Thread machining is one of the important applications of CNC machining center. The quality and efficiency of thread processing directly affect the quality of parts and the production efficiency of machining center.
With the improvement of CNC machining center performance and tool performance, the thread processing method is also constantly improved, and the accuracy and efficiency of thread processing are also gradually improved. In order to make the technical personnel reasonably choose the thread processing mode in the processing process, improve the production efficiency and avoid quality accidents, several thread processing methods commonly used in the CNC machining center are summarized as follows:
- Tap processing method
- Classification and characteristics of tap processing
Tapping is the most commonly used method for machining threaded holes, which is mainly applicable to the threaded holes with smaller diameter (d < 30) and lower hole position accuracy.
In the 1980s, the flexible development method was adopted for all threaded holes. That is to say, the tap was equipped with a flexible tapping chuck. The clamping and tapping chuck could compensate for the errors caused by the uneven rotation speed of the spindle due to the axial propulsion of the machine tool, so as to ensure the correct pitch.
Flexible tapping chuck has complex structure, high cost, easy damage and low processing efficiency. In recent years, the performance of CNC machining center has gradually improved, and the rigid tapping function has become the basic configuration of CNC machining center.
Therefore, rigid tapping becomes the main method of thread processing.
CNC machining
The rigid spring chuck is used to clamp the tap, so that the spindle enters the spindle, and the rotation speed is controlled by the machine tool to keep consistency.
Compared with the flexible tapping chuck, the spring chuck has the advantages of simple structure, low price and wide application. In addition to clamping taps, it can also clamp end mills, drills and other tools, which can reduce the cost of cutting tools. At the same time, the use of rigid tapping can carry out high-speed cutting, improve the efficiency of the machining center and reduce the manufacturing cost.
- Determine the bottom hole of thread before tapping
The processing of thread bottom hole has a great influence on the service life of tap and thread processing quality. In general, the diameter of bottom hole drill is close to the upper limit of tolerance.
For example, if the diameter of the bottom hole of M8 threaded hole is Ф 6.7 + 0.27 mm, select some diameter of Ф 6.9 mm. 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 improved.
- Click Select
When selecting taps, the corresponding taps should be selected according to the different processing materials. Tool companies should produce different types of taps according to the different processing materials. Special attention should be paid to the selection.
Because the tap is very sensitive to the processed material relative to milling cutter and boring cutter. For example, using cast iron taps to process aluminum parts is easy to cause thread teeth, random thread and even broken tap, resulting in workpiece scrapping. Secondly, pay attention to the difference between through tap and blind tap. The guide rail at the front end of the through-hole tap is longer, and the chip removal is the front-end chip removal.
The front guide plate of the blind hole is short, and the chip removal is the rear guide plate. It is impossible to ensure the depth of thread processing by using through-hole tap to process blind hole. In addition, if a flexible tapping chuck is used, the diameter and width square of the tapping handle should be the same as that of the tapping chuck; the diameter of the rigid tapping tap handle should be the same as that of the spring sleeve. In short, only reasonable selection of taps can ensure the smooth processing.
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