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Moulds for investment castings

What is investment casting

Investment casting, often called lost wax casting, is regarded as a precision casting process to fabricate near-net-shaped or finished shape metal parts from a wide range of alloys. Although the process has been used for thousands of years the most common use of investment casting in more recent history has been the production of components requiring complex, often thin-walled castings. The process is generally used for small castings (up to 5kg) but has been used castings up to 300kgs. It is generally more expensive then die casting or sand casting, but can produce complicated shapes that require little rework.

Investment casting offers high production rates, particularly for small or highly complex components and extremely good surface finish with very little machining. The process is also easily automated to provide robotic handling and control of the process prior to casting.

Basics of the Investment casting process

The investment casting process is a multi step process. The main steps are described below;-

Wax Injection
Wax replicas of the desired castings are produced by injection moulding and these replicas are often called patterns. Patterns are produced by forming the finished shape in the a die.
Assembly
The patterns are attached to a central wax stick to form a casting cluster
Mould building
The mould (sometimes called a shell) is built by immersing the assembly into a liquid ceramic slurry and then into a bed of very fine sand. Several layers are applied in this manner until it is considered robust enough to withstand the rest of the process.
Dewax
Once the ceramic mould has dried the wax is melted out. A negative impression of the assembly has then been created within the mould
Metal pouring
The mould is then filled by pouring molten metal into it. There are various methods of pouring including vacuum, anti-gravity, tilt, gravity, pressure assisted and centrifugal. As the metal cools the parts, central stick (sprue), gates etc become one solid casting
Knockout
When the metal has fully solidified the mould is broken off by vibration or by water blasting
Cut-off
The parts are detached from the central sprue by mechanical breaking or high speed saws
Finished castings
After minor finishing operations the finished parts are complete and ready for use.

Applications for investment castings

These are used in a wide range of industries including aerospace, power generation, military, medical, automotive, electronics, food, petrochemical, marine, nuclear, art, jewellery and textiles. The process produces intricate castings of near net or final shape with an exceptional finish and dimensional control. Almost any alloy can be cast using this process including aluminium alloys, bronzes, tool steels, stainless steels, satellite, hastelloy and precious metals. Parts made with investing castings often require only minimal or no further machining because of the close tolerances that can be achieved.

Who uses/buys dies for investment castings

The users of dies will of course be investment casting foundries. They are purchased, albeit indirectly, by the end users of the products. The dies tend to be quite expensive because they are generally labour intensive to manufacture. Users/buyers of these dies are therefore increasing looking to purchase them from low cost countries.

Why use S4S to help you to source dies for investment casting

Employees of S4S have over 15 years experience sourcing engineered components/patterns/moulds/dies from India and China. They can handle all activities from enquiry to delivery to your premises including expediting, quality checks, freight, customs clearance and in many cases duty avoidance. Our flexible and innovative business model ensures that our charges are fully aligned with your profit drivers and in many cases self financing.