Moulding and core making
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This document provides an overview of moulding and core making, detailing the definition and characteristics of moulds, types of moulding processes, and methods of creating sand moulds. It distinguishes between expendable and permanent moulds, as well as machine operations that enhance efficiency and accuracy in mould production. Specific methods such as jolting and squeezing for sand compaction are covered, emphasizing the importance of dimensional precision in castings.
Moulding and core making
- 1. Moulding and Core Making Prepared by, Ankit Saxena Assistant Professor ADGITM,NEW DELHI
- 2. Mould? A mould is a hollowed-out block that is filled with a liquid like plastic, glass, metal, or ceramic raw materials .The liquid hardens or sets inside the mould, adopting its shape. A mould is the counterpart to a cast. • Mould or Mould cavity contains molten metal and is essentially a negative of the final product. • Mould is obtained by pattern in moulding material (sand). • Mould material should posses refractory characteristics and withstand the pouring temperature.
- 3. Types of moulding: 1.Hand moulding- are used for odd castings generally less than 50 no. and ramming is done by hands which takes more time. 2.Machine moulding- are used for simple castings to be produced in large numbers. Ramming is done by machine so require less time. 3.Bench moulding- moulding is done on a bench of convenient height to the moulder and is used for small castings. 4.Floor moulding-moulding is done on the foundry floor and is used for all medium and large castings. 5.Pit moulding- moulding is done in a pit which act as drag and is used for very large castings
- 5. Characteristics 1.Should have the desired shape and size. 2.Must be produced with due allowances for shrinkage of the solidifying material. 3.Any geometrical feature desired in the finished casting must exist in the cavity. Consequently, the mould material must be able to reproduce the desired detail. 4.Should have are refractory character so that it will not contaminate the molten material. 5.The mould must be made from a material that can with stand repeated use. Types of Moulds Basically moulds are two types: 1.Expendable moulds- are made of sand and is used for single casting which break upon solidification. 2.Permanent moulds- are made of metal or graphite (costly) and used repeatedly for large number of castings which do not break upon solidification.
- 7. Open Mould Close Mould
- 8. Method of moulding SANDMOULDING Hand ramming is the preferred method of mould making when only a few castings are to be made from any given design, and some small foundries still make their moulds by hand moulding. In most cases sand moulds are made by specially designed moulding machines. Various moulding methods differ in following aspects: 1) Type of flask required, 2) Method of packing the sand with in the flask, Whether mechanical assistance is provided to turn or handle the mould. In all cases the moulding machines greatly reduce the labour and Skill required, and give to castings with better dimensional accuracy and consistency moulding usually begins with a pattern and a flask. Sand is generally packed in the flask by following basic techniques. Machine Moulding Moulds are produced by machines for mass production of castings. A moulding machine performs following functions: 1) Filling of sand 2)Ramming of sand 3)Lifting of pattern from mould 4) Rolling mould section Following are the main moulding machine: 1) Jolt M/c 2) Squeezing m/c 3) Sand slinger 4) Diaphragm moulding m/c 5) Stripper plate m/c M/c moulding requires mounted patterns and is faster and more uniform than bench moulding
- 9. JOLTING: i. Sand is placed on top of the pattern. ii. Pattern flask, and sand are then lifted and dropped several times. iii. Kinetic energy of the sand produces optimum packing around the pattern. iv. Jolting machines can be used on the first half of a match-plate pattern or on both halves of a cope-and-drag operation. SQUEEZING: i. Uses either an Air operated squeeze head, or a Flexible diaphragm to compact the sand. ii. Squeezing provides firm packing near the squeeze head, but the density diminishes farther into the mould. iii. High pressure machines with a flexible diaphragm (commonly called Tac cone machines) can produce a more uniform density around all parts of an irregular pattern.
- 10. i. Combination of jolting and squeezing is often used to produce a more uniform density through out the mould. ii. A match plate pattern is positioned between the cope and drag sections of a flask, and the assembly is placed upside down on the moulding machine. iii. A parting compound is sprinkled on the pattern, and the top section of the flask is filled with sand. iv. Entire assembly is then jolted a specified number of times to pack the sand around the pattern. v. A squeeze head is then swung into place, and pressure is applied to complete the upper portion of the mould. vi. Flask can be inverted and operation repeated on the cope half, or the cope and drag can be made on separate machines using cope-and-drag patterns. vii. Except for small moulds, moulding machines usually provide mechanical assistance for inverting the heavy molds. viii. Gating system and runners can be hand cut or can be made part of pattern. ix. After completing themold, tapered flask may be removed to prevent possible damage to the flask during the pour. x. As lip jacket, an inexpensive metal band, may be positioned around the mould to hold the sand in place. xi. Heavy metal weights are often placed on top of the moulds to prevent the sections from separating as the hydrostatic pressure of the melt presses the cope upward.
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