Research On Continuous Multi-point Forming Method, Equipment And Experiment

The three-dimensional (3D) surface parts have the character of thin shell, because of the merits of light weight, saving material, good force state and fluent geometric modeling, they are been widely used as the main components in civilian products, military products and high-tech product manufacturing. For a long time, in order to solve the difficult problem of forming the 3D surface parts, some flexible forming methods are developed. The flame bending which is the most widely used method for the fabrication of the ship's hull, but it has the disadvantages of low efficiency and poor quality, and it also depends on the experiences of the operator, so it needs more advanced technology. The peer forming is widely used for the fabrication of 3D surface parts in the airspace; it also has low efficiency, and needs better forming method. The multipoint forming technology has been used successfully in the 3D surface parts forming, and has solved many problems of forming 3D parts, but being a large forming device, it needs lots of capital, so many enterprises looking forward to a more affordable, efficient flexible forming equipment.Continuous Multi-Point Forming (CMPF) is a new technology for forming the sheet metal, its main principle is setting a series of adjusting elements on the bendable roller, through the rotation of the bendable roller, the sheet metal can be fed and realize the dieless, continuous and flexible forming. Through the combination of adjustable bendable rollers with different amount, different disposal and different rotation direction, it can realize many types of 3D surface flexible forming such as roll bending and spinning. Compared with the traditional method of die forming, it saves the time and money spent on the dies, realizes the true continuous and flexible forming, so it is of high value in engineering application and academic research.In order to realize the continuous line forming based on the CMPF, the roller is needed to fabricate the sheet metal by roll-bending. This roller must be bended and adjustable along the axis of the roller, and has rigid and strong in the circle of the roller, which can ensure the sheet metal deformed. So the key of the CMPF is on the framework design and control of the flexible roller. This paper proposes the steel wire applying to forming the sheet metal by comparing with spring roller, the polyurethane flexible roller, gimbals'roller and the steel wire roller, puts forward the idea of the bearing with the open, studies the adjustable method of the flexible roller and gives the path of adjustable flexible roller.The main researches are shown in this dissertation as following: 1.The novel CMPF method is proposed in this paper firstlyThrough the analysis and comparison of the general forming methods, the forming method can be divided into the whole forming and the local forming. Based on continuous or discontinuous forming, the local forming is divided into the continuous forming and the section forming, based on the deformation region, the local forming is also divided into point forming, plane forming and line forming. Through comparing with the efficiency of point forming, plane forming and line forming, line forming is the high efficient method. And the bendable and controllable forming instrument named flexible roller being applied to forming the 3D dimensional sheet metal is proposed. This technology not only realizes the deformation on the longitudinal direction, but also the deformation created on the transverse direction with the shape of the bendable roller. The principle is shown, based on the bendable and adjustable flexible roller. the forming method of roll bending and spinning has be analysis, through the different arrangement of the flexible roller. the theory of the deforming mechanism applied the bending sheet metal is analyzed for supporting the CMPF.2. The main parts design for the CMPF deviceIn order to realize roll bending and spinning by the CMPF, the main parts of the CMPF device is studied. The kinds of projects using the bendable and adjustable roller are analyzed. The merits and the defaults are displayed. Because of the steel wire having the good flexibility, high defense impact and the good transmission, the steel wire is selected as the flexible roller. And the steel wire is studied. An example of steel wire is designed. The principle of the open bearing is introduced and the open bearing component is simulated, the result of the simulation of the open bearing is proved that the open bearing can be satisfied to all devices with the CMPF. And the adjustable way is studied, two ways are shown. The adjusted amount is researched for the basic of manufacturing a new device.3. The 3D surface roll bending deviceKinds of roll bending projects based on the CMPF are shown, and the best project is selected to manufacture the roll bending device. The device mechanism, the main parameters and the structure characteristic are shown. The main structure is studied. The result is shown that the idea of feeding that creates by the chain driving the top splint move down is right. The two procedures including the continuous multi-point prior adjusting and the continuous multi-point real-time adjusting are given for forming the sheet metal.4. The experimental research on roll bending formingThe processes and the results of forming different curved surface parts by roll bending device are shown, and the effects of the sheet metal parameters and the process on forming the sphere parts are further studied. The results show that the thickness of sheet metal has a great influence on the forming of sphere parts, the thicker sheet metal parts result in the better forming quality. Then the effect of sheet metal breadth on the forming quality is researched, it shows that on the condition of the same thickness, along with the increasing of the sheet metal breadth, the vertical and horizontal rebound decrease accordingly, and the forming resistance increases gradually. The influence of one-step forming and the step-by-step forming on forming quality are also studied, and the result shows that one-step forming is usually applied to the forming of smaller vertical press displacement and greater stiffness, and the step-by-step forming is usually applied to the forming of bigger vertical press displacement, smaller stiffness and high accuracy. After studying the effect of rolling times on sphere parts forming quality, we know that the average curvature of the formed parts increases along with the increasing of the rolling times. And the average curvature of the formed parts will stabilize when the rolling times achieve a certain value, and it will not change along with the rolling times. The finite element numerical simulation on the forming of sphere parts and saddle parts have been done, and it shows that the forming quality of saddle parts is better than that of sphere parts.5. The efficient spinning forming deviceDiversiform projects of spinning forming device based on the CMPF are shown, after the analyzing and comparing of all the projects, the three roller project is selected because of its merits of simple and feasible. The general layout, operation mechanism and equipment parameters of spinning forming device based on the CMPF are given. By combining the projects of using the divided three-roller system rotating differently to form the disk parts and using the three-roller system laid symmetrically to form the cylindric parts, combining the flexible roller system rationally and the distributing the driving force scientifically, the disk parts and the cylindric parts can been formed by the same spinning forming device. The press displacement feeding device and the top splint are designed and analyzed. It shows that the top splint will get distortion when the forming force acting on, but the distortion is in the scope of the permit. And the top splint cantilever has an up displacement, but it is far smaller than the allowed error, so the design of top splint can meet the need of the device.6. The experimental research on spinning formingThe processes and the results of forming different curved surface parts by spinning device are shown, and the effects of forming process on the decreased of parts thickness is studied. Through forming a disk part as an example, the different thickness decreased rate brought by different deformed area transformation is studied. It can be seen that when the deformed area radiates form center to brim, the thickness decreased rate is higher than that of the deformed area radiates form brim to center. The effect of friction coefficient on the dick parts thickness decreased rate is also researched, and the result is shown that reducing the friction coefficient can reduce the parts thickness decreased rate, but if the friction coefficient is reduced overfull, the parts rotation will be affected. The effects of press displacement on forming the cylinder parts during the spinning forming is discussed, and it can be conclude that the appropriate adjustments of press displacement can make the sheet metal formed slowly and equally and optimize the forming process.Compared with other conventional methods of forming 3D surface parts, the CMPF can not only realize the continuous and flexible forming, but also has the famous characteristics: high production efficiency, high forming precision, good production environment, low energy consumption, low production cost, simple equipment structure, few control points and the digital and intelligent production can be achieved easily.The CMPF is a new flexible forming method. With the further study in the future, the structure of the CMPF equipments will be perfected, the characteristics of continuous and flexible will be exhibited further and the production and applying of the CMPF equipment will be realized.