Lost wax casting, also known as "investment casting," is used exclusively for casting metal jewelry, sculptures, and other objects. This guide will introduce what is lost wax casting and related content, through this article you will fully understand what is lost wax casting.
What is Lost Wax Casting?
Lost wax casting is a metal casting method in which molten metal is poured into a mold created from a wax model. After the mold is made, the wax pattern will be melted and drained. Hollow cores can be achieved by introducing heat-resistant cores that prevent molten metal from completely filling the mold. Use this casting method to capture fine detail in metal and glass.
Lost Wax Casting Examples
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What Is the Lost Wax Casting Process?
The lost-wax casting process can differ depending on the industry and application, but it generally consists of the following steps. Cast parts can be made from a wax model itself, called the direct method, or from replicas of the original wax model, called the indirect method. The direct method jumps from step one straight to step four.
- Model-making: The engineer carves a design out of wax. The size and complexity of the wax model is limited to the wax carver’s skill, and the capacity of his casting equipment.
- Creating a mold: A caster then casts this model and polishes the casting to produce a “master” pattern. The master model is used to make a wax mold out of rubber, which is heated and “vulcanized” around the master casting to make a flexible wax mold.
- Producing wax patterns: Molten wax is injected or sometimes poured into the rubber mold. This can be done over and over to make copies of the original design.
- Assembling the wax pattern: Sprues are added to the wax copies and they’re connected to create a tree-like structure, which provides paths for the molten wax to flow out and molten metal to later fill the cavity.
- Applying investment materials: The wax tree is either dipped into a slurry of silica, or put into a flask and surrounded by the liquid investment plaster.
- Burnout: After the investment material dries, the flask is placed upside down into a kiln, which melts the wax leaving a negative cavity in the shape of the original model.
- Pouring: The investment mold is further heated in a kiln to reduce the temperature difference with the molten metal. Metal is melted and then poured, using gravity or vacuum pressure to pull the metal into the cavity.
- Devesting: Once the molten metal has cooled somewhat, the investment mold is quenched in water to dissolve the refractory plaster and release the rough casting. . The sprues are cut off and recycled, while the casted parts are cleaned up to remove signs of the casting process.
- Finishing: The casted parts are filed, ground, machined, or sandblasted to achieve final geometry and surface finish. Where necessary, the cast parts are also heat-treated to enhance the mechanical properties of the material.
What Are the Best Materials for Lost Wax Casting?
One of the reasons lost wax casting is so popular is that there is no limit to the number of metals that can be applied to the process. We recommend the most common types of metal materials for you.
1. Stainless steel
The main alloys of stainless steel are chromium, nickel and molybdenum, which determine the grain and mechanical properties of the casting. The way the alloys are combined determines the heat and corrosion resistance of the casting.
2. Steel
Carbon, low alloy and tool steels are used in the aerospace, agricultural, medical and firearms industries, to name a few. Steel is chosen for lost wax casting because it is economical, available in a variety of grades, and its ductility can be adjusted through heat treatment.
3. Ductile Iron
Ductile iron castings have excellent surface hardness, modulus of elasticity, corrosion resistance and a strong strength-to-weight ratio. The biggest benefits of ductile iron are that it is cost-effective and offers a wide range of design freedom.
4. Aluminum
Aluminum is the ideal metal for lost wax casting due to its machinability and corrosion resistance. When it is alloyed with other metals and heat-treated, it develops extraordinary strength that rivals that of mild steel.
5. Cobalt
Cobalt is naturally resistant to oxidation and has a hard and shiny surface. It prevents oxidation by passivating the oxide film. Cobalt's resistance to corrosion, heat and wear makes it ideal for lost-wax casting and is used to produce parts for the aerospace, automotive industry and military applications.
6. Brass
Brass is a copper alloy known as red brass or brass, and the lost-wax casting is used for plumbing fixtures and door hardware. The main characteristics of brass are its appearance and quality of finishing and polishing. One disadvantage of using brass is its lead content, which limits its use.
7. Bronze
The properties and quality of bronze depend on the alloy it is combined with. Added elements to bronze can enhance its performance and quality.
8. Nickel
Nickel, containing nickel, chromium and molybdenum, has exceptional strength and resistance to heat, wear and corrosion. It was chosen as the cast metal because it is easy to weld and fabricate, and it is resistant to cracking and corrosion.
What Are the Main Applications of Lost Wax Casting?
It is one of the oldest known metal casting techniques dating back 6,000 years, but it is still widely used for producing jewelry, dentistry, and art. Its industrial form, investment casting, is a common way to create precision metal parts in engineering and manufacturing.
What Are the Advantages of Lost Wax Casting
1. The process is especially advantageous for high-melting-point alloys as well as for difficult-to-machine metals.
2. It is most suitable for producing small castings having intricate shapes.
3. It maintains a very close tolerance of about ± 0.05 mm.
4. It produces very smooth surfaces.
5. It eliminates most machining operations.
6. It is applicable to all low to high-melting-point metals and alloys.
What Are the Disadvantages of Lost Wax Casting
1. This process limits the larger objects due to equipment size limits,
2. The cost of equipment and process is high.
3. This process needs a high degree of skill.
What Factors Affect the Cost of Lost Wax Castings?
Let's take a look at some of the cost drivers associated with lost wax casting.
Design Complexity of Castings
Part design is a major factor affecting the cost of lost wax casting. Simple part designs with no internal passages, holes or features help reduce costs for customers.
Material selection
The metal of choice is another cost driver for lost wax casting. There are different grades of common metals and alloys. So even with the same metal, a higher purity alloy will cost more than a lower grade alloy.
Quantity of shell-building layers
As the shapes of investment castings are always different, there will exist differences in shell-building layers. For more complex structures, more shell-building layers will be needed, which will cost more.
What Is the Difference Between Lost Wax Casting and Forging?
We will use tables to outline some of the content to compare these two different metal processes.
| Lost wax | Forging | |
|---|---|---|
| Definition | Casting is a metal-working process where the metal is first heated till it melts, then poured into a mould and made to cool to obtain the shape. | Forging involves the use of localized compressive forces on the solid material in order to create desired shapes. |
| Strength | Casted material is low in strength as they are poured into a cavity which lets the material take its shape freely. | Forged material are stronger as they possess a definite grain structure which is pressed with force, increasing their mechanical strength. |
| Suitability for Hollow Shapes | Casting is often preferred for the production of material containing hollows spaces or cavities. | Forging excludes cavities and porosity from their compositions. |
| Uniformity | The casted material is not always uniform. | Forged material can be made to a uniform structure preserving consistency in shape. |
| Size Restrictions | Casting doesn’t have any size or shape limitations as all material will be melted before putting them into shape. | Materials weighing up to 50kgs can be forged yet higher power is required if material to be forged is heavier than 50kgs. In this case, casting would be the alternative. |
| Level of Complexity | Casting is able to produce complex patterns and shapes. | Forging is more focused in producing uniform and simple material. |
| Cost | Casting uses relatively inexpensive equipment. | Machines used for forging such as heavy duty industrial dies are more expensive. |
Lost Wax Casting FAQs
What is the basic process of lost wax casting?
The basic lost wax casting process involves creating a pattern and a mold, then pouring molten metal into the mold. You will then extract the solid metal casting and finish your piece. This process is customizable for different types of metal casting, along with shapes, sizes, and more.
What is a major disadvantage of the lost wax casting process?
Despite the beneficial nature of lost-wax casting, it does have its drawbacks. The most significant disadvantage is the size limitation. Because so few design engineers can produce large parts using this technique, it may not be the best option for a client who needs to fabricate a bulky component.
How much shrinkage in lost-wax casting?
Due to shrinkage on solidification, and the polishing and finishing process, your final casting will be slightly smaller by about 1-3% so you need to allow for this in your master pattern.
What metal is best for lost-wax casting?
Bronze is the metal we use most often in our process of lost-wax casting. Bronze casting grain (that's really small pieces of bronze) is heated up until it becomes molten metal. Each flask is removed from the kiln and placed inside a vacuum chamber.
Why is it called lost wax?
The “lost wax” technique is so called because the wax model is destroyed in order to create the piece. The technique is sometimes called the “lost mold” technique because the mold, too, is destroyed in the process.
When Was Lost Wax Casting Used?
Metal casting by the Indus Valley Civilization began around 3500 BC in the Mohenjodaro area, which produced one of the earliest known examples of lost-wax casting, an Indian bronze figurine named the "dancing girl" that dates back nearly 5,000 years to the Harappan period (c. 3300–1300 BC).
Lost Wax Casting Company - Besser Casting
Besser Casting is a leading investment casting company in China. We have more than 20 years of experience in the field of lost wax casting. We have a professional engineering team that oversees and handles the whole process to ensure smooth operation.
In addition, we confirm that all products meet the tolerances specified by ISO standards.
This strict adherence ensures that all of our castings are to exact dimensions.
Our sole purpose is to provide you with quality lost wax casting products at an affordable price.
If you place an order, our professionals will discuss with you the finer details of what you would like to be fulfilled.
Conclusion
Lost wax casting, or investment casting, is a casting process that uses a wax pattern to create the initial design for a part to be produced in a ceramic mold.
Lost wax casting can produce a variety of complex and intricate parts with excellent tolerances.
Lost wax casting is used to produce parts that require tight tolerances with thinner walls and exceptional surface finishes that require very little after process finishing.
The casting process for lost wax casting involves multiple steps that begin with the creation of the pattern, or master, which is made from wax.
Lost wax casting uses a wide assortment of metals to create parts with exceptional accuracy and tolerances.
Lost wax casting is a highly technical process, and with more than 20 years of manufacturing experience, we are able to provide you with lost wax investment casting services. So feel free to inquire about our services and one of our team members will discuss your project needs with you.