The rotary table supporting the floor milling key bed is constantly updating its structure. In this paper, we analyze the ZT20A, ZT30R, TKH6913A rotary machine and the ZTS20 rotary table clamping mechanism produced by our factory. The force conditions were calculated and the clamping force was calculated and then compared.
1. Turntable 2. Locking bolt 3. Top block 4 Locking nut Fig. 1 ZT20A rotary table clamping mechanism
1. Worktable boss 2 Clamping block 3. Clamping sleeve Fig. 2 Clamping mechanism of TKH6913A rotary table for machine tools and ZT130B rotary table
1,4 Clamping block 2. Worktable 3. Wedge 5 Elastomer Figure 3 Schematic diagram of clamping mechanism for rotary table of ZTS20 machine tool
The ZT20A rotary upper table clamping mechanism (Figure 1) is the simplest manual clamping mechanism. Its principle is: the use of locking bolts and lock nut screw in and out, to determine the rotary table clamping and release. When the rotary table is in the working position, the lock nut is tightened, and the rotary table is clamped by the friction between the top block and the lock bolt and the rotary table; when the rotary table is to be rotated, the lock nut is loosened, Eliminate the friction force (under the action of the spring force, the locking bolt can move along the T-shaped groove of the turntable), and the turntable can rotate freely until it reaches the working position. ZT20A uses four clamping devices, but since this device is completely manual, there is no quantitative regulation of the clamping force, which will cause a certain amount of human error, thus affecting the machining accuracy. With the widespread application of electrical control, especially PC control, the manual clamping mechanism has long been unable to meet the requirements, resulting in a floating clamping of a clamping mechanism using a hydraulic cylinder for clamping. The clamping mechanism of the TKH6913A rotary table ZT30B (Figure 2) and the clamping mechanism of the ZTS20 rotary table (Figure 3) are automatically clamped by controlling the friction between the cylinder and the clamping block and the rotary table. One of the two types of clamping is clamping the radial boss of the table through the oil cylinder, and the other is clamping the circular groove on the table through the oil cylinder. Both of these structures are clamped by the force of the cylinder and the oil pressure is controlled well. The clamping force of several clamping bodies is the same, and the force state of the table is good, which can ensure the processing accuracy better. As shown in the force analysis of Figure 2, F is the force generated by the clamping force of the clamping rod on the piston rod, acting on the axial line of the piston rod. R is the reaction force of the clamping force of the clamping block on the table. This force acts as a force and acts on the center of the clamping block, which is equal to the actual clamping force and in the opposite direction. In the design, the piston rod centerline zero torque point (fixed pin center) is 42.5m, the clamping block center distance zero torque point is 1OOmm, the cylinder piston outer diameter 120mm, the piston rod diameter 40mm, uses the double cylinder form ( See Figure 2). If the system oil pressure is set to P (MPa), then: F=2×[( 120 )2-( 40 )2]×pP≈20106P(N) 2 2 Therefore, the ZT30B, ​​TKH6913A rotary table with machine tool is obtained. The clamping force of a clamping body is 8545P(N), set to F1. The force of the wedge and the elastomer (in force) is shown in Figure 3. Firstly, the elastic body is taken as the research object, which is affected by three forces: the acting force of the table on the clamping block Q (the reaction force of the clamping force), the supporting force R of the upward vertical force, and the force of the wedge nut on it. R2 (consisting of positive pressure and friction, so it is at an angle j - friction angle perpendicular to the slope). When the pressure P of the cylinder reaches a certain value, the wedge nut and the elastic body are in an equilibrium state, and the following formula is established. Q+R×cos(a+j)=0 The wedge nut is used as the study object, and it is also affected by three forces: the vertical tensile force generated by the hydraulic pressure P and the reactive force R′2 (R′2) of the elastic body. + R2 = 0), wedge internal force R3, now only consider one side of the force, so there is force R3, its direction of action is opposite to the direction of relative motion, and the direction of the friction angle j with the horizontal direction. Its equilibrium condition is R'2×cos(a+j)=R3×cosj
F=RR'2×sin(a+j)+R3sinj It is known that the wedge angle is a=7.5°, μ=0.15, and can be obtained from the above three equations: F=R'2×[sin(a+j) ) + cos(a + j) x tgj] again R'2 = - R2 = Q/cos(a + j) F = [(120) 2 - (40) 2] x pP ≈ 10053P (N) 2 2 friction The angle j=arctg0.15≈8.53° so the clamping force Q=F=10053=22989P(N) tg(a+j)+tgj tg16.03°+tg8.53° So one of the ZTS20 rotary table is obtained. The clamping force of the clamping body is 22069.534P (N), set to F2. It can be seen that the clamping force of the two structures of the clamping body is F2=22989P(N)>>F1=8545P(N) under the same oil pressure, and F1 is generated under the action of the double cylinder, and F2 is only produced by a single cylinder. From this result, the structure using the elastomer and the wedge is much better than other structures described in the text. Therefore, it is widely used in PC-controlled rotary table design.