Introduce several thread processing methods commonly used in CNC machining centers(1)

 　　 With the improvement of the performance of cnc machining centers and the improvement of cutting tools, the methods of threading are constantly improving, and the accuracy and efficiency of threading are gradually improving. Thread processing is one of the very important applications of cnc processing. The processing quality and efficiency of the thread will directly affect the processing quality of the parts and the production efficiency of the machining center. In order to enable technologists to reasonably choose thread processing methods in processing, improve production efficiency and avoid quality accidents, several thread processing methods commonly used in cnc processing in practice are summarized as follows:

　　1. Tap processing method

　　1.1 Classification and characteristics of tap processing

　　Using taps to process threaded holes is the most commonly used processing method. It is mainly suitable for threaded holes with small diameter (D<30) and low hole position accuracy.

In the 1980s, the threaded holes used flexible tapping methods, that is, flexible tapping chucks were used to hold the taps. The tapping chucks could be used for axial compensation to compensate for the advance caused by the asynchronous machine tool axial feed and spindle speed Give the error to ensure the correct pitch. The flexible tapping chuck has a complex structure, high cost, easy damage, and low processing efficiency. In recent years, the performance of cnc processing has gradually improved, and rigid tapping has become the basic configuration of cnc processing.

　　 Therefore, rigid tapping has become the main method of thread processing.

　　The rigid collet is used to clamp the tap, and the spindle feed and spindle speed are controlled by the machine tool to keep the same.

　　 Compared with flexible tapping chucks, collet chucks have simple structure, low price and wide range of uses. In addition to clamping taps, they can also clamp end mills, drills and other tools, which can reduce tool costs. At the same time, rigid tapping can be used to perform high-speed cutting, improve processing efficiency, and reduce manufacturing costs.

　　1.2 The threaded bottom hole before tapping is indeed

　　 The processing of the threaded bottom hole has a great influence on the life of the tap and the quality of thread processing. Generally, the diameter of the threaded bottom hole drill bit is close to the upper limit of the threaded bottom hole diameter tolerance.

　　 For example, the diameter of the bottom hole of the M8 threaded hole is Ф6.7+0.27mm, and the drill bit diameter is Ф6.9mm. In this way, the machining allowance of the tap can be reduced, the load of the tap can be reduced, and the service life of the tap can be increased.

　　1.3 Choice of tap

　　 When selecting a tap, first of all, you must select the corresponding tap according to the material to be processed. The tool company produces different types of taps according to the different processing materials. Pay special attention to the selection.

　　Because the tap is very sensitive to the processed material compared to the milling cutter and boring cutter. For example, using cast iron taps to process aluminum parts can easily cause thread loss, random buckles or even tap breaks, resulting in scrapped workpieces. Secondly, pay attention to the difference between the through-hole tap and the blind-hole tap. The front end of the through-hole tap is longer and the chip removal is the front chip removal. The leading end of the blind hole is shorter, and the chip removal is rear chip removal. For blind holes with through-hole taps, the thread processing depth cannot be guaranteed. Furthermore, if a flexible tapping chuck is used, the diameter of the tap shank and the width of the square should be the same as that of the tapping chuck; the diameter of the tap shank for rigid tapping should be the same as the diameter of the spring collet. In short, only a reasonable choice of taps can ensure smooth processing.

　　1.4 CNC programming for tap processing

　　The programming of tap processing is relatively simple. Now the machining center generally solidifies the tapping subroutine, and only needs to assign each parameter. But it should be noted that the numerical control system is different, the subroutine format is different, and the meaning of some parameters is different.

　　 For example, the SIEMEN840C control system, its programming format is: G84 X_Y_R2_ R3_R4_R5_R6_R7_R8_R9_R10_R13_. Only need to assign these 12 parameters when programming.