetically.
(2) the internal force process is carried out first, and then the shape processing is carried out.
(3) it is best to connect with the same positioning, clamping mode or the same cutter processing process in order to reduce the number of repeated positioning, the number of tool changes and the number of times of the moving press plate.
(4) for multiple processes carried out in the same installation, a process with little rigidity damage to the workpiece should be arranged first.
III. Q: what aspects should be paid attention to in the way the workpiece is assembled in CNC Machining Center
A: when determining the positioning datum and clamping scheme, we should pay attention to the following three points:
(1) the standardization of design, process and programming calculation.
(2) reduce the number of clamps as much as possible, and make it possible to process all the surfaces to be machined after a single positioning.
(3) the scheme of manual adjustment for rabbit avoidance is adopted.
(4) the jig should be unobstructed, and its positioning and tightening mechanism can not affect the cutting tool (such as collision) in the process. When it comes into contact with this kind of brother, it can be clamped by the way of pulling screws by using a vice or adding a screw to the bottom plate.
Q: how to determine the cutting point of CNC machining center is more reasonable? What is the relationship between the workpiece coordinate system and the programming coordinate system
1. The cutter point may be located on the machined part, but note that the point must be a benchmark or a finely machined part, and that sometimes the point of the cutter is destroyed after the first process, resulting in the second process and the subsequent point of the cutter being unavailable, Therefore, in the first process of knife alignment, attention should be paid to the establishment of a position of the knife where there is a relative fixed size relationship with the positioning base, so that the original knife point can be recovered according to the relative position relationship between them. This relative knife position is usually located on the machine-smelling table or on the tool. The principles of choice are as follows
1)  easy to find. 
2)  programming is convenient.
3)  the tool error is small 
4)  the straightening is convenient and reliable.
2. The origin position of the workpiece coordinate system is set by the operator himself. After the workpiece is installed, it is determined by the cutter, and it reflects the high position relation between the workpiece and the machine smell zero. The workpiece coordinate system one and national, generally does not make the change, the workpiece coordinate system and the programming coordinate system both must be filled, namely in the processing, the workpiece coordinate system and the open range coordinate system are consistent