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What is the Investment Casting Process?

For customers in need of simple to complex parts created from a wide variety of metals, investment casting processes provide unique advantages. This technique uses the lost wax casting processes where a pattern of the part is made from wax.

The wax pattern becomes dipped or coated in a ceramic slurry that hardens to become a mold. The wax becomes melted out of the ceramic mold as molten metal is then poured inside. Once the metal cools, the ceramic mold is removed to show the cast metal part.

There are many key steps involved with the actual investment casting process. Yet keep in mind that it really begins with the customer deciding on the dimensions and specifications of the part along with the type of metal that will be used. When we receive this data and documents, our role in the investment casting process may begin.

Investment Casting Steps

Tooling Design and Manufacturing

Tooling design and manufacturing processes focus on the tooling needed to make the wax patterns. Tooling must also be designed and produced for the water soluble or ceramic cores.

Raw Material Inspection

We inspect the raw materials from the supplier to reassure they are what is requested for the project. We also evaluate the quality of the materials. We also want to avoid purity issues and contaminants that may cause issues during melting and pouring.

Wax Pattern Production

The wax pattern production step involves making wax patterns that are used to produce the ceramic shell molds. To create the patterns, injection molding techniques and injected molding dies are used.

Ceramic Shell Making

The next step in the investment casting process is to take the wax pattern and dip it or surround it with a ceramic slurry. The slurry has binders that allow the ceramic to harden as an even coating is obtained. The ceramic shells harden as then the wax is removed by being melted or burnt out.

Melting & Pouring

The ceramic molds become preheated. Then the pouring process begins with the molten metal entering the ceramic pattern. The molds are preheated to eliminate cold spots that may cause the molten metal to cool unevenly while it fills into all the crevices and intricate parts of the mold. Once the pouring is complete, the metal is allowed to cool as the part is finished casting.

Cutting and Cleaning

The ceramic shell becomes removed to show the cast part. Now the part undergoes a cleaning process where any gates and runners are removed using grinding, cutting, and shot-blasting techniques.

Investment Casting or MIM for Small Parts Manufacturing?

Companies are constantly searching for the most cost-efficient solution to creating small parts. Different metal working techniques provide varying results. Two methods considered for this process are investment casting and MIM.

Investment casting has been used for generations as it is the oldest metal molding process. The method involves using a wax pattern to create a ceramic mold as molten metal is poured into the mold to create the part. For metal injection molding (MIM), binder materials are placed into finely powdered metal to form feedstock. Then injection molding equipment takes the feedstock to form and harden it into parts.

MIM methods first started in the 1980s and is still considered a relatively new technology. Yet investment casting continues to be sought after for many production lines. Figuring which methods to use will depend on various factors.


Investment casting works with a wide variety of materials. Due to the ceramics used, the mold can withstand higher temperatures. So metals can melt completely as the ceramic does not quickly cool off during the pour. This advantage allows customers to have more options when selecting the metal that would be appropriate for their applications.

On the other hand, MIM is only suitable for metals that possess higher melting temperatures and for those that do not form strong oxides. Metals such as titanium, zinc, or aluminum would not be suitable with this process.

Size and Production Volume

Both MIM and investment casting can be used for small parts manufacturing for simple and complex geometries. They both work well for parts with very tight tolerances. In the case of MIM, this method is suitable for parts that require very thin wall sections, weigh less than 20 grams, or have a length that is less than 100mm.

MIM is also suitable for production volume runs that have 5000 pieces or more in a batch. As for investment casting, this process also works well for parts of varying weights and sizes, including ones that weigh less than 20 grams. Investment casting is versatile for low to high production volumes.

Tooling Costs and Finishes

Tooling costs for MIM are more expensive than for investment casting. It is for this reason that MIM is mainly used for high batch runs of parts. Customers may select investment casting when requiring more economical tooling costs for low production runs and when desiring prototyping work.

When evaluating finishes, both investment casting and MIM offers exceptional surface finishes with minimal or none secondary machining required.

Investment Casting VS Lost Foam Casting: Similarities and Differences

When mentioning lost wax casting, most people associate it to the investment casting process. In fact, the two terms are sometimes used interchangeably. However, when people start talking about lost foam casting, these metal casting processes start to sound confusing. The confusion may lie with the fact that lost foam casting is remarkably similar to investment casting. When evaluating all these processes, we can determine both similarities as well as differences between them. Here is a straightforward guide to understand each one.

What is Lost Wax Casting?

Lost wax casting is a metal mold casting process that has been in use for thousands of years. This process involves creating a wax pattern of the intended part. This wax pattern becomes coated in a ceramic slurry and allowed to harden. The wax is later removed, and molten metal is poured into the ceramic shell to create the part.

What is Investment Casting?

Investment casting is another term for the lost wax casting method. It uses the wax patterns that are later melted or burned out of the hardened ceramic mold. The process allows for near net-shape of parts with exceptional surface finishes. Often, the metal part does not need additional machining and surface finishing details. A major advantage to investment casting is that the customers can select a wide variety of metals to use with this process. Also, investment casting tighter dimensional tolerances creates simple and complex parts in a range of sizes.

What is Lost Foam Casting?

Lost foam casting processes involve making a pattern made from expanded polystyrene. The polystyrene pattern becomes coated in the refractory slurry as the shell hardens. Then the shell has sand compacted around it to provide extra stability and support. Molten metal is poured into the shell as the polystyrene becomes vaporized inside. Customers may select lost foam casting methods when looking for a process that accepts a wide variety of ferrous and non-ferrous metals while gaining simple and complex parts that may require additional machining after casting.

Similarities and Differences

Both investment casting and lost foam casting processes are similar where they use patterns to make ceramic shells that will hold the molten metal to produce parts. The produced parts seldom require additional machining and both processes can be used for simple and complex parts manufacturing. Both processes can cast parts made from non-ferrous and ferrous metals.

The biggest differences of these processes:

Searching for the right manufacturing method allows you to obtain parts that are high quality, dimensionally accurate, and meet project deadlines. For more information about these processes, contact Impro.

What to Understand About Gating System Design for Investment Casting

A major process for investment casting involves pouring the molten metal into the ceramic mold. The molten metal must fill every corner and point of the mold evenly and fully to create a near accurate part. Unfortunately, this process may lead to difficulties depending on the complexity of the part. If the metal cannot reach every point, corner, or isolated section before solidifying, this problem leads to surface defects, porosity, and scrapped parts.

To ensure the proper delivery of metal throughout the ceramic mold, a gating system is designed for optimal molten metal delivery. This gating system directs the flow of metal to the sections of the part while controlling the amount of metal feed into the mold. By carefully controlling the direction and the molten metal’s delivery rate, the gating system design prevents premature solidification as well as turbulence.

Gating System Design

Manufacturers consider the design for both the wax pattern and the gating system during the same investment casting stage. The gating system is made from the same wax material as the wax pattern and will be dewaxed (vaporized) after the ceramic slurry hardens to create the mold. The gating system design consists of several elements: the gates, the feeders, and the runners.


Along the mold will be a pouring cup where the molten metal is poured into to enter the mold’s cavities. Beneath the cup are the runners. The runner system helps to guide the metal to specific areas so that the mold cavity can fill up evenly. Some ceramic molds are designed to allow for several similar parts to be created during one pouring session. The runners ensure that the molten metal reaches each part mold at the same rate.


A feeder system has many of the same functions as a sprue and riser system that is used for sand casting processes. The feeder holds extra molten metal during the pour process. After the molten metal fills the mold and begins the cool, shrinkage and contraction may occur to leave voids. The extra molten metal in the feeder will fill the voids in the ceramic mold after this shrinkage to ensure the cavity is entirely filled.


The gates are the openings between the runners and the part’s mold cavity. It allows the molten metal to pass inside to fill every crevice and point in the creation of the part. To ensure the metal reaches every area of the mold, manufacturers may design multiple gates, called ingrates, along the mold while deciding on the size, type, and location of each gate.

After the Pour

Once the manufacturer finishes pouring the molten metal into the gating system, the part cools so that the metal can solidify. Then workers remove the gating system, and the part may undergo secondary machining and finishing stages. For some investment casting projects, workers may grind the gating system down to size.

Gating system design is a crucial factor in the investment casting process to allow the molten metal to fill the ceramic mold. For more information about this process, contact Impro.

Heat Treatment of Investment Castings

Though investment cast parts typically require little-to-no machining they often need to undergo heat treatment. Controlled heating and cooling releases internal stresses, optimizes mechanical properties and modifies surface hardness to improve durability and performance.

Impro maintains an extensive range of heat treatment capabilities. These are used to impart the required properties to parts produced by investment casting. Here’s an overview of what heat treatment does, why it’s used and the capabilities Impro can offer customers.

Metal Casting and Solidification

As soon as it’s poured into the ceramic shell or mold, molten metal begins to cool. As it transitions from liquid to solid crystals or grains form and grow in the metal. The speed of grain formation is determined largely by cooling rate. Metal in contact with the ceramic shell cools fastest while that deep in the interior of the part being cast is the last to solidify. Mold pre-heating slows the solidification rate, allowing larger grains to form.

This progressive cooling creates a structure where the hardness and toughness vary throughout the casting. In addition, contraction creates internal stresses that distort the part from the intended geometry. These undesirable characteristics are addressed by heat treatment.

Heat Treatment Processes

Heat treatment consists of raising the temperature of casting to a predefined level, holding it there while metallurgical changes take place, then cooling it at a controlled rate. The various processes are defined primarily by the peak or soak temperature attained, soak duration and the rate of cooling. In addition, some processes are performed in a vacuum or a controlled atmosphere.

Metals commonly investment cast are aluminum, steel and nickel-based superalloys. Their different compositions mean they go through different heat treatment processes.

Aluminum alloys can go through a tempering process to modify hardness and ductility and improve machinability. The most widely used processes are defined as T4, T6 and T61, each of which imparts a form of accelerated aging.

Investment cast low alloy steels and superalloys often undergo one or more of the following heat treatment processes:

Investment Casting Heat Treatment Capabilities at Impro

We operate an automated, multipurpose heat treatment line capable of:

We can also heat treat aluminum and have furnaces for vacuum heat treatment, gas nitriding, annealing and stress-relieving.

An alternative to furnace heat treatment is induction heating. In this process the part to be treated is placed inside an induction coil and heated and cooled as needed. Induction is used for both hardening and softening. It is especially useful for castings where it can provide local modification of strength, hardness and ductility.

What is the Vacuum Investment Casting Process?

Vacuum investment casting yields extremely high quality metal parts with fine detail and excellent surface finish. It’s also more complex than conventional investment casting and requires sophisticated melting and mold-filling equipment. As a result, it’s reserved for casting parts that need very high levels of structural integrity and where defects are expensive.

Why Use Vacuum?

Liquid metal tends to “churn

Applications of Investment Castings in New Energy Cars

Investment casting is a process that uses a disposable wax mold to create a permanent ceramic mold which is used to shape an object. After the ceramic mold has hardened, it is heated, causing the wax to melt and drain away. Molten metal is then poured into the ceramic mold to form the desired object. This process is used in a variety of industries, including the automobile industry. In fact, investment casting is widely used to manufacture parts for new energy cars.

Investment casting and new energy cars

Investment casting offers a number of benefits and is commonly used for intricate and complex shapes. Parts made using this process have a smooth finish, are lightweight, are very heat tolerant, require less lead time and labor than those made using most other processes and have tighter tolerances. In addition, investment casting can be used with a wide variety of materials to create objects in a wide range of sizes. These benefits make the process very well-suited to new energy cars, a category that includes plug-in electric vehicles, battery electric vehicles, fuel cell vehicles and hybrid vehicles. Just a sampling of the parts for these vehicles made using investment casting include…

  1. Motor housings
  2. Battery cases
  3. DC-AC converter enclosures
  4. On-board chargers
  5. HV/EV ECU enclosures

Working with Impro

Traceability Practices for Casting Production

Casting component production process ranges from tooling design and manufacturing to casting, secondary machining, heat treatment, surface treatment, testing, and assembly. These capabilities enable casting manufacturers to offer ready-to-use products to customers. The quality of components affects safety and efficiency of the systems into which the components are integrated. As such, many customers require casting producers to adhere to the highest standards of product traceability. This blog looks at the traceability practices for casting production.

What is Traceability?

Traceability is a process in manufacturing which allows for the tracking and documentation of raw materials, parts, and finished goods. It can be used to research any problems, or to duplicate positive outcomes. Traceability also helps to ensure compliance with government regulations. Chain traceability means a casting manufacturer can track components from raw material through distribution. Internal traceability involves the tracking of components within its own operations.

What are Traceability Practices for Casting Production?

The traceability practices casting suppliers follow provide historical information on components to customers when needed. Some of the most important practices include:

Key Benefits of Traceability for Casting Production

Traceability allows manufacturers like Impro to continuously deliver high-precision, high-quality components. Customers realize the benefits of:

Types of Inconel for Investment Casting

If you need parts to withstand high temperatures, oxidation and corrosive chemicals, consider investment casting them in Inconel. Inconel is a nickel-based superalloy that resists oxidation and retains its strength at temperatures over 1,000° F. It’s produced in a number of different compositions with some being investment cast more than others.

This blog post takes a look at Inconel. It discusses the various types and compositions and explains the benefits of making Inconel parts by the investment casting process.

An Introduction to Inconel and Superalloys

Inconel is a trade name owned by Special Metals Corporation. If you specify a part should be made from Inconel you’re asking for one of their products. Other companies make similar superalloys, but they can’t put the Inconel name on them.


Types of Titanium Alloy Used in Investment Casting

Though light and strong, titanium is difficult to machine, weld, and form. That makes investment casting the best way of producing parts in this metal.

In this blog post we’ll explain:

Strong, Light, and Corrosion-Resistant

Although titanium was discovered in the 18th Century, a high melting point, (3,020° F or 1,660° C) and a tendency to react with oxygen made processing difficult. Only in the 1960s did it start being used in the most challenging aerospace applications.

The aerospace industry likes titanium because it’s only a little heavier than aluminum yet more than twice as strong. It also resists cracking and fatigue and exhibits very little creep, all of which make it ideal for airframe components.

Two other notable characteristics are corrosion resistance and biocompatibility. A self-healing oxide layer on the skin, which behaves like the one on aluminum, helps resist attack by saltwater and most other chemicals, (although not strong acids.) This makes it the preferred metal for use in desalination plants and especially in desalination heat exchangers.

In addition, bio-compatibility means it’s a metal that can be implanted into humans without adverse effects.

Titanium Challenges

Besides the high melting point, titanium is hard to work with because it reacts readily with oxygen and it’s difficult to machine.

Reactivity is addressed by melting and pouring under vacuum. However, welding is a significant problem as it’s very hard to exclude air completely.

Machinability challenges stem from the “gummy

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