Research and development of the hottest two-stage

2022-08-26
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Research and development of two-stage coaxial multi wedge high-precision spinning pulley

pulley is an important mechanical transmission part, which is widely used in the transmission of various mechanical equipment in automobile, agricultural machinery and light textile industry. The continuous development of belt transmission technology has made the transmission forms more diversified, especially the V-belt. It combines the advantages of good flexibility of flat belt and high power of V-belt transmission. At the same time, it can absorb impact and vibration. Compared with chains and gears, it runs quietly and has great development prospects

this kind of belt pulley produced by deep drawing, extrusion and spinning with high-quality steel plate has basically replaced the previous casting and turning belt pulley. However, the existing single-stage multi wedge belt cannot be used for variable speed transmission. Therefore, two-stage coaxial multi wedge pulley came into being - this is another structural form of a new multi wedge pulley that can be used in variable speed transmission, which can meet the development needs of China's automotive equipment and transmission coupling industry

several common production methods of belt pulley

1 It is the earliest and most original traditional forming method, which is formed by machining with casting or forging blanks. It is still used now, especially suitable for single piece small batch production

2. Press welding forming

punch the steel plate into a dish shape, and then weld the two dish shaped steel plates back to each other or connect them with rivets and bolts to form a belt pulley with a groove shape

3. Press bulging method

first stretch the billet into a barrel shape or a hat shape with steps, and then use hydraulic press to use liquid punch or block die, or rigid concave die with complex structure to expand the pulley with hydraulic oil

4. Stamping, stretching and spinning forming method

first press the plate into a round piece, then stretch it into a hat shaped preform with shoulder on the hydraulic press, and finally spin out the pulley groove shaped belt pulley through the rotary press

the above four belt pulley production methods are gradually developed and continuously improved from labor. Each method is more advanced than the previous one. The fourth is the most popular forming process at present. The groove surface produced by it is very smooth and flat, and the surface has a cold work hardening layer, which increases the strength of the pulley and has high production efficiency. In fact, this new spinning technology is emerging in response to the needs of the aviation industry, and represents the cutting-edge technology and development trend of today's pulley

processing characteristics and working principle of spinning pulley

1 Process characteristics

spinning technology, also known as metal spinning forming technology, is a technology that makes the force point from point to line and from line to surface by rotation, and at the same time gives a certain pressure in a certain (radial) direction, so that the metal material deforms and flows in this direction to form a certain shape. Therefore, metal materials must have plastic deformation or flow properties. Spinning forming is not equal to plastic deformation. It is a complex process integrating plastic deformation and flow deformation

Figure 1 processing process flow of two-stage coaxial multi wedge high-precision spinning pulley

in particular, it should be pointed out that the spinning forming technology we mentioned is not a single strong spinning and ordinary spinning, but a combination of the two; Strong spinning is used for the processing of spinning shaped shells of various cylinder and cone shaped bodies. It is a relatively mature traditional process method, also known as rolling method

the main processing process of two-stage coaxial multi wedge high-precision spinning pulley is shown in Figure 1, which is composed of blanking (punching), deep drawing, trimming, shaping, spinning big end, spinning small end, punching, cleaning phosphating, electrophoresis, etc. Compared with cast-iron pulley, spinning pulley has the advantages that it is made by spinning process, no chip processing, light structure, material saving, and small moment of inertia. It is a new product of material saving and energy saving

this production method has high efficiency and good balance performance, and generally does not need to be balanced. Because the material streamline is not cut off, the surface is cold worked and hardened, the tissue density is improved, the strength and hardness of the wheel groove surface are improved, and the dimensional accuracy is high, the slip between the V-belt and the wheel groove is small, and the belt life is long

2. Working principle and process

the cold working two-stage coaxial multi wedge high-precision pulley (hereinafter referred to as "coaxial multi wedge pulley") developed by our company (Wenzhou Nanya Auto Parts Co., Ltd.) is an energy-saving patented new product, which has many advantages, which also benefits from the six position transformation of our domestic 45t three position spinning machine in the manufacturing process

let's first look at the working principle of the modified domestic 45t six position spinning machine (see Figure 2 for equipment structure). Using the rotating force generated by the spinning machine, with the radial extrusion of the lifting die wheel seat, the plastic material is stressed, and then the metal material is deformed and flows along this direction from point to line and from line to surface, so as to form the required special shape

Figure 2 structure of the modified domestic 45t six position spinning machine

the working process of this six position spinning machine is: the belt pulley cap shaped preform is put into the lower mold of the spinning machine, the main oil cylinder is opened, the new blank holding workbench (1) is moved down, the cap shaped preform small wheel is pressed, the belt pulley is driven to rotate by the main shaft, and a locating wheel seat (3) as wide as the big end groove extends into the big end groove to axially locate the belt pulley to be processed, The lifting die wheel seat (6) loads the hat shaped preform workpiece at the radial feeding speed V, and the workpiece produces plastic deformation to form a circular groove. After the groove reaches a certain depth, change the integer wheel seat to reshape the big end wheel circle, move the rear lifting die wheel seat (6) up to the small end position, spin the small end, produce plastic deformation, and form a circular groove. After the groove reaches a certain depth, change the integer wheel seat to reshape the small end wheel circle, and finally complete the two-stage coaxial pulley

it is worth mentioning that our company has made a series of scientific research achievements in the spinning process of belt pulley, including folding belt pulley, splitting belt pulley, rolling multi-v belt pulley and combined belt pulley, which have solved various technical problems in spinning forming and have been successfully used in production. By comparing national standards, international standards and customer requirements, it shows that our products not only meet various standards and customer needs, but also have reached the domestic leading level

improvement of spinning machine

the Department of manufacturing engineering of Beijing University of Aeronautics and Astronautics has developed the spinning process and spinning equipment of sheet metal pulley since 1985. By October 1987, China's first horizontal spinning machine was developed, and in 1992, a 45t three station vertical spinning machine was developed (Figure 3)

Figure 3 basic structure of the original domestic 45t three position spinning machine

the main components of the machine are organic seat (4), frame guide post (6), and the upper worktable (2) move up and down under the influence of master cylinder (1). The blank of main shaft (3) driven by bevel gear of motor output shaft is installed on the lower die seat on the main shaft, and the master cylinder is started to move the upper worktable down. The upper die base installed on the upper workbench clamps the blank and turns on the motor spindle to rotate. Start the feeding of the corresponding die wheel seat (5) and start spinning. After spinning, the main oil cylinder starts to move up the upper workbench. The ejection cylinder works, and the spinning belt pulley is ejected and unloaded through the ejector rod

from the processing process of single-stage pulley, it can be seen that the existing domestic equipment has only one upper workbench in the process of workpiece clamping, and can only complete one-stage spinning. For example, processing two-stage coaxial multi wedge type can only remove the workpiece after completing one spinning, replace the mold and then spin another stage. In the process of replacing the mold and re clamping, the coaxiality of the two clamping is difficult to be guaranteed. Therefore, the two-stage runout error of the spinning belt pulley is increased, and the two-stage wedge spacing error is also difficult to control. Therefore, it is necessary to realize two-stage spinning with one clamping

considering the large workload of two-stage coaxial multi wedge product processing, we have transformed the domestic vertical 45t three position spinning machine into a six position one

1. Add blank holder workbench

in order to complete two spinning after one clamping, it must be ensured that the outer diameter of the other stage is protected by the die when spinning the first stage, and the two axial sides of the first stage are pressed (i.e. blank holder), so as to ensure that the length and size of the product will not change when the blank is extruded during spinning. When spinning the second stage after the first stage is completed, remove the mold used to protect the outer edge (hereinafter referred to as the blank holder mold) to expose the outer edge of the second stage for spinning, and at this time, the blank must be in a compressed state

the blank holder die of the existing equipment is installed on the upper workbench. When the upper workbench drives the blank holder die to rise, the axial direction of the blank is in a free state, and the second stage will not be able to be spun. Therefore, in order to achieve one-time clamping to complete the second stage spinning, a set of blank holder device must be added

2. Add spinning stations

as shown in Figure 4, the two stages of the two-stage coaxial pulley are located in different axial positions of the pulley. At the same time, the number of grooves in the two stages of the multi wedge pulley is not necessarily equal, and the required extrusion die wheels are not necessarily the same. The existing spinning machine has only three stations, and the processing of each stage pulley requires at least two stations (i.e., two extrusion die wheels and extrusion die wheels). The position die wheel seat of the existing spinning machine cannot move vertically, Two stage extrusion with different axial heights cannot be completed

Figure 4 lifting die wheel seat

therefore, in order to achieve one-time clamping to complete secondary spinning, it is necessary to add stations and make the station die wheel seat move vertically

to sum up, the spinning machine can spin two-stage coaxial multi wedge belt pulley by adding blank holder workbench and lifting die wheel seat

key technologies and major innovations

this two-stage coaxial multi wedge high-precision belt pulley is the only similar product successfully manufactured by cold processing technology in Zhejiang Province. It has been adopted in automobile gear trains (water pump pulley, fan pulley, steering pump pulley, generator pulley), tractors, agricultural machinery, food machinery, textile machinery, and has been recognized by users

its key technology is the innovative design of the cold processing two-stage coaxial multi wedge high-precision belt pulley forming process. The innovation is that in the cold processing two-stage coaxial multi wedge high-precision belt pulley forming process, the influence of multiple clamping and mold adjustment on the belt pulley accuracy is overcome, and one-time clamping and forming is achieved, with a certain running space; So as to ensure the accuracy of belt pulley products

the main innovations are listed below

1. Process innovation, made by spinning process, chip free processing

the pulley used for variable speed transmission has high accuracy requirements. For a long time, it has been difficult to use the existing domestic processing equipment for production. Spinning belt pulley is to use spinning machine to gradually approach the processed rotating object (steel plate) through various standard molds, and force it to produce the desired deformation with external force. This kind of belt pulley made of thin steel plate by spinning method can only spin one level of wedge groove at a time, and the two-level belt pulley must undergo secondary clamping, spinning, and mold replacement twice. As a result, the coaxiality of the two-stage pulley is difficult to ensure, and the production efficiency is also very low

in this regard, we started with the reform of the production process. After years of research and practice, we changed the domestic 45t three position spinning machine into a six position spinning machine. One clamping can simultaneously process and roll out the wedge-shaped wheel grooves at both ends, ensuring the coaxiality requirements between the two stages and producing high-precision products

2. Save materials and time, high production efficiency, good balance performance, long service life

the traditional pulley material is casting (cast iron, cast aluminum and their alloys), and the production process must be approved first

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