In general, the surface of the thread is characterized by the outer (or inner) surface accuracy, the median diameter, the pitch, the profile height, and the position of the profile angle.
When the thread is rolled, the mechanism for forming each parameter is different, and each method of rolling the thread has its own characteristics (the dimensional chain is also different), so the precision of forming the thread parameters is also different.
1 When a threaded 1.1-size chain is formed on a double roller machine to form a thread, a secondary-type dimensional chain can be formed. For example, a static dimensional chain system is formed when three roller threaded rollers are used to roll threads, as shown in (b).
r,. One or three rollers cooperate with the distribution radius of the hole axis relative to the blank, the foot numbers i =1, 2, 3, respectively corresponding to the corresponding roller rollers; h, the threaded roller axis fits the journal with respect to the roller axis The radial displacement value of the axis (=1, 2, 3) r.,.
a rolling head with a shaft reference radius; da. - needle diameter; t, a threaded roller wall thickness; u - a deviation of the axis of the axis of the thread formed from the axis of rotation of the threaded roller (handle); As an example of the axial feed of the threaded roller when the machine is rolling the thread, the accuracy of forming the thread parameters is analyzed. In practice, the BHrH type roller (for thread rolling on the solid blank) and the HBrr type roller are used. (for thread rolling on hollow blanks). In both cases, the diameter of the rolling thread is formed by a dynamic dimensional chain such as a threaded roller, which is formed by all the dynamic component links of the static dimensional chain during the threading process. The static dimensional chain component is the fixed size of the threaded roller and The eccentric axis distribution angle for each blank's variable size, such as 1.1.1 affects the thread parameter error factor in the equations (), parameter r,. , u and n are invariant to the thread being rolled, and the parameter r.,. , da., t, the shape error range of each of the blanks is different, but considering the high precision of these parameters, the above error is negligible, which means that the rolling thread causes the main error of the diameter error. The factor is hi. In addition, hi is a closed loop of two other size chains, namely a roll disassembly and a resizing chain.
Figure 6-2 shows Ch according to analysis and research oA èžŸ pattern (roller rolling Wish1... solution measures; rved.h Qiu: w.cnki.net Received time: 2003*-16 according to analysis, One of the main ways to improve the dimensional accuracy of the rolled thread diameter is to ensure that h has a relatively high stability when the rolling head is working. For this reason, it is necessary to increase the precision (fan gear, center wheel, etc.) involved in forming the part size h. Reduce the number of rings of the above size chain.
(e, "eccentric value; burning-eccentric axis arrangement angle" t, e, and r, fixed part error, can be compensated by manufacturing, thermal deformation, elastic deformation error.
When the threaded roller is mounted on the machine tool, it is assumed that the axis deviation of the spindle-rotation axis of the blank is m as shown in (a), and the following dimensional chain is formed.
(o) The axis of symmetry deviation of the axis. Thus u in the equation () can be substituted into the equation using (m + n) in equation (2).
In the process of rolling the thread, n is the source of the bending deformation of the process system components, and the total value of the deformation of the blank-roller contact section is equal to n. Generally, the blank is the weakest link in the process system, and it is subjected to the bending force. At this time, the additional force necessary for the bending value n of the blank is received by the threaded roller and is close to the main shaft. During the entire cycle of rolling work, these rollers are subjected to strong loads. These rollers have relatively large forces and operate under relatively heavy conditions. As a result, after determining that the threaded rollers meet the service period, the rollers are more than others. The component is damaged first. In addition, due to the bending of the axis of the blank, the rolled thread will produce a local taper, the result will be accompanied by pitch error and tooth half angle error. Obviously, the closer the roller surface formed on the spindle axis is to the axis of symmetry, the smaller the bending deformation of the components of the process system, and the smoother (uniform) the working conditions of all the rollers on the roller, therefore, in order to improve the service life of the thread roller, The parameters of the threaded thread must be such that the spindle is not coaxial with the axis of rotation of the roller (used in practice) and is coaxial with the axis of symmetry of the roller. For this reason, the value and direction of the displacement u can be reasonably adjusted on the front plate of the roller.
2 Application examples In the petroleum equipment machine, the thread on the valve shaft (Material 20X13) (T26X5LH-8g, T30X6-7e) can be formed by rolling with a three-column threaded roller (BHTH). Through the experimental calculation, the thread roller is used. It is 5200~6500m long. Studies have confirmed that this roller surface symmetry axis is relatively close to the spindle axis. According to the theoretical method described, controlling the proper position of the mounting threaded roller can increase the life of the roller by 1.36 times (average).
The diameter dimension deviation Ad of the rolling thread is determined by the diameter dimension chain, and the rank of the function can be formed as a function symbol of the corresponding parameter change caused by the shape.
When rolling the thread, the contact zone generates thermal displacement, according to the periodic contact of the blank - roller, roller - needle roller, needle roller - matching the shaft contact pair, in the plastic deformation, on the blank The heat balance is quickly redistributed. Thus, the dimensional deviation due to thermal deformation can be determined by the following equation: the elastic deformation of the process system components that have an effect on the diameter dimension, including the blank (Ap, roller (2Ay), needle roller (Ad)). Or the roller shaft is bent (2Ar,). The diameter dimension offset is equal to: due to the elastic compressive deformation, the diameter dimension error is directional, and its direction is opposite to the thermal bending deformation direction, so they can partially compensate each other. If the rolling pressure and the component heat capacity are known, the dispersion range of the diameter size can be determined by using the formulas (3), (4) and the elastic theory and the known formula of the thermal deformation theory.
3 Conclusion The dimensional chain of rolling thread has its own characteristics (in quadratic form) and needs to be solved by systematic method. Through research and analysis, the parameters can be analyzed and revealed by increasing the parameters, positional accuracy and tool life of rolling threaded components. The essence and rolling thread conditions, in order to achieve the purpose of improving the accuracy of the threaded parameters and extending the service life of the equipment.
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