Investment Casting Process | What is Investment Casting?
investment casting tfg usa

Investment Casting

The Federal Group USA provides high-quality investment casting services for a variety of industries. The investment casting process allows for very precise metal features that can produce parts with smooth surfaces. This process can create near-net-shape parts with outstanding dimensional accuracy.

The investment casting process

An overview of the investment casting process

Investment casting (a.k.a. lost wax casting) is a metal casting technique that has been used for almost 5,000 years. The metal casting process starts with making a pattern or prototype of the desired part.

Wax patterns

wax pattern investment casting tfg usa

There are many ways to make a master mold. The best ways to make the master mold are to 3D print it, machine it from steel or carve it from wood. After the mold is made, wax is injected into it. The wax pattern will cool and create a replica of the original pattern.

The wax pattern is covered with a refractory ceramic material (a.k.a. the investment material). The ceramic material hardens and becomes a ceramic shell or ceramic mold. The wax is then heated to a high temperature, so the wax melts and drains from the ceramic shell. Common refractory materials include silica, zircon, aluminum silicates, and aluminum.

Molten metal

investment casting mold tfg usa

Pictured above: An investment casting mold.

After the molten metal is poured into the mold, the metal hardens, and the investment material is broken, revealing the finished part.

The wax pattern and ceramic mold are destroyed during the manufacturing process. A new wax pattern must be made from the master pattern to produce each new ceramic mold. Then, the process starts over for every part. The dimensional accuracy of each casting means fewer post-casting machining operations are needed

The investment casting process in 8 steps

Investment casting is a process that has been used for thousands of years. “Investment” refers to the mold being filled or invested with metal. The first use of investment casting was to produce decorations, religious figures, utensils, weapons, household goods, and jewelry. Today, this process is used to make intricate parts for many industries. 

Here are the steps:

  1. Create the pattern

    • The pattern is what creates the shape of the finished product. The pattern is made out of wax. For short runs, we can directly machine the wax pattern, but in most cases, we use a metal die based on a 3D CAD model.
  2. Build the tree

    • We attach several wax patterns to a wax rod to create a tree structure. This enables us to cast many parts at once, which lowers the cost per part.
  3. Make the shell

    • We dip the tree into a wet, clay-like material—a ceramic slurry. We let it dry. This happens multiple times so that the tree has a strong outer layer.
  4. Remove the wax

    • The shell is heated upside down. The wax runs out (this is why it’s sometimes called lost wax casting). Then the shell goes into a high-temperature furnace to burn off any remaining wax and strengthen the shell.
  5. Cast the metal

    • Molten metal is poured into the mold. We use the tree we built in the second step to define where the metal goes. Now a metal part exists where each pattern used to be.
  6. Remove the shell

    • The ceramic shell is broken away, leaving the tree structure—now only of metal—intact.
  7. Finish the parts

    • Parts are carefully cut from the metal tree structure. If needed, we can do some secondary machining to get the desired tolerances and surface finish.
  8. Inspect the parts

    • Dimensional inspection and non-destructive testing (NDT) are done to make sure that the investment castings meet all the required specifications.

Investment casting advantages & constraints

While investment casting is useful for creating complex parts, it also has a few constraints.

Investment casting advantages include:

  • High dimensional accuracy
  • Smooth surface finish
  • Flash-free parting lines
  • Compatibility with most metals
  • Ability to produce intricate parts

Our investment casting foundry has the most modern equipment, including a quality gating system plus robotic arms that help reduce many operator-error casting defects. This process also results in a smoother finish. The ceramic mold (a.k.a. ceramic shell) eliminates flashing or parting lines in the finished product.

These benefits eliminate or reduce the need for extensive secondary surface finishing to the investment castings, therefore production timelines become shorter.

This technology is popular for products that require greater precision.

Investment casting constraints might include:

  • A longer time to produce a wax pattern and let the ceramic shells dry.
  • Occasionally more expensive (but may be offset by the reduced need for secondary operations).
  • Time to make cores if you need them.

Making the dies and molds can add time to the production process. From making new wax patterns to getting the final product takes about seven days on average.

Creating the ceramic mold is the most time-consuming part of the process. It also takes longer to change the design if it is necessary. This is because new molds may have to be created.

Investment casting is a good way to make a complex component. This process is used for parts that need to be very precise. However, adding a core or cavity to the part increases the project’s complexity.

Investment casting industries and products

Investment castings are used in many products serving numerous industries. Some of these products and industries are listed below.

The investment casting process is versatile and can be used to create a wide variety of shapes and sizes. It is frequently used to fabricate small parts for cooling systems, firearms, and aerospace equipment as well as large parts such as boat anchors, forklift counterweights, and heavy agricultural machinery. The process is also popular in the automotive industry, where it is used to create many high-precision components.

investment casting chain sprocket tfg usa

Above: A chain sprocket manufactured by The Federal Group via investment casting.

Products

  • Armored vehicle accessories
  • Boat anchors
  • Boat cleats
  • Boat steering wheels
  • Chain links
  • Chain sprockets
  • Conveyor systems
  • Cooling systems
  • Engine blocks
  • Exercise / fitness equipment
  • Firearms
  • Fire hydrant components
  • Firefighting equipment
  • Gearbox housings
  • Gun turrets
  • Impellers
  • Motor housings
  • Motor mounts
  • Motorcycle brackets
  • Plow tips
  • Plumbing nozzles
  • Pulleys
  • Pump housings
  • Street lamp bases and poles
  • Snow plow components
  • Turbo chargers

Industries

  • Aerospace
  • Agriculture
  • Automotive
  • Energy
  • Electric Vehicle
  • Food Processing
  • Medical
  • Military
  • Mining
  • Nautical
  • Paper Manufacturing
  • Water Desalination

How can I benefit from net-shape parts?

Net-shape is the design-intent shape of the part. In many cases, investment cast parts are ready to use as they come out—without the need for additional finishing operations. So investment cast parts can be delivered to your production line faster saving you valuable time and money in your manufacturing cycle.

Investment castings vs. sand castings: Which should I choose?

Investment casting is not the only casting service that we provide. We also offer:

The investment casting process is typically used to produce parts that need to be very precise. This casting process makes it possible to have thin walls and complex internal cavities.

The investment casting process provides you with finer details and a smoother surface finish than other casting techniques.

For example, sand casting is a process that uses a mixture of sand and clay to create a mold around a pattern of the final product. The mixture is more porous than the wax pattern used for investment casting, this means sand casting cannot create as intricate parts. 

Why choose TFG USA investment casting services?

Equipment

tfg usa investment casting disa

Image above: Disamatic Automated Investment Casting Machine.

Having the right equipment for the investment casting process is essential. At The Federal Group USA, we use state-of-the-art technology to ensure the success of every project. Below is just some of the investment casting equipment that we leverage:

  • Specialized shell-making equipment
  • Highly automated robotic molding machines
  • Horizontal vacuum precision furnace
  • Vertical vacuum precision furnace
  • High-pressure gas quenching vacuum furnace
  • Short runs or high-volume production
  • Reliable quality assurance equipment

Automation

We use the latest wax processing technology. Our semi-automatic wax injection machines allow us to make wax patterns quickly and reduce the time it takes to finish the project.

Our dewaxing machines quickly melt the pattern without cracking the ceramic shell. We use specialized equipment to pour the molten metal without creating air pockets, minimizing the risk of defects. A thorough quality assurance process follows.

Materials

investment casting steel tfg usa

Pictured above: Raw billets / ingots used for investment casting.

We can work with the following materials and more:

Carbon steel and most steel alloys, brass, bronze, copper, aluminum, and Stainless Steels including Duplex 2205, 2507, and others.

Duplex 2207

  • A super duplex stainless steel with 25% chromium, 4% molybdenum, and 7% nickel alloy. 
  • They are designed for applications that require exceptional strength and corrosion resistance.

Duplex 2205

  • A two-phase, ferritic, austenitic 22% chromium, 3% molybdenum, 5 to 6% nickel alloy. 
  • Duplex 2205 is the most widely used duplex stainless steel grade and is characterized by high yield strengths. 
  • It has good fatigue strength and demonstrates outstanding resistance to stress corrosion cracking, crevice, pitting, erosion, and general corrosion in severe environments.

300 series 

  • Superior corrosion resistance
  • Non-magnetic
  • Scratch-resistant

400 series

  • Magnetic
  • Greater strength than carbon steel.
  • Suitable where thinner materials/reduced weight are needed

Grey, Ductile, and White Iron

  • Tool steels, mild steel, alloy steels, etc.
  • Used for a variety of purposes for ease of machinability, ductility, or compressive strength

Aluminum

  • Investment casting of aluminum makes it possible to create parts with complex shapes more quickly.
  • This process is also more flexible when using different types of alloys.
  • Parts made through this process have tighter dimensional tolerances and better surface finishes.
  • This method requires less machining and processing.

Brass/Bronze

  • Excellent machinability
  • Corrosion resistance 
  • Aesthetics

Copper-based alloys

  • Corrosion resistance 
  • Ductility
  • Conductivity—thermal & electrical
  • The price of copper can fluctuate significantly with the market. So, it’s essential to reduce waste when producing complex components of copper. 
  • Investment casting is an excellent way to minimize this waste.

Magnesium

  • Excellent dimensional stability
  • A good structural material
  • Ability to produce fine detail

Conclusion: Make an investment to learn more

investment casting facility tfg usa

Our casting process yields highly intricate and accurate parts with tight tolerances for aerospace, marine, agricultural, automobile manufacturing, and beyond.

Whether you’re exploring options for a new product or you have an existing product that you’d like to put into production, The Federal Group USA can help you with your next investment casting project. We’ve provided high-quality manufacturing services to a wide variety of industries for more than 40 years. 

Contact us today to learn more.

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