Investment casting is inherently an energy-intensive manufacturing process. That creates a challenge for a company focused on sustainability like Impro, but it’s not impossible to overcome. Here’s a look at what is and can be done.

Sustainability Challenges in Investment Casting

This is an expendable mold process where molten metal is poured into a ceramic shell. The shell is made by coating a wax pattern with layers of ceramic slurry, each one being dried before the next is applied, until it’s strong enough to take the weight of the metal.

Once the metal has solidified, the shell is broken apart to release the “tree” of cast parts and metal feeding channels and gates. The parts are cut away, cleaned up, and if necessary, sent for machining. Meanwhile, the feeding system is melted down and used again.

Shell-making and metal-melting are both extremely energy-intensive processes. In addition, investment casting consumes a lot of wax and ceramic slurry. However, there are steps that will reduce the environmental impact.

Why Investment Cast?

For complex metal parts that need high precision and smooth surfaces, there is no comparable process. The alternative would be to sand cast smaller pieces, perform extensive machining, and then assemble them into one larger and heavier part. From a sustainability perspective, this may not be any better.

Another complication is that investment casting is used for high melting point alloys like stainless steel and nickel superalloys. The ceramic shells can withstand these very high temperatures, but making suitable molds for other casting processes would be difficult and expensive.

Energy-Efficiency Actions

Sustainability-focused foundries, their suppliers, and many research institutions are all working on ways to make investment casting a more “green” process. The main actions and activities underway are:

• Optimize ceramic shell materials for thicker application and faster drying: This reduces the number of drying cycles needed, and has the additional benefit of reducing production lead time.
• Improve shell drying efficiency: Equipment makers are working on ways to dry faster using less energy. Improved airflows and layouts are two areas being looked at.
• Maximize metal melting efficiency: The latest generation induction furnaces are more efficient than earlier generations of furnace.
• Cut the size and weight of the metal feeding channels: While this metal is not wasted, energy was used to melt it, and more will be used for remelting. Advanced casting simulation software helps foundries shrink the metal feeding system needed, so reducing the total mass of alloy melted.
• Automate wax pattern assembly: The higher accuracy achieved by robots cuts scrap and can reduce the amount of secondary machining needed.
• Increase recycling: Pattern wax is an opportunity to recover and reuse material, rather than consuming more virgin wax. Likewise, work is underway on methods of recycling the ceramic shell material.
• Reduce water consumption: Most ceramic slurries are water-based, so improvements here can yield significant savings. Water is also used for cooling and, in some instances, for dust control during fettling.
• Measure and manage emissions: Fumes can be a problem, both in metal melting and in the wax room. We’re putting systems in place to both manage and control what gets released, so we can continue to be a good neighbor.

A Focus on Foundry Sustainability

Another way in which Impro focuses on sustainability is by operating to the ISO 14001 Environmental Management standard. This pushes manufacturers to measure sustainability performance, and then find ways to make improvements.

At Impro ISO 14001 is part of the top-down commitment to sustainability driven by our “Sustainability Committee”. We’ve set challenging goals and are actively measuring our progress. There’s more information about our commitment to sustainability on our website. If you have questions about this, or are interested in getting a quote for some investment casting work, contact us.