潜栅凸轮衬套注塑模具设计与分析【中文4600字】
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Materials Today: Proceedings 2 ( 2015 ) 2083 2093 Available online at ScienceDirect2214-7853 2015 Published by Elsevier Ltd. Selection and peer-review under responsibility of the conference committee members of the 4th International conference on Materials Processing and Characterization.doi: 10.1016/j.matpr.2015.07.203 Corresponding author. Tel.: +919701574596 E-mail address:drgmsa786. 4th International Conference on Materials Processing and Characterisation (ICMPC 2015) Design and Analysis of Plastic Injection Mould for CAM BUSH with Submarine Gate MohdJamsheeda*MdAaqibRahmanb M.A MoyeedcG.M.SayeedAhmedd aAssistantProfessors,Dept. of Mechanical Engineering, VIF college of Engineering and technology. Assistant Professorsb,Mechanical Engineering. NawabshahAlam Khan college of Engineering, cAssistant ProfessorsDept. of Mechanical Engineering, NawabshahAlam Khan college of Engineering., dSenior Assistant Professors, Dept. of Mechanical Engineering, M. J.Collegeof Engineering and technology, Abstract This Paper focused on Design and Analysis of an automatic plastic injection mould for production of CAM BUSH. Cam Bush is used as a indexing device in ON/OFF Load Tap changer device of high voltage transformer and serves as the connector between the indexing head and the power changing gears. An injection mould is a tool which is used for production of plastic components in large numbers in a short span of time. Modeling in done by using Unigraphics (NX 7.5) and Auto Desk Mould flow Plastic Insight is use for Mould flow Analysis for CAM BUSH filling rate, cooling system location and Location of submarine gate. The moulding tool consists of the Top plate, Cavity plate, Core plate, Spacer blocks, Ejector plate and the Bottom plate. In this six core pins and six ejector pins are provided on injection mould because the required cam bush has six indexing holes. The material use is Oil Hardened Non-shrinking Steel (OHNS) for the core and cavity, and EN353 for the Tie Rod, guide bushes, core pins, ejector pins, locator ring and the sprue bush and Mild Steel for other plates are selected. The elements of injection moulding tool has designed and analyzed. Submarine gate and Baffle circular hole cooling system has provided in the moulding tool to increase the productivity and good surface finish. The required Nylon-66 Cam bush component will produced with this moulding tool with the various parameters of injection moulding machine. 2014 The Authors. Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the conference committee members of the 4th International conference on Materials Processing and Characterization Key words: Plastic Injection Mould, CAM BUSH, Mould Floe Analysis 1. Introduction Now a days plastic are occupying a vital role in the day-to-day life. It is not at all can exaggeration, if we say that there is no field into which plastic have not stepped in right from the manufacturing at a pin to that of a spacecraft. At the middle of 19th century, plastics start a leading role in the material and in our life.Corrosion resistance are some of the aspects through which plastics are even becoming superiors to metals and attained an elevated rate of preference in every branch of manufacturing. Right from the emergency of plastics they are undergoing drastic in various aspects like design of plastic product, manufacturing processing then in testing fields and now, because of fruitful efforts of many people at last the came in work through manual labor, but with help of artificial intelligence that is, with software package like CAD/CAM. Because of high strength of weight ratio, improve chemical and temperature resistance, inherent properties of being bath thermal and corrosion resistance, transparency have made them a material choice. Plastic consume less energy during formation and can be profitably recycled. Today plastics are replacing the metals like Brass, Copper, Cast Iron, Steel etc. Plastics can be classified according to manufacturing methods in to main groups Those which soften when heated and solidifies on cooling. These are known as “Thermo plastic” and Those which harden when heated as a result of chemical change. These are known as Thermosetting or Duro plastic material” Selection of particular material for the product is another important factor. This is particularly very necessary for the product 2015 Published by Elsevier Ltd. Selection and peer-review under responsibility of the conference committee members of the 4th International conference on Materials Processing and Characterization.2084 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 determination. It should capable of withstanding stresses acted upon it as well. Each material has its own properties and attributes. Some materials are better in high environment and extremely abrasion resistance. The difficult part is to find a material that will come close to fulfilling the entire requirement of the purpose. So material should be so versatile that it suits all the consideration and requirement of our product. After considering all these points material must be selected suitable enough to satisfy all these conditions. 2. Plastic Cam Bush for Transformer The objective of the paper is to design and Analysis the injection mould tool for a cam bush of an High voltage transformer. Cam Bush is used as a indexing device in ON/OFF Load Tap changer device of high voltage transformer and serves as the connector between the indexing head and the power changing gears. The indexing head is connected to the gear by means of the shaft which is attached with the Cam Bush. The cam bush has two tail ends, one side is press fitted to the indexing crank circle and the other side is fitted to the driving mechanism. Each hole has different driving mechanism, when the indexing circle rotates and the crank pin engaged in the first hole the first driving mechanism turns on. The different type of power is obtained by means of changing the index position. Cam bush serves as the connector between crank circle and the gears. It is provided in the power changing indexing mechanism. The indexing crank circle has many indexing holes, but the mechanism has 6 drive, so the cam bush with 6 holes is provided in between the crank circle, speed indicator wheel and the shaft which is intersected in center and connected to the gears. This CAM BUSH is generally made with Polystyrene, Nylon6 and PVC. Due to high voltage regulating application this Cam Bush becomes heated up and wear off. Due to repeatedly applying pressure by regulating it, it becomes damage. Fig.1 Cam bush Solid Model and Assembly Plastics are man-made materials. They are less brittle than glass, yet they can be made equally transparent and smooth. They are light weight and at the same time possess good strength and rigidity. They resist corrosion and the action of chemicals. They can be easily molded to different shapes. Commonly used thermoplastic materials are Polystyrene, Nylon 6, P.V.C , Polypropylene etc. Mould making is an important role in plastics industries because the related products constitute more than 70% of the components in consumer products. Injection moulding is a complex but highly efficient means of producing a large variety of thermoplastic products and has many advantages, such as short production cycles, excellent surfaces of the products, and has no secondary operations, good results in moulding of complicated shapes. The design and fabrication of injection moulding tool for complex plastic products is play a wider role to meet the industrial demand especially in plastic industries. Hence, there is a demand in the industry for plastic injection moulding techniques capable of producing plastic parts. Literature review reveals that there is a lack of research on design and manufacturing of injection moulding tool for complicated plastic components. Hence, this project focused on design and Analysis of Injection moulding tool with baffle type cooling channel and submarine gate for cam bush. 3. Injection Moulding Process It is a manufacturing process for producing parts by injecting liquid molten material into a mould. Injection moulding can be performed with a host of materials, including Metals, Glasses, Elastomers, Confections and most commonly Thermoplastic and Thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mould cavity where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould maker (or toolmaker) from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. The part, the desired shape and features of the part, the material of the mould, and the properties of the moulding machine must all be taken into account. The versatility of injection moulding is facilitated by this breadth of design considerations and possibilities Injection molding utilizes a ram or screw-type plunger to force molten plastic material into a mold cavity; this solidifies into a shape that has conformed to the contour of the mold. It is most commonly used to process both thermoplastic and thermosetting polymers, with the former being considerably more prolific in terms of annual material volumes processed. 2085 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 Fig 2: Model of Injection Moulding Process Injection molding consists of high pressure injection of the raw material into a mold which shapes the polymer into the desired shape. Molds can be of a single cavity or multiple cavities. In multiple cavity molds, each cavity can be identical and form the same parts or can be unique and form multiple different geometries during a single cycle. Molds are generally made from tool steels, but stainless and aluminum molds are suitable for certain applications. Aluminum molds typically are ill-suited for high volume production or parts with narrow dimensional tolerances, as they have inferior mechanical properties and are more prone to wear, damage, and deformation during the injection and clamping cycles; but are cost-effective in low-volume applications as mold fabrication costs and time are considerably reduced. Many steel molds are designed to process well over a million parts during their lifetime and can cost hundreds of thousands of dollars to fabricate. When thermoplastics are molded, typically pelletized raw material is fed through a hopper into a heated barrel with a reciprocating screw. Upon entrance to the barrel the thermal energy increases and the Vander Waals forces that resist relative flow of individual chains are weakened as a result of increased space between molecules at higher thermal energy states. This reduces its viscosity, which enables the polymer to flow with the driving force of the injection unit. The screw delivers the raw material forward, mixes and homogenizes the thermal and viscous distributions of the polymer, and reduces the required heating time by mechanically shearing the material and adding a significant amount of frictional heating to the polymer. The material feeds forward through a check valve and collects at the front of the screw into a volume known as a shot. Shot is the volume of material which is used to fill the mold cavity, compensate for shrinkage, and provide a cushion (approximately 10% of the total shot volume which remains in the barrel and prevents the screw from bottoming out) to transfer pressure from the screw to the mold cavity. When enough material has gathered, the material is forced at high pressure and velocity into the part forming cavity. To prevent spikes in pressure the process normally utilizes a transfer position corresponding to a 9598% full cavity where the screw shifts from a constant velocity to a constant pressure control. Often injection times are well under 1 second. Once the screw reaches the transfer position the packing pressure is applied which completes mold filling and compensates for thermal shrinkage, which is quite high for thermoplastics relative to many other materials. The packing pressure is applied until the gate (cavity entrance) solidifies. The gate is normally the first place to solidify through its entire thickness due to its small size. Once the gate solidifies, no more material can enter the cavity accordingly, the screw reciprocates and acquires material for the next cycle while the material within the mold cools so that it can be ejected and be dimensionally stable. This cooling duration is dramatically reduced by the use of cooling lines circulating water or oil from a thermolator. Once the required temperature has been achieved, the mold opens and an array of pins, sleeves, strippers, etc. are driven forward to de mold the article. Then, the mold closes and the process is repeated A parting line, sprue, gate marks, and ejector pin marks are usually present on the final part. None of these features are typically desired, but are unavoidable due to the nature of the process. Gate marks occur at the gate which joins the melt-delivery channels (sprue and runner) to the part forming cavity. Parting line and ejector pin marks result from minute misalignments, wear, gaseous vents, clearances for adjacent parts in relative motion, and/or dimensional differences of the mating surfaces contacting the injected polymer. Mold or die are the common terms used to describe the tool used to produce plastic parts in molding.Sincemolds have been expensive to manufacture, they were usually only used in mass production where thousands of parts were being produced. Typical molds are constructed from hardened steel, pre-hardened steel, aluminum, and/or beryllium-copper alloy. The choice of material to build a mold from is primarily one of economics; in general, steel molds cost more to construct, but their longer lifespan will offset the higher initial cost over a higher number of parts made before wearing out. Pre-hardened steel molds are less wear-resistant and are used for lower volume requirements or larger components; their typical steel hardness is 3845 on the Rockwell-C scale. Hardened steel molds are heat treated after machining; these are by far the superior in terms of wear resistance and lifespan. Typical hardness ranges between 50 and 60 Rockwell-C (HRC). Aluminum molds can cost substantially less, and when designed and machined with modern computerized equipment can be economical for molding tens or even hundreds of thousands of parts. Beryllium copper is used in areas of the mold that require fast heat removal or areas that see the most shear heat 2086 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 generated. The molds can be manufactured either by CNC machining or by using electrical discharge machining processes. Table.1 Fits and Tolerance S.No Description Type of Fit Tolerance 1 2 3 4 5 6 7 Main Guide pillar-Main guide bush Sprue bush-Cavity plate Core pin-Core plate Push back pin-Core plate Ejector pin-Core plate Ejector Guide pillar-Ejector guide bush Register ring-Machine platen close running fit Medium drive fit Slide fit Close running fit Close running fit Close running fit Running fit H7 / g6 H7 / m6 H7 / h6 H7 / g6 H7 / g6 H7 / g6 H7 / f7 The injection molding process can be broken into three phases, (1)Filling phase: During the filling phase plastic is injected into the cavity is just filled. When designing a part to be made by the injection molding process, the most important phase to as plastics flows into cavity, in contact with the mold wall freezes quickly. This creates a frozen layer of plastic between the mold and molten plastic. The flow fronts come into contact with the mold and freezes. The molecules in the frozen layer are therefore not highly oriented, and once frozen, the orientation will not change. The Frozen layer gains heat as more molten plastic floes through the cavity and loses heat to the mold. When the frozen layer reaches a certain thickness, equilibrium is reached. This normally happens early in the injection molding process, after a few tenths of seconds. (2) Pressurization phase, the pressurization phase begins after the cavity has just filled. Although all flow paths should be filled by this stage, the edge and corners of the cavity may not contain plastic. To completely fill out the geometry, extra plastic is pushed into the cavity during the pressurization phase. The polymer injection location I indicated by the yellow cone and the plastic is green. Some time the confidence of fill result does not predict a short shot, but still states that a good quality part cannot be molded. This is because the condition at the end of the filling phase is not suitable for the part to be adequately packed during the pressurization phase.(3) Compensating phases:Plastic have a high volumetric shrinkage, around 25% from average melt temperature to solid. Therefore more material must be injected into the cavity to compensate for the plastic shrinkage as it cools. This is the compensating phase. 4. Mould Die Design When purchasing plastics mould steels, one looks, for Good machining properties, Good polish ability, Good photo etching properties, Good spark erosion properties, Safe, uncomplicated heat treatment, Minimum inclusion level, Consistently high quality, Technical assistance and advice in tool in manufacturing and application. Essential characteristic of injection mold steel like Uniform structure and freedom from internal, defects, Machinability Maximum freedom from distortion during heat treatment, Weld ability, Polish ability, Wear resistance and toughness, Steels for mould fall under two categories, Structural section of the mould, Medium carbon silicon killed forging quality steel with approximately 25% greater tensile strength then typical low carbon steel. It is annealed to approximately 165BHN. It is stress relieved for minimum deformation during machining.AISI 4130 type alloy steel is supplied pre-heated to approximately 300BHN to withstand the peening effect of flash. It has durability for heavy construction loads and long production runs. Component material is selected as NYLON-66, Nylon 66 is a polyamide made from adipic acid and hexamethylenediamine by polycondensation,NYLON-66 has Good toughness, High tensile strength, High elasticity, Good heat resistance, Excellent wear resistance, Wrinkle proof and excellent chemical resistance.Shrinkage is inherent in the injection moulding process. Shrinkage occurs because the density of polymer varies from the processing temperature to the ambient temperature. The shrinkage factor will depends on Plastic material, Processing condition, Product design, Mould design. Shrinkage allowance of Nylon 66 is 0.5% considered. The dimensions of the cam bush have been modified with considering shrinkage allowance as shown in Table 1. This total dimensions are incorporated in the mould designing of core and cavity plate. Table.2 Dimensions of Cam bush with shrinkage allowance 2087 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 S. No Component Details Actual dimension in mm 0.5% shrinkage allowance in mm Total dimension in mm 1 Diameter 1 65 0.325 65.325 2 Diameter 2 35 0.175 35.175 3 Diameter 3 28 0.14 28.14 4 Diameter 4 20 0.10 20.10 5 Diameter 5 7 0.035 7.035 6 Length 1 15 0.075 15.075 7 Length 2 15.5 0.0775 15.5775 8 Length 3 19 0.095 19.095 5. Simulation of CAM BUSH in Injection Moulding Process Analysis done for the part “CAM BUSH” to study and calculate the flow pattern, fill time and packing time by considering cooling system which will affect the part performance. Also determine the clamp force and injection pressure requires for the mould which will help to select the exact injection moulding machine and approximate cycle time. Polymer selected for analysis is NYLLON-66.Cooling holes diameter is 12mm.Gate diameter is 1.25. The global mesh density setting defines the nominal edge length for elements. The smaller the global edge length, the larger the total number of element on the model. The global setting is the single most important setting to get an acceptable mesh on the part. We can optionally also set a local mesh density on selected surfaces/regions created by importing geometry from, for example, an IGES, step, para solid, or native CAD format. This is typically done to ensure that small details in the model are properly represented, while meshing most of the part with a lower mesh density to optimize the total number of elements. The mesh is a web that consists of elements, with each element containing a node at every corner. The mesh provides the basis for a mould flow analysis, where moulding properties are calculated at every node. The mesh types supported by the software are midplane mesh, surface or fusion mesh, volume mesh. The Midplane mesh provides the basis for the Flow analysis. These meshes consist of trinode triangular element that forms a one dimensional representation of the part, through its centre. Every moulding process is supported by the mid-plane mesh. The surface mesh provides the basis for the flow analysis. This mesh consist of a mixture of different types, including regions with traditional midplane element and surface (double-skin) shell elements. The surface mesh can be 3 or 6 noded plane, straight-edged triangles. The volume mesh provides the basis for the 3D Flow analysis. These meshes consist of 4-noded, tri-element, solid tetrahedral elements. The density of the mesh is the number of elements per unit area. In general, the more elements there are in the mesh, the more detailed the analysis results, but the longer the analysis time. The mould flow fusion capability allows us to perform detailed analyses directly on a thin-wall, surface mesh model is imported from Mould flow plastic Advisers or an External CAD packages. The connectors are inserted automatically at locations determined according to the geometrical features of the model. A boundary edge is an element edge that is not connected to any other elements. Boundary edges are valid in mid plane model but must not be present in surface meshed fusion model. Boundary edges indicate holes or tears in the mesh and must be corrected either in the original CAD system used to create the model, or using mesh editing tool in mould flow plastic in sight. Following these guidelines the mesh type suited for the component is a fusion mesh. Element used for meshing is 3noded triangular element. Meshed model can be seen in below figure. Fig.3: Mesh Model 2088 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 After meshing with a suitable mesh density, we may need to clean up the mesh .normally some cleanup is necessary if the mesh was translated in from another system. MIP provides a mesh statistics report to check the quality of the mesh and a series of diagnostic displays to locate and highlight specific problems. To clean up the mesh, there is a mesh repair wizard and a mesh tool box. The mesh repair wizard is an automated tool that will find and fix most mesh problems. To perform an analysis, we need to select a suitable material in the material database. In most cases the material to use will be prescribed so we need to locate that material in the database and use it for all analysis work. In other cases, one of the analysis objectives may be to determine a suitable material. There are several techniques available to find a specific grade of material, assess the quality of the material data, fine a substitute material, and compare materials within the select material dialog. 6. Runner Design The fig shown below commonly used runner cross section shaped. The full-round runner is the best in terms of maximum volume-to-surface ratio, which minimizes pressure drop and heat loss. However, the tooling cost is generally higher because both halves of the mould must be machined so that the two semi-circular sections are aligned when the mould is closed. Fig 4: Commonly used Runner Cross-Section The trapezoidal runner also works well and permits the runner to be designed cut on one side of the mould. It is commonly used in three plate moulds. Where the full-round runner may not be released properly, and at the parting line in moulds, where the full interferes with mould sliding action. To compare runners of different shapes, the flow efficiency (L) of the melt through a runner, which is an index of flow resistance, is employed. The higher the flow efficiency of the melt through the runner, the lower the flow resistance is. Flow efficiency can be defined as L = A/P, Where L = flow efficiency of the melt through a runner. A = Cross section area. P = perimeter. Once molten plastic has been injected into the mould cavity, it takes time before the moulding has cooled and become sufficiently rigid to allow it to be demoulded. This period is called the cooling time and often forms a significant part of the moulding cycle. To allow a molded part to cool and solidify, heat must be removed from the mould. The cooling water enters from one side of the plates, circulates and leaves. This normally refers to a fill analysis or a flow analysis. A fill analysis stops when the part volume is just filled to 100%. The flow analysis is a fill analysis but continues through the packing and even cooling phases of the moulding cycle. We can identify and resolve a number of moulding issues using fill analysis before running a flow analysis. Solving filling problems is typically an iterative process requiring several analyses. Once the first fill analysis is done the results are reviewed, and a problem is identified and fixed. This may require much iteration of previous steps. There is one major assumption in the sequence described here, namely, that the problem being addressed is a filling related problem. And not packing, cooling or warpage related. The other problem, too are solved by an iterative process, but only after the filling is optimized. Once the runner system is sized, packing of the part can be investigated. Although a flow analysis can be one without a gate or runner, it is not very much recommended. The freeze time of the gate and runners significantly affects the packing of the part. Without a runner and gate, the packing analysis will be less accurate. 2089 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 Fig 5: Filling pattern of material into cavity and Air trap in component Entrapped air in the mould can escape through air vents that are ground into the parting line of the mould. If the trapped air is not allowed to escape, it is compressed by the pressure of the incoming material and is squeezed into the corners of the cavity, where it prevents filling and causes other defects as well. The air can become so compressed that it ignites and burns the surrounding plastic material. We provide vent holes to escape the compressed air after filling.We can produce a uniform volumetric shrinkage with the use of a packing profile. The volumetric shrinkage distribution should be within 2%. When there is a uniform volumetric shrinkage across the part, the likelihood of warpage is reduced. Warpage is simply caused by a variation in shrinkage, therefore, when the shrinkage variation is reduced, so is the warpage.The fill time result shows the position of the flow front at regular intervals as the cavity fills. Each colors contour represents the parts of the mould which were being filled at the same time. Fig 6: Fill Time and Confidence of fill The pressure at V/P switchover results shows the pressure distribution through the flow path inside the mould at the switch over point from velocity to pressure control. Pressure should be zero at extremities of each flow path at the end of filling. The pressure drop occurs as the cavity completing the filling and. The maximum pressure 0.8010Mpa is noted. Fig 7: Pressure Drop and Temperature at flow front Temperature at flow front result shows the temperature of the polymer when the flow front reached specified point, in the center of the plastic cross- section. The flow front should not drop more than the range shown in fig during the filling phase. Large changes often indicate that the injection time is too low, or there are areas of hesitation. If the flow front is too low in a thin area of the part, hesitation may result in a short shot. In areas where the flow front temperature increases by several degrees, material degradation and surface defects may occur. At the start of injection the result temperature is 240.1 C which shows in red colour and at end of injection the result temperature is 214.5 C which shows in dark blue colour. 2090 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 Fig 8: Time to reach Ejection Temperature and Weld lines Cycle-time optimization starts at design stage. Cooling time takes up over 50% of cycle time. Therefore understanding of cooling in the mould becomes very important. Injection molding is a cycle operation. The cycle consist of Mould closed and clamp, (few second- depends on machine speeds) Injection Fill (speed) phases, (few seconds) Switchover and pack (pressure) phases, (few seconds). Cooling time, (40 to 60% of cycle time) Actual filling time: 5.76 sec , Cool and pack time: 396.50 sec ,Mold open: 5.00 sec , Total time: 407.25 sec. The clamping force result is a time-series result which shows the force of the mould clamp over time. It is force resultant from filling and packing pressure that acts to open the mould. The clamp force is a function of injection pressure and the projected area of the part. A good clamping force results should show the maximum clamp force applied is less than 80% of the machine limits, allowing the remaining 20% as a safety force. The clamp force result can produce misleading result if the model has overlapping surfaces is added. Use pressure profiles or adjust part wall thickness to reduce the clamp force requirement. The maximum clamping force is noted as 0.194 tonnes. 7. Results and Discussions: The following result parameters that are obtained from the analysis. First Fill time :- 5.765 Sec Cycle Time :- 407.25 Sec Injection Pressure :- 0.8010 Mpa Injection Temperature :- 240.1C Average Temperature :- 240.0 C Mold Temperature :- 40.0C Maximum Clamping Force :- 0.194 tonnes Holding Pressure :- 40 Bar Clamping Pressure :- 60 Bar Injection Time :- 1.5Sec Cooling Time :- 60 Sec Shot Weight : 123 grm Injection Pressure : 1486 Bar Clamping Force : 75tons Distance between the bars : 350 x 300mm Mould thickness : 125 - 310mm Table.3 Plastic Material Mechanical Properties Material Specific gravity Melting point (F) Melting point (C) Epoxy 1.12 to 1.24 248 120 Phenolic 1.34 to 1.95 248 120 Nylon 1.01 to 1.15 381 to 509 194 to 265 Polyethylene 0.91 to 0.965 230 to 243 110 to 117 2091 Mohd Jamsheed et al. / Materials Today: Proceedings 2 ( 2015 ) 2083 2093 Polystyrene 1.04 to 1.07 338 170 8. Mould Design CAM BUSH Name of the components : CAM-BUSH Material : NYLLON-66 Weight of the component : 66grm Shrinkage Allowances : 0.5% Average wall thickness of the mould : 15mm Closed shut height of the mould : 250mm Maximum day light : 610mm Tool type : two plate, two cavity mould Distance between the tie bar : 350 X 300 mm Fig 9: Solid Model of Cam Bush Sprue Bushing: The maximum diameter of the sprue should be atleast 6mm in diameter. The minimum diameter should be greater than nozzle orifice by 0.5-1mm. The length of the sprue channel should be as short as possible and never 100mm long. The sprue included angle has to be 4-5. Design of runner: The main consideration for the designer to design a mould is the shape and cross section of the runner, the size of the runner and Layout of the runner. The different shapes of the cross section of the runner are fully rounded, semicircular, trapezoidal, modified trapezoidal, hexagonal, square and rectangular. Semi-circular cross section type runner is selected because it is easy to machine. Runner diameter calculation: D = (W *4L)/3.7= (66 *416)/3.7 = 4.39mm, D- Diameter of runner, L- Length of Runner = 16mm, W- Weight of Cam Bush= 66g.The temperature of the mould must be maintained at some constant temperature below the heat point of the plastic, in order to chill it to a rigid state. Differential cooling strains are set, if the mould temperature is not uniform and those strains may cause distortion of the moulding after ejection. The heat input is supplied by the injection heating cylinder to plasticize the material must be removed from the mould to permit ejection.Q = m x Cp x (Tmat Tmould) + Lt = 66 x 0.4x (240 40) +57.8= 9094.8cal/hr. Cost Estimation 1. Mould Cost Raw material (EN-353) = Total w.t of the EN-353 in the tool (Kg) x raw material cost per Kg = 78 x 140 = Rs10,920/- Raw material (Mild Steel) = Total weight of the EN-36 in the tool (Kg) x raw material cost per Kg = 230 x 85 =Rs 19,550/- Raw material (OHNS) = Total weight of the OHNS in the tool (Kg) x raw material cost per Kg = 40 x 115 =Rs 4,600/- Total Raw material cost = 10,920 + 19,550 +4,600 =Rs 35,070/- 2. Machining Cost Machining cost = (Milling hrs Rs/hr) + (Polishing hrs Rs/hr) + (drilling hrs Rs/hr) + (Tapping hrs Rs/hr) + (Surface Grinding hrs Rs/hr) + (H. T Rs/kg) + (CNC EDM hr hr/kg) + (CNC Milling hrs hr/kg) + (CNC Wire cut Rs/hr)= (45 x 200) + (18 x 250) + (9 x 225)
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