13-02-2013, 11:09 AM
PRODUCTION TECHNOLOGY
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CASTING PROCESSES
It is the oldest known primary and principal manufacturing processes.
It involves, prepared and allowed to solidifyon of cavity to resemble closely the required final product.
Liquid moltel metal is poured in to the cavity and allowed to solidify.
After solidification, the product removed from the mould.
Other casting processes are
Shell mould casting
Precision investment casting
Plaster mould casting
Die casting, etc.,
FORMING PROCESSES
It is a solid state manufacturing process involving minimum material wastage and high production rate. In this process, metal may be heated to slightly below the solidus temperature and large force is applied, such that the material flows and takes the desired shape.
Normally used for large scale of production.
Metal forming processes
Rolling
Drop forging
Press forging
Extrusion
wiredrawing., etc.,
Fabrication processes
It is secondary manufacturing processes, where raw materials are processed through the casting or forming processes. It involves joining pieces either permanently or temporarily to perform the necessary action. The joining can be done by heat or perssure or both. Most of the steel structural constructions are first rolled and then joined together by a fabrication processes.
Types of fabrication processes
Gas Welding
Electric Resistance welding
Electric arc welding
Thermit welding
Cold welding
Brazing
soldering
Material Removal processes
It is also a secondary manufacturing process. In this additional unwanted material is removed in the form of chips from the blank material by a harder tool to obtain the desired shape. It is normally the most expensive compared to other processes because more energy is consumed and also a lot of waste material generated. Still widely used because of its good dimensional accuracy and good surface finish.
Types of machining processes
Turning
Drilling
Shaping and planning
Milling
Grinding
Broaching
sawing
Sand Casting Terms
Flask : A moulding flask is one which holds the sand mould intact. Depending up the position of the flask in the mould structure it is referred to by various names such as drag - lower moulding flask; Cope – upper moulding flask and cheek – intermediate moulding flask used in three piece moulding. It is made up of wood for temporary application and more generally of metal for long-term use.
Pattern : Pattern is a replica of the final object to be made with some modification. The mould cavity is made with the help of the pattern.
Parting line : this is dividing line between the two moulding flasks that makes up the sand mould.
Bottom Board : this is a board normally made of wood which is used at the start of the mould making. The pattern is first kept on the bottom board, sand is sprinkled on it and then the ramming is done in the drag.
Match plate pattern
In this kind of pattern, one half of the pattern is clamped to one-side of the match plate and the other half to the other side of the plate to prepare the mould. Later the match plate will be removed.
Material for the this pattern is METAL.
Gates and runners are also attached to the match plate.
Generally employed for mass production of small casting with higher dimensional accuracy.
Even though the construction cost is high, it can be compensated with high production rate and greater dimensional accuracy.
Principles of Gating System
Mould should be filled in the shortest time possible with out having to raise the temperature.
Molten metal should flow with out any turbulence and air.
Slag and other waste material should not enter into mould.
Metal flow should be maintained such that no gating or mould erosion takes place.
Make sure that the molten metal reaches the mould cavity completely.
The gating system should be economical and easy to implement and remove after casting solidification.
Finally casting yield should be maximised.