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Shell molding is a metal casting process that molten metal melting in a Medium-Frequency Induction Electric Furnace pours into a shell.
The thin-walled shell is created by precoated sand around metal pattern to form each shell half and combining two shell halves.
Shell molding, also known as shell mold casting or the Croning process, is a form of metal casting dating back to the middle of the 20th century. Compared to previous metal casting techniques,
shell molding is able to produce more complex parts with a higher degree of precision.
Shell mold casting is often lumped in with more common processes, like greensand casting, but it’s really not the same thing (more on that later, in the comparisons post).
Qianhao has established a shell molding casting production line in recent years. Comparing it with investment casting, the difference of the two lies only in shell making process,
the subsequent process shares the same production line.
Shell molding process has the following outstanding advantages, which in some cases can replace investment casting process,
and will have better prospects in the future.
1.Shell molding process produces castings whose high dimensional accuracy and good surface finish that are close to those produced by waterglass lost wax process, but are better than those produced by other sand casting process.
2.More environmental friendly in shell making material and process.
3.Higher productivity and lower cost compared with water glass lost wax process.
4.Shorter lead time.
Disadvantages:
Metal pattern cost is high and is only ideal for large volume orders.
Highly complicated shapes cannot be formed.
Material Range：Carbon steel , Alloy steel
Max linear Size(W*C*H)：1200mm*800mm*650mm
Min thickness:6mm
Casting Weight Range：0.5-100Kgs
Casting Dimension Tolerance：CT8
Casting Surface Roughness：Ra12.5-25um
1.Making of Metal Pattern
A two-piece metal pattern is created in the shape of the desired part with a pouring cup to introduce molten metal into the ‘shell’. To create a two-part shell,
in which two halves are combined to create a full shell, two metal patterns must be produced.
2.Creating the shell
Set temperature, pressure and curing time for the metal pattern. When the pattern is heated to the appropriate temperature, the precoated sand is shot into the cavity.
The shell half is then ejected from the metal pattern when it is cool.
3.Mold Assembly
The two halves are sealed using glue, or a combination of glue and other fasteners to form a shell which is similar to the ceramic shell used in the investment casting process.
4.Baking
The completed shell is baked at the oven at setting time and temperature.
The subsequent process is the same as the investment casting technology-----
5. Sand filling
The shell is then placed into a flask and send to the vibrating table. The shell is firmly supported by sand and is ready to get poured.
6.Pouring
The metal (steel scrap) is melting in the induction electric furnace and certain alloy is added to each furnace if necessary. Metal is heated to 1530-1580℃
in molten state and is poured into the shell while it is still hot – liquid metal flows into the pouring cup,
through the central gating system, and into each mold cavity on the tree. The pre-heated mold allows the metal to flow easily through thin, detailed sections.
7.Shakeout
Once the metal is sufficiently cooled and solidified inside the shell, it's time for shakeout. Shakeout is basically vibrating the shell and casting so that the shell breaks apart and fall way.
After removal, the castings are sent to sand blasting to remove the extra sand on their surface.
After that the casting are separated from their gating system tree by using different methods such as manual impact, sawing, cutting, etc.
8.Finishing
Finishing operations such as grinding, soldering, sand blasting, machining and straightening are commonly employed to smooth the part at the gates and remove imperfections such as sand holes,
slag eyes, flash burrs, bulging, deformation and so on. After passing visual inspection,
depending on the part that being cast, heat treating is to be employed to harden the final part.
Investment casting is one option for creating intricate parts and components. There are several specific steps in the entire process to design and create the desired workpieces. It is named such because the workpieces are created around a shelled casting, which is later removed once the workpieces have been poured into the mold and are set.
Investment casting can produce a wide variety of products and prototypes, but it is important to choose the correct investment casting material for your application.
The right material helps you get the desired functionality, save on the cost of materials, eliminate unwanted casting defects, and limit the need for secondary processes after the casting is complete.
Investment Casting also known as precision casting or Lost wax casting, is a manufacturing process in which a wax pattern is used to shape a disposable ceramic mold. A wax pattern is made in the exact shape of the item to be cast. This pattern is coated with a refractory ceramic material. Once the ceramic material is hardened, it is turned upside-down and heated until the wax melts and drains out. The hardened ceramic shell becomes an expendable investment mold. Molten metal is poured into the mold and is left to cool. The metal casting is then broken from of the spent mold.
Final parts can display smooth surfaces and dimensional precision while allowing for lower weight, thin walls, or other beneficial properties.
Determining which properties can be successfully incorporated into your part largely depends on material choice.
Stainless Steel
Stainless steels feature superior durability in comparison with many other materials. The potential of the material has led to increased use in investment casting by designers and engineers.
Applications for stainless steel include gearbox parts in automotive applications, various gears, camp components, and golf club heads.
Low Alloy Steel
Low alloy steels are among the most frequently used steels in the mechanical world due to their affordability and beneficial mechanical properties.
Specialized heat-treating processes make it possible to engineer parts that have differing properties in different areas of the same workpiece.
For example, varying heat treatments can be used to make one surface tough and impact-resistant, while another surface becomes wear-resistant.
Aluminum Alloy
Aluminum alloy is the most used material in investment casting. Industries that use it most frequently include aerospace, avionics, electronics, and military.
Castings are now offered for demanding applications like airframe components thanks to the material’s improved strength and the availability of quality castings made from aluminum-silicon-magnesium alloy.
Carbon Steel
Carbon steel is a common low-cost material that comes in a variety of grades, with the classifications varying based on the amount of carbon content.
The strength, ductility, and performance of carbon steel can be improved in industrial applications through heat treatment.
Its ferromagnetic properties make carbon steel useful in motors and electrical appliances. It is safe, durable, and has a high structural integrity, making it one of world’s most frequently used alloys.
Super Alloy
Super alloys based in nickel and cobalt have common uses in the aerospace, energy, medical, chemical, and marine industries.
Nickel-based alloys are stronger at high temperatures and cobalt-based alloys have superior corrosion, oxidation, and wear resistance over their nickel-based counterparts.
Super alloys increasingly replace sheet metal because they provide high rigidity and superior service characteristics while remaining a cost-effective option.
Copper Alloy
Copper-based alloys are corrosion-resistant and feature low rates of wear. They are frequently used in applications such as ship or pump propellers, electrical components, and plumbing components.
A versatile material, there are more than 400 different alloys featuring a wide variety of properties.
Many part types can be investment cast from copper-based alloys. More common types of copper-based alloys include bronze and brass.
The strongest copper alloy is beryllium-copper, which has similar properties to high-strength alloy steels but with a higher corrosion resistance over longer periods.
Cast Iron
Iron castings, which often include gray iron and ductile iron, are known for their high accuracy and an affordable price tag.
Ductile iron has high strength, heat-resistance, and toughness, but it has a more complex production process than other steels. This leads to a higher production cost than cast steel.
Investment Casting Manufacturer
Looking for an excellent Investment Casting,Precision Casting,Lost Wax Casting partner? One that provides outstanding service, exceptional quality, and low costs - all within short lead times? Look no further than Qianhao Metal Casting,for your casting needs.
Different Investment Casting Products We have made for world Clients
Qianhao handles each job with an optimal process to achieve the lowest cost, best quality, and highest efficiency.
Investment Casting Foundry
Steadfast dedication to the field of precision casting and machining for 30 years, Qianhao is a globally recognized manufacturer of high-valued added and complex castings for global industry leaders.
Whether you require complex cast components weighing just a few grams or large components of up to 50 pounds, or your needs include high volume, rapid prototype, or short-run projects, you can count on the experience, innovation, and dedication of Qianhao Investment Casting to work for you.
Full-Service Casting Capabilities
Backed up by our modernized workshops, reliable equipment and advanced manufacturing technology, Qianhao is devoting to manufacturing high quality industrial products for our customers. .
We have abundance of experience in lost wax casting, lost form casting, shell molding, sanding casting, water glass casting,forging, precision machining, surface treatment, sheet metal, welding, and assembling which we would like to share with you and be of your service.
As for the custom finishing touches, Qianhao Precision Casting handles all plating and finishing. This includes phosphate coating, polishing, hand polishing, passivation, pickling and electropolishing.
Provide Our Customers with the Best Molding Solutions
We are Committed to Delivering the Highest Quality Investment Castings.
Rail parts Casting
Automotive Parts casting
Construction equipment casting
Forklif Equipment casting
Agricultural Machinery casting
We already have had cooperation with some the world's Top 500 companies as one of their major precision metal parts suppliers in China.
Shell Molding FAQS
Q1: What is shell molding?
A1:Shell molding, also known as shell-mold casting, is an expendable mold casting process that uses resin covered sand to form the mold. As compared to sand casting, this process has better dimensional accuracy,
a higher productivity rate, and lower labour requirements. It is used for small to medium parts that require high precision.Shell molding was developed as a manufacturing process during the mid-20th century in Germany.
It was invented by German engineer Johannes Croning.Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold. However, in shell mold casting,
the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern. The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. A reusable pattern allows for higher production rates,
while the disposable molds enable complex geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.
Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly using cast iron, carbon steel, alloy steel, stainless steel, aluminium alloys,
and copper alloys. Typical parts are small-to-medium in size and require high accuracy, such as gear housings, cylinder heads, connecting rods, and lever arms..
Q2: what is advantages of shell molding?
A2:Shell mold casting, also known as shell molding, is a metal casting process that uses a mold made from resin-covered sand. It's similar to sand casting,
but shell molding has several advantages, including:
Dimensional accuracy: Shell molding is more dimensionally accurate than sand casting.
Productivity: Shell molding is more productive than sand casting.
Labor requirements: Shell molding requires less labor than sand casting.
Surface finish: Shell molding produces a smoother surface finish than sand casting because it uses finer sand and resin.
Intricate designs: Shell molding allows for more intricate designs than other casting methods.
Q3: Limitations of the shell molding casting process
A3:There are some disadvantages to the shell mould casting process including:
The gating system must be part of the pattern because the entire mould is formed from the pattern, which can be expensive.
The phenolic resin is expensive, although not much is required because only a shell is being formed.
Equipment costs can be high
Poor material strength is achieved compared to other casting processes
Shrinkage can be a problem
High porosity can be a problem.
Secondary machining often required even though the surface finish is better than can be achieved with sand casting.
Labour costs can be high if the process isn’t automated.
Q4: What is the difference between shell mold casting and investment casting?
Shell molding
A4:Uses a metal pattern tool coated with sand that contains a resin. When heated, the resin melts and cools to form a thin shell around the pattern. The shell is then removed from the pattern,
the two halves are assembled, and molten metal is poured into the mold. Shell molding can produce parts with less than five millimeter wall thicknesses and good dimensional accuracy for complex castings.
However, shell molding is limited to parts that weigh less than 30 lbs.
Investment casting
Uses a shell made of ceramic, plaster, or plastic that is formed around a wax pattern. The wax pattern is then melted and removed in a furnace,
and metal is poured into the shell to create the casting. Investment casting can produce parts with intricate inner cavities, thinner walls, and excellent surface finishes.
It can also meet tighter tolerances than shell molding, and works with both ferrous and non-ferrous metals. However, investment casting can be more expensive than shell molding due
to higher labor costs and the need for complex wax pattern creation. The process also requires highly skilled labor and can have weight and size limitations.