Metal casting processes

 

Metal casting processes

•     Casting is one of the oldest manufacturing process. It is the first step in making most of the products.

 

•     Steps:

-     Making mould cavity

-     Material is first liquefied by properly heating it in a suitable furnace.

-     Liquid is poured into a prepared mould cavity

-     allowed to solidify

-     product is taken out of the mould cavity, trimmed and made to shape

 

We should concentrate on the following for successful casting

operation:

(i)Preparation of moulds of patterns (ii)Melting and pouring of the liquefied metal

Solidification and further

(iii)   cooling to room temperature (iv)Defects and inspection



Advantages

•    Molten material can flow into very small sections so that intricate shapes can be made by this process. As a result, many other operations, such as machining, forging, and welding, can be minimized.

•    Possible to cast practically any material: ferrous or non-ferrous.

•    The necessary tools required for casting moulds are very simple and

inexpensive. As a result, for production of a small lot, it is the ideal process.

•    There are certain parts (like turbine blades) made from metals and alloys that can only be processed this way. Turbine blades: Fully casting + last machining.

•    Size and weight of the product is not a limitation for the casting process.

Limitations

 

•     Dimensional accuracy and surface finish of the castings made by sand casting processes are a limitation to this technique.

 

•     Many new casting processes have been developed which can take into consideration the aspects of dimensional accuracy and surface finish. Some of these processes are die casting process, investment casting process, vacuum-sealed moulding process, and shell moulding process.

 

•     Metal casting is a labour intensive process

 

•    Automation: a question

 

 

Typical sand mould




Important casting terms

 

Flask: A metal or wood frame, without fixed top or bottom, in which the mould is formed. Depending upon the position of the flask in the moulding structure, it is referred to by various names such as drag – lower moulding flask, cope – upper moulding flask, cheek – intermediate moulding flask used in three piece moulding.

Pattern: It is the replica of the final object to be made. The mould cavity is made with the help of pattern.

 

Parting line: This is the dividing line between the two moulding flasks that makes up the mould.

 

Moulding sand: Sand, which binds strongly without losing its permeability to air or gases. It is a mixture of silica sand, clay, and moisture in appropriate proportions.

 

Facing sand: The small amount of carbonaceous material sprinkled on the inner surface of the mould cavity to give a better surface finish to the castings.

 

 

Core: A separate part of the mould, made of sand and generally baked, which is used to create openings and various shaped cavities in the castings.

Pouring basin: A small funnel shaped cavity at the top of the mould into which the molten metal is poured.

 

Sprue: The passage through which the molten metal, from the pouring basin, reaches the mould cavity. In many cases it controls the flow of metal into the mould.

 

Runner: The channel through which the molten metal is

carried from the sprue to the gate.

 

Gate: A channel through which the molten metal enters the mould cavity.

 

Chaplets: Chaplets are used to support the cores inside the mould cavity to take care of its own weight and overcome the metallostatic force.


 


Riser: A column of molten metal placed in the mould to feed the castings as it shrinks and solidifies. Also known as “feed head”.

 

Vent: Small opening in the mould to facilitate escape of air      .



Comments

Post a Comment

Popular posts from this blog

Laser Cutting Machine

Laser cutting     is a fabrication process which employs a focused, high-powered   laser beam   to cut material into custom shapes and designs. This process is suitable for a wide range of materials, including metal, plastic, wood, gemstone, glass, and paper, and can produce precise, intricate, and complex parts without the need for custom-designed tooling. There are several different types of laser cutting available, including fusion cutting, oxidation cutting, and scribing. Each laser cutting process can produce parts with precision, accuracy, and high-quality edge finishes, and with generally less material contamination, physical damage, and waste than with other conventional cutting processes, such as mechanical cutting and waterjet cutting. However, while laser cutting demonstrates certain advantages over more conventional cutting processes, some manufacturing applications can be problematic, such as cutting reflective material or material requiring secondary ma...
Read more

Biomechanical engineering

Image
 Biomechanical engineering is a field that integrates principles of mechanical engineering with biological systems, particularly focusing on the interaction between mechanical factors and living organisms. Here are some key aspects and applications of biomechanical engineering: Biomechanics : This involves the study of the mechanical aspects of biological systems, such as how forces affect cells, tissues, and organs. Biomechanical engineers apply principles from mechanics (statics, dynamics, fluid mechanics, etc.) to understand and analyze biological structures and functions. Medical Devices : Biomechanical engineers design and develop medical devices such as prosthetics, implants, orthotics, and assistive devices. These devices aim to improve mobility, enhance bodily functions, or replace damaged biological structures. Tissue Engineering : This field combines engineering principles with biology to create biological substitutes that restore, maintain, or improve tissue function. Bi...
Read more

Coordinate Measuring Machine Probes

Image
  A  Coordinate Measuring Machine  is defined by the ability of its probe. As with CMMs, there are several types of probes available. There is the contact probe, which measures the workpieces by making contact with them. The non-contact probe that employs lasers or machine vision probes which scan with optical sensors. Contact probes are a more accurate way of measuring. However, the laser or machine vision probes are far quicker to use, while still holding a high degree of accuracy. There are also multi-sensor probes which combine both touch and optical scanning, giving the benefit of both types in one probe. Coordinate Measuring Machines: Contact Probes The two most common contact probes are Touch Trigger Probes and Analog Scanning Probes. Touch Trigger Probes: A touch trigger probe has a stylus that is attached to a bearing plate. This is then connected to pressure sensors inside the housing of the probe. Each time the probe makes contact with the workpiece, it generat...
Read more