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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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.
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 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.
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.
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.
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.
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.
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 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.
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.
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.
Contact us to discuss your requirements of customized lost wax investment casting. Our experienced sales team can help you identify the options that best suit your needs.
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.
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.
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.
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 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.
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.
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.
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.
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.
Lost-wax casting is a highly versatile technique and can be used to cast objects in gold, silver, brass, copper, bronze, and aluminum.
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.
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.
When it comes to investment casting of metal parts manufacturing factors such as design requirements, cost, and feasibility to manufacture dictate which casting process is most suitable to manufacture a product. This article describing investment casting is intended to help you make an informed casting decision.
Investment casting produces precise components while minimizing material waste, energy, and subsequent machining. It can also ensure the production of very intricate parts. This makes the investment casting process quite useful to design engineers.
The goal is to understand what is meant by investment casting. So, What exactly is the investment in &#;investment&#; casting? The term &#;invested&#; historically carries the meaning of &#;clothed&#; or &#;surrounded.&#; Investment casting employs a shell made of ceramic, plaster, or plastic that is formed around a wax pattern. The wax pattern is melted and removed in a furnace and metal is poured into the shell to create the casting.
What is investment casting used for? Let&#;s break down the investment casting production process for a greater understanding:
Creating the Pattern
Mounting the Wax Patterns and Creating the Tree
Creating the Mold Shell
Size range:
Although most investment castings are small, the investment process can produce castings weighing more than 1,000 pounds. This capability is limited to a relatively small number of investment casters and requires special expertise in handling. Most cast parts fall in the ounces to a 20-pound range.
Versatile and intricate shapes:
Investment casting provides consistent and repetitive close tolerances along with intricate passages and contours. Many of these configurations are impossible to produce. For example, where machine tools cannot reach. Achieving net-shape or near-net-shape cast components can dramatically reduce post-cast processing costs.
Investment casting is a good alternative to weldments or fabricating. Many components can be combined into a single casting. The more that are combined, the better the manufacturing efficiency. Converting multi-piece components to a single investment casting typically delivers more dimensional accuracy and reduced part complexity.
Accurate and Smooth Surfaces:
The ceramic shell used is built around smooth patterns produced by injecting wax into a polished aluminum die. A 125 micro finish is standard, and even finer finishes are not uncommon.
Investment castings contain no parting line because only one mold is used rather than two half molds (such as in the case of sand casting). Standards for surface blemishes and cosmetics are discussed and agreed upon with the customer based on the function.
Below is a comparison of relative surface finishes that can be expected from various casting process:
Casting ProcessRMS RangeDie20 &#; 120Investment60 &#; 200Shell Mold120 &#; 300Centrifugal &#; Standard tooling400 &#; 500Centrifugal &#; Permanent Mold20 &#; 300Static &#; Permanent Mold200 &#; 420Normal Non-Ferrous Sand300 &#; 560Normal Ferrous Green Sand560 &#; 900Dimensional Accuracy:
Typically, &#;standard&#; investment tolerances are +/-0.010&#; for the first inch and +/- 0.004&#; for each succeeding inch.
The design phase can result in a drawing that reduces or even eliminates previous machining requirements to produce the same part.
The cost of any part increases in proportion to the preciseness of its dimensional requirements. Whether if it&#;s castings machined parts or fabrications. A close design review will permit modification to tolerances, undercuts, blind holes, etc. to allow higher production yields and lower piece costs. If closer than cast tolerances are necessary, the machining required for investment casting will be less than conventional castings or fabricated components.
Quality and Integrity:
Casting integrity is an important feature of the process. Investment casting has a long history of serving demanding sectors such as gas turbine engine, petroleum, chemical, defense, and medical.
Tooling Cost:
For low quantity requirements, it may be more expensive than other methods if permanent tooling is pursued. For those applications, SLA or printed patterns may be a cost-effective alternative (even for a quantity of one).
Initial costs are another key factor when determining whether investment casting brings the greatest value. The investment cast tool usually consists of multiple parts fitted together to produce the complex components. This &#;front end&#; cost is not insignificant but can be easily offset by the lack of subsequent machining and/or fabrication.
Size Limitations:
It&#;s possible to create investment castings in a range of sizes. There is an upper limit on that range, which is less than other shaped technologies like sand casting.
Very small structures:
Investment casting is an excellent choice for thin-walled applications, but very small internal shapes that use cores can present challenges. Holes typically cannot be smaller than 1/16&#; (1.6mm) or deeper than 1.5 times in diameter.
Timing:
The multi-step investment casting process is more time consuming than other processes. The processing time can be shorter than other alternatives.
As with most materials and design decisions, a discussion with a metals expert can help drive the best decision. To learn more about the metal investment casting process or to determine if it is a fit for your application, please contact us.
If you want to learn more, please visit our website customized stainless steel investment casting.