A Complete Guide to the Investment Casting Process

Wax investment casting process is widely used to manufacture precision castings by investment casting manufacturers. It can cast metallic very precisely. The process of investment casting mold is to first form a ceramic, plaster, or plastic shell around the wax object. Then remove the wax and complete the investment moulding process. Finally, the metal is poured into the shell to form investment casting products. Usually, there are 8 investment casting process steps in the investment casting foundry.

Nowadays, precision investment casting has become very popular in these investment casting suppliers, because of lower production cost, and waste. More and more industries need precision casting services with professional investment casting companies. It has been used in many industries manufacturing, such as power generation, automotive, oil and gas, space exploration, medical, agriculture, construction, commercial, and consumer products.

What Is Precision Investment Casting Process?

investment casting process

8 steps of investment casting process :

  1. Creating a wax pattern
  2. Wax tree assembly
  3. Shell building (slurry coating and stucco coating )
  4. Wax removing
  5. Metal pouring
  6. Shell knock off
  7. Cut off
  8. Individual castings

More detail in the investment casting process flow chart.

why is it called precision investment casting?

Investment casting is a casting process with a history of hundreds of years. Its production history is very long. The method used in the investment casting foundry is mainly lost wax casting. Therefore, investment casting is also called lost wax investment casting, which includes pressing wax, repairing wax, assembling trees, dipping slurry, melting wax, casting molten metal post-processing. It involves coating a wax pattern with a liquid material. We call it “investment casting” because the mold used in the casting process will be “invested” by the liquid refractory material.

Lost wax investment casting uses wax to make a wax mold of the part cast and then coat the wax mold with mud, a mud mold. After the clay mold is dried, the investment casting foundry put it in hot water to melt the internal wax mold. Then take out the clay mold from the melted wax mold and fire it into a pottery mold. Generally, a pouring port is left when making a mud mold. At this time, the investment casting foundry pour the molten metal from the pouring port. After the melt has cooled, the required parts are made. Investment casting is also called precision casting. This and lost wax are both a manufacturing process. One-time ceramic mold investment casting using wax molds is called lost wax casting, and liquid metal modeling is called precision casting.

8 investment casting steps:

The investment casting process, also called the investment moulding process, has 8 main steps in the investment casting foundry. The primary step is creating a investment casting pattern for its basic function of shaping ceramic shell which will cast the final metal parts.

Investment casting pattern

Investment casting pattern

Crating wax pattern is the first step of investment casting mold for investment casting manufacturers and also the basis of the precision investment casting process.

The wax pattern is made by injecting the wax into a metal mold.

Wax Tree Assembly

Wax Tree Assembly

The finished wax pattern will assemble at a wax sprue for mass production because make small parts at one time is not economical. With this wax sprue, these investment casting manufacturers will have a combination of many wax patterns, which will later provide voids for molten alloy, and the sprue also creates a flow path for the liquid molten alloy into the void.

The “Gates” indicates the wax connects the pattern and the sprue, and they control the direction and flow of the molten alloy into the void created by the wax patterns.

Shell Building

After creating a wax tree, use the investment casting coating process to build a ceramic shell around the tree, and later, the molten alloy will be poured into the shell.

There are two steps to building a shell: slurry coating and stucco coating.

  • Slurry coating: Dip the wax tree into a ceramic bath or slurry.
  • Stucco coating: apply the sand or stucco onto the wet surface.

Waiting for the mold to become dry and repeated the investment casting coating process until the shell can tolerant the stresses of the casting process, and the shell was built.

Wax Removing

Wax Removing

Removing the wax which inside the shell relates to the investment casting materials quality that investment casting companies used. So it is very important that explain the lost wax investment casting.

There are two methods to finish the investment casting lost wax process:
Steam-dewax autoclave: this kind of dewax machine removes the majority of the wax, this wax can be reused.

Flashfire oven: burns off the rest wax and make the shell hard. Make a clear and tough shell for casting.

Most investment casting companies use both methods in concert.

Metal Pouring

Metal Pouring

You should ensure that the shell is preheated to a specific temperature to avoid solidification or freezing off during the injection process. The shell should keep the temperature until the shell is filled.

Induction melting means investment casting companies use a ceramic cup which also called a crucible to melt alloy. And when the alloy reaches its melting point, it can be poured into the shell.

Shell knock off

Shell knock off

When you finish the metal pouring process, you should remove the shell investment casting materials next. There are three common mechanical methods to remove the shell.

Hammer, High-Pressure Water Blast, Vibratory Table

Though the shell also can be removed chemically, while it will take the problem of health and the environment.

investment casting process

Cut off

When you remove the shell from the tree, you should cut the part from the sprue, and ground of the gates. Manufacturers always cut off parts with a chop saw, torch or laser, while laser has limited applications.

investment casting process

Individual casting

The last step of investment casting mold can be finished by vibratory, belting, or hand grinding or polishing. Deal with the automated process is efficient.

 

These are the 8 common investment casting steps. Some of the investment casting materials used by investment casting plants are mentioned above.

4 Advantages of investment casting process

  1. Superior surface finish: the ceramic shell was made according to the smooth-surfaced wax pattern. Coat the wax pattern with the ceramic, and when you remove the wax, you will get a superior finished surface.
  2. Complex, near-net geometries: the wax pattern inside the ceramic is nearly the final shape, and the feature of liquid ceramic can round the wax pattern and any details of it. When the wax was removed, the shape still retaining. Therefore, pour the melted metal into the shell and wait for it cool. You will get the final geometries.
  3. Wide range of alloys: the ceramic shell is very hard that can tolerant the extreme heat temperatures of melted metal. The melting point of most metals is lower than the tolerant point of the shell. Therefore the investing casting can be used in a wide range of alloys.
  4. Fine detail: the liquid ceramic shell will warp all the details that the wax pattern has, so the final product will have fine detail.

precision investment casting process Applications

The applications of investment casting mold are nearly in the field of all manufacturing industries, such as power generation, firearm, automotive, aerospace, military, gas and oil, food service, and energy industries.

The metal investment casting can produce nearly every kind of metal parts like triggers, hammers firearm in the firearms industry. Every industry which applies metal parts can use the investment casting process to produce its parts.

The investment casting process can also be divided into the water glass and aluminum investment casting process.

alloy steel casting

Steel Valve body casting

Steel Pump Investment Casting

Automobile investment casting

Summary

The above is the introduction of investment casting process steps. As one kind of manufacturing method, investment casting products by pouring molten metal into a shell. With a lower investment casting cost and friendly environment, metal investment casting has become popular in the investment casting plant. 8 precision casting process is lower-cost and efficient. And it can be seen in many situations, such as automotive, aerospace, food service, etc.

Dawang steel casting is a professional investment casting foundry in precision castings services. If you want to know more information about the investment casting process and investment casting quotation, leave your comment or connect with us.

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