112124, 0:44 PM Manufacturing Processes-1 MEM-103 Manufacturing Processes-1 Welcome Student Lecture Notes MEM103 Home Lesson 1 CASTING PROCESS Lesson 1 Download ‘Supplementary Material 1.0 Objectives 4. Casting Simulations 1.1 Casting Process 2. Self-check questions 1.1.1. Advantages of Casting Process 3. Frequently asked questions 1.1.2 Applications 4. Terminal questions 4.2 Sand Casting Process 113 Casting Terminology 1.4 Gating System CASTING PROCESS The principle of casting is similar to process of ioe making in @ house. For making an ice cube, the water (liquid) is poured into a tray of desired shape (mould) and placed in fridge (Le. cold environment, below 0°C). It can be observed that water (any liquid) will take the exact form or shape of the vessel (tray) that contains it. Further, when water (any liquid) is frozen (solide), it wil have the exact form or shape of the vessel (tray) that contains it. Therefore, consider the ice cube example and examine what is invoived in "casting" of water. The water, a liquid at room temperature, is poured into a vessel (he ice cube tray) and then we solify ((teeze) the water inthe freezer and we have made ice cubes. Each cube is the exact shape and size of the compartment that contained it. In this case the water is the material cast, the ice cube try isthe vessel fr "mould" and the “ridge” solcies the water by cooling or freezing it. Tne steps in casting process are: making a mould of a suitable material melting the metal and heating t to a specific temperature, pouring it into the mould and allowing the metal to solidify and cool. After cooling casting is removed from the mould 1.0 Objectives ‘fier going through this lesson, you willbe able to 4. To understand the process of casting along with its application and advantages. 2.To understand the steps involved in casting 3, To be able to acquaint with casting terminology, 14. Casting Process Its a manufacturing process in which molten material is poured into a mould (or cavity) and allowed to freeze so as to take the shape of the ‘mould. The term casting is used to denote both the product and the process. The section of the workshop were metal castings are produced is known as foundry or foundry shop. Casting process is based on the property of Iquids to take up the shape of the vessel into which they are poured. Molten metal when poured into a cavity of desired shape flows into every recess and comer ofthe cavity and fils the space. When this metal solidifies, it has the shape and size (of the cavity and thus, ina single step, simple or complex shapes can be made from any metal that can be melted. 1.1.1 Advantages of Casting Process Cast metal products and processes offer advantages unavailable from products made by other manufacturing techniques. The following are reasons thal make casting process important in manufacturing industy. 41, Cast components are net or near-net snape, 2. Almost all metals and alloys can be cast. 43, Thre are almost no restrictions on part weight or size 4. Invicate parts can be produced as single cast components. 5. Castings can be manufactured to include complex interior cavities. 6.Allthe industty’s products are fully recyclable. 1.1.2 Applications Cast parts range in various sizes and variety of shapes (such as the individual teeth on a zipper to an engine block of a heavy duty truck). Sc~ of the examples of castings are cylinder blocks of airplane engine, piston rings, machine tool beds, water supply and sewer pipes, locomo wheels, huge propellers etc. Figure 1.1 gives some cast pars, Fig. 1.4 Cast Parts in typical automobile 4.2. Sand Casting Process ‘The most universal method of making castings is by using sand moulds, Sand moulds are made by ramming sand in a metallic or wooden flask ‘Such a casting process is commonly refered to as sand casting process. -ntps:imsvs-do vlabs.acinimem109/Unt3lossont tm wa112124, 0:44 PM Manufacturing Processes-1 Patter Making Pattern Core haking toons sana fo] owas y Heal ot bef Neta into el and Loe Removal > ‘and. Lye for detects, & Motal Mouis || coaing |” | ofrisers finishing | |g cy imensions ches Fig. 4.2 Production steps in a typical sand ting process The stops required for making metal castings using sand casting process are mentioned below and also depicted in Fig. 2.2: Step 1: Pattern making Step 2: Core making, Stop 3: Mould making, Step 4: Melting of metal and pouring, ‘Step 5: Cooling and soliification, and Step 6: Cleaning of castings and inspection ‘Step 1 -Pattern making The frst step in sand casting is pattern making. The pattern Is a physical replica ofthe exterior of the casting with dimensional allocation for shrinkage and finishing used to make the mould, The cavily in tne mould is prepared with the help of the pattern and isa replica of the casting required. Itis constructed in such a way that it can be used for forming an impression in sand or other material used for making the mould. The pattern can be made from anything as long as itis robust enough to be handled during the mould making process. Patterns are usually made of ‘wood, plastic, metal, or plaster. A pallor has to be made before making a mould Step 2 - Core making The next step in the process is core making. If the casting is to be hollow, additional pattern called cores are used to create these cavities in the finished product. Cores are pre-determined shaped mass of dry sand, which are placad into the mauld before pouring the molten metal to create the interior contours of the casting. They are typically made of a sand mixture - sand combined with water and organic adhesives called binders- \hich is baked to form the core, This allows the cores to be strong yet collapsible, so they can be easly removed from the finished casting, Since cores are made in moulds, they require a pattern and mould, called a core box. ‘Step 3 - Moulding [Moulding isthe mull-step process in which moulds are created with the desired cavity ina sultable material ike sand, o pour the molten metal. The mould is made by packing some reaclly formed aggregate material, such as moulding sand, around the patter. When the pattem is withdrawn, its imprint provides the mould cavity, which is ultmately fled with metal to become the casting. A mould is required to got the desired shape and size of the metal casting. Sand is a good refractory material for most ofthe metals and is mostly used for moulding. Stop 4 -Melting & Pouring Melting isthe preparation ofthe molten metal for casting, and its conversion from a sold to a quid state in a furnace. It's then transferred in ladle ta the moulding area ofthe foundry where i is poured into the moulds. After the metal has solidified, the moulds are vibrated to remove the ‘sand from the casting, a process called shakeout. For melting of the metal during casting diferent types of furnaces are used. The type and size of te furnace may depend on the size of casting, quantiy to be produced, production rate, and metal tobe cast Stop 5 - Cleaning Cleaning generally refers to the removal ofall materials that are not pat of the finished casting. Rough cleaning isthe removal ofthe gating systems from the casting, Initial finishing removes any residual mould or core sand that remains on the piece ater it is free of the mould ‘Trimming removes any unnecessary metal, In the last stages of fishing, the surface ofthe casting is cleaned for Improved appearance. 1.3 Casting Terminology The Fig. 1.3 presents the cross-section of a typical two-part sand mould and incorporates many fealures of the casting process. The casting starts with the construction of a pattern, a duplicate of the final casting with allowances. The moulding material is then packed around the Pattern, and the patter is removed to produce a mould cavity. The term casting is used to describe both the process and the product when riolten metal is poured and solidified in a maul Flask The flask isthe box that contains the moulding aggregate. Cope -ntps:imsvs-do vlabs.acinimem109/Unt3lossont tm 218172126, 0:44 PM Manufacturing Processes-1 In a two-part mould, the cope is the top half ofthe pattern, flask, mould or core. Open Riser Pouring Basin Cope: Drag) Fig. 4.3 Cross-section of a typical two-part sand mould, presenting various mould components and terminology Drag The drag is the bottom half of any ofthe patter, flask, mould or core. Acore is a sand shape that is inserted into the mould to produce internal features on a casting, such as holes or passages for water cooling. Core Print ‘Acre prints the region added to the pattern, core, or mould thats used to locate and suppor the core within the mould. The mould material and the core then combine to form the mould cavity, the void into which the molten metal wil be poured and solidified to produce the desired casting Parting Line The parting line or parting surface is the interface that separates the cope and drag halves of the mould, ask, or pattern, and the halves of a core during some core-making processes. Draft ‘The drafts the taper on a pattern or casting that permits it to be withdrawn from the mould, The mould or die used to produce casting cores is known as a core box. Pouring cup The molten metal is not directly poured into the mould cavity because it may cause mould erosion. Molten metal is poured into a pouring basin which acts a8 a reservoir rom wnicn t moves smoothly into the sprue. Spruce ‘Sprue helps in feeding metal othe runner, which in turn reaches the cavity through the gates, The sprue may have either stright or taper shape. In straight or parallel sprue, the metal contracts inwards and is pulled away from the sprue walls, as shown in Fig. 1.4. In a tapered sprue, the liquid metal ows dawn fly n contact with walls and this reduces turbulence and eliminates sucking of gas or air fom the mould. A tapered sprue is illustrated in Fig. 1.4 Damage Pattern: | f= Draft Angle — c ‘Sand Mold ————————— Poor Good Fig. 4.4 Straight and tapered sprue Sprue base ‘This isa reservoir for meta atthe bottom ofthe sprue to reduce the momentum ofthe faling molten metal. The molten mata, as it moves down the sprue gains in velocty, some of which is lost inthe sprue base well, and the mould erosion is reduced. This molten metal changes direction inthe sprue base and flows into the runner in a more uniform way. Riser The riser is designed to serve as a reservoir of metal which stays liquid longer than the casting and "feeds" liquid to il any shrinkage cavities which tend to develop in the casting. Ifthe metal does not appear in the riser, it signifies that either the metal is insufficient to fil the mould cavity -ntps:imsvs-do vlabs.acinimem109/Unt3lossont tm sia112124, 0:44 PM Manufacturing Processes-1 for there is some abstraction tothe metal low between the sprue and riser. Runner Runner is used to take the molten metal from the sprue base and distribute it to several gate passageways around the cavity. Gate The gate is a channel, which connects runner with the mould cavity ang through which molten metal fows to fil the mould cavity. In top gating, the motten materia falls directly into the mould cavity through a neight as shown in Fig. 1.5 (a). Pouring CUP Strainer Core Cope, uit Mould Cavity RT US pe Drag «Mould Cavity Drag {a) Top Gate (b) Bottom Gate (c) Parting Gate Fig. 1.5 Different types of gates In bottom gating, shown in Fig. 1.5 (b, the molten material enters the mould cavity from the bottom and hence there is ne problem of scouring ‘and splashing. But, in case of bottom gating system since molten material enters from bottom, if freezing of molten metal takes place then it Could choke off metal flow before mouid is ful, Bottom gating creates an unfavorable temperature gradient and makes it difficult fo achieve directional solidification. Bottom gating is used for heavy castings. in parting gate the molten material enters the mould atthe parting plane, as shown in Fig. 15 (0) 1.4 Gating System Gating systems are necessary for the molten meta to flow into the mould cavity. The gating system is the network of channels used to deliver the molten metal from outside the mould into the mould cavity. The way in which the iquid metal enters the mould has a decided influence upon the quality and soundness of the casting, the diferent components of a gating system should be carefully designed and produced. Different ‘components of gating system are shown in Fig, 1.5 Pouring CupSite Riser Casting Fig. 1.6 Components of gating system Lecture 2 {© MEM103-Dayalbagh Educational Institute (www.delac.n) Alay Kant Upadhyay -ntps:imsvs-do vlabs.acinimem109/Unt3lossont tm 48