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CASTING - PAGE UNDER CONSTRUCTION


Casting is a 7,000 year old process in which a liquid material is poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. Some molds can be made in two halves and a core added if the cast needs to be hollow in a certain place.

The solidified part is then ejected or broken out of the mold to complete the process. Once cooled the cast part is then normally machined to remove excess material before it can be called a finished product. The cast can be turned or milled to achieve tighter tolerences and finishes. Holes are reamed or tapped and the product may be

In modern industrial casting processes the casting materials are usually metals and various alloys, Casting is most often used for manufacturing complex shapes that would be otherwise difficult or uneconomical to manufacture by other methods.

DIE CASTING

HOT CHAMBER DIE CASTING


Hot-chamber die casting machines rely upon a pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, which allows the molten metal to fill the "gooseneck". The pneumatic or hydraulic powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.


COLD CHAMBER DIE CASTING


Cold Chamber machines are used when the casting alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace. Then a precise amount of molten metal is transported to the cold-chamber machine where it is fed into an unheated shot chamber (or injection cylinder). This shot is then driven into the die by a hydraulic or mechanical piston. The biggest disadvantage of this system is the slower cycle time due to the need to transfer the molten metal from the furnace to the cold-chamber machine.


/images/Diecastaly.jpgAluminium Die Cast Part


 


FORGING VS CASTING

Forging offers uniformity of composition and structure. Forging results in recrystalisation and grain refinement as a result of the process. This strengthens the product particularly in terms of impact and shear strength.

Forged steel is generally stronger and more reliable than casting due to the fact that the grain flows of the steel are altered, conforming to the shape of the part.

The advantages of forging include:

  • Generally tougher than alternatives
  • Will handle impact better than castings
  • The nature of forging excludes the occurence of porosity, shrinkage, cavities and cold pour issues.
  • The tight grain structure of forgings making it mechanically strong. There is less need for expensive alloys to attain high strength components


For general as well as large and complex components - casting is a versatile method of manufacture.

We use castings for a wide range of parts and components that are too large, complicated, intricate or otherwise unsuitable for the forging process. We can forge parts up to 10kgs but the sheer energy required to forge larger items makes casting a much more viable alternative.

The advantages of casting include:

  • No real upper size limit in casting weight
  • Large range of alloy choices
  • Tooling is often less expensive than forge dies
  • Smaller production “runs” required
  • Complicated/complex parts are no problem


CHARTWAY CAN ADVISE ON TOOLING AND WHICH ROUTE TO TAKE, HELPING YOU TURN YOUR CONCEPTS INTO PRODUCTION PARTS

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