Pattern and their types
- 1. ME8352: MANUFACTURING TECHNOLOGY-I PATTERN AND THEIR TYPES Presented by S.Kannan Assistant Professor Department of Mechanical Engineering Vel Tech Engineering College Avadi-Chennai-62
- 2. INTRODUCTION TO CASTING • Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. • It is most ancient process of manufacturing metallic components.
- 4. PATTERNS • In casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process. • It is not exact replica of the exact desired casting. • It is slightly larger than the desired casting, because of allowances.
- 5. TYPES OF PATTERN 1. Single piece pattern 2. Split piece pattern 3. Loose piece pattern 4. Gated pattern 5. Match plate pattern 6. Sweep pattern 7. Skeleton pattern 8. follow board pattern 9. Shell pattern
- 6. TYPES OF PATTERN 1. Single piece pattern: It is simplest of all pattern is made in one piece. It is suited for limited process only. 2. Spilt piece pattern: It is used for intricate casting for usual shapes. These two patterns are joined together with the help of dowel pins.
- 7. TYPES OF PATTERN 3. Loose piece pattern: Some patterns usually single piece are made to have loose pieces in order to enable their easy with drawn from the mould.
- 8. TYPES OF PATTERN 4. Gate pattern It is simply one or more loose patterns Having attached gates and runners. 5. Match plate pattern It is a split pattern having the cope And drags portions mounted on opposite sides of a plate (usually metallic),Called as match plate.
- 9. TYPES OF PATTERN 6. Sweep pattern A sweep is a section or board (wooden) of proper contour that is rotated about one edge to shape mould cavities having shapes of rotational symmetry. 7. Skeleton pattern sweep patterns, these are simple wooden frames that outline the shape of the part to be cast and are also used as guides by the molder in the hand shaping of the mould.
- 10. TYPES OF PATTERN 8. Follow pattern Follow board pattern consists of tool that is a simple wooden board which is used in processes where casting structures are weak and they may break after the application of force.
- 11. TYPES OF PATTERN 9. Shell pattern Shell pattern is specially used for obtaining hollow shaped structure. Along the center the parting process is done
- 12. REQUIREMENTS OF A GOOD PATTERN • Secure the desired shape and size of the casting. • Cheap and readily repairable. • Simple in design for ease of manufacture. • Light in mass and convenient to handle. • Have high strength and long life in order to make as many moulds as required. • Retain its dimensions and rigidity during the definite service life. • Its surface should be smooth and wear resistant. • Able to withstand rough handling.
- 13. DESIGN CONSIDERATION IN PATTERNS 1. Proper allowance should be provided. 2. The parting line should be carefully selected. 3. Proper material should always be selected. 4. The wall thickness and sections should kept as uniform as possible. Abrupt changes should invariably be avoided. 5. The use of offset pairing, instead of cores, should be encouraged to as great extent as it is possible. Abrupt changes should invariably be avoided.
- 14. PATTERN LAYOUT Pattern making consists of two different stages to prepare a layout and to shape the different parts. Layout consists of the following steps: a. Initially study the drawing pattern and select a wood that can suitably accommodate two views. b. Take on surface of the wood as base and plane the adjacent surface. c. Take a folding rule and measure the dimensions as per the drawing. d. Prepare the layout by using various measuring and marking tools locating position of core prints and surface to be machined.
- 15. PATTERN MATERIALS • Wood: Piece and short run production • Metal: Large scale and mass production • Cement, Plastics for example epoxy resin: Batch production.
- 16. ALLOWANCEs 1.Shrinkage allowance After solidification of the metal from further cooling (room temp.) dimensions of the patterns increases. So pattern size is bigger than that of the finished cast products. 2.Machining allowance Machining allowance or finish allowance indicates how much larger the rough casting should be over the finished casting to allow sufficient material to insure that machining will "clean up" the surfaces.
- 17. 3.Draft or tapper allowance Pattern draft is the taper placed on the pattern surfaces that are parallel to the direction in which the pattern is withdrawn from the mould to allow removal of the pattern without damaging the mould cavity 4.Distortion allowance This allowance is taken into consideration when casting products of irregular shapes. When these are cooled they are distorted due to metal shrinkage
- 18. 5.Rapping or shake allowance To take the pattern out of the mould cavity it is slightly rapped to detach it from the mould cavity. So the cavity is increased a little.