In modern industrial production, the use of CNC rounds to treat threads can considerably improve the efficiency of production, ensure the precision of the treatment of the thread and reduce the operators’ labor intensity. However, the following phenomenon is common in the training and teaching of CNC LATHE internships in higher professional colleges: some teachers and most students are annoying about the treatment of threads, especially during the treatment of multiple threads, and they are even more at a loss. The following is a description of the treatment steps and methods of multi-head threads thanks to real treatment and analysis of threaded parts.
1. Basic characteristics of the wires
In mechanical manufacturing, threaded connections are widely used, such as the connection between the spindle of a CNC tower and the mandrel, the resistance of the screws on the square tool holder to the tool and the transmission of the nut with . It is a protruding and a continuous groove with a specified dental shape formed along a spiral line on the cylindrical or conical surface, including two types: external thread and internal thread. Depending on the shape of the wire section, there are mainly four types: triangular wire, trapezoidal wire, serrated thread and rectangular wire. Depending on the number of threads, they can be divided into unique thread and multi-line thread. Among the various machines, the functions of threaded parts are mainly as follows: one is for connection and tightening; Triangular wires are often used for connection and robustness; Due to their different uses, their technical requirements and their processing methods are also different.
2. Treatment method
With the development of science and technology, CNC machine tools are often used for treatment in addition to using ordinary machine tools. This does not only reduce the difficulty of machining the wires, improves the effectiveness of the work and ensures the quality of the treatment of the thread. Three instructions for CNC machine tools are commonly used for the treatment of threads: G32, G92 and G76. Among them, the G32 instruction is used to treat threads in one blow, which has heavy programming tasks and complex programs; treatment in advance. The G76 instruction surmounts the drawbacks of the G92 command and can complete the piece of the white with the finished thread at the same time. And the program is simple, which saves programming time.
Multi-thread shooting on ordinary towers has always been a difficult point: once the first thread is finished, a small tool holder must be fed manually and corrected with a dial meter to precisely move the tip of the tool in the axial meaning by a spinning then treat the second thread; Or open the wheel box, adjust the mesh phase of the gear, then treat the other head threads in turn. Assigned by the pitching error of the ordinary tower screw, the transmission error of the wheel box, the movement error of the small drag plate, etc., it is difficult to reach a high precision of the lead and the height of multiple threads. In addition, during the entire processing process, there are inevitably problems such as the wear of tools and even the punch with a knife. All of this requires the operator to have a rich experience and superb skills. However, in mass production, personal experience and operator’s skills cannot guarantee the efficiency of production and product quality. In the current modernization of the manufacturing industry, the application of high-precision CNC machine tools and high performance CNC systems facilitates precision difficult to control by numerous ordinary machine tools and traditional processes, and the ‘Production efficiency and product quality are also very guaranteed.
III.
Now, taking the GSK980T tour of the Fanuc system, the M30 × 3 / 2-5G6G machining thread as an example, to illustrate the CNC machining process of multiple threads:
Piece requirements: The length of the thread is 25 mm, the chamfered at both ends is 2 × 45 ° and the roughness of the surface of the teeth is RA3.2. The material used is 45 # round steel billet.
1. Preparation. Thanks to the analysis of the machining parts, use the manual to find the basic parameters of M30 × 3 / 2-5g6g: the part is a double wire screw with a 3 mm advance and a step of 1.5 (This parameter is an important basis for checking the table). ; By subtracting the turn of the large diameter turn. The relationship between the total volume of the thread back-food tool and the height is a recent empirical formula ≈0.65p. The large diameter is the basis of the programming of the outer circle of the filming wool, the average diameter is the standard for detecting the size of the thread and the basis of the debugging threads procedures, and the small diameter is the Base on the preparation of wire processing procedures. There are certain retracting size filming tools on both sides.
2. Correctly select the machining tool. There are many types and materials for wire reversal tools. For 45 # round steel material, the YT15 cement carbide rotation tool should be used. In addition, it is also necessary to consider the form error of the thread and the angle and symmetry of the thread rotation tool on the thread. By turning 45 steel threads, the tilt angle of the edge is 10 °, the main rear angle is 6 °, the secondary rear angle is 4 °, the angle of the tip of the tool is 59 ° 16 ‘, the left and right edges are straight lines and the radius of the arc of the tip of the tool is based on the formula R = 0.1444p is determined (where P is the height), The ray of the corner of the tool is very small and you must be particularly careful during grinding.
4. Multiple thread treatment method and program design
The Multi-Tête Programming Method is similar to that of single head threads and is implemented by modifying the initial position or the initial angle of the cutting wire. Assuming that white has been treated as required and that the thread reversal is T0303, the following two methods are used for programming and treatment.
1. Use the G92 command to treat cylindrical multi-head threads. Instruction G92 is a simple instruction of the thread cutting cycle. Head of the head. The program is modified as indicated on the image. (The origin of the room is located in the center of the right side)
2. Use the G33 instruction to treat cylindrical multi-head threads. During programming with instruction G33, in addition to considering the thread wire (value F), the number of thread heads (value P) must also be considered to explain the indexing angle of the axial direction of thread.
Where: X, Z – The Final point coordinates for absolute size programming (using diameter programming).
U, w—— The coordinates of the final point of the wire for incremental size programming (using diameter programming)
F – The Wire Guide
P-Number of the heads of thread
3. Control factors for multi-thread treatment. When you use the treatment of the multi-head program, special attention should be paid to the following problems:
(1) Determination of the S280 pin speed. Given that the lathes CNC treatment wires rely on the spindle coder to operate, the spindle coder has an extreme identification requirement for the spit of the wires of different leads during machining, which must be Determined by the empirical formula S 1200 / P-80 (where P is the lead of the thread), S cannot exceed 320r / min, so S280R / min is taken.
(2) Surface roughness requirements. The last step in the treatment of the wire mainly uses a repeated cut, which can obtain a smoother dental surface and meet the requirements of RA3.2.
(3) Control of the processing process by lots. In addition to the normal requirements for setting the tool before the section operating procedure for the sample, the wear value of the tool must be defined in the Fanuc CNC system between 0.3 and 0.6 . And the recording data to make the value The value is reduced by 0.2, perform the second automatic processing and save measurement data. Repeat until the size of the average diameter is deleted. In the subsequent processing of the lots, modifications of the dimensions can be inspected at random with the gauge of the wire ring and can be compensated by modifying data X in the program or by adjusting the wear value of the tool.
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