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Working principle of slow wire processing

 Slow wire walking, also called low-speed wire walking, is a kind of CNC machining machine tool that uses continuously moving fine metal wire as an electrode to pulse spark discharge on the workpiece to generate a high temperature of over 6000 degrees, ablate metal and cut into a workpiece. The principle of wire processing is the phenomenon that there is a gap between the wire electrode and the workpiece, and the metal is removed by continuous discharge. Since the slow-moving wire cutting machine adopts the method of wire electrode continuous feeding, that is, the wire electrode is processed during the movement, so even if the wire electrode is worn out, it can be continuously supplemented, so it can improve the machining accuracy of the parts and slow the wire. The surface roughness of the workpiece processed by the cutting machine can usually reach Ra=0.8μm and above, and the roundness error, linear error and dimensional error of the slow-moving wire cutting machine are much better t

Hydrostatic guideway of CNC machining lathe

The static pressure slide rail (TTW guide) of the CNC machining lathe transfers the oil with a certain pressure through the throttle to the oil cavity between the sliding surfaces of the slide rail (TTW guide) to form a pressure oil film to float the moving parts , Make the sliding rail (TTW guide) surface in a pure liquid friction state.   CNC machining General CNC machining usually refers to computer digital control precision machining, CNC machining lathe, CNC machining milling machine, CNC machining c17200   beryllium   copper   and milling machine, etc. The feed route of finishing is basically carried out along the part contour sequence. Therefore, the focus of determining the feed route is to determine the feed route of rough machining and idle stroke. In the numerical control processing, the control system issues instructions to make the tool perform various motions that meet the requirements, and the shape and size of the workpiece are expressed in the form of numbers and lette

Introduction of KOVAR parts

KOVAR parts are commonly used as metal casing materials in the electronic packaging industry. Because they have a linear expansion coefficient close to that of molybdenum group glass, and can produce less sealing stress during the sealing (melting) process with molybdenum group glass, so To obtain good air-tightness, in order to make the metal tube and shell to achieve air-tight sealing, in the entire sealing process, the annealing process undoubtedly plays an important role as a link between the previous and the next. The internal stress generated during KOVAR  machining also prepares the material structure for the implementation of the subsequent process-the sealing process of the metal parts. The main purpose of annealing Kovar shell before sealing is to: (1) Eliminate machining stress. When Kovar undergoes plastic machining deformation during cold working, about 10% to 15% of the applied energy is converted into internal energy, which is commonly referred to as internal stress,

Drive the preferential presetting of the spring frame of the vehicle

The secondary spring system of the original electric locomotive consists of 4 sets of the same ordinary cylindrical compression springs. Its parameters are: spring material diameter d=48mm, maximum working circle diameter D=230mm, effective working circle number n=6.6, free height H0= 528mm, working height H=431mm. The characteristic curve of the spring is approximately straight, with stable stiffness and simple structure. However, the spring stiffness is mainly along the axial direction, and its transverse shear and bending stiffness is very poor, and its anti-resonance ability is poor. After the train speeds up, its snake-like movement and shaking phenomenon intensify. Therefore, it is necessary to improve the spring system of electric locomotives.

Improvement of the spring system. The improved spring parameters and characteristics take into account the special position of the secondary spring (between the bogie and the car body) and specific functions (supporting the car body and damping), under the premise of ensuring equal free height , The cylindrical spiral compression spring is improved into a conical compression spring with equal pitch. The distance t can be calculated by the following formula: H0=6.6t+1.5dT=(528mm-1.548mm)/6.6=69.09mm*large working radius R2=115mm, *smallest working radius R1=101.8mm, and the pressing time distance d=d1 -R2-R1nd2=47.96mm The stiffness of the improved conical compression spring is increased, the characteristic curve is gradually increasing, and the anti-resonance ability is enhanced.

The effect of the bending moment at the end of the spring on any section A indicates the effect of the unit transverse force on any section A. The improved spring bending stiffness and transverse stiffness. The bending stiffness of the spring is set as the distance from any section A of the conical spring to the end of the spring, then = R1 +R2-R12ntan In the formula, is the polar angle of the helix; is the helix angle.

The effect of the spring end bending moment on any section A is as shown. The torque generated by the bending moment M of the spring force end on the section A and the bending moments in the two directions are respectively Tt=McoscosMb=-McossinMn=Msinds=R1+R2-R12ncosd where Tt is the torque on the section of the spring material; Mb, Mn is the bending moment on the section of the spring material; ds is the length of the tiny section of the spring material.

The effect of unit lateral force on any section A is shown in the figure. When Pr=1, the torque and bending moment produced by the unit force on the section A respectively, Ip is the polar moment of inertia; Ib and In are the moments of inertia; E is the elastic modulus of the material; is the Poisson’s ratio. Substitute the reference value R1=101.8mm, R2=115mm, n=6.6, d=48mm, E=2G(1+) (=0.25, G=80109Pa), Ip=2Ib=2In=d4/32 into the formula, after integration Get Fr=(544011.7/(EIn))MM=(EIn/544011.7)Fr=95798N, so the bending stiffness is 95798N.

The bending stiffness of the original cylindrical spring can be calculated according to the formula (7-42) in the literature <1>. M=Ed416D2nH(2+)Fr=42604.5N. Therefore, the bending stiffness of the original cylindrical spring is 42604.5N. This shows that the bending stiffness of the conical spring is Improved. The lateral stiffness is as shown, the torque and the bending moment of the A section caused by the lateral force Pr are respectively (because it is very small, sin=0, cos=1) Tt=PrR1+R2-R12ntancos3

From the literature <1> formula (7-51), the transverse stiffness of the original cylindrical spring is obviously, the transverse stiffness of the conical spring is higher than that of the cylindrical spring.

Conclusion At present, the spring system of most foreign locomotives is still cylindrical spring, but the railway quality is higher than that of our country. The cost of the same transformation of the railway system in our country will be very high. Therefore, in our country, the key to improving the stability and safety of vehicle operation is to improve the spring system of the locomotive. Through the theoretical derivation and quantitative calculation of the new design scheme in the article, it is proved that the transverse stiffness and bending stiffness of the improved spring system are significantly increased, thus realizing the active control of the resonance of the locomotive during high-speed operation, and greatly improving the high-speed operation of the locomotive. Safety and stability. This design has been used by Zhuzhou Electric Locomotive Factory in the manufacture of the new Shaoshan SS9 train.

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