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Core Making

​The core is a molded sand insert that is used to create the interior surfaces of an iron casting. A core looks like the void it creates within an iron casting. A core box is the tooling used to create the core. At Waupaca Foundry, we use three types of core making processes:

  • Isocure cold box
  • Warm box
  • Shell

The Isocure core making process

In this process, no heat is applied to the core box and a phenolic urethane resin is added to the sand. A catalyst, in this case amine gas, is introduced into the core box and purged through the core with superheated air. This process is very fast and cost effective for large cores.

At Waupaca Foundry, we use core machines that are supplied, as well as custom built by Waupaca Foundry engineers. Providing a variety of benefits, our cold box core machines are:

  • versatile and can run vertically or horizontally
  • flexible and manufactured in sizes that can accommodate up to 150 liters of sand
  • speedy and allow quick changes
  • adaptable and can move in six directions allowing us to make complicated cores

The warm box core making process

In this process, Waupaca Foundry uses a furan system in which furan resin is added to the sand and the catalyst is heat. Cores are baked in a heated box to 450 degrees until the outside of the core hardens; the core continues cooling outside of the hot box. This process is ideal for cores with thin sections because the cores resist breakdown and erosion by molten metal.


The shell core making process

In this process, sand is pre-coated with a resin and poured into a pre-heated core box. In this case, there is no catalyst and the surface is heated until it forms a thin, hard shell. The sand on the inside of the core is uncured and can actually be poured out and reused. This process is ideal for:
  • Lighter castings where weight is critical
  • Fine dimensional controls that require a fine finish