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Report on deconstruction of a DC Motor Hair Dryer

Report on the deconstruction of a DC Motor Hair Dryer Introduction This report presents the analysis and evaluation of the design of a typical household appliance (hairdryer). The primary objective of conducting this research is to engage in reverse engineering while aiming at analyzing and understanding a fundamental approach to design work. The aspects of safety, functionality, manufacture, and material are factors of consideration for the design of hairdryer. In design, the integrated approach involves bringing together specialism to execute a useful practice to create manufactured products to meet the market requirements. The engineering design approach entails a series of operations from concept to end of life for the product. For this report, a DC hair dryer with a folding handle was chosen based on relevant aspects of the engineering design process, and it is one of the products that has been developed over a century hence considered as a mature consumer product. Several technical innovation and material changes provide useful information necessary for this research as well as supporting the electromagnetism course. According to the design for the material of the hairdryer, the machine has a variety of components including metals, polymers, and minerals (mica) that gives a good overview of materials to learn from, which substantiates course work. Objectives i.	To exercise the guidelines recommended in reverse engineering for a typical household appliance. ii. To research on properties and the application of various materials used in making hair dryer. iii. To determine material selection in both technical and design approach. Working Principle of Hair Dryer The main objective of hair dryers is to speed up the evaporation of water from the hair’s surface. Factually, when the hair dryer is turned on, it emits hot air, which increases the temperature of the air surrounding, hence affecting each of the hair strands. Usually, warm air contains more moisture than room temperature air, making water move from hair to air in the surrounding. Further increase in temperature disengages the air molecules by overcoming the attraction between them, making it transform from liquid to gas state. To generate a blast of hot air, the hair dryer requires an electric circuit, motor-driven, and heating element (BCD Technology, 2016). The electrical energy is transformed by the components above into convective heat as described below: When the hair dryer is plugged in, the current flows in the designed electric circuit turns ‘on’ the switch. Power is then supplied to the bare coil-wire heating element that performs as a resistor. When the wire gains more heat, the consequence of getting hot results to voltage drop from 240/125V to 12V. The resulting 12V supplied to the motor spins it, consequently, rotating the fan. The rotating fan generates airflow, which is directed to the barrel section of the hairdryer, through the heating element. The heating element warms the air flowing through it by forced convention principle. Therefore, hot air blast out at the end of the barrel. Components This report will present an in-depth analysis of the wire used in making the heating element of the hairdryer in terms of material selection. i.	Heating Element According to the disassembled parts, heating element consisted of two main sections, namely: conductive bare coil wire and the non-conductive material with resistor wire mounted on it. Nilsson and Riedel (2008), in their book, “Electric circuits” highlighted that the mounting part of the heating element is made of ceramic, fiberglass, plastic and high resistant metal. For the case of this report, the mounting portion of the heating element was made of high resistant serrated metal, as shown below.

The review from the disassembled hair dryer shows that the handling part and the body exhibits low thermal conductivity and lightweight as the essential properties of consideration during the design and material selection process. Therefore, considerate critical elements noted included low density, low thermal conductivity, waterproof, and corrosion resistant. iii. The DC Motor The disassembled hair dryer contained DC with two permanent magnets with a current rating of 0.1A to 5A and operating voltage range of 9.0V to 24.0V. As a low voltage DC Motor, when the electrical poles are exchanged, motor runs in different direction. The stall torque in favor (desired) rotation is less and produces maximum output with high efficiency (Xia, 2012). According to Kysanelectronics.com website catalog, most hair dryers use DC Motors with cross reference number RS-385SA-2073 with VDC of 20. When there is no load, the motor runs at a speed of 17200rpm and operating current of 0.2A. At maximum efficiency, the speed of the DC Motor will be 14420rpm and current of 1.04A. The torque will be 9.49mNm and output of 14.3W (Refer to http://www.kysanelectronics.com/Catalog/2.pdf). Usually, applying the current to the motor leads to the generation of the magnetic field that drives the armature. iv. Magnets The disassembled part of the DC motor revealed that it contained two permanent magnets. Having the two magnets will result in the attraction of opposite poles and repulsion of like poles. This principle is used to create the torque or the rotational force from the magnetic field that sets the DC Motor in motion (Amin, Rehmani & IGI Global, 2015). The current flowing through the wire also creates a circular magnetic field making the wire to be referred to as the source and center of rotation. Adding the current causes the stator and armature form a stable magnetic and electromagnet fields pushed or rotated within the created field. The two described permanent magnets described as shown inside the open casing below.

v.	Fan Among other components of the hairdryer described above, a fan is also another critical component that makes it a complete system. The fan blades are made of plastic light material designed to effectively perform its function with ease, which remains to be a critical factor of consideration. The fan blows air from the back filter, across the heating element coil. The air gets heated up when it passed through the dryer. The resultant effect is evaporation of water as warm air reaches to the wet hair. The pictures are shown below. Disassembly From the discussions above, hair dryers contain several components to make it a complete system and operational. An attempt to open a hair dryer requires one to have the right equipment. Since external screws were not conventional, spanner slot coated screw was used to avoid tampering with the equipment. Considering the environment of its operation, its screws should be made of stainless steel (coated with the specified color of enamel paint) to prevent corrosion. The spanner screwdriver was used in opening the symmetric part of the hair dryer from Fig. 4 to Fig. 5 shown above. The operation exposes control switches, wires, and other electric circuit components. Majority of elements in that section are fixed without fasteners, an indication of smart design. The available 2 screws are used to prevent the power cable from pulling off while the electric wire is soldered. The handle is made of Polypropylene PP thermoplastic material (Acrylonitrile Butadiene Styrene) with high resistance to chemical corrosion and physical impacts. Acrylonitrile Butadiene Styrene has low melting temperature hence making it effective for injection molding manufacturing operation. Therefore, the material was chosen based on its toughness, hardness, and resistance to impacts (Gilbert, 2016). Opening the symmetrical part permits the inspection of the entire housing of the hair dryer, which consists of two main sections: barrel and back filter, attached to each other. The strength and flexibility of Polypropylene PP were put to the test by introducing the screwdriver as a lever of separating their coupling. The result was, the hair dryer is not design-to-open or fixed. Another material inside the hairdryer was the polycarbonate (PC), used to make the fan. The material exhibited toughness, high strength, transparency, light weight, thermal, and dimensional stability as the primary fundamental properties (Hirdaleina, 2006). Despite being heavier and less flexible than PP, polycarbonate is tougher with high vibrational dampening effect; making the fan spin faster.

Summary Disassembling of the hair dryer helped in addressing the aspect of reverse engineering as a critical approach of deconstructing human-made systems purposely for revealing its designs, architecture and extract more information useful in answering scientific research questions. The key objectives listed above were addressed in the report in detailed information, accompanied by cited research sources.

References Amin, M., Rehmani, M. H., & IGI Global. (2015). Operation, construction and functionality of direct current machines. Hershey: Engineering Science Reference, an imprint of IGI Global. BCD Technology (2016). What Inside a Hair Dryer: Working & Princple of Philips Hair Dryer. [online] YouTube. Available at: https://www.youtube.com/watch?v=Hyb8kq_L4Ys [Accessed 16 Jun. 2019]. Gilbert, M. (Ed.). (2016). Brydson's plastics materials. William Andrew. Hirdaleina, I. (2006). Effect of polycarbonate (PC) on mechanical properties of acrylonitrile-butadiene-styrene (ABS). Skudai: Universiti Teknologi Malaysia. Kysanelectronics.com. (n.d.). [online] Available at: http://www.kysanelectronics.com/Catalog/2.pdf [Accessed 16 Jun. 2019]. Nilsson, J. W., & Riedel, S. A. (2008). Electric circuits. Upper Saddle River, N.J: Pearson/Prentice Hall. Xia, C. (2012). Permanent magnet brushless DC motor drives and controls. Hoboken, N.J: Wiley-Science Press.