Aluminum Rims Production in a Flexible Manufacturing System - Coursework Example

Aluminum Rims Production in a Flexible Manufacturing System Aluminum Rims Production in a Flexible Manufacturing System Introduction Production of parts in Flexible Manufacturing Systems has been in the rise to respond to increased consumer demands. Flexible Manufacturing Systems allow for a development of many product variants. The use of this system only requires one to feed carefully in the required specifications of the material to be produced. For this project, multi-spoke Aluminum rim is to be produced as a product family. The specific variants of the classified variants categories chosen for the project are: 1. Size- 24 inch rim 2. Design- Multispoke Rim 3. Color- Black ( Powder coating) Multi-Spoke Aluminum rim is a complex. The best method to be used is die casting. This method allows for a production of complex parts. The use of aluminum casting in the automotive industry has tremendously increased over the past decades.. The driving force for the increase is automotive weight reduction for efficient and improved performance. For aluminum alloy rim production, Al-Si casting alloys commonly used as a raw materials. The use of Al-Si is majorly informed by its excellent casting properties. The main alloying materials of Al-Si castings include Magnesium, Silicon, Manganese, Iron, Strontium, Beryllium, Titanium and zinc. Each material gives special features to the alloy casting so that the resulting has desired properties. The percentage compositions of these materials greatly affect the final alloy properties. Aluminum casting alloy rims are produced through of the use of low-pressure die casting. This method is used due to its many advantages. Some of the advantages of this process include design versatility, high dimensional accuracy, good surface quality, low equipment & dies cost, high productivity, good mechanical strength and its economic nature. Production Process Production of Aluminum rims involves several production steps. The steps are: I. Melting of Al Alloy II. Degassing Process III. Low-Pressure Die Casting IV. Solidification of Al Alloy V. Real-Time Radioscopic Inspection VI. Painting Step 1: Melting of Al Alloy The melting of Aluminum alloy for low –pressure die-casting involves three different operations. The operations are: i. Melting down of virgin ingot ii. Re-melting of scraps from the foundry or trimming operations and then reconstitution of the melt by the use of suitable additions. iii. Holding of quantities of the molten metal at a controlled temperature. For melting process, electric furnaces and reverberatory furnaces are used. After the process of melting, the molten metal normally has two transfer operations: Firstly, there is the transfer of the molten metal between two furnaces, i.e., from the melting furnace to the holding furnace. The molten metal is then automatically transferred from the holding furnace to a shot chamber of the die casting machine. The system is set so as to transfer the metal above or at the holding temperature. A schematic diagram schematic of a shaft melting furnace is shown below. Exhaust gas control (1, Ingot loading gate(2), Confidence zone (3), Preheating zone(3), Melting zone (4), Holding unit (5) Step 2: Degassing Degassing is the process of removing hydrogen gas from a metal melt. Before the start of die casting, the molten metal from the holding unit is taken through a degassing process. The inert gases are normally used for degassing operations of aluminum melt. For inert gasses, removal of hydrogen gas from a molten metal depends on the reaction at the molten metal-gas bubble interface. The reaction is as shown below. Where H is the concentration of hydrogen concentration, K1 is a constant, which depends on temperature and pH2 is known as partial pressure of atmospheric hydrogen, For a newly formed bubbles where pH2 = 0, the transfer of hydrogen gas from the molten to the bubbles at the interface is expressed as follows: Where CI is the initial hydrogen content; CF represents final content of hydrogen; CΘ is known as the hydrogen solubility in the molten metal for hydrogen pressure standard, and K is a constant. K depends on the mass of the molten metal. A schematic diagram degassing process is shown below The process is normally automated in a Flexible Manufacturing System. In this process, an inert gas is forced into the flow of molten metal alloy through the injection nozzles. An insoluble gas such as nitrogen, chlorine or argon is then bubbled through the molten gas. The hydrogen gas diffuses into the bubbles in accordance with the above equation. In this process, amount of hydrogen gas gradually reduced. Step 3: Low-Pressure Die Casting Forcing melt under specified amount of pressure into permanent dies results into die-castings. In die-casting there is molten flow at high velocities caused by the application of pressure. Due to this high-velocity fillings, pressure die-casting more complex shapes can be produced than as compared to permanent mold castings By the use of low-pressure die-casting, complex shapes can be produced than in permanent. Rates of production are normally higher, and metal costs are lower than those of other casting methods. Also, there is high dimensional accuracies without major alterations. In Aluminum rims production, the principles of vertical low-pressure die casting are applied. The diagram below is a schematic for vertical low pressure die-casting. Here, the melt is introduced into the steel die from below by means of a low-pressure gas applied to the metal in a furnace. Air is emptied from the die, and the melt is drawn into the shot chamber by a vacuum. The pressure for injecting the melt and clamping the dies are closely controlled by one accumulator source. The accumulator source ensures maintenance of a pressure balance even in case there is a malfunction. The die -casting machine is placed over a water-filled tank, which is fitted with a conveyor for the purposes of transporting the castings to the next point for cooling operations The dies used for die -casting dies are similar to heat- exchangers. The optimum die temperature for a particular casting is normally determined by section’s thickness and the required finish. When the optimum temperature of a die has been determined, it should be maintained within a range of ±6°C. In the case of casting Aluminum alloys, the temperature range should be 220 to 315°C. Computer system is used to control the die temperatures so as to produce the required sections thickness. Lubricants are applied to the die to prevent sticking of cast to the die and also to provide the casting a good finish. A correct choice of lubricant will enable metal to flow smoothly into cavities that cannot be filled otherwise. The time cycle required to produce casting is dependent on the weight and size. These fundamental factors are interconnected with die opening and closing time, machine capabilities, injection time, metal temperature, pouring time, dwell time and die lubrication. Step 4: Solidification of Aluminum-Silicon Alloy The Al-Si casting alloys are expected to possess certain properties. These include low porosity, small dendrite sizes, and small grain size. Obtaining small grain sizes can be attained by producing turbulence in a liquid by the use of a low thermal conductive mold and then adding grain refiners. Aluminum -Silicon is a eutectic system with only two solid solution phases. There are three major groups of Aluminum alloys, with silicon. These include Hypo-eutectic 2.0 – 7.0%, Eutectic 8.0 – 13.0% and Hyper-eutectic 16.0 – 25% The melt is solidified in an automated system obtain fine grins. Solidified rims are then automatically passed to the painter for painting. The painting color is chosen according to the customers’ requirement. The below shows a schematic of the Aluminum rims production process Step 5: Quality Control Quality is the most important parameter from any production plan. It is what dictates customers’ decisions in the selection of a particular product among competing products. Consequently, improving quality is a crucial factor resulting from business competitive position, growth and success.. There are two aspects of quality, i.e., quality of conformance and quality of design.. The quality of conformance is a measure of how well a given product conforms to the required specifications while quality of design includes parameters such reliability, design differences, which are obtained through an engineering development of a product There are several ways in which quality of the rims can be evaluated. The following are the major elements that are used to check the quality of Aluminum rims: a. . Performance-this is a question of whether the product will do perform the intended job. b. Reliability- this is a question of how often the product fail. c. Durability-A measure of how long a product last. d. Serviceability- AH measure of how easy is it to repair the product. e. Aesthetics-A question of the look or appearance of a product, i.e., whether a product is attractive. Real-Time Radioscopic Inspection (X-Ray Inspection) X-Ray inspection is specifically applied to casting materials, which are produced for the airplane industry and automotive. The method has been used for the last decades and is widely employed in Aluminum rims production lines. In this technique, feeding line from the casting machines to the Real Time Radiographic system transports the rims to the inspection unit. In the setup, the robotic manipulator, controlled by an automatic system or an operator helps the operator to effectively inspect all the territories of the wheels and to clearly see the defects on the screen. Consequently, the operator of a RTR system chooses the accept or reject option for the inspected rim. The typical image of Aluminum rim obtained by means of X-Ray inspection system is shown in the figure below. References Bawa, H. S. (2004). Manufacturing processes, : Tata McGraw-Hill Education. Davis, J. R. (2003). Aluminum and aluminum alloys. Materials Park, OH: ASM International. Jha, N. K. (2012). Handbook of flexible manufacturing systems. , : Academic Press. Raouf, A., & Ben-Daya, M. (2005). Flexible manufacturing systems: Recent developments: Recent developments. , : Elsevier. Tempelmeier, H., & Kuhn, H. (2010). Flexible manufacturing systems: Decision support for design and operation. New York, : John Wiley & Sons. Totten, G. E., & Mackenzie, D. S. (2003). Handbook of aluminum: Vol. 1: Physical Metallurgy and Processes. , : CRC Press. Upton, B. (2013). Pressure Diecasting: Metals — machines — furnaces. , : Elsevier. Read More