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.
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.
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
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:
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.
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.
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.
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.
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.
Remove the shell
The ceramic shell is broken away, leaving the tree structure—now only of metal—intact.
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.
Inspect the parts
Dimensional inspection and non-destructive testing (NDT) are done to make sure that the investment castings meet all the required specifications.
While investment casting is useful for creating complex parts, it also has a few constraints.
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.
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 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.
Above: A chain sprocket manufactured by The Federal Group via investment casting.
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
Aerospace
Agriculture
Automotive
Energy
Electric Vehicle
Food Processing
Medical
Military
Mining
Nautical
Paper Manufacturing
Water Desalination
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 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.
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
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.
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.
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.
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
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.
For more information Precision Investment Casting, please get in touch with us!