Manufacturing the Chassis of a Typical Motorcycle - Essay Example

Manufacturing the chassis of a typical motorcycle Like all other manufacturing and engineering processes, making motor cycle chassis is a vast . Any single process like welding, molding or casting, forging etc. will take pages to describe each individually. However, main steps needed in the manufacture of a motorcycle frame are discussed here. Material selection The material selected for tubing and sheet metal will differ with the volume and cost of manufacturing. This will also depend on the final quality of the frame, which should be consistent with the overall motorbike quality. Since most of the automotive body components are made from cast-able aluminum, we will discuss here, the characteristics for aluminum casting with reference to its various grades, as this is the best non-ferrous casting alloy and most popular for use in making of motorbike frames. Aluminium alloy Condition Casting method UTS (MPa) Yeild Stress (MPa) % elongation in 50mm Hardness (HB) 357 T6 S 345 296 2.90 90 380 F D 331 165 3.00 80 390 F D 279 241 1.00 120 The casting methods referred above are “S –for Sand casting”, “D –for die casting”. Permanent mold casting is not preferable for aluminum (above information is comiple from Manufacturing Engineering and Technology by Kalpakjian & Schmid ) Accordingly, the proper aluminum grade is to be selected, depending on the type of casting. In most of the cases, “Twin Spar” type aluminum is used for the manufacture of a motorbike frame. The further techniques and processes for the manufacture of this chassis involve welding, tube manipulation and profiling, sheet metal work and Jigging, tooling. These are described here in brief The following choices of materials and processes can be adopted in those cases where huge quantity turnout is not required. Aluminum tubing or welded steel frame Welded steel or stainless steel and fabricated steel backbones, as well as twin spar. Riveted and cast aluminum backbones. Various processes involved for the manufacturing of a motorbike frame are broadly listed as follows. 1. Casting This process is involved when the product turnover is huge .As indicated above, the sand casting or die-casting techniques are used for the manufacture of a motorbike chassis. However die-casting is the technique mostly used for the aluminum chassis manufacture. The process can be either hot chamber or cold chamber die casting methods. The molds involved are required to be quality tested frequently due to their high ware and tear. Various casting processes have their respective advantages and limitations. Some of them are detailed below Casting process Advantages Limitations Sand casting It has low tooling cost and any metal can be cast without any limit to weight Due to its rough finish, finishing is required. It has wide tolerances also. Die casting It is one of the best-used techniques for body frames and other auto components as it gives very good product surface finish. Very high production rate can be achieved. While it is limited usually to non-ferrous metals, the die cost is very high. It has long lead time also. Expandable pattern casting Can cast most metals into complex shapes without any size limitation. Is used in auto industry for components and body frame casting. Pattern strength is low and cast quantities are lower. Plaster mold casting It gives good dimensional accuracy and can cast very intricate shapes. The porosity is low It has long mold making time. Only non-ferrous metals casting can be done. It can cast in limited sizes only with low production volume. Ceramic mold casting Can cast intricate shapes that need close tolerances. Gives fine surface finish, No visible limitation is noted here. Permanent mold casting It can give high production rate with high dimensional accuracy and low porosity Shapes are limited. It has high mold and tooling cost. Metals with high melting point can be cast here. Investment casting It can cast almost any metal. Give high surface finish and precision accuracy. Size of the part is limited. The pattern and tooling cost as well as labor cost is high (source: Manufacturing Engineering and Technology by Kalpakjian & Schmid) Apart from the nonferrous metals like aluminum, which are used for die-casting to manufacture the motorbike chassis, other non-metal materials are used currently. These include high resistance and strong polymer based compounds that may need a different casting procedure. 2. Forming This will include the techniques like welding to form the component into the required shape and size. Different welding processes are detailed here, briefly. Welding Process There are two basic methods of melding process involved—electric and gas welding. Both have different techniques, as will be described here. Electric Arc welding The road-going version of Norton featherbed frame was manufactured using electric arc welding process only. However, the technology has advance a lot since then and it is now found that electric arc welding may not be suitable for the chassis building as the requirement of the tubing wall thickness here is more than 2mm, which makes the material expensive. Metal Inert Gas welding This is also called CO2 gas welding. The weld material is in the form aof a wire or electrode and the gas fed as a shroud is the mixture of carbon dioxide and argon. While, the process is used mostly for steel tubing and other structures, it can be used for aluminum and stainless steel as well. All body chassis frames, which have welded steel or aluminium tubing, are processed through this technique. The advantages are: Due to its high speed, the labor cost is reduced. There is very less distortion due to low heat input. It means clean welding as no adulteration of weld occurs due to non-presence of any flux. Little expertise is required. Filling in the gaps is excellent resulting in lesser time spent on joint preparation etc.. However, the disadvantages can include Tubing, which have less than 1.8 mm wall thickness can have some undue stress concentration, as the weld filet is convex here..: Apart from above welding methods, tungsten inert gas welding known as Heli-arc or argon-arc welding can also be utilized as this method gives high accuracy of welding, with reduced stress concentration and its application for all wall thicknesses. It is used in SS or aluminum fabricated backbones etc. Distortion This is the off-shoot of any welding method and it has to be tackled in an effective manner. The weld cooling process causes the distortions.after the welding isover, the cooling causes contraction for both the metal and the weld. The two have different coefficient of contraction and expansion. Hence the distortion. The built in stress caused by this leads to the weakness in the metal. To minimize the distortions, the welding sequences need to be properly planned. In a motorbike chassis, there are a few areas where fine tolerances are required. These include the steering head, rear pivot housing or the alignment of drive sprockets etc..One method to avoid distortion and stress build-up, is by welding each joint individually and separately before taking the nest joint for welding. 3. Sheet metal work This includes tube and sheet metal procedures. Tube types required for the manufacture of motorbike chassis are usually of round shapes. While these tube types resist the bending loads coming from all directions, this type of section also reduces the torsion and compressive loads. There can be other noncircular tube sections, like the tapered oval tubing, that is being used by BMW, just to match the tube properties with the applied loads. This is also to make the fork structurally balanced, while following the velocette’s lead. Tube profiling requires matching of tubes with the mating structure. For doing so, all tube sections except the square or rectangular tube sections need to shape the ends to match the structure. This will involve the milling cutter machine tool and sometimes the grinders also do the job.. 4. Machining This includes the use of milling machines, abrasion, buffing and polishing machines,. Broaching and fine finishing machines are used to give the aesthetic appeal to the chassis. 5. Plating Electroplating process is used to get the attractive finish, as it highlights any visual defects like bumpy welds or scratches.. However, Plating has its own disadvantages as the trapped acid formation resulting from this process can cause stress accumulation at various joints and it may lead to failure due to fatigue. Trapped acids can also result in internal corrosion and rusting of certain areas. In certain cases nickel platting is preferable to chromium platting. However, it can be seen that Rickman Metisse frames are nickel plated only. 6. Painting As many paint finishes are availble, spray painting is thebest and mostly used process in the manufacture of the motorbike chassis. However, the proper touching up matching the original paint is almost impossible, when scratches come up. 7. Plastic coating On its first application, this process gives the best finish. However, on the appearance of scratches etc., there is no touching method that can be done as in case of paint. Further, the scratches may cause corrosion at these points resulting in the erosion of metal surface, eventually. For the purpose of corrosion resistance, anodizing process can also be applied, This is useful for the aluminum body frames as the oxide film, thus made can act as a preventive for the corrosion. Quality control Quality control measures will involve the checking on mainly two parameters of the product. One is the product features and second is the optimum removal of deficiencies. Product features are the design parameters of the product, which also characterize the customer requirement and satisfaction. In a motorbike chassis, the product features will include the aesthetic features that may be required by the customers at large. Optimum removal of deficiencies means that the product meets the design parameters and specifications, and is free from any defects including out of tolerance conditions. Here are the two conditions of quality control, for the above, defining the requirements of each. Product features Freedom from deficiencies To check distinguished features like aesthetics appeal, ease of use; size, weight, design configuration and performance functions. Reputation of the product, durability and serviceability of the product, availability of the spares and its reliability as well as durability. No test failures. No missing parts. Adherence to the design specification.. Tolerances with in the limits. Absence of any overall defects. (Info collected from : Automation, Production Systems, and Computer-integrated Manufacturing by M. P.Groover) There are both traditional and modern quality control methods. The traditional QC techniques require mainly the “test by sampling”, in which a sample component is drawn to be tested out of a batch of same product. The concepts of traditional quality control technology include the following: The company has deputed various functions to the individual departments. Sales and marketing division is responsible for the customer relationship building. While the quality control is the responsibility of the inspection division, it follows the production of the goods. The production department may difer with the QC or inspection department as this division would like to ship only quality tests passed product, whereas the production department is interested to ship all the products. The objective of inspection department is simply to eliminate the defects found, as it lays importance to the concurrence of the design specifications with the finished product. Under Modern quality control techniques, the concept of total quality management (TQM) is apparent. The management approach called TQM has mainly objectives like involving the entire work force for continuously improving the product quality aimed to achieve the ultimate goal of customer satisfaction. Following are the main features of TQM: Every piece must be free of all defects. The customer is the king and customer satisfaction should be on the top of QC agenda The quality checks are carried at various departments, as same are called internal customers. The pattern follows the production chart, where the next department takes the job in hand only after the earlier processing has been QC okayed. Once the internal customers are satisfied, the product is shipped for sale to the actual buyer who is an external customer. Quality control is not the job of inspection department only but it flows from the top management of the company, involving the entire staff. Hence, the quality concept is built at the various stages of the production itself. Sources Manufacturing Engineering and Technology by Kalpakjian & Schmid ‘Motorcycle handling and chassis design’ by Tony Foale Manufacturing Processes for Engineering Materials by Kalpakjian Bnet.com..motorcyle production Fundamentals of Modern Manufacturing by Mikell P Groover Read More