The Ultimate Guide to Choosing lost wax investment casting
Lost Wax Casting Guide: Definition & Process [+ How To Start]
Lost wax casting, also known as 'investment casting,' is the process by which a single metal object is cast from a wax model. It is a highly versatile process that achieves exceptionally detailed results. This guide will cover how to start lost wax casting and what you can create with the process.
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What is lost wax casting?
Lost wax casting builds a mold around a sacrificial wax model. After the mold investment is set, the wax is melted out and forms a cavity where the metal or glass flows in. Using this method of casting captures fine details in both metal and glass. This ancient method has been used since B.C. to visually capture the stories of ancient cultures and religions throughout history.
What is the lost wax process used for?
Lost wax casting is a 6,000-year-old process still used in both manufacturing and fine art. The precision and accuracy of the process have made it an ideal method for producing objects with thin walls, intricate details, and close tolerances. The process is used to create parts for transportation, agricultural, and medical industries, to name just a few. It can be used to create objects from simple to complex in various metals by casting an original wax model or pattern. The wax model makes an expendable mold that can only be used once in casting. This guide focuses on the lost wax casting process with metallic alloys. You can also use lost wax casting techniques to create cast glass objects. To learn more, head to our glass casting guide.
The lost wax casting process in 8 steps
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. The description below is based on smaller-scale casting processes, often used for jewelry. While essentially the same, in larger castings the mold material is made of Ceramic Shell (colloidal silica and various grades of silica), rather than plaster.
Tools and Materials
Create a model in wax
Create your desired design in wax before building a mold around it. This wax model can only be used once. After that, shape it with texturing tools, a soldering iron, and a heat gun. Many experienced wax sculptors swear by repurposing dental tools to sculpt and carve unique designs in wax effectively. Hollow out your wax model if possible.
When shaping your pattern, make sure you account for any anticipated shrinkage when the metal cools. Patterns may also be gated with sprues to allow the molten metal to flow into the mold. This is especially important if your design contains small intricate elements that may not fill with metal during the casting process.
Make your mold
You can make a mold using a combination of plaster and silica. Use a gram scale to measure each ingredient and mix equal parts by weight of plaster, silica, and water until the investment has the consistency of heavy cream. Plaster gives the mold support and silica has a high refractory, so it can withstand a lot of heat.
' When working with dry materials, make sure that your work area is well ventilated, and wear a respirator when working with dry investment.
Remove the wax
The easiest way to melt the wax out of a small mold is in a microwave. First, remove any metal clamps you might have added to your mold, then prop it up on clay supports over a small container underneath to collect the wax. Heat in short bursts in the microwave until all of the wax has dripped into the small container. You can also burn out the wax in a kiln.
Choose the metallic alloy
All metal castings are produced from either ferrous or non-ferrous alloys. Alloys are a mixture of elements that provide the best mechanical properties for the final cast's use. Ferrous alloys include steel, malleable iron, and gray iron. Non-ferrous alloys most commonly used in casting are aluminum, bronze, and copper. If you are working with precious metals in a jewelry studio, you may work with silver, copper, gold, and platinum. Less common, but especially spectacular, are metal castings with iron, which casts molten iron into a ceramic shell or resin-bonded sand mold.
Melt the alloy
Melting processes vary between alloys because each alloy will have a different melting temperature. Essentially, melting consists of placing the solid alloy in a crucible and heating it over an open flame for smaller projects or inside of a furnace for larger amounts.
Pour into the mold
Pour the molten metal into the mold cavity. If it is a small casting, you may simply pour from the crucible where the metal was heated directly into the mold. However, a larger casting may require a small team to support heating the metal inside a furnace and transferring the metal into a larger crucible or ladle before being poured into the mold.
' Make sure to follow all recommended safety guidance when pouring molten metal. Wear protective clothing, including natural fiber clothing, long pants and sleeves, insulated gloves, and safety goggles. Work in a well-ventilated space to avoid any risks from dangerous fumes. Ensure you have a chemical fire extinguisher nearby and keep your walkway between the furnace and the mold clear. Allow the mold to solidify before moving on to the next step.
Release the cast from the mold
When the metal has cooled and solidified, you can remove it from the mold. You will want to quench the plaster in water after the metal has solidified. The water will help break away the mold. If you cast it into a ceramic shell, you can break the mold and chip it away using the necessary equipment.
Finish your piece
File and polish your solid metal cast! Finishing techniques include scrubbing away excess mold material in water, breaking off the casting gates with clippers for small objects, or even an angle grinder for large pieces. You can also choose to polish or patina your metalwork to give it color and dimension.
How to learn lost wax casting
At The Crucible, you can learn to cast metals for small or large projects in different types of metallic alloys. The Crucible offers a wide variety of classes teaching lost wax casting and metalworking techniques. So whether you want to learn the fundamentals of casting or something more advanced, The Crucible has you covered.
In our Jewelry Department, you can cast small-scale silver and bronze objects from wax and organic objects. Our Foundry Department guides you in casting larger projects in bronze and aluminum using ceramic shell molds. Lost wax casting doesn't stop at casting metals'you can even learn to cast glass into molds in our Glass Casting and Coldworking Department.
Lost wax casting classes at The Crucible
Casting Wax to Silver
Learn the ancient process of lost wax casting sculptural jewelry. Experimenting with different types of wax, you will carve, cast, and finish at least one small fetish, pendant, or ring in silver or bronze. Students are encouraged to bring in personal sketches and ideas.
Foundry I: Ceramic Shell Process
Ceramic shell is a mold material used in the lost wax casting method. Learn basic wax-working techniques and explore basic metal finishing in this fascinating course. You will create a wax sculpture and build ceramic shell molds, transforming your original wax piece into bronze or aluminum.
Foundry II: Ceramic Shell Process
This class is for people with metal casting experience who have completed waxes to cast. We can also accommodate 3-D printed PLA (best unpigmented). Students will prepare their patterns, gate them, build the ceramic shell mold, cast in either bronze or aluminum, destroy the mold, and remove the gates.
Bell Casting
Bell Casting introduces participants to bell design and the lost wax foundry technique. In this class, you can design, cast, and finish a bell approximately six inches in diameter. This entry-level class provides a foundation for further exploration in this versatile foundry approach.
Iron Casting
In Iron Casting, you will explore mold construction and preparation while building a sand mold with resin-bonded sand to cast your own iron sculpture. Learn the steps required to prepare the cupola for an iron pour. At the spectacular iron pour event, students prepare iron and coke charges, operate the cupola, and pour molten iron into their new mold.
Design and Make Your Own Waffle Iron
In our Foundry, you can make your own stovetop waffle iron with a waffle pattern of your own design. We will make sand molds and use a cupola furnace to melt the iron. At the spectacular iron pour event, students prepare iron and coke charges, operate the cupola, and pour molten iron into their new mold.
Kiln Casting Glass Sculpture I
In our Glass Casting & Coldworking Department, you can create a glass sculpture using the ancient technique of lost wax. In this class, you will learn wax sculpting techniques to create wax positives that are invested in a refractory material to create a mold. The mold is de-waxed to create a void that is filled with glass melted in a kiln. When cooled the refractory is divested and the wax positive is now glass.
Lost wax casting FAQs
Can I lost wax cast at home?
It is best to start lost wax casting in an established casting studio with a professional instructor. Lost wax casting can involve more advanced equipment that can be costly to set up. The safest and least expensive way to start lost wax casting is in a public class. Once you have experience and a strong understanding of the process and tools involved, you may explore setting up a lost wax casting studio at home.
What metals can you use for lost wax casting?
Lost-wax casting is a highly versatile technique and can be used to cast objects in gold, silver, brass, copper, bronze, and aluminum.
What are the differences between lost wax casting and die casting?
The most significant difference between the die and lost wax casting process is the mold material. Die casting uses a metal mold, which is a nonexpendable mold. Lost wax casting uses a mold made out of plaster or ceramic shell, an expendable mold. In the die casting process, molten metal is forced into a mold cavity with high pressure.
What kind of wax is used for lost wax casting?
Microcrystalline wax is best for modeling because it is pliable and slightly sticky. In addition, it's medium-soft consistency makes it easy to work with. Paraffin wax can also be used for lost wax casting, but it is not ideal for modeling. Paraffin wax is best used as an additive to harden an already existing wax model. Different kinds of specialty wax can also be used. Each type of specialty wax has a specific purpose, such as carving, modeling, or patching, and requires knowledge of their different melting points.
A Comprehensive Guide to the Investment Casting Process
Investment casting, also known as lost wax casting, is a 5,000-year-old metalworking technique that blends ancient craftsmanship with modern precision. From intricate jewelry to high-performance industrial components, this versatile process remains a cornerstone of advanced manufacturing across diverse industries.
Now, let's break down the investment casting process into eight essential steps that highlight how this ancient technique works in modern manufacturing.
The Investment Casting Process in 8 StepsAs we've learned, 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.
Wax Patterns
A master mold can be created in several ways, including 3D printing, machining from steel, or carving 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.
Molten Metal
Pictured above: An investment casting mold for the wax pattern.
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.
Now that we've explored the step-by-step process, let's examine how investment casting has evolved, from its traditional roots to modern advancements.
Investment Casting Methods: Traditional vs. Modern ApproachesInvestment casting was first used to create jewelry and tools and has evolved over time to seamlessly blend art and science, achieving intricate designs and precise components.
While traditional investment casting used hand carved beeswax as the pattern material, modern approaches include advancements like 3D printing and rapid prototyping with various materials. Every aspect of the modern investment casting process has benefited from modern technology. As a result, modern parts manufactured with the investment casting method are more precise, consistent, and cost-effective.
Today, modern investment casting procedures achieve tighter tolerances and complex geometries using high quality waxes, foams, and plastics. Advanced foundries increasingly use robots and automation to lower costs, speed up the manufacturing process, and ensure greater detail in the final product. Even further, high performance alloys and sustainable practices have enhanced the capabilities of investment casting.
While modern advancements have greatly improved investment casting, it's still important to consider both the advantages and potential limitations when choosing this method.
Investment Casting Advantages & ConstraintsWhile investment casting is useful for creating complex parts, it also has a few constraints.
Investment Casting Advantages Include:
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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 ability to trim and smooth the wax patterns prior to building the tree and coating it with 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.
Investment Casting Constraints Include:
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.
Given these advantages, it's no surprise that investment casting is widely used in numerous industries requiring precision and complex parts
Investment Casting Industries And ProductsInvestment 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.
Products Manufactured
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
Turbo chargers
Industries Served
Aerospace
Agriculture
Automotive
Energy
Electric Vehicle
Food Processing
Medical
Military
Mining
Nautical
Paper Manufacturing
Water Desalination
Given the complexity and precision required in investment casting, ensuring the highest quality in the final product is critical. This is where modern quality control and inspection methods come into play, safeguarding the integrity of each cast component.
Quality control and inspection is an integral part of the investment mold casting process. Manufacturers and metalworkers meet high standards of precision using modern inspection and testing methods. Learn more about the role of non-destructive testing and what makes investment casting products different from other casting methods.
Ensuring High Standards: The Role of Non-Destructive Testing (NDT)
Non-destructive testing (NDT) includes various techniques to evaluate the integrity of cast metal components and determine the quality of finishing without causing any damage to the component. For example, radiography is commonly used for detecting internal defects, such as voids or inclusions deep within the material, while dye penetrant testing is more appropriate for surface defects, allowing technicians to find cracks or other imperfections on the external part of the cast.
The ability to detect even the smallest internal and surface defects is especially important for components manufactured for critical applications, such as those in the medical field, where precision is vital for health outcomes.
Various NDT methods preserve components while allowing for detection of flaws. Methods used include ultrasonic testing, radiography, and dye penetrant testing. These NDT techniques identify cracks, voids, and inconsistencies throughout the casting process, reducing the risk of faulty parts and enhancing the overall investment casting process.
Other methods, including visual inspections, magnetic particle testing, and eddy current testing, contribute to the safety and reliability of components. Using multiple NDT methods to inspect the casting without destroying it is a critical step in manufacturing, essential for maintaining high safety and performance standards across various industries.
Dimensional Accuracy and Surface Finish: What Sets Investment Casting Apart?
The level of accuracy that can be achieved with modern investment casting methods sets it apart from other casting methods, including sand casting and die casting. Although the investment casting mold creation process makes it unsuitable for large parts, it is ideal for producing small components with intricate details and smooth finishes. Investment casting can achieve tight tolerances in the range of 0.005 inches, which is significantly more precise than what can be achieved with sand mold castings.
To achieve exceptional precision, investment casting begins with a highly accurate pattern, often created using modern methods like 3D printing and CNC machining. While the accuracy of investment casting starts with a precise pattern, the precision must be carried throughout the entire process. Dimensional accuracy is achieved by meticulously controlling every stage of the process, from mold making to pouring the molten metal.
In addition, investment casting achieves exceptionally smooth finishes, unlike sand casting and other metal manufacturing methods. The smooth ceramic molds used in investment casting result in a fine finish that often eliminates the need for further machining. This feature makes investment casting the preferred method for high-performance parts.
Future of Investment Casting: Trends and InnovationsModern metal manufacturing continues to benefit from technological trends and innovations, and investment casting is poised to benefit from advancements in artificial intelligence and robotics. Developments in investment casting materials and techniques, such as special alloys or pattern materials, will continue to enhance the capabilities of investment casting.
The Role of Automation and AI in Investment Casting
Like most industries, metal manufacturing is benefiting from automation and artificial intelligence. Robotics play an important role in making investment casting more efficient and precise by streamlining various stages of the process. Automation reduces production time, minimizes errors, and enhances the overall efficiency of investment casting.
AI-Driven Quality Control and Predictive Maintenance
Automated systems and robots are more accurate than people, able to identify inconsistencies and imperfections in investment casting long before the naked eye could detect them. By detecting imperfections earlier, robots reduce waste and produce higher quality metal castings. Robots can also operate under conditions that would be hazardous to humans, such as extreme temperatures.
Furthermore, AI has also begun to revolutionize the process by introducing machine learning algorithms that assist in defect pattern recognition. These AI-driven systems analyze vast amounts of casting data, allowing them to detect minute defects or inconsistencies in real-time, long before they become visible to the human eye.
This proactive detection minimizes waste and significantly improves overall product quality. Additionally, predictive maintenance is another critical AI application in investment casting. By continuously monitoring casting machinery, AI can predict potential failures or downtime before they happen, ensuring a more streamlined and efficient production process.
The Future of Investment Casting
As the robotics field continues to advance, the safety and precision of investment casting are enhanced. Automated systems are used in assembling patterns, building investment casting shells, and pouring molten metals. Robotic systems are also used during the demolding stage and many are equipped with cameras and defect detection systems to ensure components meet the highest quality standards.
As technology continues to evolve, investment casting will remain a critical process, marrying ancient techniques with cutting-edge innovation.
Potential Developments in Materials and Techniques
As history has shown, developments in various materials and techniques used in investment casting will continue to enhance the precision and quality of components. From pattern creation using 3D printing with plastics and advanced polymers to the integration of high performance alloys, the potential developments in investment casting are promising.
Rapid prototyping with 3D printing is still a relatively new development, allowing patterns with complex shapes to be created faster. In the future, rapid prototyping could lead to opening doorways for new materials to be used in precision casting, reducing costs and increasing production efficiency.
It's difficult to imagine a world without stainless steel, but investment casting was developed thousands of years before its invention. The first metals used in investment casting included elements like gold and copper and alloys like bronze and pewter. Just in the last century, innovations in aluminum, cobalt, and magnesium alloys transformed various industries with components designed to handle extreme conditions.
Should You Choose Investment Casting?At The Federal Group, our extensive expertise in investment casting ensures that your components are crafted with the highest precision and quality. Whether you're looking for intricate parts or high-performance components, we're here to guide you through the process and meet your exact specifications.
Contact us today for a consultation or quote to find out how our investment casting company can meet your needs.
Want more information on lost wax investment casting? Feel free to contact us.