Incremental Sheet Forming - Essay Example

INCREMENTAL SHEET FORMING By Presented to Table of Contents INCREMENTAL SHEET FORMING 11 1 FORMING:- 11 1.1 SHEET FORMING:- 12 1.2 FLEXIBLE FORMING:- 13 2. INCREMENTAL SHEET METAL FORMING:- 13 2.1 General characteristics of Sheet Metal Forming:- 14 2.2 Mechanism of incremental Sheet forming:- 15 2.3 Principles of incremental sheet metal forming:- 15 2.3.1 Processing Stage:- 15 3. Types of Incremental sheet metal forming:- 16 3.1 Single Point Incremental Forming:- 16 3.2 Two point Incremental Forming:- 17 4 Advantages and Disadvantages 18 4.1 The main advantages of the SPIF Process:- 18 4.2 The main disadvantages of the SPIF Process:- 19 4.3 Advantages of Two point incremental sheet metal forming (TPIF):- 19 4.4 Disadvantages of Two Point Incremental Forming are:- 20 5 Influence of Process parameters:- 20 5.1 Tool Paths:- 20 5.2 Vertical Step Size:- 21 5.3 Tool Rotation:- 21 5.4 Tool Diameter:- 21 5.5 Effect of Wall Angle:- 22 6 Conditions for data Processing:- 22 7. Viability 23 7.1 Mechanical:- 24 7.2 Economical:- 24 7.3 Ecological:- 25 8 Applications of Incremental sheet metal forming process:- 26 8.1.a Application of ISF in Non-Automotive sector:- 26 8.1. b Application in Non-Automotive sector:- 27 8.1. c Application in the Medical field:- 28 8.2 Applications of ISF in the Automotive sector:- 29 8.2.1 Applications of ISF in Prototyping:- 29 ISF Automobile part:- 30 9 Conclusions:- 31 References 0 INCREMENTAL SHEET FORMING 1 FORMING:- Forming process involves metal piece modification or a sample by subject deformation, i.e. With the omission of any material through removal. The job is done via pressure or heat, or mechanical power. There is a possibility of using both. The process of forming sheet metal involves mechanical energy use at room temperature. They contain various operations such as coining, bending, rolling, drawing, pitch bending and roll forming among others Fig 1 Forming Processes. 1.1 SHEET FORMING:- The film forming has a number of different procedures of forming that have been used. The production of a sheet metal is usually done with dies or punches, which are processed with accordance of the unit’s proportions and shape. The manufacturing process is desirable for mass production because of the shared value of dies and punches with production of a large number. The performance of film forming distinct rolls to achieve a particular image was done in the past. This process is known as sheet metal rolling, but the process is possible for production of natural shapes. Therefore, the search for new sheet metal forming solutions has been started. The developments took the route of searching for new shapes of rolls, which in turn paved a way for new forming scopes. (Mecanica 2009) However, in a severe world industrialization competition, there is the need to obtain the demand for increasingly complex shapes. For the demands of complex requirements, metal plate stretching attempts have been made by outstanding prototypes, to reach the final shape. In order to contour the high volume demands, the use of presses for short lead times and production costs began. The main benefits of this method is the need for the formation of a significant essential tool for the plate formation. This increases cost of the tool, as a result of high production costs. The presses system establishment is suitable for mass production. Nevertheless, in the current global fierce competition, there is a need for more and more products that are complicated by the demand. For the achievement of the final requirements, attempts for sheet metal extension on exceptional prototype have been made to achieve the optimum shape. The formation of stretch metals on presses was adopted to handle mass production demands with more batch measurements at lower costs of manufacturing. However, the system was disadvantaged in that every product needed a specific tool, for the sheet metal development. This increases the device costs which results in higher production costs. Therefore, presses forming can be appropriate only for mass production. There is a constant need of prototype development because of the creation of new products each day by the industry. 1.2 FLEXIBLE FORMING:- There has been a shift of focus towards processes of plastic forming that are more suitable for products that are customized in the past few decades. This resulted to the starting of different processes where forming was done without the tool or through a cheaper supporting tool than the original tools. After the development of this issue, the Incremental sheet forming process had been started and was widely researched. This procedure is performed on a CNC milling machine-tool with CAD/CAM computer support. 2. INCREMENTAL SHEET METAL FORMING:- Incremental sheet metal forming is a technology that uses innovation and high elastic forming. It creates new dynamics of metal forming. The ISF process is based on the layered manufacturing concept, in which there are straight slice divisions of the model. The process involves the use of a slick instrument that is spherically headed or a ball ended. The definition of the trajectory along which the device should go is guided through an NC computer program allowing the device to carry in 3-D space. The tool moves downwards, contacts the plate, then draws a horizontal level curves and then makes a move downwards, draws the following contour in a sequential manner. The trajectory that the tool should go along is defined directly from a CAD model that is made. The rotation of the tool can be done to create local deformation and a desired shape creation, by sheet metal, deepening. The process depends on the machine-tool’s ability to withstand the forming loads. The chucking of a sheet metal component all around with a significant chuck acts as work piece and is clamped in the holder. The experimental setup is shown in Fig. 1. The handy plastic deformation is caused by the force between the tool and the workpiece, enabling the creation of a 3-D account by the progressive movement of the tool against the work piece. This process avoids the need for expensive dies. (Bramley, Brissaud, Countellier & McMohan, 2005) Incremental sheet metal forming using a stiff device is not a new methodology of sheet metal forming because some traditional processes may be also called incremental sheet metal forming processes. The typical example of this case is Spinning. Fig 2 Spinning process. This involvement of a roller and a mandrel in the process where the clamping of the specimen is done. The designing of the mandrel is aimed at a shape of a product while the roller is common. Pushing the roller against the rotating mandrel hence deforming the sheet metal. Through this method, only axis-symmetrical parts could be formed in relation to the mandrel shape. The other case is hammering, where the forming process uses a number of hammers and simple-shaped dies. The two processes are normal and used for products manufacturing design . However, they have also been employed for prototyping of different shapes in automotive and craft industries. The small batch and prototype production are manufactured through traditional technologies that are hugely expensive and demanding when compared to incremental sheet metal forming. Currently, the development of incremental forming is focused in traditional procedures modernization and new system expansion of sheet metal forming. 2.1 General characteristics of Sheet Metal Forming:- Sheet metal parts are made by forming material, in certain circumstances such as like cold or humid conditions. Large volume sheet metal parts can be formed in a hot condition as it has a lower resistance which leads to deformation when the product is heated. Sheet metal forming techniques is used in mass production. Some of its features are high yield, easy maintenance, high quality long life and clear geometrical accuracy. The following chart shows the general characteristics of the process of plaque formation. Each approach has different properties from those of others.(Verma & Bhattacharjee 2008) 2.2 Mechanism of incremental Sheet forming:- This operation can be done on a standard milling machine with the help of CNC machine. It uses a rounded ball point tip which is called as Burnishing tool. The tool can be made easily with the CAD/CAM design. In the process contact of the tool to the metal sheet formation, it draws an image on the metal and the next contours are done according to the trajectories given by the CNC. This device’s earlier days, the method was tried without the help of any supporting tool where only natural forming configurations could be achieved. Later on, better results could be achieved through the help of a support. 2.3 Principles of incremental sheet metal forming:- 2.3.1 Processing Stage:- Primarily, the 3D CAD model of the calculated plate deformation either by positive or negative die has to be obtained by the software. It is then converted into design solutions and image positioning by the restricted software regularly by LS-DYNA. The final product is then milled by the tool. These approaches are 2 types:- Asymmetric Positive support:- This process entails deformation of the sheet metal fairly. Here, tool gets in touch with the sheet metal and slides to the Z axis and progressively takes the vertical deformation that is termed as step size (∆h). The deformation is carried from the ultimate position of the metal and consecutively contours to the centre. Fig 3 Positive support Asymmetric Negative Support:- This method employs the same process as the previous one. However, the only difference is that the final product form is produced via vertical step size in negative deformation. The deformation in this procedure is done in a spiral manner from the centre of the work piece to the edges.(Grote & Antonsson, 2009) Fig 4 Negative post 3. Types of Incremental sheet metal forming:- This method is only limited to small size pack productions. It also plays an important role in complex shapes and sizes pattern which can be achieved easily with a simple tool and the support of some specification supports. The CNC system gives the route for this method. The forming process via incremental steps with certain parameters, with or without a support of a number of contact points in the system are classified into two varieties. The two incremental sheet metal forming types are:- 1) Single Point Incremental Forming (SPIF) 2) Two Point Incremental Forming (TPIF) 3.1 Single Point Incremental Forming:- This process is known as Die-less forming because it does not use any die or aid in its process. This benefit makes it cost effective and operationally supremely flexible. There is an increased representation relationship within this method better than many traditional processes. Moreover, it also has some limitations in terms of geometrical accuracy. This problem’s solution can be achieved through further investigations and the geometry of the final outcome can be improved through the use of step by step SPIF. (Banabic, 2007) Fig 5, Single point incremental forming In this method, the sheet metal is clamped tightly to the holder tightly, and the deformation is done from the extreme point of the sheet with some minimum allowance distance to clamping which does not lead to the product failure. The contours are drawn by the trajectory fed by the CNC machine. This forming model has several research and analysis in process currently. 3.2 Two point Incremental Forming:- This method uses a partial die, or little help to make the final shape of the product. It usually tends to provide much better geometrical accuracy because the deformation is done between two set points. One near the contact metal tip and the device while the other between metal and the support. This method has a slight edge on SPIF because of its finest geometrical precision than the other processes. However, it affects shrinkage in the sheet formability. This benefit makes it more convenient for commercial purposes where the priority is in forming complex shapes. Fig 6, Two Point Incremental forming In this process dies is done with cheap materials like wood or epoxy resins. Die can take the place of either negative or real form. If the die is certain, the blank housing needs to be moved in Z direction is to adjust with the positioning with the tool. The different tool paths can be used for this die. The two commonly used are contours with categorised constant step size which have series of incremental constant height. The second is a variable step size but with the same toolpath employed with a set of contours. In some way, this would be an advantage as it minimizes the scallop pattern thus improving the final product’s top condition. This process opened ways for many modern forming techniques that have higher product quality. The techniques have been researched proving that complicated shaped and perfect geometry tolerances can be achieved. However, the cost of this process in comparison to the other one is ideally more expensive. This is because of die or partial support consumption and also the use of specific individual die for each piece that is to be formed for limited flexibility issues in this process. Even though Incremental sheet forming is a die-less approach, we only consider this TPIF as ISF process because the forming method of the material is in an incremental step till the final appearance is achieved. The process can be done in a series of steps with the screen position being considered as it plays an enormous role. (Davim, 2013) 4 Advantages and Disadvantages 4.1 The main advantages of the SPIF Process:- The following are the main advantages of SPIF:- 1. CAD can be used to calibrate and render Operational parts directly. 2. A specialized hemispherical round tip forming device known as Burnishing tool is required for the process. 3. The component geometry can be improved by manipulating the system parameters into considerations. 4. The process can be used for Rapid Prototypes or small volume production. 5. Because it does not have die in this process, there is a potential drastic reduction of value if the method is employed. 6. It does not require either positive nor negative dies so it is die-less forming, though it requires a base plate to provide a clear angle difference at the film surface contact area. 7. The start-up Rapid Prototypes designs are usually solid, but can be easily processed through this process. 8. It has a high degree of flexibility which is useful in complex models production with different dimensions. 9. It has a small plastic deformation because it is a step by step process also it can achieve higher strains. 10. It is particularly helpful for the development of deep formability materials due to its ability to achieve higher formability. 4.2 The main disadvantages of the SPIF Process:- The following are the main disadvantages of the SPIF process:- 1. The deformation time is exceedingly high in comparison to other traditional methods. 2. Occurrence of Springbuck. 3. The forming must be done in several stages, in order to get the final product in 90 degrees; however, it is not suitable for steep angles achievements in one step. 4. It is only preferred for small group sizes that are not more than 1200. 4.3 Advantages of Two point incremental sheet metal forming (TPIF):- The main advantages of TPIF are as follows:- 1. It can be used to perform complex shapes. 2. Better geometrical accuracy can be achieved because the plate is fixed and is transferable. 3. It uses dies therefore no failure if we tried for high wall angles. 4. More formability is achieved. 5. The process can be done on regular milling machine. 6. The process is comparatively extremely low in noise when considered with other forming processes. 4.4 Disadvantages of Two Point Incremental Forming are:- 1. The process is expensive, because of support or a qualified die use in place. 2. It is always short on rigidity in the existence of the die. 3. Has a spring-back effect. This effect is a very common in these kinds of process. Precautionary steps are usually taken to counter this effect prior to the forming starts. The program should be calibrated in such a way that we can get the final geometry within the allowable limits. 5 Influence of Process parameters:- There are many exercise parameters which affect the outcome of the product. In this effect, it is necessary to tackle them one by one. 5.1 Tool Paths:- Fig 7; Toolpaths Tool paths play a vital role in forming Incremental sheet metal. The way the device makes the path over the sheet decides the geometry and can also affect the outcome of other process parameters in doing so. The ways of contour drawing are numerous, and it depends on the specifications. The work item is usually set at a particular distance from the blanked edges to take care of the deformation stresses at the edges. The trajectories can originate from either the corner and take a step size of (∆h) and can continue forming from the same step at a relatively recent area. However it can also arise from nucleus and can be done sparingly while the tool rotates in the anti-clock direction. It can draws contours from anywhere on the sheet. The most influential factor in this is the preferable step size employed. (Luo, 2014) 5.2 Vertical Step Size:- Fig 8 ; Step size This is another method framework which highly instigates the product manufacturing time. Increasing the deformation step size is reducing the geometrical accuracy. Selection of absolute vertical step sizes is extremely crucial because extremely low values results to a higher number of steps in the process by several times. It leads to higher simulation time. 5.3 Tool Rotation:- Tool rotation forms an pivotal role also in the surface quality of the finished metal. Low and medium rotational speeds are employed to achieve finer results and reduce stresses. If the procedure is performed with high speed, there will be fracture change or forming that are unsettled at some places. The rotational speed, therefore, should not be extremely low or unusually high, but moderate. In brief, a larger vertical step size should be taken in need of more deformation. 5.4 Tool Diameter:- Fig 9; Tool diameter The tool diameter is an significant parameter in the geometry accuracy of the product. It influences the sharpness of the product. The tool diameter would depend on the feed that is given and the necessary strength. For instance, going for a larger feed with low tool diameter would affect the staircase effect. If the use of larger tool diameter results in bluntness of the product then consideration should be taken on the diameter. 5.5 Effect of Wall Angle:- Fig 10; Wall angle Wall angle poses serious constraints to the intended shape of the product. In common practise, wall angle more than 600, are not preferred. Higher forming angles will proceed to the crack formation even at lower forming depths. Therefore, the desired product’s geometry must be at times modified with the screen angle constraints. (Lehmhus D., Busse M., Herrmann A. S., & Kayvantash K., 2013) 6 Conditions for data Processing:- After the processing of computer aided diagrams using some specific software’s like AUTOCAD, we got to examine it in the finite element analysis for production of the different kinds of stress. We use DYNA 3D to scrutinize these stresses. It is globally used software for incremental sheet forming. It is a finite element method which is remarkably effective for analysing static deformation of the object. It depends on mass and machine rate at which the deformation is taking responsibility for this analysis results. If the results are matching with the requirements, then the next forming process is taken. If not, then the variable needs to be changed. We can also increase the computing life and minimize the inertia pressure implementation that results to crash through this technology. Figure below shows how different parameters are used in forming numerical simulation. The round shaped ball pointed tool with 2mm diameter is set on the first path which is to be drawn on the sheet. The initial set point has to be 2.25mm away from the boundaries. The reason is to give some distance from the edges to eliminate the element of plate bending. Fig11; FEA 7. Viability The many advantages and limitations of Incremental sheet metal forming are in practise. Consideration should be taken to determine if this method is feasible both practically and theoretically. The process is possible though with some limitations on its back just like majorly system having its own advantages and disadvantages. There are a number of explanations as to why this is still the preferred and quickly used technique in the industry. The 3 main explanations to support this assertion are:- Mechanical Economical Ecological 7.1 Mechanical:- The Minimum requirement The Maximum requirement Maximum Dimension < ~ 20mm >~ 3m Geometrical Tolerance 0.5mm 5mm Minimum Radius < ~ 1 mm 50 mm Surface finish Good Very flavourful Wall angle 00 900 Sheet thickness 0.4 mm 2 mm With the above minimum and height requirements it can be seed clearly that the incremental sheet forming depends on many quantities and quality of work done. If either of these parameters is compromised it results in poor quality of the end product. However, if all the parameters are considered together at the same time and be processed with the limits of each other, there would be a formidable resultant output. Finally, anything done well within the desired yield range for a better product. 7.2 Economical:- Fig 12; Comparison between traditional and ISF Through the basic principal of this process, it would be economically feasible only if this method is used for small batch production. This is what is shown in the above figure. When the details of the batch size and construction cost are compared with the traditional techniques such as stamping and deep drawing, the slope of the ISF is seen as attractive constant throughout the graph. However, as the cluster size increases in a traditional method the cost per product decreases. This is because the TPIF method uses a partial die that should be made for each and every product. Therefore, this method is only possible in the case that the batch size of the production is between 200 to 1200 parts. 7.3 Ecological:- The Ecological effect concerns in Incremental sheet metal forming can be contributed through two categories. 1) Energy Savings 2) Material Savings Energy Savings Material Savings No Die required Yes, Yes, Need of transportation Yes, No Reworking instead of Scrapping Yes, Yes, Lower forming forces Yes, No Smaller machines Yes, Yes, From the above table, it can be seen as it does not require a die for the process is both energy and material assets. This is because there are no wastages of scrap items in large quantities in the process. This method can be done on a small lathe to the milling machine, which are guided, by the CNC machine. It reflects the conservation of energy and material. Moreover, transportation and forming forces do not contribute to substance saving, yet they are energy saving sources. From these defined ways, it is clear that the process can be carried out in full scale, in industrial usage despite the drawbacks and limitations. (Lefebvre, Banhart, & Dunand, 2007) 8 Applications of Incremental sheet metal forming process:- The greatest incremental sheet metal forming application can be classified into two key sectors. 1) Non-Automotive sector. 2) Rapid prototyping in Automobiles. 8.1.a Application of ISF in Non-Automotive sector:- ISF is vastly used in non-automotive fields for its compatibility in machining products, which can be used in everyday purposes. They products include solar ovens, tanks making, and seats for different purposes like bike and car seats. This process is also used mightily in the Medical sector. For, examples like knee caps, Dental plates e.t.c. Next is the processed images for this field. Fig 13 ; Applications 8.1. b Application in Non-Automotive sector:- According to research papers, the specification is that aluminium can be formed to solar oven cavity with ISF immensely economically in comparison to other conventional processes. Initially, oven pouch is designed from fiberglass and painted black. The ability to create and provide hollow formations made it easier for redesigning of other parts of the product. Fibreglass had some drawbacks with the thickness of the metal formed and also about the time taking process. However, the accuracy of the product can be improved through further research and developments. Below is the epitome of solar oven. Fig 14 ; Applications of Non-Automotive Sector 8.1. c Application in the Medical field:- One of the most prominent fields of ISF is the medical field. This field has vastly benefited because ISF can be processed either by the use of rapid prototyping or physical models. Below is a summary of how ISF is used in this sector. Fig 15 ; Applications of Medical field Explanation of the cycle above As evident in the above picture, there is a need for personal use of a right leg design. This is processed by:- First, the measurements and range of the result is obtained by scanning the spring to get a replica. Then it is processed effectively by CAD software’s such as AUTOCAD. We check for any dimensional changes that may be required before going for a solution and form positioning design by the use of software called ANYSYS. In this case, we check for any plastic deformation zones and go ahead in case of none. Later it is then simulated in CAM interface called LS-DYNA which would be an interface between CNC and the software. In accordance with the steps given in the software, forming is done in milling machine. Finally, desired output is arrived at depending on the system parameters that were taken. 8.2 Applications of ISF in the Automotive sector:- ISF is majorly used in this sector because of Prototyping. 8.2.1 Applications of ISF in Prototyping:- The main advantage of ISF can be clearly characterised in this section because of formability. This method is often profitable because any sheet material can be formed into prototypes if they are within their limits. ISF is vastly considered for the auto sector that is vastly known. This sector is dominated by many automobile giants who have ventured in it. The first patent in this area was taken by Mitsubishi way back in 1970’s. Tremendous technique and interest in this area has been depicted by companies such as BMW, Toyota and Honda. Personal works have been patented by many companies i.e. Honda is in collaboration with Amino, to have patented for some replacement parts. The companies have tried to patent for every process possible. Companies like Toyota and BMW has also filled for patents because of their field flexibility and developments. (Tichkiewitch, Tollenaere & Ray, 2007) This model was made from ISF for heat shield for exhaust manifold. Many other prototypes are depicted in the following figure. Fig 16; Applications of prototyping ISF Automobile part:- Fig 17 ; Use in Automobile Complex shapes as the above can also be done by ISF. 9 Conclusions:- In summary, the aspects of flexibility, formability and accessibility of incremental sheet metal forming are discussed above in details. This is a small batch production process that uses no dies, economically than many traditional processes. It is especially helpful for prototyping of new products as for trails in the industry, do not need to make dies which are expensive. The process can be performed by a simple tool having a hemispherical surface. This tool can be easily obtained from designing CAD/CAM software’s. Moreover, because of its formability- due to immense plastic deformation area can be achieved by having significantly higher strains. Because of all the usages it is widely acceptable in many industries especially automotive industry, medical field and also in Aeronautical industry for fuselages designing etc. This method is widely and globally used in many fields. One can get the best possible right geometrical model accurately by alternating the system parameters. To reduce the amount of work, new investigations are proposed in this field with the inclusion of traditional methods. This method is called as HYBRID technology. For this technique to create a sheet metal, it is clamped and a series of steps done. Fig 18 ; Hybrid Technology Hybrid system is first done by spell forming, giving excellent accuracy for tensile stress. The final stage of forming is the incremental sheet forming. This process progressively reduces the forming duration if employed. However, this method is still under thorough investigation. Moreover, there are lots of researches on schedule to minimize the problems, associated with the micro forming / ISMF. The main objective of the concepts is to minimize the primary process time by use of various forming zones through numerous tools that work in parallels. This gives the improved surface finish as well as sheet metal formability. The introduction of laser to enhancing the stretching ability and formability of stretch plays a greater role in the research. References Mecanica, E., 2009. Single Point Increment Forming. Available: http://Fenix.techico.ulisboa.pt/dissertacao. Last accessed 19 May 2014. Banabic D., 2007. Advanced Methods in Material Forming. New York: Springer. Bramley, A., Brissaud D., Countellier D. & McMahon C., 2005. Advances in Integrated Design and Manufacturing in Mechanical Engineering. Netherlands: Springer. Davim J. P., 2013. Modern Mechanical Engineering: Research, Development and Education. Portugal: Springer. Grote, I. K., & Antonsson E. K., 2009. Springer Handbook of Mechanical Engineering. New York: Springer. Lefebvre, P., L., Banhart, J., & Dunand D., C., 2007. MetFoam 2007: Porous Metals and Metallic Foams. Pennsylvania: DEStech Publications, Inc. Lehmhus D., Busse M., Herrmann A., S., & Kayvantash K., 2013. Structural Materials and Processes in Transportation. Weinheim: VCH Verlag. Luo, Z., 2014. Smart Manufacturing Innovation and Transformation: Interconnection. United Kingdom: British Library. Tichkiewitch S., Tollenaere M., & Ray P., 2007. Advances in Integrated Design and Manufacturing in Mechanical Engineering II. Netherland: Springer. Verma R. K., & Bhattacharjee D., 2008. Automotive Sheet Metal Forming. New Delhi: Tata McGraw-Hill Publishing Company Limited. Read More