Investment Casting – Everything You Need to know About It

Also known as precision casting, the investment casting process is exactly what the name tells you. It is a technique used in the metallurgical world to facilitate and speed up the process of making identical metal pieces and parts of machinery.

It has an interesting past in the art world, with ancient research showing how it does use to be the choice to make jewelry and decoration. But today it is a mass used procedure with a lot of factory workers involved.

In this article, you will learn more about this process. You will understand how it works and what makes it so economical. So if you are interested in this technique that is present in your daily life, keep reading!

What is investment casting?

carbon steel casting

This is a investment casting process that exceeds all expectations when it comes to precision. The casting process is, in general, made by pouring liquid material into a mold cavity. This liquid will cure over time by a chemical reaction or cooling. To complete the process, the solidified portion, also known as a casting, is ejected or broken out of the mold.

With the use of wax, plastic, or even wood, a mold is made with the pattern intended. Then the casing is made and it is hardened in high temperature chambers. After that the liquid metal is poured into it and allowed to cool down. The precision of this technique comes especially from this part.

The wax and the material used for the mold is the perfect pattern, and it can have a lot of curves or sharp edges. It can even have some dents and scratches. But the casing will fill all these spots, and they will stay in place after the material is melted away.

And as soon as the liquid metal is poured into it, it will fill every inch of the casing, even the spots and dents. This provides the perfect surface. If the pattern is perfect, the piece will also be.

What is investment casting used for?

It is a manufacturing technology for precision casting. This is because it can reproduce patterns of complex shapes with fine detail.

Today, this can mainly use in the investment casting companies of metal parts and parts for machines. Investment casting is used in the firearms, food service, gas and oil, and energy industries.

Investment castings are employed in a variety of sectors, including guns, food service, gas and oil, and the energy industry. And is present in your daily life like in the pieces in your refrigerator, car and more. Instead of making every single one alone in a investment casting foundry with heavy machinery and lots and lots of people, they can make thousands with permanent casting and even disposable ones.

And can even use it for art and decorations. In fact, It can use for the industry. But small business owners and artisans can make it on a smaller scale with different kinds of materials to make art and jewelry.

Why is it called investment casting?

Investment casting is a centuries-old casting technique based on lost-wax casting. The procedure is known this way because the mold pattern used in this casting process is “invested” with liquid material. During the investment casting process, investment materials are used to create a mold into which liquid metal can be poured.

What is the difference between casting and molding?

INVESTMENT CASTING
investment_casting

Now that you know what investment casting is, and that it involves molds, you must be wondering if there is a difference between the two.

And yes, there is. The fundamental distinction between molding and casting is the material used in the operation. Casting is normally done with metal, but molding is done with plastics. In both cases, the molten material is poured into a die or mold to make the final shape.

And here is an aluminum investment casting step in which technology plays a great part. Today, the 3D Printing business has become more accessible to people, making the molding process even more common.

You can find a lot of small business online that uses the plastic models made with the 3D Printing machine to make molds. Resin is the most common material used by them to make arts and crafts with these molds. They make trivets, earrings, and a lot of figures with these molds.

In larger scales, some investment casting foundry and industries are starting to see a benefit in using the 3D printed models to make permanent molds. That way the pattern and modeling processes can be cheaper and faster, demanding less time and money for similar results. Even though the more precise the 3D printing machines are, the more expensive she is gonna be.

But speaking of that, what types of aluminum investment casting are there?

Types of investment casting in industries

There is not just one type of metal in the investment casting coating process. In fact, the range may surprise many people. It is an economical and very versatile process. Investment casting can be used for a variety of applications. Investment casting is a great choice for people who prioritize quality and time savings.

There are many types of castings, such as:

  • Stainless Steel Casting.
  • Carbon Steel Casting.
  • Metal Casting.
  • Rapid Prototype Casting.
  • Aluminum Investment Casting
  • Brass Casting
  • Bronze Casting
  • Cobalt Casting
  • Tool Steel Casting

See? There are a lot of possibilities, and not only for metals, but for the casing too. Different types of results demand different types of casting. Some are more popular than others, but here are some of these possibilities that can be done.

● Sand casting

A method of manufacturing castings in a sand mold. Sand casting may produce steel, iron, and the majority of nonferrous alloy castings.

This method is great for precise details and complex-shaped patterns. It has a subjectively low cost, and it is most used with automotive parts and pieces.

● Gravity die casting

This is a molding technique in which molten material is injected with a metal mold by gravity then cooled and solidified inside the mold to produce a casting.

But there is a need to evacuate the air inside the mold, so actions after the process must still be taken. This method is actually more prone to cracking and breaking, so there is a need to be extra careful with the final product.

● Low Pressure Casting

This method uses pressure to make sure that the casting cristalyzes and guarantees the best quality of the product. It is great for thin castings, and uses all the melted metal needed, leaving less scraps.

The simple equipment also helps in the cost-efficiency value. The is also less need for labor, and its simplicity helps with the training and use of the materials.

● Centrifugal Casting

In this casting technique, raw materials are converted into a spinning mold, which is then filled and cemented by centrifugal force.

This method uses way less metal than the others. The spinning process is a good choice to make the liquid material pierce through every corner of the project. But there are a few disadvantages to this process. It involves much more machinery, and the final quality might not be the best.

● Vacuum die casting

An advanced die-casting process that improves the mechanical properties and surface quality of die-casting parts by removing or significantly reducing the pores and dissolved gasses in the process by extracting the gas from the mold cavity. This is a great way to make thinner castings, and less machinery is needed.

● Squeezing die casting

Squeezing die casting is a process of immediately obtaining the product or blank by hardening liquid or semi-solid metal under increased pressure and flowing shaping. It provides the benefits of high liquid metal usage, a simpler process, and consistent quality.

It is a metal forming process that uses less energy and has a wide range of possible applications. Also helps with eliminating pores and other possible defects of the piece.

● Lost foam casting

It is a revolutionary casting process in which a model cluster is formed by combining paraffin or foam models that are comparable in size and shape to the casting. After brushing and curing the refractory coating, it is vibrated by burying it in dry quartz sand. The liquid metal occupies the model location after solidification and cooling after being poured under pressure applied to vaporize the model.

So as soon as it is ready, you will have a high precision casting piece. This method is also great for the planet, is clean and it doesn’t pollute.

● Continual casting

It works on the idea of continually pouring molten metal into a specific metal mold known as a crystallizer. The hardened (crusted) casting is constantly drawn out of the opposite end of the mold and can be any length or set length of casting.

For its quick cooling action, the material is tough and strong. It is also a very economical process.

● Investment casting

As for aluminum investment casting is the process of making a pattern from a fusible material and covering the pattern surface with many layers of refractory material. The design is then melted out of the mold shell to obtain a mold with no separating surface. Finally, the process fills after baking at high temperatures.

This one has the higher accuracy when it comes to surface dimension and geometric characteristics.

Advantages and Disadvantages of the Investment Casting

You already know how cost-efficient and high-quality the investment casting is, Now let’s compare your advantages and disadvantages!

Advantages

  1. It gives a smooth finish to the final product.
  2. It has a faster production
  3. Tight Tolerances
  4. Affordable Tooling
  5. High-range size variation
  6. Vast material variety (ferous and non ferous)

 Disadvantages

  1. Longer lead time
  2. A bit more expensive than sand casting

This is in fact a great process. And an amazing option for those who don’t want complex steps and still get a near perfect final product.

But why is wax used in the investment casting process?

During the mounting and finishing operations, sticky waxes are widely utilized. These waxes assist in the bonding of different pattern waxes together or in the construction of a sprue assembly. The wax helps in the formation of a strong adhesive between the pieces, allowing them to withstand the handling of workers while the ceramic shell is being created.

Wax is the best material to help the mold to be precise and strong. The tighter the mold is, the smoother and more accurate the final product will be. She can melt later, in an easy and quick way. But the mold made by it stays clean and smooth, not interrupting the finishing of the piece. It is also a non-expensive material, making it a common option for all the industry.

What is the difference between investment casting and sand casting?

Sand casting and investment casting are two processes for producing metal objects that involve pouring molten metal into molds. Despite the fact that these technologies are thousands of years old, they have been developed through time to reduce the quantity of metal utilized and the amount of machining and polishing necessary. However, there are substantial distinctions between these two metal component manufacturing procedures.

Their process may seem similar, but the key difference is in the mold. One uses sand and the other uses wax.

Investment casting also has a high pre-production cost to develop a wax design and ceramic shell, and then make smooth finished items. While sand casting is less expensive than investment casting, it requires an after-process to cope with the rough surface of the end product.

Let’s understand both methods to have a better view of how these differences affect each investment casting coating process.

how Sand Casting & Investment casting differences affect each process.

investment_casting
steel casting grades

Sand Casting

In this method, a mold is made by compacting sand around the pattern or model of the completed project. One can tear the design apart, you can remove it from the mold. You can reassemble the two mold pieces and pour the molten metal into the holes. When the metal has cooled enough, it can remove the parts. Can retrieve the sand again and the pieces separated.
Thus, the mold made of sand can be reused or recreated. The cost can reduce since it can remove the sand from the mold and crush it to make it again.
Usually, these molds make out of two parts. They join tightly together, so the material can pour inside. But the mold can not reuse. They get mostly destroyed in the process. Since the sand is reusable, other molds are easy and quick to make.

This is also great with detail and complex-shapes pieces, but the final product can not turn out as accurate.

Investment casting

As for the investment casting, things are a bit different. Its finished products are smooth and basically perfect, full of detail and strong.

In this case, the mold is made by building a wax version of the final product. Then the mold goes into a high-temperature place, and the wax model melts away.

Several wax designs can be built into a tree and carefully connected using wax rails and sprues to cast multiple components at once. After that, the “tree” is continuously dipped in a ceramic slurry, which hardens as it dries.

The tree and its designs are heated to dissolve the wax after getting numerous layers of ceramic that have been allowed to solidify. The wax in the sprues and gates likewise flows out of the tree, forming tunnels and pipelines for the molten metal to follow and fill the mold fully.

The difference between this process and the sand casting process is the mold that can not be reused or retrieved. The wax melts at higher temperatures, but the sand only dissolves, but it can be remade again.

How is the process of investment casting?

Now you will learn step by step how these molds are made, and how the finished product is put on the market.

sand casting gating system

1. Pattern creation

First must create the pattern for the final product. I can do this in a lot of ways. Can inject The wax into a die, shaped manually from a block of wax, or produced using a 3D printer and the suitable wax material.

investment casting process

2. Making a tree

A tree is a structure where the molds are put together. At this stage, it is referred to as a tree since each separate wax design is effectively a “branch” and will be combined into one finished artwork after the process is completed.

3D Printing Investment Casting

3. Casting it

The shelled casting is added around the tree after it has been built. The tree is first immersed in a ceramic slurry. Then it is immersed into fine sand stucco. So that it can utilize, the molding must be completely dry. These steps can repeat until the mold is thick enough to withstand casting forces.

sand casting

4. Removing the wax

The wax patterns must remove before the chosen material does put into the freshly shelled mold. This is frequently accomplished by heating the wax in an oven. To heat the wax, steam can alternatively utilize. The mold can turn upside down to allow the liquid wax to drain and reuse to make fresh wax designs.

carbon steel casting

5. Pouring the material

After the wax is removed, the material of choice is poured into the hole left by the wax. The liquid will take the form of the mold and be allowed to cool down. It will remain like that until it is fully dried and solid. Now is the time to finish it.

carbon steel casting

6. Removing and finishing the product

After cooling, the mold needs to break to reveal the final result. The next step is to polish the item!

Now you will learn step by step how these molds are made, and how the finished product is put on the market.

A brief history of the investment casting process

Investment casting first became popular as a contemporary industrial method in the late 1800s, when dentists began employing it to investment casting companies crowns and inlays, as reported by Barnabas Frederick Philbrook of Council Bluffs, Iowa in 1897.   William H. Taggart of Chicago, whose 1907 publication reported his discovery of a technique, accelerated its application.

He also created an investment material and an air-pressure casting machine, as well as a wax pattern compound with exceptional qualities. But during World War II, there was a rise in demand for precise net shape production and specific alloys that could not be molded using regular processes or needed excessive machining. The industry shifted to investment casting. Following the war, it was employed in a variety of commercial and industrial applications that required intricate metal pieces.

However, investment casting has a long history going back thousands of years. Its early use was for mostly decorations, and jewelry, with natural beeswax patterns, clay molds, and manually driven bellows for stoking furnaces.

Examples do discover worldwide, including long lost civilizations, including Tutankhamun’s tomb in Egypt, Aztec and Mayan Mexico, and the Benin culture in Africa. The method created intricate artwork in copper, bronze, etc., and gold.

Investment Casting Applications

With the expanded availability of higher-resolution 3D printers, 3D printing is now can utilize to create significantly bigger sacrificial molds for investment casting. Space Technology used the process to print the mold for a new tiny satellite. Which was then dipped in ceramic to make the investment cast for a titanium space bus with an integrated fuel tank and integrated cable routing.
Gun makers commonly use investment casting to produce low-cost rifle receivers, triggers, hammers, and other precision components. And it is present in your daily life, including parts of your refrigerator and car. The pieces needed to mount these electronics, and many others, are mass produced with these techniques and similar.

Conclusion

Investment casting is a worldwide known method to mass produce parts and pieces for machinery. It is economic and cost-effective for the industry. Investment casting provides precision components while reducing material waste, energy consumption, and later machining. It may also assure the creation of exceedingly complicated pieces. This makes the investment casting method very valuable for design engineers.

This procedure does use for manufacturing little parts for over 5,000 years. It was first used to make jewelry and decorations, and to this day small business owners and artisans use this method to make art on a smaller scale. Many businesses seeking lightweight and sophisticated components regard this sort of casting as the future.

By dipping a wax or appropriate polymer design into the refractory material slurry, an investment casting pattern is coated. This dipping operation is done numerous times to improve the coating thickness and strength once the refractory material coating has solidified.

After the final layer has solidified, the wax is melted and molten metal, or even other materials, are poured into the cavity made by the wax design. Metal casting is removed from the refractory mold once the metal has solidified within the mold.

This process has many advantages, such as high range sizes, it can replicate complex-shaped patterns with ease, and makes strong products. The cost is not as expensive as it can be, so it is a good option for those who want to achieve a high quality product with simple tools.

To create the complicated components, the investment cast tool is often made up of many sections that are fitted together. This “front end” cost is high, but it is readily compensated by the absence of later machining and/or construction.

There is a lot to learn about the metallurgical world and how it affects our daily life. From a small piece in a car that can prevent accidents or give us comfort, to a part of a space bus!

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