Core and core prints and types of cores by polayya chintada

Core and core prints and types of cores by polayya chintada

1. P roduction Technology: CORE AND TYPES OF CORES COURSE CODE: C211 REGULATION: R19 2 nd BTECH 2 nd SEM PREPARED BY : POLAYYA CHINTADA M.TECH,M.B.A,(PhD) ASSISTANT PROFESSOR LENDI INSTITUTE OF ENGINEERING AND TECHNOLOGY

2. 2 PRODUCTION TECHNOLOGY SYLLABUS UNIT 1: Introduction: Importance and selection of manufacturing processes. Casting Processes : Introduction to casting process, process steps; pattern: types, materials and allowance; Cores: Types of cores, core prints, principles and design of gating system; Solidification of casting: Concept, solidification of pure metal and alloy; Special casting processes: Shell casting, investment casting, die casting, centrifugal casting, casting defects and remedies. provide insight into Working principles of different metal casting processes and gating system COURSE OBJECTIVE: COURSE OUTCOMES: Explain different metal casting processes and gating systems. (L2) APPLICATIONS: Identify different patterns and their allowances (L3) 1 . Heavy Equipment : Construction, farming and mining 2. Defence : Vehicles, artillery, munitions, storage and supporting equipment 3. Hardware : Plumbing industry pipes, joints, valves and fitting Identify the various casting defects. (L3 )

3. CORE Core can be made by sand +binder+water The shape of the core depends on to the shape of the internal feature to obtained Core is metal or sand body, which is set into the prepared mould before closing or pouring it . These are used to produce holes, projections, cavities in casting. Cores are used where some shapes cant be produced by pattern core as a sand shape is generally produced separate from the sand mold and is then baked (hardened) to facilitate handling and setting into the mold. Cores may be made up of sand, metal, plaster or ceramics. Cores are used in sand molding as well as permanent molding core is kept on seat in the mould box prepared by pattern.

4. EXAMPLES OF CORE AND ITS PRODUCTS

5. CORE FUNCTIONS & CHARACTERISTICS Different Functions (Purposes) of Cores For hollow castings, cores provide the means of forming the main internal cavities . Cores may provide external undercut features Cores may be employed to improve the mold surface Cores may be inserted to achieve deep recesses in the castings. Cores may be used to strengthen the molds Cores may be used to form the gating system of large size molds . A Core must possess Sufficient strength to support itself and to get handled without breaking. High permeability to let the mold gases escape through the mold walls. Smooth surface to ensure a smooth casting. High refractoriness to withstand the action of hot molten metal (metal penetration etc.). High collapsibility in order to assist the free contraction of the solidifying metal. Characteristics of (dry sand) Cores

6. TYPES OF CORES Cores may be classified according to The state or condition of core Green sand core Dry sand core The nature of core materials employed Oil bonded cores Resin bonded cores Shell cores Sodium silicate cores D. The shape and position of the core Horizontal core Vertical core Hanging or cover core Balanced core Drop core or stop off core Ram up core Kiss core. C. The type of core hardening process employed The hot box process The cold set process Fluid or cast able sand process Furan-No-Bake system Oil-No-Bake process

7. Green sand cores Green sand cores are formed by the pattern itself. A green sand core is a part of the mold. A green sand core is made out of the same sand from which the rest of the mold has been made i.e., the molding sand. DIS ADVANTAGE S Lack of strength Difficult to make long narrow core features

8. Dry sand cores Dry sand cores (unlike green sand cores )are not produced as a part of the mold. Dry sand core are over come some of the dis advantages of green sand core Dry sand cores are made separately and independent of the mold. A dry sand core is made up of core sand which differs very much from the sand out of which the mold is constructed. A dry sand core is made in a core box and it is baked after ramming. A dry sand core is positioned in the mold on core-seats formed by core-prints on the patterns. A dry sand core is inserted in the mold before closing the same.

9. Horizontal core Fig. shows horizontal core. A horizontal core is positioned horizontally in the mold. A horizontal core may have any shape, circular or of some other section depending upon the shape of the cavity required in the casting. A horizontal core is supported in core seats at both ends. Uniform sectioned horizontal cores are generally placed at the parting line. A horizontal core is very commonly used in foundries .

10. Vertical core Fig. shows a vertical core. On the cope side, a vertical core needs more taper so as not to tear the sand in the cope while assembling cope and drag. A vertical core is named so because it is positioned in the mold cavity with its axis vertical. The two ends of a vertical core are supported in core seats in cope and drag respectively. A big portion of the vertical core usually remains in the drag A vertical core is very frequently used in foundries.

11. Hanging or cover core Fig. shows a hanging (cover) core It is known as hanging core because it hangs; it is also called cover core if it covers the mold and rests on a seat made in the drag. A simple hanging core is one which is not supported on any seat rather it hangs from the cope with the help of wires, etc. A hanging core is supported from above and it hangs vertically in the mold cavity. A hanging core has no support from bottom. A hanging core is provided with a hole through which molten metal reaches the mold cavity. Hanging cores can be made up of either green or dry sand.

12. Balanced core Fig. shows a balanced core. A balanced core is one which is supported and balanced from its one end only . only blind holes or holes which are open at one side are produced by balanced casting. A balanced core requires a long core seat so that the core does not sag or fall into the mold. A balanced core is used when a casting does not want a through cavity.

13. Drop or stop off core Fig. shows a Drop or stop off core. A stop off core is employed to make a cavity (in the casting) which cannot be made with other types of cores . A stop off core is used when a hole, recess or cavity, required in a casting is not in line with the parting surface, rather it is above or below the parting line of the casting. Depending upon its shape and use, a stop off core may also be known as tail core, saddle core, chair core, etc.

14. Y ours : POLAYYA CHINTADA M.TECH,M.B.A,(PhD) ASSISTANT PROFESSOR