Lost Wax Casting

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Introduction

Here is everything you need to know about lost wax casting on the internet.

You will learn:

• What is Lost Wax Casting?
• The Lost Waxing Casting Process
• The Metals Used in Lost Wax Casting
• The Parts Produced Using Lost Wax Casting
• And Much More...

Chapter 1: What is Lost Wax Casting?

Lost wax casting is a casting process that uses a wax pattern to create a ceramic mold for creating a part or product design. It has been known over the years as lost wax or precision casting due to its accuracy in recreating parts with precise tolerances. In modern applications, lost wax casting is referred to as investment casting. The original process was named lost wax casting but is presently used interchangeably with investment casting.

Lost wax casting distinguishes itself from other casting techniques through its use of a wax model to form the initial mold. This method allows for the creation of highly detailed and intricate designs.

Chapter 2: What is the lost wax casting process?

Lost wax casting, also known as investment casting, is employed for producing components with precise tolerances, thinner walls, and finishes that often need minimal post-processing. This technique is distinctive for its ability to replicate CAD designs by forming a wax pattern of the intended piece.

The Lost Wax Casting Process

The lost wax casting process encompasses several stages, starting with the formation of a master pattern, typically made from aluminum. The method used to create this pattern impacts the accuracy and detail of the final cast.

CNC Rendering

The initial step in the lost wax casting process begins with the creation of a 3 dimensional CAD rendering of the part to be produced, which will be used to create the aluminum die.

Creation of the Die

The die is crafted based on the CAD design, serving as a negative impression of the part that will be cast.

Producing the Wax Pattern

Semi-liquid wax is poured into the die to create the wax pattern, with adjustments made for shrinkage. This step can be repeated as needed based on the quantity of parts required.

Wax Pattern Tree

The wax patterns are linked via a runner to create the sprue, which can be connected to additional pattern groups to form a cluster. Collectively, the sprue, runner, and wax patterns are known as a tree.

Shell Building

To create the shell, the pattern is submerged in a ceramic slurry, which forms a rigid outer layer around it. An opening is left at one end of the wax tree to allow for the wax to be removed.

Dewaxing

The hardened ceramic shell will be where the molten metal will be added to form the final part. To accomplish this, the wax on the interior of the ceramic shell has to be removed, which is done by placing the ceramic shell in an autoclave or oven. As the ceramic shell is heated, the wax melts and runs out of the shell. It is this part of the process that gives lost wax casting the name "lost wax".

Burnout

Even after the dewaxing phase, some residual wax and moisture may remain in the mold. To eliminate these remnants, the mold undergoes a burnout procedure, where it is heated to temperatures exceeding °C (°F). This step not only removes any leftover wax and moisture but also solidifies and strengthens the ceramic mold, making it ready for the molten metal.

Casting

The ceramic mold is positioned with the open side facing upwards to facilitate the pouring of molten metal. This can be achieved either by letting gravity fill the mold or by applying pressure to force the metal in. The choice of method depends on the mold's size and the type of molten metal used.

Knock Out, Divesting, or Cleaning

The ceramic material forming the mold must be removed, and this can be done through several techniques. These may include hammering, blasting, high-pressure water, or employing chemicals such as liquid nitrogen.

Cutting

After removing the ceramic mold, the completed part needs to be detached from the gates and runners. This is typically done using a grinder, and the leftover material is often collected for recycling.

Shot or Sand Blasting

Though the part is fully molded, it will need to be sandblasted to remove scales and residual ceramic to enhance its finish. This can be completed in a variety of ways that include shot, small metal balls, or sand blasting.

Surface Treatments

Some parts need additional protection against rust, corrosion, and environmental damage. This extra layer of defense is applied by immersing the part in an anti-rust solution or oil. Other surface treatments can include painting or galvanizing.

While the process outlined above is a common method for producing lost wax castings, it is not the only technique available.

Chapter 3: What are some leading machines for lost wax casting?

As previously mentioned, the objective of lost wax casting is to produce parts with exceptional accuracy and tight tolerances. Fortunately, several manufacturers specialize in lost wax casting machinery and have refined this process. Below are five prominent brands of casting machines available in the United States and Canada, including specific models and their notable features:

Kerr Corporation:

Model: Centrifico Casting Machine

Features: The Centrifico is a top-tier centrifugal casting machine ideal for small to medium-sized jewelry manufacturing. It ensures precise and reliable casting outcomes with its digital temperature control and adjustable speed options. The machine also includes a safety mechanism to prevent accidental over-rotation.

Neutec/USA:

Model: J2R Casting Machine

Features: The J2R is a compact, easy-to-use casting machine designed for smaller casting tasks. It employs advanced induction heating technology for efficient metal melting and features programmable casting cycles, digital controls, and a built-in vacuum assist to enhance casting quality.

Rio Grande:

Model: Neutec® PulsePoint&#; Plus 140

Features: The Neutec® PulsePoint&#; Plus 140 is a versatile casting machine suited for both small and large-scale production. It uses pulse-arc technology to provide precise control over the melting process, minimizing metal oxidation. The machine features customizable casting programs, options for vacuum and pressure casting, and an intuitive touchscreen interface.

Romanoff International Supply Corporation:

Model: Vulcan 3-550 Casting Machine

Features: The Vulcan 3-550 is a robust casting machine designed for high-volume casting needs. It is built to handle large flasks efficiently and offers precise temperature control, adjustable speed settings, and a specialized air cooling system for expedited flask cooling. Additionally, it includes a safety interlock system for operator protection.

Indutherm GmbH:

Model: VC Casting Machine

Features: The VC represents advanced technology in casting machines, suitable for industrial-scale production. It features induction heating for rapid and effective metal melting, with advanced casting functionalities including precise temperature control, vacuum and pressure casting options, and an easy-to-use touchscreen interface. It also includes an integrated cooling system for quick flask cooling.

Note that availability and specific models may change, so it's advisable to consult with the manufacturers for the most current product details.

Leading Manufacturers and Suppliers

Chapter 4: What metals are used in lost wax casting?

Lost wax casting involves using a variety of metals to produce components with high precision and exacting tolerances. The selection of metal depends on the specific design requirements and the nature of the part being produced. The versatility in metal options is one of the reasons lost wax casting is so widely utilized.

Lost Wax Casting Metals

Stainless Steel

Stainless steel castings primarily use alloys of chromium, nickel, and molybdenum, which influence the material's grain structure and mechanical characteristics. The specific combination of these alloys impacts the casting's resistance to heat and corrosion. With at least 10% chromium content, stainless steel effectively resists oxidation and corrosive liquids.

Steel

Carbon, low alloy, and tool steels are commonly utilized in various industries, including aerospace, agriculture, medical, and firearms. Steel is favored for lost wax casting due to its cost-effectiveness, availability in multiple grades, and ability to be heat treated to modify its ductility.

Ductile Iron

Ductile iron castings provide excellent surface hardness, modulus of elasticity, corrosion resistance, and a high strength-to-weight ratio. Its key advantages include cost-effectiveness and a broad range of design flexibility.

Beryllium Copper

After heat treatment, beryllium copper exhibits superior thermal and electrical conductivity, with a hardness surpassing that of steel and thermal conductivity exceeding that of aluminum. Castings made from this alloy offer excellent ductility, are easily weldable, and can be machined with ease. Copper alloyed with 2.0% to 2.5% beryllium boasts outstanding wear resistance, toughness, and anti-galling properties.

Aluminum

Aluminum is well-suited for lost wax casting because of its excellent machinability and resistance to corrosion. When alloyed with other metals and subjected to heat treatment, it achieves remarkable strength comparable to low carbon steel. Additionally, the fluid properties of aluminum alloys enable the creation of parts with thin walls.

Cobalt

Cobalt exhibits inherent resistance to oxidation, maintaining a hard and shiny surface protected by a passivating oxide layer. Extracted from natural alloys through smelting, cobalt's properties of corrosion, heat, and wear resistance make it highly suitable for lost wax casting. It is utilized in aerospace, automotive industries, and military applications, as well as in orthopedic implants due to its exceptional durability.

Brass

Brass, which comes in red and yellow varieties, is a copper alloy often used for castings in plumbing fixtures and door hardware. Its key attributes include its aesthetic appeal and excellent finishing and polishing capabilities. However, the presence of lead in some brass alloys limits its applications due to health and safety concerns.

Bronze

Bronze's characteristics and performance are influenced by the alloys mixed with it. Tin enhances its strength, while lead improves its lubricity but reduces overall strength. Manganese and aluminum are often added to boost corrosion resistance and strengthen the alloy.

Nickel

Nickel contains nickel, chromium, and molybdenum and has exceptional strength as well as resistance to heat, wear, and corrosion. It is chosen as a casting metal because it can be easily welded and fabricated with resistance to cracking and corrosion. Nickel alloy castings are used in applications where there is extreme heat and corrosion, such as aerospace, marine environments, and chemical factories. Common Inconel nickel alloys are Inconel 600 and 625.

Chapter 5: Which industries rely on lost wax casting?

Lost wax casting, also known as investment casting, is used to create a diverse range of parts and components. The method's precision and ability to handle intricate designs make it suitable for manufacturing items with thin walls and tight tolerances. Common products include general hardware like brackets, valves, and pump components.

Industries benefiting from lost wax casting encompass aerospace, medical, robotics, military, and automotive sectors.

Aerospace

Lost wax casting plays a crucial role in the aerospace industry, including both aircraft and spacecraft construction. Components made using this technique are integral to various parts of these vehicles, from the bearings that operate doors to critical engine components.

Automotive

The automotive sector extensively utilizes lost wax casting for crafting engine components, compressor parts, and gearbox elements. Aluminum castings are employed for constructing space frames and suspension systems, while stainless steel is used for parts like fuel filler doors. Lost wax casting is also applied in the production of drive and powertrain assemblies, fuel systems, and convertible tops. These castings, made from both ferrous and non-ferrous metals, are tailored to meet specific requirements. The method is advantageous for its ability to provide excellent lubrication between metal parts and its durability.

Examples of automotive components produced through lost wax casting include the fuel pump housing, injector clamp, turbo wastegate, oil supply bend, and shifting finger, as depicted in the engine image below.

Oil and Gas

Parts produced for the oil industry via lost wax casting must exhibit specific characteristics to withstand the harsh conditions of oil and gas drilling. Operating in extreme environments demands components with outstanding wear and corrosion resistance. Lost wax casting is used to manufacture various parts such as gate valves, tube handling devices, elevator components, valve brackets, slip linkages, and locking levers. Commonly used metals for these parts include aluminum, stainless steel, and alloy steel.

Chemical Industry

The chemical industry contends with significant challenges related to corrosion and erosion, which can affect the mechanical properties of its components. Parts intended for this sector must withstand extreme temperatures and pressures to ensure worker safety. Lost wax casting is employed to produce components that can handle temperatures from °F to °F. Common products include bullhead tees, catalyst tubes, elbows, ethylene coils, heater hardware, and static cast fittings.

Food Industry

Components for the food industry are used in a range of applications, from harvesting and processing raw materials to food canning and beverage bottling. Lost wax casting is employed to produce items such as meat slicers, poultry processing tools, ice machine parts, and racks and grills for food preparation. These components are designed to resist acidic food chemicals and offer exceptional strength for dependable performance.

Medical

In the medical field, lost wax casting is crucial for creating medical implants that adhere to stringent standards and regulatory requirements. These castings offer superior density and mechanical properties, with additional processes employed to enhance implant longevity and eliminate issues like porosity. Additionally, surgical tools such as forceps are produced using lost wax casting, as it allows for parts to be easily sterilized and eliminates the need for further machining.

Power

The power industry faces growing demands for components that are durable and resistant to wear. Parts must withstand challenges such as abrasion, erosion, cavitation, fatigue, and corrosion, especially under high temperatures. To meet these requirements, lost wax casting producers use materials like cobalt, nickel, and stainless steel. These components are meticulously machined and coated through various processes to ensure they endure the harsh conditions of power industry applications.

Dentistry

Cobalt and nickel alloys are used to manufacture dental prosthetics due to their cost-effectiveness compared to silver or gold. These metals offer excellent mechanical properties, ensuring high performance, durability, and a suitable appearance for dental applications.

Tools

In the tool industry, lost wax casting is employed to produce components from steel alloys known for their high tensile strength, hardness, and elasticity. This method ensures that tools are durable and can handle shock and heavy mechanical loads. The advantage of lost wax casting lies in its capability to produce intricate designs directly, minimizing the need for additional post-casting work, while also delivering precise dimensional accuracy in the final products.

Pharmaceutical

Similar to the medical field, pharmaceutical industry components must be capable of enduring sterilization procedures. High-grade stainless steel is commonly used for these parts, offering resistance to corrosion, high temperatures, and meeting stringent hygiene standards. A key benefit of lost wax casting for pharmaceutical tools is the smooth finish of the components, which helps prevent the accumulation of bacteria and supports overall cleanliness.

Hoisting

In the hoisting industry, safety is paramount due to the vertical and horizontal use of parts in lifting and transport systems. Steel alloys are typically used for their superior tensile strength and elasticity. Lost wax casting is favored for manufacturing hoisting components because it allows for intricate designs and flexibility, ensuring precise adherence to design specifications. This method enables the creation of complex shapes without requiring additional mechanical post-casting processing.

Chapter 6: What are the advantages of lost wax casting?

The lost wax casting process has seen rapid growth due to its numerous advantages. It offers significant flexibility in terms of types, shapes, dimensions, and design of the products. Engineers favor lost wax casting, or investment casting, for its ability to create intricate and complex designs without concerns about shrinkage or post-processing finishes.

The Benefits of Lost Wax Casting

Smooth Finishes

Products created through lost wax casting typically require no further finishing since the molds are made from ceramics. The surface roughness average (RA) of a cast part is around 125, reflecting the minimal peaks and valleys on the final surface.

Production Turnaround

Fast production turnaround is crucial in modern manufacturing. Lost wax cast parts eliminate the need for additional finishing, enabling rapid production and shipment, which reduces handling and labor time.

Affordable Tooling

The initial investment in lost wax casting equipment is relatively low, making it a safer option. The process generally requires only four main machines, with the option to add more equipment as needed.

Tolerances

The precision of lost wax casting is a major advantage, with tight tolerances standard at ± 0.005. CAD designs are replicated with high accuracy to meet exact application requirements.

Variety of Metals

Lost wax casting supports a wide range of metals, including bronze, stainless steel, alloy steel, iron, aluminum, and copper. This versatility offers engineers a broad selection for part design and makes the process adaptable to various industries.

Size Range

The process accommodates a broad size range, from small dental implants to large aircraft engine parts weighing thousands of pounds. The size and weight of the cast parts are determined by the capabilities of the mold handling equipment.

Production Costs

Lower labor costs result from reduced manpower requirements. The process demands fewer resources and less time, with no need for post-processing, contributing to overall cost savings and high-quality parts.

Waste

Lost wax casting minimizes waste by allowing for the recycling and reuse of materials. Unlike other methods that generate waste from post-processing, lost wax casting avoids this by producing parts without the need for finishing processes.

Environmental Factors

The process supports environmental sustainability by reusing wax and ceramics for future projects, thus reducing landfill waste. Dies, molds, and wax can be used multiple times without replacement.

Complexity and Intricacies of Designs

Lost wax casting enables the production of lightweight parts with intricate features and fine details. Engineers have extensive design flexibility, resulting in durable parts with consistent dimensions and configurations from the first to the last unit.

Chapter 7: What are the causes of defects in lost wax casting?

Like any production method, lost wax casting can encounter errors and defects. Such issues often arise from operational mistakes, but they can be minimized through careful examination and adherence to procedures throughout the casting process.

Defects in Lost Wax Castings

Gas Hole

Gas holes, which can appear as internal or external features, vary in shape. External gas holes are typically visible and can be detected through visual inspection. They often result from inadequate mold preheating, poor exhaust design, or improper pouring techniques.

Addressing these issues involves meticulous attention to the molding process, including proper material storage, tilting the mold while pouring, and maintaining the correct pouring temperature.

Shrinkage Cracks

Shrinkage cracks appear as voids on the casting surface and are typically caused by incorrect mold temperature, inadequate coating control, or design flaws. To mitigate these issues, it is important to enhance mold temperature management, adjust the coating layer, implement pressure devices for the riser, and carefully regulate the cooling rate.

Slag Hole

A slag hole is a cavity filled with slag, typically located at the bottom, around the runner, or in a corner of the casting. It results from poor pouring practices or inadequate gate design. Preventing slag holes involves proper gate design, tilting the mold during pouring, and controlling the flux effectively.

Thermal and Cold Cracking

Thermal cracks are dark grey or black due to oxidation and are often visible during inspection. They are related to shrinkage or slag inclusion and typically occur at casting angles, thickness junctions, and sections between the pour riser and the casting. These cracks are caused by high cooling speeds, which increase internal stress. Preventing thermal cracking involves examining wall thicknesses and transitions and adjusting coatings appropriately.

Cold Shut

Cold shuts are surface cracks with rounded edges and scale in the middle, appearing in thin horizontal or vertical planes or wall joints. They can be caused by venting issues, low temperatures, improper coating, poor riser positioning, or slow pouring speeds. Addressing cold shuts can be achieved through improved design with proper runners, exhaust systems, and tilting during pouring.

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Misrun

Misruns occur when the mold cavity is not fully filled, often due to a cold shell, cold metal, or a slow fill rate.

Inclusions

Inclusions are craters of varying sizes resulting from non-metal particles in the casting. They may also appear as cavities or irregular shapes with refractory materials. Causes include cracks in the wax mold allowing ceramic debris into the mold cavity.

Conclusion

• Lost wax casting, or investment casting, is a casting process that uses a wax pattern to create the initial design for a part to be produced in a ceramic mold.
• Lost wax casting can produce a variety of complex and intricate parts with excellent tolerances.
• Lost wax casting is used to produce parts that require tight tolerances with thinner walls and exceptional surface finishes that require very little after process finishing.
• The casting process for lost wax casting involves multiple steps that begin with the creation of the pattern, or master, which is made from wax.
• Lost wax casting uses a wide assortment of metals to create parts with exceptional accuracy and tolerances.

Leading Manufacturers and Suppliers

OEM Investment casting

Investment casting (also known as lost wax investment casting) produces parts with fine detail and excellent as-cast surface finish.  Investment castings shape into internal or external features, thin walls, and internal passageways to get to a near-net shape.  These features often lead to significant cost savings in material, labor, and machining compared to other metal casting processes.

In investment casting a detailed wax pattern of the finished part is created and mounted onto a wax "tree" that includes the metal delivery system (gates and risers).  The tree is alternately dipped into a ceramic slurry and sprinkled with stucco material, and then allowed to dry.  This process is repeated until a thick shell exists over the wax pattern.  

The wax pattern is then melted, leaving a cavity within the stucco material in the shape of the pattern.  Molten metal is poured into this cavity.  Once the metal solidifies the shell is broken away through a shakeout process and the gating material is removed, leaving the finished part.

Investment casting is one of the oldest manufacturing processes, dating back thousands of years, in which molten metal is poured into an expendable ceramic mold. The mold is formed by using a wax pattern - a disposable piece in the shape of the desired part. The pattern is surrounded, or "invested", into ceramic slurry that hardens into the mold. Investment casting is often referred to as "lost-wax casting" because the wax pattern is melted out of the mold after it has been formed. Lox-wax processes are one-to-one (one pattern creates one part), which increases production time and costs relative to other casting processes. However, since the mold is destroyed during the process, parts with complex geometries and intricate details can be created.

Investment casting can make use of most metals, most commonly using aluminum alloys, bronze alloys, magnesium alloys, cast iron, stainless steel, and tool steel. This process is beneficial for casting metals with high melting temperatures that can not be molded in plaster or metal. Parts that are typically made by investment casting include those with complex geometry such as turbine blades or firearm components. High temperature applications are also common, which includes parts for the automotive, aircraft, and military industries.

Investment casting requires the use of a metal die, wax, ceramic slurry, furnace, molten metal, and any machines needed for sandblasting, cutting, or grinding. 

The process steps include the following:

Pattern creation

Pattern creation - The wax patterns are typically injection molded into a metal die and are formed as one piece. Cores may be used to form any internal features on the pattern. Several of these patterns are attached to a central wax gating system (sprue, runners, and risers), to form a tree-like assembly. The gating system forms the channels through which the molten metal will flow to the mold cavity.

Mold creation

Mold creation - This "pattern tree" is dipped into a slurry of fine ceramic particles, coated with more coarse particles, and then dried to form a ceramic shell around the patterns and gating system. This process is repeated until the shell is thick enough to withstand the molten metal it will encounter. The shell is then placed into an oven and the wax is melted out leaving a hollow ceramic shell that acts as a one-piece mold, hence the name "lost wax" casting.

Pouring

Pouring - The mold is preheated in a furnace to approximately °C (°F) and the molten metal is poured from a ladle into the gating system of the mold, filling the mold cavity. Pouring is typically achieved manually under the force of gravity, but other methods such as vacuum or pressure are sometimes used.

Cooling

Cooling - After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting. Cooling time depends on the thickness of the part, thickness of the mold, and the material used.

Casting removal

Casting removal - After the molten metal has cooled, the mold can be broken and the casting removed. The ceramic mold is typically broken using water jets, but several other methods exist. Once removed, the parts are separated from the gating system by either sawing or cold breaking (using liquid nitrogen).

Finishing

Often times, finishing operations such as grinding or sandblasting are used to smooth the part at the gates. Heat treatment is also sometimes used to harden the final part.

What are the advantages of the investment casting process?

1.Great versatility; suitable for casting most metals.

2.Will allow very intricate castings to be produced.

3.Smooth surface finishes are possible with no seam line so machining and finishing are reduced or eliminated.

4.Allows un-machinable parts to be cast accurately instead.

5.Excellent dimensional accuracy

6.High volume production can be achieved with low repeat costs.

7.Can be used to prototype and prove designs prior to die casting tooling investment.

8.Is ideally suited to smaller, intricate or complex designs although we can cast up to 200kg

What could be disadvantages of the shell mold casting process?

1.Preparation of the wax patterns and shell moulds is time consuming so can be expensive.

2.Investment casting is not well suited to very high volume manufacturing due to the cycle times.

History of Investment casting

Industrial casting was first mentioned by the monk Theophilus Presbyter around AD. However, we are pretty sure that investment casting started more than years ago. The earliest examples we have of investment casting come from ancient civilizations such as Harappa, Aztec, Mayan Mexico, the Benin civilization in Africa, Mesopotamia and ancient Egypt. In fact, molten castings have been found in the tombs of King Tutankhamun.

The first molten castings were wax molds made from clay molds and natural honeycomb or beeswax. To make them, bellows were manually operated as furnaces. In the s, dentists began using investment casting to make fillings and crowns. During World War II, manufacturers began to invest in casting metal alloy parts, precision net-shape and near-net-shape manufacturing.

Today, manufacturers make molds from a variety of alloys and refractory materials and use wax molds formed from a mixture of pure and synthetic waxes. Instead of hand-held bellows, they cast them in a foundry.

For many years, Zen Young Foundry has been providing customized metal casting services for various industries and project types.

Six Industries Where We Can Provide Customized Services:

Pump & Valve Parts

Compressor Parts

Train & Railway Parts

Cylinder & Gear Box

Mining & Engineering Machinery Casting Parts

Auto & Aerospace Parts

If you are looking for a solution that fits your custom metal Sand casting project, Zen Young can help you produce perfect metal parts through a reliable casting process. We always welcome special material and difficult parts and would like to help our comstomers utmost.

The material we can supply

Zen Young have capabilities to produce Cast iron&#;Stainless steel&#;Copper and Aluminum parts from start to finish. Whether you have a design ready for casting, or you need a custom casting design, we can help

We work with our customers to design patterns and molding methods for each custom casting. Original castings or ready-to-use castings can be provided. Secondary finishing operations, including powder coating, are additional options. Contact us with any questions about the casting process and also for more information on how our casting services can meet your project requirements.

If you want to learn more, please visit our website lost wax casting stainless steel supplier.