Investment casting is a cost-effective process for many industries when they are looking for highly accurate metal parts that are made out of a wide range of alloys. The typical process to create a cast part is to use a wax pattern that will be covered in a ceramic slurry to form a shell. Then the shell will be filled with molten metal and cooled to form the part.
Creation of the wax pattern is typically done by using metal dies as the injected wax fills the die. Water-soluble or ceramic cores will be in the die to make the intricate and complex internal parts. However, more industries are looking at 3D printed investment casting for wax patterns as a more cost -effective approach.
A 3D printer can be used by many industries to create products made from materials such as plastic. However, these machines can 3D print out parts in resin, metal and even food for certain industries. When it comes to investment casting, wax or resin plastic may be chosen depending on the manufacturer and their available equipment.
For 3D printing, a stereolithography (SLA or SL) process is used. Stereolithography is an additive manufacturing technique that takes the material and lays it down layer by layer to create the pattern. Each layer is cured by using either an ultraviolet light or a laser until the entire pattern is made. This process is also called vat polymerization.
When the pattern is complete and covered in the ceramic slurry, the wax will be melted out or the resin will be burned out. Any ash that remains will be removed during the cleaning process.
One of the major benefits is that 3D printed patterns are an additive production process that only uses a set amount of materials to create the pattern. This factor eliminates waste that is typically created by using subtractive manufacturing methods. Since the materials are added in layers, the patterns can be designed with highly complex geometries and intricate shapes without impacting the overall pattern creation cost.
Another benefit is that 3D printing can be used for patterns that are needed as prototypes. The prototype pattern can easily be placed into the assembly for testing without damaging the application. This process can allow the customer and manufacturer to create the necessary changes at this early stage of the investment casting process before full production begins.
Investment casting using 3D printed patterns are usually sought after when a customer does not desire or need a second machining of the cast part. The process usually creates parts that are highly precise and intricate with smooth surfaces. It is also ideal when a customer is on a tight time-to-part deadline as they do not have to wait for the manufacturer to create the appropriate tooling for the processes.
One of the most common metals used in investment casting processes is aluminum. Aluminum’s high strength to low weight ratio makes it ideal for industries requiring durable parts that are also lightweight, such as aerospace, medical, and electronics. This metal also has superior corrosion resistance, exceptional electrical and thermal conductivity, a resistance to harsh environments, and a resistance to high temperatures. When aluminum is used for investment casting, the parts have a smooth finish.
Customers may pick from a wide range of aluminum alloy grades for the parts. Let’s review some of the more common grades of aluminum used in investment casting processes.
A356 aluminum alloys consist mostly of pure aluminum and silicon with the lower additions of magnesium, iron, copper, zinc, and manganese. This alloy provides high amounts of strength, good elongation, and excellent ductility. The A356 grade is considered an all-purpose aluminum because it is used throughout manufacturing industries to make simple and complex parts. It is readily made and available, which helps to lower its costs.
F357 alloys are foundry-grade metals that contain mainly aluminum, silicon, and magnesium. The alloy does not contain any beryllium, as it may be used as a substitute for other aluminum alloys that contain this metal, such as A357 grades. Properties of this alloy include high strength and heat treatability.
C355 alloys is a cast-grade aluminum that has higher levels of copper along with aluminum, silicon, iron, magnesium, manganese, zinc, and titanium. It is considered less ductile than A366 yet contains very high strength. This alloy also has good weldability and corrosion resistance.
A major advantage to investment castings involves the types of metals used to produce parts. Any metal that can be melted can be cast using this process. Investment casting metals come in two categories: nonferrous and ferrous metals. Selecting which metals within these two groups will be based on your application. When determining the differences between metals, the major factor depends on if there is iron present.
Ferrous metals contain iron while non-ferrous metals do not. Due to this iron, metals possess greater levels of conductivity. The metal also possesses a good tensile strength that allows it to experience high levels of stress without breaking. Possessing this great mechanical property along with strength and durability allows customers to use ferrous metals for parts in electrical and high-stress applications.
The one thing to keep in mind is that due to possessing iron, many ferrous metals are prone to corrosion. Applications where there will be an abundance of moisture, humidity, solvents, motor oils, and other caustic substances may wear out the part until it fails. To work around this problem, ferrous metals may have additives such as chromium placed into the melt to provide better corrosion resistance. By enhancing these alloys, the manufacturer may develop investment castings that can be used in such harsh environments.
Types of ferrous metals include steel, cast iron, stainless steel, and carbon steel. Typically, ferrous metals are less expensive than non-ferrous metals as they are often used in a variety of applications including aerospace components.
For non-ferrous metals, the absence of iron makes many of the metals in this group less prone to possible corrosion and rust. These metals are very malleable, light weight and have a low tensile strength. They may also be magnetic or non-magnetic, providing additional options based on the applications.
There is no question that robotics is used throughout manufacturing and logistics industries. When it comes to the supply chain, robotic arms perform repeatable tasks at high speeds while maintaining quality. Yet this technology is not overlooked in the component manufacturing fields. Robotics are also found in investment casting processes to create parts.
Investment casting is a method where a wax pattern is dipped into a ceramic slurry to create the shell mold. Then the molten metal is poured inside and hardened to produce the part that later undergoes finishing. Throughout the entire operations, automation and robotics are used. Many wax injection machines are automatic or semi-automatic as a conveyor belt moves the patterns along the plant floor to the different process departments.
Using robotic arms and conveyor belts allows the patterns to be moved to different facility areas with little human handling. This strategy minimizes the likelihood of the pattern becoming damaged while it is moved. Also, the robotic arms help to create more molds per minute, reducing lead times for high production runs.
Another process that uses robotics is the wax pattern assembly. Some wax trees have many parts. These parts become affixed to the rest of the sprue to create the pattern assembly. Robotic arms perform this time-consuming task around the clock ensuring all pattern parts are connected in a consistent manner.
Shell making processes also rely on robotic arms that will dip the wax pattern into the ceramic slurry which often involves multiple layers. Using robots in the process promotes greater levels of quality consistency and worker safety. The robotic arms also ensure that every wax pattern receives an even coat across all surfaces.
Repeatability: Robotic arms are programmed to perform their specific tasks based on the inputted data. This process ensures that every component produced will have the same accurate dimensions and quality even for high production volumes.
Consistency: Robots cannot stray from their programmed settings. Parts and components maintain their consistency even with the robots operating 24 hours a day and 7 days a week.
Boost Productivity: Robots may run at all hours of the day. They do not require breaks and their productivity does not change due to the long hours. This advantage helps manufacturers to increase their productivity and reduce lead times.
Investment casting methods use wax patterns dipped in ceramic slurry to create molds that will form the metal parts for customers. To make the wax patterns, the manufacturer has to design and manufacture tooling.
Since customers are getting custom-made parts from the manufacturer, the tooling is created for each specific project. The tooling design and manufacturing occurs before all other investment casting process steps. Some manufacturers will build all their tooling in-house, while others will contract other companies to perform the tooling.
When it comes to tooling, most costs are quoted at the beginning of the project. These are one-time expenses, as the tooling becomes the property of the customer. Costs vary greatly for tooling, as one project may cost higher than another project for a single customer. Here is what to understand when looking at tooling costs when creating investment casted parts.
The size of the part controls tooling costs. Larger parts need large tools to handle them. This factor leads to a manufacturer needing more materials to make the tooling. A larger part size also directly influences the amount of time it will take to machine mold cavity in the tooling.
The volume of the part impacts tooling costs. Higher volume parts need multi-cavity tooling to improve throughput. Multi-cavity tooling requires complex tooling design and more materials to make. The number of cavities in the tooling also directly influences the amount of time it will take to machine the tooling and to validate the tooling once it is completed.
Parts that have intricate internal pieces may need cores made that will go into the wax patterns for the molds’ creation. These cores require separate tooling. Tooling costs may rise depending on the intricacy of the core’s design.
Casting complexity involves how simple or complex the part is. Parts with complex geometries require tools that have many moving parts. As more mechanisms are added to the tools, the price of the tooling also increases.
In some instances for long production runs of high volume parts, tooling begins to wear out during the wax pattern manufacturing process. Tooling costs are factored based on the type of material used to make the tool and the part’s material that becomes machined and cut. This circumstance typically occurs when cutting extremely hard materials. Most of the wearing for tooling occurs where moving parts encounter each other as they cause friction and abrasion. When tooling needs repairs, it is done quickly without significantly impacting production times.
Keep in mind that there is no master list when it comes to tooling costs due to the varying nature of each customer’s project. Some tooling costs could be as low as $1,000 while other projects could go over $20,000. Working closely with the engineering team allows you to further understand the tooling design and manufacturing process. Then you can create the part manufacturing budget that is viable for your company.
When talking about casting processes, two specific techniques may be mentioned: investment casting and centrifugal casting. While both involve pouring a metal into a ceramic mold or die, the methods on how these two particular techniques differ. Let’s take a look at these methods and figure out which one is right for your part.
Investment casting involves creating a wax pattern of the part. This pattern is then covered with a liquid ceramic that hardens into the shell mold. The wax is melted or burned out as the mold is then filled with molten metal and allowed to cool to form the part. The mold is removed to reveal the part as the ceramic shell is only used one time for each part.
Investment casting is ideal for simple and complex parts. The method may be used for low and high-volume production runs, as well as for prototyping components. In certain circumstances, the part may not need additional heat or surface treatments to endow the metal with certain mechanical capabilities. The investment casting method works with a variety of metals and is used in numerous industries such as automotive, medical, industrial equipment, aerospace, and energy.
For centrifugal casting, molten metal is poured into a die as the entire die spins. The centrifugal force of the spinning die forces the molten metal to be evenly distributed throughout the mold. Once the metal cools, the part is removed from the die as the die can be reused for the next part. There are two types of processes: horizontal centrifugal casting and vertical centrifugal casting.
Centrifugal casting is typically used for parts of very large sizes, such as one going up to 135,000 lbs. It may be used when certain metal materials cannot be cast using other casting processes. It is also ideal when the part is symmetrical and can rotate on its axis.
Investment casting is usually the top choice when you have parts with intricate details and shapes. It is also ideal when only requiring small to medium production runs or prototypes. If the part has very tight tolerances or very thin walls, investment casting is the preferred method. If you need large castings, castings made from metals that cannot work with other processes, or parts with very large diameters over 15 feet, centrifugal casting may be the appropriate choice.
Customers have different choices when it comes to getting their parts manufactured. Deciding on which process to use typically comes down to manufacturing capabilities, product feasibility, and costs. When evaluating the costs for investment casting, many customers talk about how expensive it is to get this process.
Costs may vary between customers based on their specific manufacturing needs, such as the number of parts that are required. Yet there are several key cost drivers that should be taken into consideration when deciding on a manufacturing technique. Let’s look at some of the cost drivers associated with investment casting.
The design of the part plays a major factor in investment casting costs. Simple part designs with no internal passageways, holes or features help to lower costs for customers. Yet when the component has more complex geometries and require complicated core designs, these features require that the gating system will ensure that the molten metal reaches all required areas to have a high quality product with no defects. This extra work may raise the production prices.
Complex components and larger parts may also need additional shell layers. These additional layers add strength to walls that may be inherently weak, such as along elongated holes or slots. With the additional shell layers and intricate designs, the drying process may take longer and slow down the production process. All these factors can make the project expensive.
The metal chosen is another cost driver for investment casting. Base metals and alloys come in varying grades. So, a higher purity alloy versus a low grade alloy, even when using the same metal, will have higher costs. Customers also have to purchase more metal than will actually be used to cast the part. Other cost factors include rarity and availability. A metal that is harder to mine and process makes its availability limited, as this factor may increase costs.
Customers should also keep in mind the changing metal market. A metal that was inexpensive and readily available a few months or years ago may experience price increases due to shortages.
Production Technique, Heat Treatment, Surface Treatments and Testing Requirements
Every manufacturer has production techniques and technology that is specific to their operations and services. These prices vary based on their capabilities. They may also offer certain technologies to help create cost-effective solutions to customers, such as 3D printing technology offered at Impro for small production runs and rapid prototyping.
There are many terms that are used throughout the casting manufacturing process that may be confusing for many customers. These terms may refer to unique processes or may be another name for a specific process. One such term that a customer may hear is “expendable mold casting.
Customers who are looking for investment casting processes for their parts and components may find themselves with very restricted schedules. The component they need may be part of a larger assembly that has its own time to market demands. These factors cause customers to figure out the best manufacturing process to offer them components based on specified deadlines.
Investment casting lead times will vary based on the customer’s specification and requirements. Each process of the investment casting method has its own timeline, yet here are typically investment casting times.
At Impro, we offer 3D printing technology to cut down on lead times for prototyping parts. Called rapid prototyping, this process may take anywhere from 30 minutes to 7 days to produce a customer’s part depending on the part’s size as well as its complexity.
There will be occasions when lead times will be stretched out farther than typical times. This factor often occurs when the part is very complex. A complex part forces a manufacturer to take extra time to design and develop the required tooling.
Another instance when a part’s lead time may be long is when it is a brand-new part for the customer. The part’s prototyping may go through several levels of modifications and adjustments until it is suitable for the application. Validations and testing could add several more days to several more weeks to the schedule.
To get a more accurate lead time for a particular project, it is always best to reach out to the part’s manufacturer. At Impro, we can discuss your project and possible techniques that could cut down on the lead time so that you obtain the component faster. Contact us today to learn more about our processes and techniques
For customers in need of simple to complex parts created from a wide variety of metals, investment casting processes provide unique advantages. This technique uses the lost wax casting processes where a pattern of the part is made from wax.
The wax pattern becomes dipped or coated in a ceramic slurry that hardens to become a mold. The wax becomes melted out of the ceramic mold as molten metal is then poured inside. Once the metal cools, the ceramic mold is removed to show the cast metal part.
There are many key steps involved with the actual investment casting process. Yet keep in mind that it really begins with the customer deciding on the dimensions and specifications of the part along with the type of metal that will be used. When we receive this data and documents, our role in the investment casting process may begin.
Tooling Design and Manufacturing
Tooling design and manufacturing processes focus on the tooling needed to make the wax patterns. Tooling must also be designed and produced for the water soluble or ceramic cores.
Raw Material Inspection
We inspect the raw materials from the supplier to reassure they are what is requested for the project. We also evaluate the quality of the materials. We also want to avoid purity issues and contaminants that may cause issues during melting and pouring.
Wax Pattern Production
The wax pattern production step involves making wax patterns that are used to produce the ceramic shell molds. To create the patterns, injection molding techniques and injected molding dies are used.
Ceramic Shell Making
The next step in the investment casting process is to take the wax pattern and dip it or surround it with a ceramic slurry. The slurry has binders that allow the ceramic to harden as an even coating is obtained. The ceramic shells harden as then the wax is removed by being melted or burnt out.
Melting & Pouring
The ceramic molds become preheated. Then the pouring process begins with the molten metal entering the ceramic pattern. The molds are preheated to eliminate cold spots that may cause the molten metal to cool unevenly while it fills into all the crevices and intricate parts of the mold. Once the pouring is complete, the metal is allowed to cool as the part is finished casting.
Cutting and Cleaning
The ceramic shell becomes removed to show the cast part. Now the part undergoes a cleaning process where any gates and runners are removed using grinding, cutting, and shot-blasting techniques.