Analysis and Research on the processing technology

Analysis and Research on the processing technology of V-shaped thrust rod

thrust rod is mainly applied to single axle or double rear axle heavy vehicles with non independent suspension of trucks or buses, connecting the frame and axle. Its purpose is mainly to overcome that the leaf spring can only transmit vertical force and lateral force surface, but not traction, braking force and corresponding reaction torque. At present, All types of thrust rods are widely used in trucks and buses produced by major domestic OEMs. In recent years, a new type of thrust rod, namely V-shaped thrust rod, has been used on high-end passenger cars and heavy vehicles in some main engine plants. The thrust rod assembly device for truck suspension, as an integral part of the multi axle suspension system of the truck, is usually set on the middle and rear axles of the truck: one end is hinged with the body, and the other end is hinged with the middle axle: its function is mainly to transmit the longitudinal force and its moment, the transverse force and its moment, such as traction, braking force and the centrifugal force when the truck turns. At present, the structural form of the commonly used automobile V-shaped thrust rod assembly is shown in Figure 1. The function of the thrust rod assembly is to transmit not only vertical force and torque, but also lateral force and torque. At the same time, the working condition of the truck is bad. If the thrust rod is not sealed well, the sediment is very easy to enter the end, accelerating wear, resulting in the decline of the performance of the whole assembly and greatly reducing the service life, so its working environment is extremely bad

figure 1bbc thrust rod

the traditional thrust rod is connected by riveting with two ends and a rod body. There is only one size relationship, which has the characteristics of simple structure, convenient detection and easy product quality assurance. However, BBC thrust rod is called V-shaped thrust rod because its shape is very similar to V-shaped, which is different from ordinary thrust rod, It is formed by riveting the rod body and the other two ends on a V-shaped end (i.e. bbc-end). There are three different ends on a pair of thrust rods, which have a strict dimensional relationship with each other. For example, the central size between end a and end B is, and the size between end a, B and bbc-v end is 621.5mm. Therefore, this brings certain difficulties to product quality assurance and production and manufacturing. As the main body of the V-shaped thrust rod, the V-shaped end is difficult to ensure the processing of the product, and the riveting of the V-shaped thrust rod is also very difficult to ensure

in the development of BBC thrust rod (V-shaped thrust rod), through careful analysis of product drawings, it is considered that the difficulties in the development of V-shaped thrust rod are: first, the processing of V-shaped end; The second is the riveting of the thrust rod

v-shaped end structure is shown in Figure 2. The difference between it and ordinary end is: first, the aperture is large, and the blank shape is relatively complex; second, the product quality is heavy, and a V-shaped end weighs more than 40 Jin. Therefore, in order to ensure the processing quality of products, we must redesign and choose from tooling, equipment, cutting tools and cutting parameters

Figure 2

process analysis of end processing

because the blank of bbc-v end is formed by forging, and its parting surface is on the axial plane of the two rod parts and the cylinder hole, there is a die shifting slope on the front and back sides of the cylinder hole, that is, the two planes are uneven, which seriously affects the processing of the product. Therefore, the first process of product processing must be milling one end face of the product, and then the subsequent process can be processed

the cylinder hole and its end face of the product are the benchmark for subsequent processes and the riveting of the rod body and end assembly. Therefore, the hole processing must be processed earlier in the front. At the same time, if the product completes rough machining, semi precision machining and precision machining under one-time clamping, then the product needs to cut a large amount of cutting allowance during rough machining, so the selection of cutting parameters should be as large as possible, The cutting force generated in the cutting process is large, and a large amount of cutting heat will be generated at the same time. In order to ensure production safety, the product will not fly out in the processing process. The clamping force used in product clamping is large. Once the product is removed after processing, one side of the product will recover and deform due to the loss of clamping force, resulting in out of roundness; On the other hand, the product will have large thermal expansion and cold contraction under the action of cutting heat, and the product size will also change with the change of temperature, so the product size cannot be controlled. Therefore, in order to ensure the product quality, the rough machining, semi finishing and finishing of the product must be carried out separately. In this way, a large amount of cutting allowance is cut off during the rough machining of the product, and then it is removed to make it natural failure, eliminate the internal stress, and then flow into the semi finishing and finishing processes

when the rod imitates the bamboo joint, because there is an angle relationship of 48 ° 29 'between the two rod parts, the size of the angle error directly affects the center size 517 between the two ends of the thrust rod Mm precision, therefore, when imitating the bamboo joint of one end of the rod, the mutual position size and allowance between the two rods must be considered. When imitating the central hole of the bamboo joint of the other rod, the qualified central hole must be punched with the positioning of the processed rod of one end. When imitating the bamboo joint, the angle of 48 ° 29 'can be formed between the two rod parts to process qualified products. Therefore, the process route of end processing is as follows:

(1) milling the plane of one end of the cylinder hole

(2) rough drilling the pores φ 54mm

(3) rough turning cylinder hole to size φ 104mm, leaving 4mm of semi fine turning and fine turning allowance,

(4) semi fine turning and fine turning cylinder holes are processed to the drawing size φ 108+00。 087

(5) control the total thickness of the reverse side of the car and the size of the reverse side hole

(6) drill a central hole at one end and pay attention to the machining allowance of the two rod parts

(7) imitate the shape of the bamboo joint at one end

(8) drill a central hole at the other end to ensure that the included angle between the two rod parts is 48 ° 29 '

(9) imitate the shape of the bamboo joint at the other end

the design of the end processing tooling and the selection of equipment

according to the previous analysis of the process route of end processing, Know the key and difficult points of the end processing: the first is the processing of the cylinder hole of the product, and the second is the processing of the slub shape of the product rod (including the processing of the center hole of the two rod parts). Therefore, in the tooling design, the turning processing of the cylinder hole of the end and the tooling of the slub imitation Institute of the end rod are the main

1. Tooling design

(1) fixture design

because the parting surface of the blank of the ordinary end is in the center of the product, and the reverse side of the blank is a relatively flat large plane, the positioning of the product is accurate and the clamping is reliable. As a professional end processing unit, the processing of the ordinary end is designed and manufactured with relatively mature tooling fixtures, the product quality is easy to ensure, the processing is relatively easy, and the tooling is also simple, The bbc-v end is different. Because the angle between the two rod parts protruding outward of the product is 48A, and the line width of the engraving is ° 29 ', and the axis lines of the two rod parts and the hole are on the same plane, the parting surface of the blank is on the axis plane of the two rod parts. Because the bottom of the reverse side of the blank has the cutting edge of the parting surface and the inclination of the mold pulling, the reverse side of the product is uneven, causing difficulty in product positioning. Therefore, in order to make it processed smoothly, At the same time, reduce the cost of fixture design and manufacturing, and first directly select the standard φ The 320mm three jaw chuck is also designed with special clamping jaws as shown below. The clamping orientation during product processing is shown in Figure 3

figure 3

one of the grippers has a V-shaped surface at the bottom, which is designed to eliminate the influence of blank trimming on product positioning. According to the machine tool fixture design manual, the length of the V-shaped surface is 20mm, which is used to eliminate the freedom of movement in only one direction and allow its rotational freedom to exist. In this way, according to the selected three jaw chuck, The other two rotational degrees of freedom are eliminated by two support locating points in the other two special clamping jaws in the three jaw chuck, and the clamping jaw with automatic centering and clamping function eliminates the other two degrees of freedom. Therefore, the whole fixture can eliminate five degrees of freedom, which meets the processing conditions. In addition, due to the 48 ° 29 'angle between the two rod parts of the product protruding outward, the rod part protrudes outward nearly 100mm, and the thickness of the whole end is 95 mm, so the height of the clamping jaw is high, the clamping jaw is subject to large force during clamping, the clamping jaw is easy to deform, and the clamping jaw rigidity is poor. Therefore, in order to ensure that the product can be processed normally, the clamping jaw material is 45 steel, the heat treatment hardness is hrc43-48, and the counterweight position is reserved during design, In order to reduce the influence of excessive centrifugal force on the machining accuracy of products and the spindle of machine tools when the machine tool rotates

(2) fixture design for profiling

v-shaped end when imitating bamboo knots, because there is an angle of 48 ° 29 'between the two rod parts, each rod has a certain angle relative to the end surface of the cylinder hole. In order to process the rod bamboo knots normally, it must take the cylinder hole and its end face as the benchmark, position the front of the end, and eliminate three degrees of freedom (two rotational degrees of freedom, one plane moving degree of freedom), The center of the cylinder hole is positioned by a short cylinder to eliminate two degrees of freedom of movement, and the other degree of freedom of rotation is eliminated by the mandrel and the ejector pin of the rod. In this way, the six degrees of freedom have been eliminated, so that the fixture positioning is reliable. Therefore, only a positioning short mandrel with an angle of 24 ° 15 'with the vertical direction is installed on the designed clamp, so that the rod can be kept horizontal, meet the processing conditions, and process qualified products. When processing another rod slub, in order to keep the positioning datum consistent, the positioning mandrel with the same angle as the above positioning mandrel must be redesigned, but the positioning mandrel with different drop can be processed into qualified products only by installing it on the clamp during processing. The profiling fixture is shown in Figure 4

figure 4

2 Equipment selection

through the analysis of the product, it is found that although the dimensional accuracy and surface roughness requirements of the product are not too high, the smaller equipment cannot meet the processing requirements due to the larger overall size and heavy weight of the product. Therefore, according to the existing equipment conditions in the workshop, C630 is selected to undertake the processing task of the product hole. When imitating bamboo knots, due to the large turning radius of the product (240 × Sin48 ° 29 ′=180mm), the product is heavy, so the machine tool with good rigidity and high efficiency must be selected. Therefore, ce7132 profiling machine tool is selected

selection of cutting tools

according to the previous analysis of product drawings, we know that the processing difficulty of V-shaped end is the processing of end cylinder hole. Therefore, in the design and selection of cutting tools, it is mainly how to ensure the smooth processing of qualified products. When machining ordinary ends, because its inner hole is simple, the hole diameter is small, the blank is small, and the weight is light, therefore, the choice of tools can directly use ordinary inner hole tools. The bbc-v end is different. Due to the heavy quality of the product and the protruding rod, the ordinary tool used to process the ordinary end obviously cannot adapt to the processing of the product, so the rigidity of the tool must be increased. After the calculation and analysis of material mechanics, it is decided to choose the diameter of φ 50mm, 45 steel, Quenched and tempered after heat treatment, the material with hardness of HRC is used as the tool body, so that it can meet the production needs in the actual processing

determination of cutting parameters

after the design of tooling, cutting tools and machine tools is selected, the products can be processed. According to the previous process arrangement, rough machining is carried out first when machining the cylinder hole at the end, and then semi finish machining and finish machining are carried out. During rough machining, a large amount of blank allowance is mainly cut off, and then finish machining allowance is left. Therefore, there is no great impact on the quality of products. The selection of cutting parameters is also in the selection of tools, tooling When the rigidity of the machine tool is enough, it should be taken as large as possible, so the cutting depth is taken as 3.5mm and the feed rate is taken as 0.65mm/r during rough machining