Manufacturing Processes and Materials used in Automobile Manufacturing - Research Paper Example

 Abstract The manufacturing of car in automobile industry involves various phases and innumerable processes. Three parts have been selected namely car body panels, bumper and door handles to study their material selection and manufacturing process and to analyze them in detail. The study entails the necessity of using High Strength Low Alloy Steel (HSLA) for manufacturing of car panels through stamping process. Car bumpers are manufactured using glass fibers composites by using the process of “hand lay- up”. Car handles are manufactured through range of materials starting from plastics to metals depending upon the requirement. Manufacturing processes also vary in this case ranging from die casting to sand casting depending upon the intricacies involved and number of parts manufactured. Details of all three are discussed separately in paragraphs ahead. Table of Contents Introduction 2 Body Panels 3 Material Selection 3 Alternative Materials 4 Manufacturing Process- The Stamping Facility 5 Bumper 8 Material Selection 8 Alternative Materials 10 Manufacturing Process 10 Car Handles 11 Material Selection 11 Alternative Materials used 11 Manufacturing Process 11 Conclusion 12 Introduction The study is being done to study the manufacturing processes involved in fabricating three different parts of a passenger car and the material used. The parts selected are following 1) Body Panels 2) Bumper 3) Door Handles The study also focuses on the material properties that are essential to make these parts so that they could serve their intended purpose. Also analysis with respect to manufacturing process and material used is also done since the type of manufacturing process adopted to make a part is linked to the mechanical properties of the material Body Panels Car body panels include car hood, doors, side and back ends of a car. Following picture will clear the scope of parts that come under the umbrella of body panels. All such parts are manufactured in automobile stamping facility. Material Selection Automobile industry nowadays is posed with various challenges with respect to higher fuel efficiency while maintaining the durability of metallic structures they erect for driving. Consequently an amalgam of materials is chosen that possess required mechanical properties i.e. are strong and have minimal weight so as to keep a check on fuel consumption to carry the load. Nowadays High Strength Low Alloy (HSLA) Steels with lower thicknesses are used for manufacturing of car panels (Kalpakjian, 2010). They have higher dent strength, higher yield stress (strength) values, good toughness and better fatigue strength. Another important aspect in selecting the material for panels is its ductility so that it could be drawn into required shapes by applying different manufacturing facilities in “stamping facility”. The degree of ductility is measured through ductility diagram which has two important parameters- strain hardening exponent (n- value), plastic an-isotropy (r- value). (Kalpakjian, 2010) These factors actually determine the type of manufacturing technique adopted to make panels. Further the material properties are ensured so as to facilitate shaping the steel into required shape and then getting them joined together through different welding techniques like sheet metal arc welding, TIG welding etc. Aluminum killed HSLA steels having thicknesses 0.6mm to 0.9 mm are used for fabrication of body panels. The following table shows the application of different grades of HSLA in manufacturing of different body panels of a car along with relevant yield strength values. Alternative Materials Steels Used for Body Panels Yield Strength (N/m2) Application Dual Phase Steels Alloys- Mn, Mo, Cr, V 400 to 500 Mech. Properties- High Yield Strength, Good Ductility. Applications: Doors, Roof, Hood Rephosphorised Steel Alloy- P up to 0.08 % 220 to 260 Mech. Properties- Slightly Lower Yield Strength, Higher Ductility. Applications: Doors, Roof, Rear Floor, Pillar (Source: Drishtikona Files Ch: 05) Research in identifying the best fit between “weight” and “material mechanical properties” is being done worldwide to replace steels. For instance studies show that Aluminum can replace steels in manufacturing car body panels reducing the weight of car by approximately 20% (Sheet Metal Stamping in Automotive Industry). Manufacturing Process- The Stamping Facility The type of manufacturing process depends on the design of panel to be produced, other than the material and its mechanical properties. However, following processes are an integral part of any automobile stamping process- Blanking, Sheet Metal Drawing, Sheet Metal Piercing, Notching and Hemming. Each individual process is discussed separately to highlight the steps followed in attaining the desired product (E. Shalash, 1996.) 1) Blanking Removing of a “work piece” from a primary metal sheet or piece through shearing process. The blanking process forces a metallic punch on the primary strip of metallic sheet placed on the die and shears away the part of sheet from the primary piece . The removed piece is the new work piece that is further worked upon to form different panels of car body. (Kalpakjian, 2010) Following pictorial representation depicts the process of blanking- Figure 2: Blanking (Source: Advantage Fabricated Process – Stamping) 2) Sheet Metal Drawing The sheet metal drawing process involves a punch and a die. The shape of the punch is same as that of the base of the drawn work piece. Its fits in the die to give ‘ blank” the required shape. Blank work piece is placed on the die and is pressed into the die cavity by the punch through application of calculated force. The work piece form the shape of punch and die that is then sent for further processing. Following pictorial representation shows the sheet metal drawing process put in action for manufacturing of panels- (Kalpakjian, 2010). Figure 3: Sheet Drawing Process (Source: Advantage Fabricated Metals) 3) Piercing It is the process of making internal features (holes, slots etc) inside a work piece after being deep drawn into required shape. Following picture shows the diagrammatic representation of the process (SIMTEC, 1999). Figure 4: Piercing Process (Source: Advantage Fabricated Metals) 4) Notching and Hemming It is a shearing process in which unwanted metal is removed from the drawn work piece to give it a “trimmed” look. After the body panels of a car are deep drawn, the unwanted metallic scrap is removed manually from the work piece to give the work piece its desired shape. It is a process in which “burred” or rough ends of the drawn work piece are rolled over on to itself. This process of rolling the end to itself is called hemming. It is done to give a “finished look” to the work piece. Further hemming is also done to weld different parts of the panels during assembly. After notching and hemming, the finished part is sent to the assembly line for assembling in car body through bolted or welded arrangements as per requirements. Bumper In car bumpers are installed on front and rear end of a car. They are installed with a purpose to absorb collusion energy when a car makes an impact with a hurdle. They absorb the mechanical energy when car makes impact with something. In this way they help in ensuring that no harm occurs to the hood panels, air cooling system, lights and other front end paraphernalia of a car. In present time, strength to weight ratios are an important factor in determining the material of bumpers as conventional steel bumpers have low strength to weight ratio. Material Selection Nowadays composite bumpers are fabricated for passenger cars as they have high strengths and low weight resulting in high strength to weight ratio as compare to steel bumpers. Some glaring positives of using composite bumpers are as follows (S. Prabhakaran, 2012) 1) High strength 2) Absorb more collision energy 3) High corrosion resistance Composite bumpers constitute following ingredients- 1) Glass fibers 2) Epoxy resin 3) Hardener 4) Wax Glass Fibers Glass fibers provide reinforcement to the resin and gives required mechanical strength. Different grades of fibers are available like- S- Glass fibers, E- Glass fibers, C- Glass Fibers. In case of bumpers, E- Glass fibers are used for making the required composite as they have the maximum impact strength. The term “E” refers to the “electrical” application of the fibers i.e it is used in making composite related to electrical applications. (S. Prabhakaran, 2012) Epoxy Resin Glass fibers are mixed with liquid epoxy solutions having low viscosity and high fluidity which gets entangles the glass fibers and provide strength to it. It is chemically compatible to glass fibers and gives strength to the composite. (S. Prabhakaran, 2012) Hardener and Wax They help in getting the composite hardened and solidify to form the required composite. Alternative Materials Low Alloy Steels, Brass and Graphite. The requirement for material selection depends on strength to weight ratios, capacity to absorb collision energy, corrosion resistance etc. Manufacturing Process Hand lay- up process is used to fabricate composite bumpers. Dimensional check is made by making mould with respect to steel bumpers and similar dimensions are kept. Liquid resin solution is applied to the mould followed by placing layer of glass fibers over it. A roller is then applied to squeeze the glass fiber layer with the resin. The thickness of the composite is varied as per requirements and by putting more or less layers of glass fibers over the resin solution. Since squeezing/ reinforcement is done manually therefore the process is called “Hand Lay- up Process”. Following diagram shows the pictorial presentation of “Hand lay- up Process” (S. Prabhakaran1, 2012). Figure 6: Hand Lay-Up Process (Source: S. Prabhakaranl, 2012) Car Handles Car handles are installed on the door panels of a car for the ease of passengers. They are of various designs and materials which points towards various metallurgies and manufacturing processes used for their fabrication. Material Selection Car handles are usually made of brass and other exotic metals to give a more catch look to the car. The unique designs and colors of handles add to the beauty and façade of the car. The metals used are usually those that have high levels of ductility which helps them to form any shape when subjected to force and give spotless surface finished after assuming the desired shape. Alternative Materials used PVC, Plastics, Low Alloy Steels, Fiber Composites. The selection of material s depends upon the requirements of the manufacturer. Manufacturing Process The most common manufacturing process involved is of die casting in which the work piece is subjected to a force by the punch which deforms the work piece plastically to assume the shape of the mould. This process is used when number of parts to be manufactured is large. Handles with more intricacies require the process of sand casting in which desired shape of the handle is made inside sand with all required cavities and minute detailing. Molten metal is poured into the cavities which after getting solidified assume the shape of the sand mould that is required. The sand mould is then detached from the solidified work piece to get the required design handles. Thereafter, machining of the required part is done to remove unwanted material to form the finished product. To give enhanced shelf life to the part polishing, brushing and lacquer is done to make product more appealing. Figure 7: Sand Casting Process (Degarmo, 1974) Conclusion The study highlights the different materials required to manufacture different parts of a car ranging from High Strength Low Alloy Steels (HSLA) to different grades of plastics to various grades of glass fibers composites required for car bumpers. Further the material selection also influences the type of manufacturing technique employed to manufacture the part which ranges from die casting to sand casting and hand layup techniques used to manufacture car bumpers. Works Cited Advantage Fabricated Metals- Blanking Process, Composites World - Manufacturing a Reinforced Thermoplastic Car Hood SIMTECH, (1999) Introduction to Sheet Metal Forming Processes Degarmo, E. P. (1974). Casting. In Materials and Processes in Manufacturing (4th). Collier Macmillan E. Shalash, (1996). Optimal Automotive Door Body Fitting for Body in White Assembly, Faculty of Graduate Studies and Research , Department of Industrial and Manufacturing Systems Engineering , University of Windsor Kalpakjian, & Schmid,. (2010). Manufacturing Engineering and Technology (6 th ed). Retrieved from http://www.gobookeee.com/get_book.php?u=aHR0cDovL2RsLm1ldGFsbHVyZ3llbmcuY29tL2ZpbGVzL1BoeXNpY2FsJTIwUHJvcGVydGllcyUyMG9mJTIwTWF0ZXJpYWxzLnBkZgpNYW51ZmFjdHVyaW5nIEVuZ2luZWVyaW5nIGFuZCBUZWNobm9sb2d5IEth Sheet Metal Stamping In Automotive Industry. (2012, August). In http://drishtikona.files.wordpress.com/2012/08/ch5.pdf. doi:http://drishtikona.files.wordpress.com/2012/08/ch5.pdf S. Prabhakaran, K. Chinnarasu, & M. Senthil Kumar. (2012). Design and Fabrication of Composite Bumper For Light Passenger Vehicle. International Journal of Modern Engineering Research, 2(4), 2552-2556. doi:ISSN: 2249-6645 Read More