From small rings and bolts to the most important and most intricate parts of heavy machinery, casting metals have come a long way and have made great innovations all these years. Starting way back between 3200 and 4000 B.C., metal casting is one of the best methodologies created by man that is still known to exist and fully develop and innovate as time goes by. There are numerous methods, types, and ways of metal casting, but there is one method that has become so popular in major industries, especially the automotive industry, worldwide. That is investment casting. What makes it the best and, by far, the most popular is what we are going to talk about in this entry. Join me as I guide you with in-depth knowledge about investment casting.
Table of Contents
What is Investment Casting
Investment casting, sometimes called precision casting or lost-wax casting, is a manufacturing method that involves using a wax model to create a disposable ceramic mold. Investment casting is a method of dealing with a metal that makes items with smooth and uniform surfaces by placing a ceramic shell over a wax template.
Investment casting still involves the traditional method of pouring melted metal into a die in order to take the shape of the die. What makes it stand out from the traditional metal casting process, despite its similarities, is that investment casting has a very interesting methodology and process. It is proven to produce outputs very close to the die, making a near-net shape that requires little to no adjustments in its final shape. Investment casting also proves to be an economical choice amongst major industries as it lowers production and material costs. According to research on investment casting, using it can result in a 60–75% reduction in material waste during production. That kind of efficiency attracts more and more industries to shift to investment casting, making it more and more popular than other metal casting options available in the production market.
Investment Casting Process
The process of investment casting involves intricate and precise yet very effective and efficient step-by-step procedures, and we are going to cover all of them. From start to finish, here is the process of investment casting. Below is a video for the guidance & detailed steps.
- Producing Wax Patterns
- Assembling the Sprue or “Trees”
- Creating the Ceramic Shell Mold
- The Lost-Wax Process
- Pre-Casting Process
- Removing of the Ceramic Molds From the Solidified Metal
- Separating the sprue/tree from the end product
- Final Cleaning
Step 1: Producing Wax Patterns
This is the disposable representation/replica of the end product in wax form. Produced by injecting melted wax into metal dyes and then machine-pressed until dry. This wax dries and solidifies quickly as it was injected into these dyes in a paste form, making mass production of a certain model or parts fast and easy. It not only increases productivity but also lowers the costs of these high-volume productions as quantities can be met in less time than different conventional metal casting methods.
Aside from injecting wax into metal dyes, the modern style of 3D printing is also used to produce these wax patterns. Commonly used for prototyping orders or very short-run purchases since making a dye pattern for low-volume production is very not economical. In this process, designs are made using stereo lithography from a 3D CAD data.
Step 2: Assembling the Sprue or "Trees"
The process involves assembling the wax patterns onto the feed system called the sprue, or “a tree” when finished. Made from reclaimed wax, it is carefully engineered to create a sufficient pathway for the next process.
Step 3: Creating the Ceramic Shell Mold
A.I. programmed or industrial grade robotic machines, which are commonly used nowadays, will now start investing ceramic layers into the wax patterns. Gradually dipping the wax patterns and sprue on the ceramic compound forming a solid shell needed for the following casting process. The process will start by coating the wax patterns with a primer coat of less viscous ceramic. This should be done in very controlled conditions as this will then take the most accurate form of the wax pattern. This process will be done carefully and meticulously. Primed wax patterns will now be dipped in a more viscous and coarse ceramic compound and will be dried again. It will be repeated till a completed mold takes form.
Step 4: The Lost-Wax Process
or the process of removing all the wax from the mold, wax pattern, and wax sprue included. Either done with a steam autoclave, a flash fire furnace, or an industrial-grade dewaxing oven, the shell or the mold will be ready for casting.
Step 5: Pre-Casting Process
The molds will now be taken into the pre-casting process where they will be reheated. Molds will be heated to approximately 1500 – 1900 degrees Celsius or even further to “stress-test” the molds. Ensuring that the mold can withstand the temperature stress that will be caused by the molten metal, it will hold on to the next process. This preheating process will also strengthen the ceramic mold, which is vital to ensure the close-to-perfect quality of the end product.
Step 6: Casting
Having reached the proper pouring temperature, the molten metal will now be poured into the ceramic molds while they are still pre-heated. The already high temperature of the molds will help the molten metal take every inch of the inner geometric form of the molds, easily making the outer details of the end product as precise as the model.
Step 7: Cooling
This process is very self-explanatorily as the metal will be cooled in the proper environment and conditions until it takes its solid form
Step 8: Removing of the Ceramic Molds from the Solidified Metal
or cleaning. This includes vibro cleaning machines, which use continuous vibrations to separate the metal from the ceramic molds; specifically designed and engineered blasting machines; or chemical cleaning, which is used to bring out the end product from the ceramic mold.
Step 9: Separating the Sprue/Tree from the end product
Cutting each individual part away from the sprue and in-gate residues will be removed with grinding.
Step 10: Final Cleaning
To make the end product flaw-free and free from any post-process residue. Also, to expose the detailed surface and make it presentable and smooth.
Investment Casting Materials
While investment casting is very popular amongst industrial productions, it is also proven effective even at the noncommercial level. Precision casting or low quantity production investment casting has been shown to be just as effective as industrial quantity. As long as you have the main materials for investment casting and some education and proper training, you can easily engage in investment casting. Proper types of equipment and pieces of machinery are a given when it comes to investment casting procedures, but as for the materials, there are 3 vital materials needed for investment casting.
Your Choice Of Metal
- Stainless steel
- Low alloy steel
- Carbon steel
- Super alloy
- Copper alloy
- Cast iron
Comparing stainless steel to many other materials, it has higher durability. The material’s promise has encouraged designers and engineers to use it more in investment casting. Stain steel applications include gears, camp equipment, golf club heads, and automobile gearbox components.
Low alloy Steel
Due to their accessibility and favorable mechanical characteristics, low alloy steels are among the most utilized steels in the mechanical industry. Designing parts with varying qualities in numerous places of the same workpiece is feasible using specialized heat-treating methods. One surface can be challenging and impact-resistant by applying different heat treatments, whereas another can become wear-resistant.
A typical low-cost material, carbon steel is available in several grades, with the classifications altering depending on the quantity of carbon present. Heat treatment can enhance carbon steel’s performance, flexibility, and strength in industrial settings. Because of its ferromagnetic qualities, carbon steel is a good material for motors and electrical equipment—one of the most widely used alloys due to its safety, toughness, and excellent structural integrity
Super alloys based on nickel and cobalt are frequently used in the marine, aerospace, energy, medical, and chemical sectors. Cobalt-based alloys outperform their nickel-based counterparts in terms of corrosion, oxidation, and wear resistance, while nickel-based alloys are more robust at high temperatures. Because they offer increased flexibility and improved service qualities while still being a cost-effective solution, super alloys are replacing sheet metal more and more frequently.
Alloys based on copper have low wear rates and are resistant to corrosion. They are widely utilized in applications, including electrical and plumbing parts, ship or pump propellers, and electrical components. There are more than 400 distinct alloys, a versatile material with many qualities.
Gray iron and ductile iron are two types of iron frequently used in castings and are renowned for their great precision and low cost. High strength, heat resistance, and toughness are characteristics of ductile iron, although its manufacturing is more complex than other steels. As a result, cast steel has a lower production cost.
Wax for Pattern
Reclaimed wax is the standard choice for making wax patterns in investment casting. It may not be as strong as virgin wax, but that is the point. Not only because it will come as an economical choice for mass-producing disposable patterns, but cleaning reclaimed wax away from the mold during the lost-wax process is easier compared to using virgin wax.
This is the most crucial material in investment casting because it will make the mold that will form your end product. The formulation of the ceramic compound is known to be the “trade secret” of most in the investment casting industry, where the formulation of a certain ceramic compound is the vital material to achieve great results. Innovations that include laboratory studies are continuously made to formulate ceramic compound solutions that could withstand much harsher temperatures while maintaining an accurate geometric form, especially during the cooling process right after the molten metal is poured into the ceramic mold.
When to Use Investment Casting (Applications)
High precision is not the only selling point of investment casting; versatility is another one. Unlike standard die casting, which can only handle non-ferrous metals or metals that don’t contain any iron, investment casting can handle both ferrous and non-ferrous metals. Investment casting can accommodate a wide range of metals as its materials while still providing highly accurate, high-precision components. This major factor and selling point of investment casting proves to be a vital part of the ever-growing innovations in aircraft systems, highly advanced automobiles, and more compact heavy machinery. More highly intricate industries specializing in brake systems, and medical and dental devices are now all shifting to investment casting as the primary source for their parts and equipment.
Because of its well-known accuracy in mass-producing metal cast products, you should seriously consider using this casting methodology, particularly in the automotive industry. Continuous growth in the automotive sector, not to mention unstoppable innovations, will keep investment casting’s precision and ability to mass produce at an economical rate very viable in every kind of way. Especially when it comes to engineering electric cars and smart cars, marketing a “more precise driving experience” should require more precise parts as well, which are easily and proven achievable with investment casting.
Below are the application that Investment Casting be Used For:
- Aerospace and defense
- Power generation
- Oil and gas
- Space exploration
- Medical / orthopedics
- Commercial and consumer products.
Investment Casting Pros & Cons
Of course, it will have its ups and downs, with more pros and fewer cons. But to be fair and not be biased, here are some pointers one should consider regarding investment casting.
- Near Net Shape output. The desired shape of the tool is produced with little to no adjustments in its final phase. Investment casting can produce various precise parts while providing and maintaining excellent surface texture and finish, so additional adjustments in post-production are greatly reduced.
- Materials, tools, parts, equipment, etc. produced with investment casting are known to be stronger than those produced with other casting methods. This includes higher wear resistance and higher resistance to corrosion.
- Regardless of whether you use a non-ferrous or ferrous metal as a material for casting, better grain flow can also be easily achieved with investment casting, making it tougher and more sought after in the production industry market. Any industry that uses investment casting for its parts, machinery, and equipment will benefit from having more durable equipment because it will reduce operating costs.
- It is very economical in producing large and complex metals as it can produce several at one go. It is also very economical as there are no after production costs as in the sand casting process. This is because the products come out with surfaces that are already smooth.
- It is reliable. This is because if all processes are followed, it will always lead to a desired output.
- It has good dimensional accuracy. It does not shrink the metal to be produced nor does it expand it. The brings out accurate metals as were in the designs.
- There is low tooling cost.
- Environmental friendly as wax can be reclaimed and reused in the next cycle of manufacturing.
- Can make intricate shapes that are non-symmetrical and have internal designs.
- Have a fine surface finish therefore do not require after labour services in making the surface fine. This is a slight cut in cost production.
- You will need a specific kind of manpower, especially for producing wax patterns. (e.g. One of which is that they must have strong knowledge of 3D CAD.)
- Exclusively designed types of equipment and machinery are needed, making the start-up process prove to be more expensive compared to other casting methods.
- More ideal and designed for high-volume mass production.
- It is known and proven to be difficult with a prototype or small-scale production, as materials and production costs tend to increase by doing so.
Investment Casting Manufacturer
There you have it! With all this information at hand, I could say that investment casting is by far the best method of casting. Lesser materials wastage and the ability to mass produce everything at a near net shape precision.
If you are looking for Investment Casting Manufacturer for your project, you could contact us. Leisheng Machinery is a leading Investment Casting Foundry in China. Founded in 1991 & start to providing Investment Casting Service since 2006. ISO9001:2015 Certificated company. Support various material.