CNC Machining Technology of Sealed Pipe Taper Thread

Sealing pipe taper thread is currently a more effective way of pipe taper connection, which is gradually used in the process of liquid transport and gas sealing. In order to further improve the quality of the sealing pipe connection, it is necessary to perform numerical control processing on the pipe taper thread, which requires us to adopt effective technology to do the corresponding work. Based on this, this article discusses the CNC machining technology of the 55° sealed pipe taper thread, which is believed to be helpful to the needs of related parties.

1. Functional characteristics of 55° sealed pipe thread

In the 55° sealed pipe thread, there is no need to add any sealant, which can effectively avoid the leakage of the sealant. The threads in the threaded sealing tube are divided into cylindrical internal threads and conical external threads. When the pressure is lower than 5×105MPa, cylindrical internal thread can be used for connection, so that the connection is very tight; while the conical external thread is generally used under high temperature and high pressure. This kind of thread is more suitable for use on pipes, cocks and other accessories connected by threads, and its sealing is very good, and it is often used in liquid transportation [1].

2. 55° sealing pipe taper thread CNC machining process

The taper thread of the pipe is mainly divided into two forms: cone and cylinder, while the taper thread of the outer pipe does not have a cylinder. By designing the ratio of the taper profile of the pipe cone to 1:16, the distance between the base surface and the pipe end and the effective length must conform to the corresponding standards. Based on the combined analysis of Figure 1, Table 1 and Table 2, according to the data in the table and related formulas, the size of the thread in the management process can be calculated.

3. Determination of the command parameters for thread turning

3.1 Top diameter of thread

In the process of thread cutting, the top diameter of the final machined thread is plastically expanded due to the extrusion of the tool, which will have a great impact on the thread assembly and normal use. The processing personnel must first consider this issue during the processing. . And before thread cutting, in the cylindrical machining process, some more material should be removed, the outer cylinder is cut smaller, and the inner cylinder is cut larger, and the cutting is usually controlled within 0.2~0.3 mm.

3.2 Thread profile height

The height of the 　　 tooth profile cannot be less than 0.6495 p, and the tooth depth in the diameter direction can be set at about 1.3 p.

3.3 Layered depth of cut

There are two processing methods for thread processing at this stage. One is to use high-speed steel materials for low-speed processing; the other is to implement high-speed processing through carbide and coated tools. The programming process must be based on the material of the tool. Set the speed of rotation [2-3]. And CNC machining is usually high-speed machining. During the machining process, the value of the first cut is about 0.5 p, and then 0.7 times the previous cut to decrease. The cutting depth of the single cut should be less than 1, and the minimum cut of the single cut should not be lower than 0.1.

3.4 Thread start and end axial dimensions

When the technician installs the thread on the CNC lathe, due to the certain mechanical characteristics of the servo motor, in the process of processing the thread, the tool should reach the specified feed speed from the initial stop state, or directly drop from the specified feed speed to Zero, there needs to be a transition process in the drive system, and there is an acceleration process in the starting process, and a deceleration process in the stopping process. In this process, the pitch is not accurate. Therefore, when performing thread turning, the corresponding acceleration start section and deceleration retraction section should be set at both ends, and the values of both ends should be selected reasonably, otherwise the tool will cut when accelerating or decelerating, which will cause the mechanism to occur. Damage and produce substandard products. There is a great correlation between the values of the acceleration and deceleration segments and the dynamic characteristics, thread pitch and accuracy of the machine tool drive system. Therefore, technicians should effectively set the two-stage value according to the mechanical characteristics of the servo drive system. Generally, the acceleration start section is greater than 2 times the lead; the deceleration retreat section is between 1 and 1.5 times the lead [4]. In addition, in the process of applying the canned cycle, it should be noted that the ordinate of the starting point is larger than the nominal diameter of the thread, in order to prevent scratches on the machined surface when the tool is retracted [5].

4. Case study

4.1 Process analysis

It can be seen from Figure 2 that the outer diameter and inner hole of the pipe cone have not been processed and processed. The origin of the pipe cone workpiece coordinate system is directly designed at the intersection of the rightmost end surface of the pipe cone thread and the center line. Then use the centering chuck to clamp the leftmost end of the pipe cone material, and set the extension length to about 60 mm. First, the technician can use the trial cutting method to perform tool setting, and then use a 90° external turning tool to machine the large diameter of the thread after completion [6]; second, before using the 55° thread turning tool to process the pipe taper thread, first The radius difference between the starting point and the end point of the small diameter of the pipe cone is calculated, and the number of teeth is controlled between 3 and 4 during processing; finally, the part is cut directly by the cutting tool of the outer circle, and the length is controlled at 60 to 65 mm.

4.2 CNC machining program for sealing pipe taper thread

The CNC machining program of sealing pipe taper thread is as follows:

• O0001;
• G40 G99 T0101 M03 S600;
• G00 X55 Z5;
• G71 U1.5 R1;
• G71 P10 Q20 U0.3 W0.05 F0.15;
• N10 G00 X47;
• G01 Z0 F0.1;
• X48.5 Z-23;
• N20 X55 F0.5;
• G70 P10 Q20;
• G00 X100 Z100;
• T0202 M03 S200;
• G00 X55 Z8;
• G92 X46 Z-25 R-0.75 F2.309;
• X45.5;
• X45.;
• X44.7;
• X44.4;
• X44.2;
• X44.1;
• X44.05;
• G00 X100 Z100;
• T0303 M03 S400;
• G00 X55Z 5;
• Z-64;
• G01 X29 F0.1;
• X55 F0.3;
• G00 X100 Z100;
• M05;
• M30;

5.Conclusion

In short, the effective CNC machining and management of the thread of the pipe cone can not only improve the accuracy of the thread, but also greatly improve the efficiency of lathe processing. Therefore, the numerical control processing of the pipe taper thread can greatly improve the connection quality of the sealed pipe. In addition, management personnel should adopt high-efficiency technology for numerical control processing, so as to promote the continuous development of numerical control processing technology.

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Link to this article：CNC Machining Technology of Sealed Pipe Taper Thread

Reprint Statement: If there are no special instructions, all articles on this site are original. Please indicate the source for reprinting.：Silicone And Casting，Thanks！^^