Resistor Types and Manufacturing Techniques - Essay Example

Name Course Title Date Part 1 - Current resistor types and manufacturing techniques Carbon resistors are manufactured by putting a thin layer of carbon film on a ceramic rod. The rods are heated and tumbled in a retort in the presence of hydrocarbon gas. They can also be made using a mixture of fine graphite or carbon dust and a binding material like clay. The resistance of is controlled by varying the thickness of the film layer or by varying the ratio of carbon dust to the ceramic. The mixture is made into cylindrical shape and the metal wires are connected to each end for electrical conductivity, before coating with insulting material. They are available with a tolerance of ±0.25% to ±5% with less than 1W. They are trimmed using a laser which leads to high self-inductance and makes them not suitable for use at a frequency of over 30MHz (Herman, 2012). Carbon film resistor produced much less noise than carbon composition type. It produces a noise which is proportional to the voltage stress in the film (Mazda, 1981). Carbon Composite Resistor: Carbon composite resistors consist of cylindrical solid materials with metal or wire ends caps for attaching the leads. They are coated with insulating material like plastic or paint, with colour coding of its value. They are produced using a solid block of material of carbon, ceramic and binder material. The resistance depends on the amount of carbon in the filler material. Since the carbon composition is affected by the environmental conditions like humidity, the resistance tends to change over time. They therefore have poor tolerance of 5%. The resistor is limited to a rating power of less than 1W and has low inductance making them ideal for high frequency applications but can also suffer from thermal noise and stability when hot (Minges, 1989). They are rugged and cannot be damaged by large currents, but have poor stability, large temperature coefficients of resistance, and high noise especially shot noise cause by DC current (Mazda, 1981; Herman, 2012). Metal film resistor: They are very similar in construction to carbon film resistors, but metal alloy is used as the resistive material rather than carbon. The material used is nickel – chromium alloy which provide small resistance tolerances compared carbon film resistors with tolerances of as low as 0.01%. They are available at 35W but have low or no resistance at the wattage of above 1-2 W. Metal film resistors has low noise especially thermal noise and are more stable than carbon resistor with little change in temperature with applied voltage. They are used for high and radio frequency applications. They are widely used in general and semi-precision application (Herman, 2012). Metal oxide resistor: They are hard glassy oxide form on a ceramic or a glass. There are different techniques used to manufacture this type of resistor. In one of them, a semiconductor material is doped with antimony which controls the electrical characteristics of the component. They are also made by coating a thin film of metal oxide, typically tin oxide on a ceramic rod. They have similar features as metal film resistor but they have better current surge handling capability and high temperature rating compared to metal film resistors. Although they have low contact and shot noise and can handle high frequency than wire wound resistor, they are have the least temperature stability and hence have high thermal noise (Mazda, 1981). Wire wound resistors: Wire wound resistor is manufactured by winding high resistant wire usually made of nickel chromium alloy, around an insulated material like ceramic, plastic or glass. The ends of the wire are soldered to two caps connected to the ends of the core, before coating with paint or enamel at high temperature. The resistance can be varied by varying the length, diameter or the alloy of the wire. The wire leads usual have a diameter of a range between 0.4mm to 0.8mm but can be less or more. It has a resistance tolerance of 0.005% and can be have a power rating of 50W. Some resistors with a power rating of 5 to 10% have power ratings in kW. They have high inductance and capacitance and are therefore used main for low frequency applications. They are considered the quietest because they only have thermal noise but not contact or shot noise (Herman, 2012). In general, Wire wound resistors has the least noise because of thermal noise. It is followed by metal film resistor, metal oxide resistor, carbon film resistor, and resistor which has more noise is carbon composition resistor. Thermal noise cannot be reduced because it is independent on the material of the component. It can only be reduced by reducing the resistance of the material. Contact noise is common in carbon composite resistor, carbon film resistor, metal oxide resistor and metal film resistor and can increase at low frequencies because it has an inverse frequency characteristic. Shot noise is dependent upon the DC current (Groover, 2010). Part 2 - Analysis of Resistor Manufacturing Output The table below shows the number of resistor components produced by the two machines in the factory. Resistor Value (Ω) Machine 1 machine 2 90 72 12 Total 10,000 10,000 The table showing the number of components for each machine with their percentage tolerance Tolerance Machine 1 Machine 2 1% 2855 3334 2% 1735 1938 5% 3681 3586 10% 1656 1118 >10% 73 24 The standard deviation components produced for machine 1 = 358.6918715 and for machine 2 = 358.6919. The standard deviations of the components sold (excluding rejects) are 361.5041322 for machine 1 and 359.2727 for machine 2. The histogram shows that the output of machine 2 lean more to the left of the histogram than machine 1. In other words, machine 2 produces more components with low tolerance than machine 1. Machine 1 also records more rejects. It can also be seen that a large overall quantity of resistor components with 5% tolerance are produced, followed by resistors with 1% tolerance. The sets of data show what is happening during the process and therefore forms factual basis for making decisions. By comparing the data from the two machines, it can assessed whether there is one which is underperforming and assumption can be made about the cause of the problem. On other words, it enable the management team to create and test working assumptions about the production process and develop plans that will be used to improve the main quality of services production (Leitner, 2011). Why there are low prices for the components The company cut their price but produces components in large quantity so that they can benefit from economies of scale. They have advantages over their competitors because of price and logistics and therefore attract more customers and strengthen their advantage even more. In the process they get more profits and get feedback loop of success making difficulty for rivals to deal with (Schwenker and Bötzel, 2007). Table showing the total prices of the components for the two machines Tolerance Unit Sales Machine 1 Total sales Machine 2 Total sales 1% 0.016 2855 45.68 3334 53.344 2% 0.012 1735 20.82 1938 23.256 5% 0.005 3681 18.405 3586 17.93 10% 0.001 1656 1.656 1118 1.118 >10% 0 73 0 24 0 Total sales (£) 86.561 95.648 According to the data obtained above, machine 1 needs to be recalibrated. This is because it produces less sales of £86.561 compared to the second machine which produce £95.648. Machine 1 also produces more rejects compared to machine 2. Rejection rate For machine 1 For machine 2 From the above calculation, the reject rate for machine 1 is more compared to that of machine 2. Machine 2 produce resistors with higher precision than machine 1 which produce more of less precision and more rejects. References GROOVER, M. P. (2010). Fundamentals of modern manufacturing: materials, processes, and systems. Hoboken, NJ, J. Wiley & Sons. HERMAN, S. L. (2012). Electrical principles. Clifton Park, NY, Delmar, Cengage Learning. MAZDA, F. F. (1981). Discrete electronic components. Cambridge, Cambridge University Press. MINGES, M. L. (1989). Electronic materials handbook. Materials Park, OH, ASM International. LEITNER, M. (2011). Economies of Scale in Semiconductor Manufacturing How to Achieve and to Destroy. Munich, GRIN Verlag GmbH. http://nbn-resolving.de/urn:nbn:de:101:1- 2014020622813. SCHWENKER, B., & BÖTZEL, S. (2007). Making growth work how companies can expand and become more efficient. Berlin, Springer. http://public.eblib.com/choice/publicfullrecord.aspx?p=302075. Read More