Type: Process Essays
Sample donated: Franklin Dunn
Last updated: July 24, 2019
This chapter is mainly describingthe theory and research which have been defined and done by various researcheryears ago.
Related information of previous studies is extracted as referencesand discussion based on their research about gel coat thickness, laminatecomposite structure, mechanical and physical propertiesMaking a casting is one of the oldestmanufacturing techniques known to mankind and an immediate method for creatingmetal parts. The essential castings can be backpedalled to out of date China isthe fourth century B.C. Through the casting system,fluid metal is filled a shape that matches the last estimations of the finishedproduct.
While all metals can be cast, the most common are aluminium, iron,copper-base, and steel combinations. The range of casting is in weight fromless than an ounce to single parts measuring a few hundred tons as shown atfigure 2.1 Casting process of metal parts 4th century B.C. (Habashi, 2007) Defectssuch as porosity and shrinkage are exist in sand casting process to permanentmould casting. Design is the progress to make improvement of high quality andcost effective of the casting product. In designing a decent permanent mould,the part geometry assumes an important part.
The primary reason for designingthe moulds is to concentrate the fluid metal compression until to the last partof the casting to solidify. Besides, comprehensive set of economical permanentmould is important to produced. The first part that must consider in sandcasting mould preparation is the gating system. (Groover,2012)The design of framework is extremely basicto the casting processes since it will influence the ensuing design proceduresand impact the quality of the casting product. Besides, gating designs is theimportant part must be considered if not it could lead to various defects suchas gas porosity, shrinkage, flow lines, cold shuts and poor surface finish.
Astandout amongst the most approaches was using a continuous gating system and abigger size runner, and the fluid metal speed through the gating was slightlyreduced. (Butler,2001) (Jhavar,Paul, & Jain, 2013), the authors describe the causes offailures and repairing alternatives in designing of die and mould in the designstage. Designing of permanent moulds for casting can be considered as art andscience. The rigging system which is runners, gates, risers, overflows and cooling channelsare the most important partof the mould. Presently, the current practice in designing mould is anexperimenting method where based on trial and error. The experimentationstrategy exclusively relies upon learning and experience of design engineers.However, this practice leads time consuming and high cost.
This paperpresents the connecting rod crankshaft as a case study. The objective of thisresearch is to design and analysis the systems for die casting using computerengineering analysis software. The simulation presents the analysis of staticpressures, velocity magnitude, turbulence kinetic energy, internal energy andcell Reynolds numbers. Based on the simulation results, the die casting wasdeveloped.The die casting process is a name given to metal castingprocesses that utilize metal moulds or permanent dies. There are really severaldistinct processes included under the general name.
The die casting process hasthree main sub-processes. These are permanent mould casting, also calledgravity die casting, low-pressure die casting, and high-pressure die casting.The three processes differ mainly in the amount of pressure that is used toforce the molten metal into the die.
In fact, the useful of the mould dependslargely on the pouring temperature, the material of the mould and thecomplexity of the component being cast. Figure 2.2 illustrated the process treeunder permanent mould casting process. (Kalpakjian, S. &Steven, 2009)The alternate elements that have been consider are mouldpreheating, mould coating, rigging system, gating design, runner design and whetherthe operation is manual or automated. The end use of the casting also has abearing (If the auxiliary capacity is the main criteria, and not itsappearance, a mould can be utilized longer before disposing).
In spite of thefact that, all things considered, the permanent moulds are metallic, graphitemoulds, used at times, also come under the category of Permanent Moulds. Whensand cores are used, it is called a Semi-Permanent Moulding (SPM) process. (M. S. Ramaprasad& Malur N. Srinivasan, 2012).
(Lampman, 2009) describes permanent mould casting is a casting process that uses non-expendablethat are either made from metal or graphite. Permanent mould processes involvethe production of castings by pouring molten metal into permanent metal moldsusing gravity, low pressure, vacuum or centrifugal pressure and simple reusablecores are usually made of metal. High volume production of non-ferrous metal due to therepeatability used is one of the permanent mould advantages. Furthermore, thesurface finish for the permanent mould is more better compared to theconventional method which is sand casting. The immense heat transfer rate acquiredby methods for metal moulds can additionally refine and enhance the last caststructure, and along therefore the mechanical properties of the castings due tofaster cooling rate. Moreover, the other benefit that it has is it also adimensional stability, geometric fidelity, and near net shaped castings. (Ravi, 2004)Die casting mould have a good surface roughness than conventionalmethod which is sand casting because it is production of castings with uniformwall thickness with 3.
0mm can be cast, closer dimensional tolerances and bettersurface finish that will restricted undercuts that will enhanced mechanical properties(Lampman, 2009). As shown on Figure 2.3 is the illustrates of tolerance rangeagainst surface roughness of various process include die casting and sandcastings process.The disadvantages or designlimitations for the die casting mould is due to high cost, metal dies, longerlead time for die production and for changes to the die caused by a castingdesign change (Butler, 2001). Die casting mould casting has a few contraints, for example, notall compounds are appropriate for die casting mould casting because of the relatively high tooling costs, and a long set-up time of theprocedures because of that, a highly generation volume is required to keep thisprocess economically variable manufacturing option. The process can be restrictivelycostly for low production amount.
Furthermore, some shapes cannot be made usingdie casting mould casting, because of parting line location, undercuts, ordifficulties in removing the casting from the mould. Finally, coatings are required to protect the mould from attack bythe fluid metal (Lampman, 2009). Otherwise, die casting process is in general limited to smallercastings. Besides, its higher the pouring temperature of the fluid metal and itwill shorter the life of the mould. (Zheng, Wang, Zhao, & Wu, 2009). Table 2.1 shown the gravity die casting and other castings.Defects reduce the performance and increase the cost of castings.
It is critical to understand the mechanism of defects and microstructure on theperformance so that an effective tool can be developed to prevent defects andcontrol the microstructure. There are several defects that happen in castingprocesses. Those defects are dependent on the chemistry of alloys, castingdesign, and casting processes (Lampman 2009). (Strojniški, 2013) describes defects produced in aluminium alloy die casting diesduring die operation. The most frequent defect is thermal fatigue cracking.Hardness and toughness is measured on specimens cut from different parts ofused die casting die. The results show a significant difference in materialmicrostructure and hardness between the surface and the core. Figure 2.
4 shown theseveral types defect of casting.As one ofthe oldest manufacturing methods, casting involves pouring molten metal into amould cavity that is con?gured to the shapes and dimensions of the ?nishedform. The methods of shape casting can be divided into several broadcategories, as illustrated in Figure 2.5.
The main categories are expendablemoulds with permanent patterns, expendable moulds with expendable patterns andMetal or permanent mould processes. (Strojniški, 2013).Otherwise die casting mould is also called permanent mould,it does not mean that the moulds are permanent. Indeed, the administration lifeof the mould depends generally on the pouring temperature, the material of themould and the unpredictability of the component that being cast.
PermanentMoulds are used in many variants of casting processes like Gravity Die Casting(GDC), Low Pressure Die Casting (LPDC), High Pressure Die Casting (HPDC),Centrifugal Casting (CFC), Squeeze Casting (SC) and Continuous Casting (CC). (M. S. Ramaprasad& Malur N. Srinivasan, 2012)The mostimportant things to consistent and have a good casting design is how to choosea suitable geometry. For make a cost-effective casting design, there are sixparameters based on physics that must considers. There are four considerationsbased on casting properties such as, liquid metal fluid life, solidificationshrinkage type, slag/dross formation tendency and pouring temperature.Furthermore, there also have two other design parameters are based onstructural properties which is section modulus and modulus of elasticity.
Geometry is not only the result of the product function design, it also influencesthe of cost-effective that are economically produced, machined, and assembledinto a final product (Lampman, 2009) In designing a permanent mould thereset of general guidelines that can be followed such as design the part to makea shape of cast is easy, locate the parting line of the mould in the part,locates the design gates to allow uniform feeding of the mould cavity, selectappropriate runners geometry for the system and locate mould features such assprue, screen and riser as appropriate (Kalpakjian, S. &Steven, 2009)The riggingsystem includes the system of sprues, runners, gates, risers, and chills thatchannel and control the ?ow of liquid metal into the mould cavity, feed thecasting as it solidi?es, and control the heat transfer and rate ofsolidi?cation in critical regions. Rigging system design speci?es the size,dimensions and location of sprues, runners, gates, risers, and chills thatcomprise the system. In the traditional approach, an expert casting engineerdesigns the rigging system, usually after the geometry of the casting has beenspeci?ed. Rigging design decisions typically include selection of thefollowing: orientation of the cast part, parting line, potential sites forchills and chill types, sprue height and location, runner types andcon?guration, ingate sites, choke area, riser sites and con?guration, andpouring rate and temperature. (Stoll, 2009)(Banchhor & Ganguly, 2014) describes risers are used for prevention of shrinkage defects(Figure 2.6). However, they decrease the usage rate of metal and extend thecooling time of castings after solidification as well.
Therefore, proper risersize needs to be designed to satisfy feeding with the smallest volume. (Howells, 2003) describes risering, deals with the development of suitablereservoirs of feed metal in addition to the desired casting shape so thatundesirable shrinkage cavities in the casting are eliminated or moved tolocations where they are acceptable for the intended application of thecasting. When metals solidify and cool to form a casting, they generallyundergo three distinct stages of volume contraction, or shrinkage. Solidshrinkage, also called patternmaker’s shrinkage, is accommodated by making thepattern and, therefore; the mold cavity, somewhat larger than the desireddimensions of the ?nal casting. Liquid shrinkage and solidi?cation shrinkageare the concern of risering practice.
In the absence of risers, a casting wouldotherwise solidify as shown in Figure 2.7. (Lampman 2009)To determine the correct riser locations, the designer should makeuse of the concept of directional solidi?cation. If shrinkage cavities in thecasting are to be avoided, solidi?cation should proceed directionally fromthose parts of the casting farthest from the riser, through the intermediateportions of the casting, and ?nally into the riser itself, where the ?nalsolidi?cation will occur. Shrinkage at each step of solidi?cation is thus fedby liquid feed metal being drawn out of the riser.
(Kalpakjian, S. & Steven, 2009) Figure 2.8 shown the direction and progressive solidification incasting.