Investment Casting

What is investment casting

Investment casting is an industrial process based on lost-wax casting, one of the oldest known metal-forming techniques.

Investment casting, also known as lost wax casting, is a manufacturing method in which a wax pattern is created and then coated with a ceramic slurry to make a mold. The wax is then melted out of the ceramic mold and molten metal is poured into the cavity. The molten metal solidifies, and the ceramic shell is then broken or blasted off, generating a metal casting.

Advantages of Investment Casting

· Dimensional accuracy

· Less machining required to finish parts

· Little to no material waste

· Lower per-part cost

· Can provide lower lead times than machining

· Compatible with simple or intricate designs

· Reduce assembly time and cost by eliminating fabrication weldments

· Broadest range of alloy choices

Investment Casting Process

WAX INJECTION

Replicas of the desired investment casting are produced by injection molding or for smaller volumes using rapid prototyping. These replicas are referred to as patterns.

ASSEMBLY OF WAX TREE

Patterns are then attached to a central wax stick, called a sprue, to form a casting. This is called a wax tree.

CERAMIC SHELL BUILDING

The shell is built by immersing the wax tree assembly in liquid

ceramic slurry and then into a bed of fluidized fine sands. Up to eight layers may be applied in this manner depending on the shape and weight of the part.

DEWAX

Once the ceramic is dry, the wax is then melted out, creating a negative impression of the assembly within the ceramic and sand shell. This process uses autoclaves to maintain shell integrity.

Pouring

Before casting, The processed shells are placed back in the oven to be pre-heated. When the shells are at the proper temperature and the molten metal has been prepared and qualified. The shells are removed from the oven and the metal is poured into the shells.

KNOCKOUT

Once the metal is cooled and solid, the ceramic shell is broken off by vibration or water blasting.

CUT OFF OF PARTS

The parts are then cut away from the central sprue using a high speed saw.

Shot Blasting/Sand Blasting

To remove scales and achieve better surface finish, investment castings will be shot blasted or sand blasted by small steel balls.So all the foundries must be equipped with shot blasting machines.

Inspection

Inspection is also a step for investment castings quality control. Our QC will do dimensional inspection, 100% surface inspection, inner defects inspection and other inspection jobs according to requirements of products.Only after all the products inspections are qualified,we can delivery to our customers.

Package

As all the products are exported to overseas market, so, normally we will pack investment castings with ploybags, and then put them into standard wooden cases. Of course, all the package must be carried out on the basis of free from damage. We can also supply custom package service according to customers’ special requirements.