Application and development of spin forming technology and equipment

1 Introduction

Spinning technology is a traditional technology with a long history. According to the literature, it originated in the Tang Dynasty of China. The spinning process of metal was developed by the ceramics process. After the middle of the 20th century, with the development of industry and the development of aerospace industry, the general-purpose process was applied to the field of sheet metal forming, which promoted the research and development of the process. After the middle of the twentieth century, ordinary spinning has made significant progress in the following three aspects: First, the ordinary spinning equipment is gradually mechanized and automated. In the 1950s, equipment for simulating manual spinning was used, that is, hydraulic power was applied. The drive or the like drives the reciprocating movement to realize the feed and the return stroke, thereby reducing the labor intensity. Second, in the 1960s and 1970s, semi-automatic spinning machines controlled by electrical and hydraulic programs were introduced that could be fed in one direction and multiple passes. Third, due to the development of electronic technology, in the late 1960s, on the basis of semi-automatic spinning machines, CNC and recording revolving machines were developed. The rapid development of these devices has brought the spinning process into medium and large-volume production [1-11].

Strong spinning was developed on the basis of ordinary spinning in the 1950s. It was first used in folk industry in Sweden and Germany (for example, processing containers such as pots). Due to the advanced nature, economy and practicability of the spinning process, and the process has the characteristics of small deformation force and material saving, in the past 40 years, the spinning technology has been greatly developed, not only in the aerospace field, but also It has been widely used in civil industry such as chemical industry, machinery and light industry. At present, spinning technology has become increasingly mature and has become a new field in metal pressure processing.

In the past 20 years, the spinning forming technology has advanced by leaps and bounds. High-precision numerical control and recording and spinning machines have emerged and rapidly applied, and are now developing in the direction of serialization and standardization. In many countries, such as the United States, Russia, Germany, Japan and Canada, we have produced advanced and highly standardized spinning equipment. These spinning equipments have been basically shaped, the spinning process is stable, and the products are diverse and applicable. More and more extensive [19].

The development status of China's spinning technology is far from the advanced level of foreign countries. However, in recent years, great progress has been made, and the accuracy and performance of many products are close to or reach the advanced level in foreign countries. Many domestic research institutes (such as Beihang Modern Technology Research Institute, Heilongjiang Spinning Technology Research Institute, Changchun 55, etc.) have developed spinning machines with better performance.

2 spinning technology

2.1 Introduction to spinning technology

2.1.1 Spinning technology definition and classification

Spinning is an advanced process that combines the characteristics of forging, extrusion, drawing, bending, ring rolling, cross rolling and rolling, and has no cutting process. The metal blank, flat blank or preform is used for the tail. The top is tightly pressed on the spinning mandrel, and the mandrel and the blank are rotated by the main shaft, and the spinning wheel presses the material from the side of the blank onto the rotating mandrel, so that the material is continuously plastically deformed point by point, thereby obtaining Hollow rotating body parts in various busbar shapes. The processing principle of the spinning process is shown in Figure 2-1.

According to the change of the thickness of the blank during the spinning process, the spinning process is generally divided into two types: ordinary spinning and strong spinning.

Ordinary spinning is referred to as general rotation. According to the traditional view, the thickness of the blank remains basically unchanged during the general rotation process. The forming mainly depends on the circumferential shrinkage of the blank and the elongation deformation along the radial direction. The important feature is that the blank can be clearly seen during the molding process. The change in the diameter.

The basic methods of ordinary spinning are: deep drawing spinning (drawing), reducing diameter spinning (shrinking) and expanding diameter spinning (expanding).

Deep drawing spinning refers to the spinning forming method during the drawing of the blank. As shown in Figure 2-2-a. It is the most important and widely used forming method in ordinary spinning. The bending plastic deformation of the blank is its main deformation mode. Deep drawing spinning can be divided into simple drawing spinning and multi-pass drawing spinning.

According to the change of the thickness of the blank during the spinning process, the spinning process is generally divided into two types: ordinary spinning and strong spinning.

Ordinary spinning is referred to as general rotation. According to the traditional view, the thickness of the blank remains basically unchanged during the general rotation process. The forming mainly depends on the circumferential shrinkage of the blank and the elongation deformation along the radial direction. The important feature is that the blank can be clearly seen during the molding process. The change in the diameter.

The basic methods of ordinary spinning are: deep drawing spinning (drawing), reducing diameter spinning (shrinking) and expanding diameter spinning (expanding).

Deep drawing spinning refers to the spinning forming method during the drawing of the blank. As shown in Figure 2-2-a. It is the most important and widely used forming method in ordinary spinning. The bending plastic deformation of the blank is its main deformation mode. Deep drawing spinning can be divided into simple drawing spinning and multi-pass drawing spinning

。

Shear spinning refers to changing the thickness of the blank without changing the outer diameter of the blank to produce a spinning method (conical thinning spinning) of various axially symmetric thin-walled members such as a cone. The molding method is characterized in that the rotating wheel is less stressed, the half cone angle and the wall thickness influence each other, the material flows smoothly, the surface is smooth and the forming precision is high, and the material which is difficult to form by drawing and spinning is relatively easy to be formed. The theoretical calculation formula followed in the spinning process is:。

According to the actual wall thickness T11 of the post-spinning workpiece and the theoretical value T1, it is divided into two types of spinning methods: over-spinning (T11>T1) and under-spinning (T11<T1).

The cylindrical thinning spinning means that the rotating wheel is pressed against the tubular blank rotating at the same time as the core mold and moves along the axial direction of the tube blank to produce a thin-walled long cylindrical member. This spinning process always follows the principle that the volume of the metal material is constant. There are two spinning methods as shown in Figure 2-4, that is, the positive rotation (b) of the flow direction of the material and the moving direction of the rotating wheel and the flow direction of the material. Reverse rotation (a) opposite to the direction of movement of the rotating wheel.

Depending on whether the spinning wheel is on the same section, the strong spinning can be divided into offset spinning (Fig. 2-5) and synchronous spinning.

2.1.2 Spinning technology process elements

Ordinary spinning is mainly to change the shape of the blank, and the wall thickness changes little or not, and the design calculation of the shape and size of the blank is a key technology. The technological elements are the spinning wheel motion track, the diameter of the spinning wheel, the spinning gap, the feed rate, the spindle speed, the spinning linear velocity, the radius of the round corner of the wheel, the angle between the front side of the rotating wheel and the mold bus bar.

The strong spinning is mainly to change the wall thickness and diameter of the workpiece, and the length of the workpiece will be changed accordingly. The process elements are the diameter of the wheel, the radius of the wheel, the front angle of the wheel, the back angle of the wheel, and the angle of attack. , spindle speed, feed rate, spinning gap, spinning pass, thinning rate, workpiece half cone angle, spinning line speed, etc.

Of course, for material requirements, it is required to have a high elongation, a reduction in area, and a tensile and yield strength.

The heat treatment of metal materials is also the main factor in the spinning process. Due to the strong pressing and tensile stress during the spinning process, the material hardens seriously and must be softened by heat treatment. In order to change the mechanical properties of the final workpiece, it is necessary to carry out the necessary Heat treatment.

2.2 Spinning technology in different fields

The shape of the spinning product is various (as shown in Figure 2-6), and various operations such as forming, reducing the diameter, closing, sealing, flanging, crimping, pressing, etc. can be completed by spinning, and the products are widely used in various rows. Various industries (Table 2-1).

Figure 2-6 Spin-formed workpiece shape

Table 2-1 Various rotary parts

2.3 Process technology of typical spinning products

2.3.1 Strong spinning of cylindrical parts

Figure 2-3-b shows the process of strong spinning of cylindrical parts. The material deformation process always follows the principle of volume constant. The change of the shape of the workpiece is the thickness reduction of the cylinder wall before and after spinning, the diameter is smaller, and the length is shortened. The increase of the product inner diameter will also vary from process to process due to different process parameters. The final product elements are cylinder outer (inner) diameter, wall thickness, length, straightness, roundness, etc. 1 calculation.

among them:

L1--work length

L0--blank length

S0--blank thickness

S1--Workpiece thickness

Di--inner diameter

In the strong spinning of cylindrical parts, there is a special spinning method which is delamination and spinning. It refers to the spinning process in which a plurality of rotating wheels are mutually offset in the circumferential direction and the thickness of the blank is sequentially thinned in the radial direction. (Figure 2-2). This spinning method can complete multi-pass spinning in one spinning process, which improves the production efficiency, and the workpiece diameter accuracy is improved due to the constraint on the material deformation zone [2].

The formulation of the process plan and parameters mainly consider the elongation of the blank material, the reduction of the section, the tensile strength, and the yield strength. Spinning single pass material thinning rate can not be greater than the limit thinning rate

The final product can be formed by adding a heat treatment softening process in the middle of multi-pass spinning. The main process parameters are pass reduction ratio, spinning gap, rotary feed ratio, rotor forming angle, round corner radius and error. The distance between the forming angle and the spinning gap should be reasonably matched, and the material responsible for the leading edge of the rotating wheel is prone to local uplift, accumulation and instability cracking.

The design of the blank is mainly based on the principle of constant volume (Equation 2-1). Considering the factors such as the spinning efficiency according to the arrangement of the pass, the change of the diameter before and after the spinning should also be considered. Generally, the feed ratio of the rotary wheel is generally conducive to shrinking. The diameter and the feed ratio are small to facilitate the law of expanding the diameter.

2.3.2 Conical cylindrical shearing and spinning

Figure 2-3-a shows the shearing and spinning process of a tapered workpiece. In addition to following the principle of volume invariance, sinusoidal theory is the main theory that must be relied upon in this process (Equation 2-3/2-4).

Sheet forming cone:

S1=S0*sinα               （式2-3）

Preform shaped cone (two or more shear spinning):

The change of the shape of the workpiece is mainly the thinning of the wall thickness, the reduction of the taper and the increase of the height. The final product elements are the height of the cone section, the half cone angle, the wall thickness, the diameter of the known position, the straightness of the cone section, and the circle. Degrees, etc.

There are often three kinds of deviation states in the actual shear spinning, namely "zero deviation", "positive deviation" and "negative deviation", which are expressed by the deviation rate Δt (formula 2-5).

When △t=0, it is “zero deviation”, that is, the actual wall thickness is equal to the theoretical wall thickness; when Δt>0, it is “positive deviation” or “under-rotation”, at which time the actual wall thickness is greater than the theoretical wall thickness; When Δt<0, it is “negative deviation” or “over-rotation”, and the actual wall thickness is less than the theoretical wall thickness. These three states can be adjusted as needed for the process. Only when "zero deviation" is used, the workpiece has good moldability and high precision.

The formulation of the process plan and parameters are also considered due to factors such as the elongation of the material being rotated and the shrinkage of the section. According to the degree of deformation, the shear spinning pass can be appropriately increased, and a heat treatment process is added in the middle of the pass to soften the material and increase the spinnability. In the shearing spinning of aluminum alloy material, due to the large degree of deformation, the workpiece can be formed by hot spinning, specifically, the blank is uniformly preheated to above the recrystallization temperature, and the spinning mold is heated to 200~300 °C. In the spinning process, the acetylene flame can be used to directly heat the blank to ensure that the temperature does not decrease too fast, so that the material is in a softened state, which is favorable for spin forming. In addition to the error-free distance, the main process parameters are strongly spun with the cylinder. In order to increase the area of the material deformation zone and prevent the tensile stress of the material from being too large, the material at the leading edge of the rotor is locally raised too high, and the rotary wheel is mostly used. Large rounded universal spinner.

The design of the blank is mainly based on the shear spinning sine theory, and the wall thickness of the workpiece is in a specific relationship with the taper. Due to the large change in shape, local instability and cracking should be prevented during spinning.

2.3.3 Head forming

The head is an important part that is widely used in boilers, chemical containers, oil tanks, nuclear reactors, missiles and satellites. Its specifications are developing in the direction of large-scale, and the application fields are also expanding. The use of spinning to process large and medium-sized heads has unparalleled advantages in other processing methods [21].

Figure 2-7 shows the spinning process of the head. The spinning of the head is usually formed by sheet metal. The wall thickness does not change or change very little before and after deformation. The diameter changes greatly, or shrinks or expands. Stable or partial thinning, there are two ways of one-way forward spinning and reciprocating swing multi-pass progressive spinning (a and b in Figure 2-7). Product elements are head profile, known position diameter, height, wall thickness, etc.

Figure 2-7 Head spinning

The main technological elements are the trajectory of the rotary wheel, the spinning pass, the ball spin spacing, the spinning speed, whether it is hot or not, etc. The involute trajectory is most favorable for spin forming, and the pass spinning pitch is determined. Extremely important, directly affecting the success or failure of the spinning process.

At present, two methods are mainly used in cold-spinning forming of heads at home and abroad. One is the one-step method, that is, the slab is spin-formed once on the spinning machine. The second is the two-step method, that is, the slab is pressed into a spherical crown shape along the slab exhibition surface on the drum machine, and then turned on the spinning machine. The one-step spinning head has a working efficiency much higher than that of the two-step forming head process, and the product quality is good. At this stage, the one-step spinning head has been in a dominant position and has matured.

The spin forming of the head is divided into cold spinning, warm spinning and hot spinning. Cold spinning refers to the spin forming of the blank sheet at normal temperature. Due to the plasticity limitation of the material, there are not many head materials that can be formed by cold spinning. The head spin forming technology is mainly used for the forming of the plate head and some heads which are difficult to be cold deformed. Spin forming, which typically heats the metal to a temperature below the recrystallization temperature or forge temperature, is referred to as warm spinning. Hot spin forming is performed by heating the metal to a temperature above the recrystallization temperature or the forging temperature. As the temperature increases, the plasticity of the metal increases. The influence of deformation speed on plasticity is a complicated problem. As the deformation speed increases, there is both a side that reduces the plasticity of the metal and a side that has the opposite effect, and the deformation speed has different effects at different temperatures [22]. .

2.3.4 wheel squeezing pressure

Wheel 辋 spinning technology is a new rim forming process that has been developed in recent years. It is mainly used for the wheels of magnesium-aluminum alloy materials (Fig. 2-8), and some of the wheels are made of steel. The production of aluminum wheels for passengers under 17 inches in foreign countries has become the mainstream for spinning and forming of forging blanks or ring blanks. In recent years, the 22.5-inch truckless tubeless wheel has been manufactured by forging and spinning in foreign countries. With its beautiful appearance, light weight and high strength, it has become a strong competitive point for steel wheels.

Figure 2-8 Aluminum alloy wheel

The traditional wheel manufacturing process is casting (casting) - heat treatment - machining - final surface treatment at a lower pressure (generally 20 ~ 60KPa), which is suitable for mass production, high productivity, high yield, aluminum liquid The high utilization rate, but the surface quality is not good, the cost is slightly higher, and the wheel produced by the forging-annealing-spinning-heat treatment-machining-surface treatment (spraying or electroplating) process greatly improves the manufacturing precision. The dense metallographic structure and better mechanical properties make it easier to reach the strength requirements of the hub, light weight, smooth surface and greatly reduced machining allowance. This technology has developed into a mature technology in Germany and other developed countries. At present, there are few companies in China that use this technology to study and trial production.

The wheel spinning process can generally be carried out by means of plate splitting (Fig. 2-9-a) or by using a cast (forged) blank for strong spinning (Fig. 2-9-b). The split-type spinning process is to pass the disc-shaped slab through the layering process with the boring wheel, so that the blank is smashed into two parts in the middle of the thickness direction, and then the forming wheel is gradually formed into a general rotation; the strong spinning process is The cast (forged) aluminum blank is subjected to several cycles of strong rotation to achieve the rim profile size requirements.

Figure 2-9 Wheel spinning

2.3.5 Seamless overall cylinder spinning

Spinning seamless gas cylinders are new processes and products that have been developed in recent years. There are four types: steel seamless gas cylinders, aluminum alloy gas cylinders, composite steel inner cylinders, and composite aluminum. Inner cylinder. Mainly used in breathing gas cylinders, CNG natural gas cylinders, medium and large high-pressure gas transport cylinders and other fields.

The traditional gas cylinder manufacturing method is the stamping bottle shoulder and the bottom of the bottle, and then welded with the pipe fitting or the coil welding bottle body, the manufacturing process is complicated, the cost is high, and the product sealing property and pressure bearing capacity are not ideal. Spinning cylinders have a vast market with their unique overall seamlessness, and have completely replaced the cylinders made by traditional methods.

The most common process for seamless integral gas cylinder spinning has two kinds of process routes according to different materials. The aluminum alloy gas cylinder material is mostly 6061 aluminum plate or aluminum bar material, and the process route is plate stamping/aluminum ingot heat (350 °C). ~450°C) Back-extruding into a cup-strong rotating straight wall part-hot closing (400°C~450°C) universally formed shoulder and bottle neck, steel (mostly 30CrMo) cylinder is hot spinning of tubular parts (900 ° C ~ 1000 ° C) back cover - strong rotating straight wall part / or non-rotating - hot closing (900 ° C ~ 1000 ° C) universally formed bottle shoulder and bottle neck. Figure 2-10-a shows the process of the hot-spinning process of the cylinder, and Figure 2-10-b shows the section of the product after the closing.

What should be paid attention to in the spinning spun is the spinning equipment, the hot spinning temperature, the general rotation and the trajectory, and the inner wall of the bottle shoulder should be prevented.

Figure 2-10 Cylinder closing and spinning

2.3.6 Wheel spinning

According to the groove type and processing technology of the pulley, it can be divided into three categories: split wheel, folding wheel and multi-wedge wheel (multi-V pulley). As a new process product, these spinning pulleys have been widely used in auxiliary equipment driven by internal combustion engines such as automobiles, tractors, etc., such as cooling fans, generators, water pumps, air conditioners, compressors, power steering pumps, etc. Agricultural machinery, household appliances, household machinery and other equipment. Due to the different structural characteristics of the three types of spinning pulleys (Fig. 2-11), the processing technology is also different. The basic structure of the plate spinning V-belt is single-slot, double-slot and multi-slot. The basic structure of the plate-spinning multi-ribbed pulley is a folding type, which is divided into three wedges, four wedges, six wedges, seven wedges and eight wedges according to the number of wedge grooves.

The boring wheel is generally formed by blanking a blank, which is formed by spinning on a spinning machine from a thickness of one-half of the thickness of the material and shaping and spinning (Fig. 2-11-e). Because the processing technology is relatively simple, the main factor affecting the quality of the product is the flatness accuracy of the blank itself, so the punching die for punching is required to be higher.

Figure 2-11 Structural features of the spinning pulley

The folding wheel is formed by stamping and drawing, and is spun on a spinning machine, and is formed by appropriate axial pressure. Usually, the final one-time grinding and spinning are performed by a mold with a fixed tooth pitch and a spinning wheel. Meet product accuracy requirements. Since the folding wheel does not have metal flow during the forming process, but the shape changes, the process is relatively simple, and there are few factors affecting the quality.

The multi-wedge wheel is also formed by stamping and drawing, and then spin-formed on a spinning machine. Since the tooth profile is formed by extrusion and metal flow and plastic deformation on the wall thickness of the material, there are many factors affecting the final quality of the product, including the upper and lower molds, the shape of the rotary wheel, the spinning pass, and the material. Etc. (Figure 2-11-f).

Figure 2-12 Composite pulley spinning

2.3.7 Internal and external longitudinal tooth cylinder spinning

The powerful spinning technology can be used to manufacture thin-walled parts with vertical teeth (automobile clutch housing), sliding sleeves, "drive inner shape" of the drive shaft, and the twisted tooth shape of the drive wheel. The development and popularization of this technology has reduced the cost of processing this type of part, and at the same time greatly changed the forming structure of the workpiece. Strong spin forming with longitudinal cylindrical teeth is a complex material plastic forming process. At present, due to the complexity of the processing itself, the existing plastic forming theory is not enough to derive its actual calculation formula. The best choice of process parameters is mainly based on experience.

There are a variety of workpieces with longitudinal teeth, the main tooth shape is shown in Figure 2-13.

图2-13 带纵齿工件齿形

The main process factors for spin forming with longitudinal tooth workpieces are workpiece material, mold material, internal and external tooth profile, mold tooth profile, friction condition, process and heat treatment.

The blank for manufacturing thin-walled parts with longitudinal teeth is generally formed by a flat sheet blank, which is subjected to pre-forming processing such as drawing, die forging or tube section forming, and then the cylindrical member is attached to a special forming mold and spin-formed. The forming of the part usually requires only one spinning pass. Only in the case of a special workpiece geometry or a long workpiece, it is necessary to use a multi-pass process to pre-form the material before finalizing the rotation. Finishing and forming.

The outer longitudinal tooth profile can also be machined with high precision by a spinning process, which is formed by means of an internal spinning method by means of a rotary wheel and a hollow die with internal teeth, which is limited by the diameter. Another method is to spin-form the contour profile of the workpiece by means of one or more adapted toothed wheels through a single radial feed motion.

Figure 2-14 Sheet metal forming internal and external tooth workpiece

2.3.8 Bellows spinning

The bellows type energy-saving heat exchanger has the characteristics of high heat exchange efficiency, small volume, light weight and self-absorbing thermal deformation, and is well received by users. At present, the production methods of various heat exchange bellows are welding, hydraulic pressure, molding, rolling, etc. These processes have problems of complicated equipment, narrow application range and high cost. The spinning forming heat exchange bellows is a kind of New processing technology. Since its invention in the early 1990s, its products have been widely used.

The spinning process is shown in Figure 2-15. The process elements are the shape of the rotary wheel, the feed speed of the rotary wheel, the spindle speed, the heating temperature and the heat influence range, and the single-wave axial compression amount Δl (refer to each forming one) Waveform, the compression length of the tube blank along the axial direction, which is the key parameter affecting the shape of the corrugation and the thickness reduction of the local wall thickness. △l is too large, which will cause the tube blank to bend and destroy the formed waveform, △l is too small, The local wall thickness reduction is increased). It is easy to produce a diameter reduction effect in the spinning, resulting in a partial wall thickness. The main product factors are straightness, pitch accuracy and depth of field accuracy (Figure 2-16).

1 Spindle 2 Bellows 3 Spinning wheel 4 Heating mechanism 5 Pressure mechanism

Figure 2-15 Principle of bellows spinning

图2-16 波纹管

2.3.9 异型件旋压

图2-17 旋压异型件

钛合金气囊内胆属航天飞行器配件，工件图如下。

图2-18 钛合金气囊内胆

该气囊所用材料为TA7，这种材料的机械性能σb=785Mpa，ψ=25%，板材壁厚为1.5，要求普旋时壁厚减薄率不大于8%。由于材料强度高，断面收缩率小，形面复杂，在成形时存在较大的困难。

分析该工件结构为两片完全相同的半环型薄壁件焊接而成，因此，如果能旋压出半环薄壁件再焊接即可，考虑到形状的复杂性，采用分模旋压方案，先旋出半环内形面（图2-19-a为内形面旋压模具），再换装外形面旋压模具（图2-19-b为外形面旋压模具），旋出外型面。

a shape of the inner surface spinning mold b shape surface spinning mold

Figure 2-19 Titanium alloy bladder liner spinning mold

The material used for the missile nose cone is 6061 aluminum alloy. The workpiece and process are shown in Figure 2-20.

Figure 2-20 Missile nose cone

The main process of the workpiece is blanking I-sheet stamping II-shear spinning III-shear spinning IV-shear spinning pressure V. Since the sheet feeding state is T6 state, the material elongation rate is low, which is not favorable for bearing. Larger pressure processing, so the material is completely annealed before spinning to reduce the spinning deformation resistance and improve the plasticity of the material. At the same time, the intermediate annealing process can be appropriately applied between the spinning passes.

3 spinning equipment

3.1 Different types of spinning equipment

Spinning machines can be divided into various types according to their movement mode, spindle orientation, number of rotating wheels, etc., and can be roughly divided into powerful spinning machines, general rotary machines and special spinning machines according to their functions. The powerful spinning machine is mainly composed of flow spinning and shear spinning. The equipment requires high dynamic and static stiffness, and the rotating pressure and spindle torque are large. The general-purpose machine is mainly formed with a complex curved-mesh-shaped workpiece of colored metal, and the rotating head of the equipment is less subject to the rotating pressure. The special spinning machine mainly undertakes the workpiece processing tasks of one or less kinds of similar structures, such as a gas cylinder closing machine, a hub spinning machine, a belt spinning machine and the like.

3.2 Key device of spinning equipment

3.2.1 Control system

The earliest spinning machine mainly relied on manual control of the trajectory of the rotary wheel, which required high technical requirements for workers, poor consistency of the workpiece and low efficiency. Later, using analog electric signals, PLC and other control parameters of the spinning machine, the automation of the spinning machine is greatly improved, and mass production can be realized. With the rapid development of professional technologies in the field of electronic power microelectronics, the recording control rotary press and the digital control spinning machine have appeared. This is a big advancement in the control mode of the spinning machine. The recording and returning spinning machine only needs The manual spinning process of the workpiece is taught to the spinning machine control system. The recording system will automatically process the same product in the same path through the “memory” function to achieve automatic mass production. The current CNC spinning machine has more auxiliary functions, such as automatic loading and unloading, automatic changing of the rotating wheel, constant line speed, etc. The control system with more installed capacity is SINUMERIK 840D, FAGOR, etc. The 840D has 6 channels and 6 spindles. Each channel can realize the function of independent movement of each linear axis.

3.2.2 Power System

Spindle simulation and digital frequency conversion realize stepless speed change and constant line speed. Spindle DC and AC variable frequency motors can provide large torque. The linear head of the rotary head is powered by a high-precision ball screw by a servo motor, and is determined by a semi-closed loop control method using a rotary encoder, or by a full-closed control method by a straight line and a circular scale; the linear axis of the rotary head can also be used. The hydraulic motor and hydraulic cylinder are controlled by proportional-servo valve to meet the large screw pressure requirement. In order to improve production efficiency, advanced technologies such as more advanced linear motors and electric spindles will be continuously applied to spinning equipment, thus providing conditions for theoretical research on plastic deformation of high-speed and ultra-high-speed spinning materials.

3.2.3 Spindle box and guide rail

Due to the small infinitely variable range, the mechanical gear shifting mechanism is often added to expand the spindle shift range. The typical transmission scheme is the variable frequency motor-gearbox-spindle box, which is adjusted by the shifting mechanism to achieve the shift range adjustment. Infinitely variable speed can be achieved in the shift range. Due to the support of the numerical control system, some spinning machines also have the spindle directional rotation function, which can also play a certain role in some special spinning, and at the same time can easily realize the material deformation constant line speed function in spinning.

Due to the simple structure and convenient use, the sliding guide rail has many practical applications at present, but due to the sudden change of dynamic and static friction, it is easy to cause "crawling" phenomenon and affect the stability of the equipment. Because the static pressure guide has a very thin oil film, its friction coefficient is very small, which can better overcome the creep phenomenon during the spinning process, but the roller seat is subject to a large tilting moment, the guide rail It is difficult to balance, which is easy to cause the geometric accuracy of the workpiece to deteriorate. It is currently used on some large spinning equipment. Due to the small force and high rigidity of the rolling guide, the practical application is not much.

3.2.4 Rotary wheel seat and rotary head

The rotary wheel seat has an integral structure and an open structure. The integral type usually has the respective rotating wheels mounted on the same frame mechanism, and the axial movement of each rotary wheel is controlled by the same signal and driven by the same power, thereby eliminating the synchronization error and being able to rotate in a large rotation. Stable work under pressure. The open structure has high flexibility and can realize multi-wheel multi-path synchronous spinning. In the general rotation and special equipment, the open structure is more used. The disadvantage is that the rigidity is poor, the spinning pressure can not be too large, and the rotary head is more Easy to shake.

According to the number of installation wheels, the rotary head has several wheels, two wheels, three wheels and several wheels. The automatic rotary wheel can be realized on the more advanced spinning machine. The single wheel mechanism is simple, flexible and convenient to use, and the two-wheel, three-wheel and multi-wheel can realize multiple thinning by the wrong-spinning in one spinning, thereby improving production efficiency.

3.2.5 Spinning tooling

The mandrel is an indispensable process equipment in the mold spinning, mainly bearing the strong spinning pressure during spinning, supporting the deformation of the workpiece, ensuring the inner wall surface of the workpiece, and forcing under the joint action of the rotating wheel The material yields deformation and is subjected to large friction during the deformation process. Therefore, the core mold is required to have high strength, rigidity and hardness, and the hot-spinning core mold should also have high heat resistance. The material should be made of various tool steels with quenching hardness between 50 and 60 HRC. The structure is a simple rotary body, which has an internal cooling type, an automatic unloading type, a combined split type and a simple integrated structure. The determination of the diameter of the mandrel should mainly consider the rebound and expansion and contraction of the material after the workpiece is spun.

The rotary wheel is in direct contact with the outer surface of the workpiece and is subjected to great friction. The rotary wheel is required to have a high hardness (HRC 55 to 65), a smooth finish, and a rounded corner accuracy. The rotary wheel can be divided into a circular arc type, a double cone surface type, a step type, etc. (Fig. 3-1), and the round corner radius rρ of the circular arc wheel is an important factor affecting the spinning quality, and the commonly used range is

Rρ ≈ (1~3)t0

图3-1 旋轮形式

The double-cone surface and the step-surface rotating wheel have two forms: a light-spun whole section and a non-light-completed section. The double-cone surface rotary wheel has a simple structure and a large versatility, and is generally applied to the spinning of a cylindrical member, and the main forming parameters are mainly used. For the forming angle αρ and the fillet radius rρ, the forming angle is generally 15°~45°. If the forming angle is too large, the material bulging and stacking tendency tends to increase before the rotating wheel, and it is easy to destabilize and pull, too small and easy to expand. The function of the smoothing section of the rotary wheel is to reduce the surface irregularity of the workpiece by utilizing the elastic recovery effect of the material. The existence of the smoothing section reduces the radius of the round corner of the rotary wheel and also improves the forming accuracy of the workpiece. The stepped wheel is a guide section added in front of the double-cone rotor forming section to prevent material from bulging, stacking, and sometimes pre-forming.

The model is applied to hydraulic equipment without CNC and profiling devices, which plays an excellent role in the traditional hydraulic equipment and increases the spinning range of the equipment.

3.3 Special spinning equipment

3.3.1 Wheel spinning machine

With a high degree of automation, it is a key equipment in a large-scale production line, which can produce a production cycle of 2 to 4 pieces per minute. It has two structures, vertical and horizontal. The rotary head can be fed positively and negatively at high speed. The roughing and finishing process can be completed in one step, the auxiliary process is less, and the product quality and efficiency are higher. 2).

Figure 3-2 Wheel spinning machine

3.3.2 Belt spinning machine

Most of them are vertical spinning machines. The diameter of the spinning pulley can be produced from 40~450mm. The structure is single wheel, double wheel and three wheel. In the past, China mainly relied on imported special belt spinning equipment (vertical structure), and now it has basically realized localization, and has formed several automatic production lines of various specifications to provide domestic demand for tens of millions of pieces. The performance of the equipment has basically reached the advanced level in foreign countries, and it has the characteristics of good rigidity, high precision, good reliability, advanced control system, convenient debugging, high production efficiency and beautiful appearance.

3.3.3 gas cylinder hot closing spinning machine

The main feature of the hot-spinning spinning machine is that it can realize the three-axis linkage operation of two linear axes (x, z-axis) and one rotating shaft (B-axis), and also has a heating function, and is equipped with an automatic loading and unloading device. It can be used for closing the bottom, reducing the diameter and bending the curved arc. The main shaft, the tail top, the wheel base and the rotary handle are forced cooling, which can automatically control the ignition, flameout and blank temperature maintenance. Some equipments are equipped with optics. The temperature monitor is used to control the temperature very well, and the heating is generally performed by flame or medium frequency induction heating. At present, the application of domestically produced equipment has gradually increased, and several gas cylinder production lines have been formed in various regions such as Northeast China, Beijing, and Shanghai to meet the needs of domestic and even foreign pressure vessel markets. Figure 3-3 shows the cylinder hot-spinning spinning machine.

3.3.4 Other special spinning machines

There are two main types of large head spinning machines, namely the "two-step" forming (pressing drum + spinning and flanging) spinning machine, and the "one-step" forming (multi-pass universal forming) spinning machine. Mainly composed of the fuselage, spinning roller, forming stick, top tightening, power mechanism, control system and so on. The core of the combination is the combined motion trajectory of the spinning roller and the forming roller. Figure 3-4 shows the head spinning machine.

Figure 3-4 Head spinning machine

The turning and crimping spinning machine processes the workpieces of different shapes through the rotation of the turntable. The pressure wheel mechanism is the key core technology. The calculation of the motion track is complicated, and the spinning pressure of the spinning arm is relatively small, but the requirements are The spinning mechanism is sensitive and rapid, the forming is simple and quick, the product performance is improved, the production efficiency is improved, and the cost is reduced.

In recent years, China's demand for large-scale heads is increasing. The development of domestic head spinning equipment has basically met the development needs of the domestic market. With the support of national policies, through the research of recent decades, large-scale head spins have been improved. The pressure equipment has basically achieved localization.

4 Differences in spinning technology and equipment at home and abroad and their respective characteristics

Compared with the advanced level in foreign countries, the development status of China's spinning technology has a certain gap in terms of product type, dimensional accuracy, equipment capability and automation degree, as well as in process theory research. Many scientific and technological workers are working on this research work, and have made great progress in the past 20 years. Many products have precision and performance close to or reach the advanced level in foreign countries. A few domestic institutions of higher learning, such as Harbin Institute of Technology, Beihang University, Xigong University, etc., as well as some powerful research institutes have been developing CNC spinning machines, and theoretical discussions and development of new processes. Especially in recent years, some factories in China have introduced advanced CNC spinning machines from abroad, which has made China's spinning technology more and more mature. Many domestic research institutes (such as Beihang Modern Technology Research Institute, Heilongjiang Spinning Technology Research Institute, Changchun 55, etc.) have developed more stable and reliable types of spinning machines, which have a certain share in the domestic market, but some The model still relies on imports.

In the field of spinning, foreign countries not only have advanced equipment but also master the spinning technology of mature systems. For example, LEIFELD's ST56-75NC three-wheeled powerful spinning machine can perform a variety of high-precision thin-walled cylindrical parts with a variety of curved busbars. The largest 400T two-wheel vertical spinning machine in the United States can process any alloy cylindrical parts. The wall thickness tolerance of some precision parts can reach 0. 38mm and the surface roughness Ra3.2. Japan's Toshiba Machine Co., Ltd.'s high-efficiency spinning machine combines hydraulic profiling with CNC to hot-screw high-pressure cylinders of various shapes.

In addition, spinning technology in many developed countries, especially in the United States, Japan, Germany, etc., is improving day by day, both in terms of equipment design and manufacturing, theoretical and technological research, and application of spinning technology. China's spinning technology began in the early 1960s. After decades of efforts, China's theoretical research on spinning technology equipment and spinning process theory (such as stress-strain finite element analysis of spinning process, new process new method) And the theoretical exploration and research) has made a lot of progress, making the application of spinning technology more and more extensive, but still can not adapt to the needs of China's national economic development, especially in the theoretical research is still a weak link, which has become a high-end affecting China The equipment use efficiency and spinning process further promote the application of constraints. Therefore, strengthening the theoretical research of spin forming technology and establishing the basic data of the system is an important part of the development of spinning technology in China.

5 Discussion on several problems in spin forming technology

5.1 workpiece surface roughness problem

Surface roughness is the main parameter to measure the surface quality of the workpiece. It usually refers to the arithmetic mean deviation Ra of the contour, that is, the arithmetic mean of the absolute value of the contour offset within the sampling length L:

All the spinning parts are processed by the method of not removing the material, and the original outer surface roughness is required. Usually, the value is taken as Ra3.2~12.3, which has become a convention in the spinning boundary, but the parameter is analyzed in detail. It does not reasonably reflect the quality of the outer surface of the spinner. As shown in Figure 5-1.

图5-1 旋压件表面微观粗糙度分析

a is the distance between adjacent spinning dents when the spinning feed rate is f (mm/n), h is the height of the dent between the dent and the dent, and the value of h does not change during the same spinning process. Calculate the roughness of the spinning part according to the definition of roughness

According to the actual situation, if f=1.0mm/n, that is, a=1mm, the angle of attack of the wheel is 30°, and the actual drawing knows that h=0.042mm, then Ra=0.042mm=42μm, that is, the roughness is Ra42, which obviously does not Reasonable, so the traditional roughness calculation method can not effectively reflect the surface quality of the spinning parts, so a special parameter that can accurately reflect the surface quality of the spinning parts is needed.

Analyze the surface texture characteristics of the workpiece and propose the concept of spinning the workpiece. For the surface roughness of the spinning workpiece, the roughness is expressed by the degree of rotation.

Among them, 5L is the standard evaluation length, generally L=2.5mm, and 1% is the optimization coefficient. The degree of spine can be used to accurately represent the quality of the outer surface of the spinning workpiece, and the degree of integration of the height, width and density of the spine can be clearly expressed. Like the example above,

That is, the degree of rotation is 5.25. This is a comprehensive evaluation parameter. The larger the value, the rougher the swirl and the worse the surface quality.

5.2 High speed spinning

At present, the spinning plastic deformation speed of almost all rotatable materials is in a relatively low state. The rotation speed of the core mold is generally between 50~300 n/min, and the feed ratio of the rotary wheel is less than 2mm/n. It is recommended to develop a new high-speed rotation. Pressing equipment, in the spinning of non-ferrous metals (with and without mold), the spindle speed is increased to 500n/min or higher, even higher than 1000n/min, and the deformation law of high-speed spinning state of non-ferrous metals is analyzed. In order to open up new research directions for the precision control of the general-purpose non-ferrous metal in the future.

6 Spinning equipment and technology outlook

In order to meet the needs of China's industrial production development, we should continuously improve the stability of the whole machine system and the advanced nature of the control system in terms of equipment, and develop towards large-scale, serialization, high-precision, multi-purpose, multi-functional and automation. And continue to develop new spinning products, expand the application field of spinning technology, develop new spinning equipment, increase the automation of equipment and industrial production lines, and continuously improve the forming quality of products (such as dimensional accuracy and shape). Accuracy, surface quality and performance, etc., focus on the development of complex curved busbars, different cores and combination of new products, composite manufacturing of various materials, such as composite spinning, spinning, and various materials. The theory of deformation mechanism and experimental research will be intensified, and a more comprehensive, systematic and reliable spinning foundation theory and quality control system will be formed as soon as possible, and the development of comprehensive intelligent spinning will be gradually carried out, which will be machine, electricity, liquid, microelectronics, Advanced technologies such as light, detection, sensing technology, and artificial intelligence are applied to spinning technology to establish a general-purpose spinning parts manufacturing System, so that can automatically identify product drawings and status, automatic spinning rough design, planning and manufacturing solutions, process intelligence establishment, automatic optimization of process parameters are adjusted.