When it comes to manufacturing, every component needs to meet its exact specifications to create a final product. There are various processes available to make necessary parts unique to a product, but investment casting is one technique that stands above others in many ways.
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Investment casting is an old way to form metal using minimal machinery and energy. It is best for creating intricate parts, and it is still beneficial in today&#;s industrial environment.
This blog will explain why this old-world metal forming technique stands the test of time and how various industries use it today.
The metal forming process known as investment casting dates back almost 5,000 years. Other names for this technique include lost-wax casting and precision casting. Manufacturers use this technique to accurately cast metals with a high heat tolerance using a plaster, plastic, or ceramic mold and a wax pattern that melts away.
The pattern and mold creation process sets investment casting apart from other metal fabrication methods like die and sand casting.
Here is a breakdown of the process:
This casting process is excellent for creating products and prototypes. It has widespread applications across various industries, primarily the automotive and industrial industries.
So, what is the best metal for casting? Well, how different industries use the castings today depend on the metals they need, but refractory metals with high melting points work best.
Design engineers use this material the most in investment castings. A blend of aluminum, silicon, and magnesium is strong enough to create premium automotive components, but casters also use the alloy for electronics and industrial equipment.
Steel is known for its durability, which is why this variety of metal is a popular choice for various components. Casters use this material to craft everything from auto parts to golf club heads. For a full review of the benefits of stainless steel investment casting, read another article we published here.
Metalworkers turn to titanium alloy when making castings that need to be strong enough not to fracture when it has a crack. For example, golf clubs and marine components are a common choice for titanium castings.
This method is ideal for crafting small, complex geometric shapes that have intricate features with one mold.
Investment casting is highly versatile. Because you can combine multiple wax patterns to create one unique mold, you can configure parts you could not make with a machine or tools, making it a worthwhile alternative to weldments.
Dimensional precision and smooth finishes are other benefits of this casting method. The casters form the ceramic shell around even patterns, leaving behind no parting line because only one mold makes the casting, not two. The result is a smooth finish averaging around a 125 micro finish, but post-process smoothing can achieve a more refined finish, if necessary.
Other advantages of investment casting include:
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.
This process is best for casting small intricate components. Parts exceeding 75 pounds are better suited for other casting methods.
Investment casting shells also have limitations on their size and depth. They cannot be smaller than 1.6mm or deeper than 1.5 times the diameter. If your casting design requires cores and cannot fit these requirements, you may need to seek another process.
This technique is more complicated than other casting processes, and it requires a substantial amount of preparation and specialized equipment. As a result, the upfront cost of investment casting can be more expensive than sand casting or die casting, but the production cost per unit decreases with larger orders.
Investment casting may have roots dating back 5,000 years, but it still has beneficial applications in modern society. Throughout the world, industries rely on precision casting to produce intricate components with smooth finishing, unique geometric shapes, and tight tolerances, including the industrial,, automotive, firearm, food processing equipment, and agricultural equipment manufacturing industries.
We use specialized shell making and wax processing equipment to fabricate patterns and cast quality components quickly. If you would like to learn more about our investment casting services and receive a free quote on your upcoming project, contact our team today.
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Steps of Lost Wax Investment Casting Process
Investment casting is a multi-step process that produces near-net shape precision casting parts. The process begins with wax being injected into a die to create a replica pattern of the finished product. The patterns are then affixed to wax runner bars to create the cluster. A special machine dips the cluster repeatedly into a slurry to develop a ceramic shell, and then the wax is removed in a steam autoclave. Once the wax is removed, the ceramic shell is preheated and then filled with molten metal to create the desired castings.
Investment casting requires a metal die (usually in aluminum), wax, ceramic slurry, furnace, molten metal, and other machines needed for wax injection, sand blasting, vibratory tumbling, cutting, and grinding. The lost wax investment precision casting process mainly involves the following steps:
1- Metal Die Making
Based on the drawings and requirements of the desired casting parts, the metal die or mold, usually in aluminum, will be designed and produced. The cavity will form the same size and structure of desired castings, under the premise of considering the machining allowance.
2- Wax Injection
Also as known as pattern formation, lost wax casting patterns are created by injecting molten wax into the metal die produced in last process. The special wax injextion machines should be used for this process
3- Slurry Assembly
After fixing (if needed), the wax patterns are then attached to a gating system, which usually is a set of channels through which a molten metal flows to the mold cavity. After that, a structure like a tree is formed, which is suitable for mass casting at the foundry.
4- Shell Building
The investment castings outer shell casing is built up through dipping into a ceramic bath and then immediately coated with sand for several times. The process is usually repeated for many times and last for days in order to make sure the shell strong enough to withstand the molten metal later on.
5- De-waxing
The inner cavity of precision investment casting is then dewaxed, which leaves a hollow outer ceramic shell layer. The hollows are just the same space as the desired castings. During this process, the wax could be collected for re-usage.
6- Pouring & Solidification
Before pouring, the ceramic shell with cavity should be pre-heated. This prevents shock and the ceramic shell from cracking once the liquid metal at a high temperature is poured into the cavity. The chemical composition of the molten metals should also be tested before casting.
7- Sawing or Cutting
Once the molten metal has been cooled and solidified, the cast part(s) is then removed from the gating system tree cluster via shaking, cutting or friction sawing off the individual raw casting.
8- Shot Blasting and Secondary Processing
The casting part is then fully customized through grinding or additional heat treatments. Secondary machining or surface treatment might also be required depending on the requirements of the part.
9- Packing and Delivery
Then the lost wax casting parts will be fully tested for the dimensions, surface, mechanical properties and other required tests before packing and delivery.
Are you interested in learning more about high quality precision lost wax investment casting manufacturer? Contact us today to secure an expert consultation!