Casting is an ancient manufacturing method that began in the 1890s. The two casting processes in common use today are investment casting and die casting. Investment casting and die casting are similar, but there are major differences. Investment casting is a process in which wax is injected into a metal mold. In contrast, die casting is a process in which molten metal is pressed into shape using high pressure.
This article will provide an overview of both techniques and their main advantages. You will learn the differences between investment casting and die casting. This will help you choose the best technology for your job.
Table of Contents
What is Investment Casting?
The investment casting process is based on the lost wax casting method. It consists of coating a wax mold by dipping it into a refractory slurry. In the first step, the mold is covered with refractory material.
When the final coating has hardened, heat is used to melt the wax, leaving a mold cavity in the shape of a part. The manufacturer then injects liquid metal into the mold, replacing the wax mold with metal. Finally, the metal cools and hardens in the mold and the casting is removed.
Main Advantages of Investment Casting
Following are the different advantages of using investment casting in your project:
Design flexibility
Investment casting is flexible in design and is well-suited for manufacturing complex parts. It is suitable for different materials such as aluminum alloys, cast iron, and other metal alloys. In addition, this casting method is widely adaptable. This is because it is not limited by size, shape, or thickness.
Tighter tolerances and complex shapes
This technique is a precision casting method. It consistently produces shapes with tight tolerances and fine designs. Standard tolerances for investment casting range between ±0.010 inch and ±0.004 inch. Unlike similar processes, investment casting helps achieve near-net-shape and net-shape parts. This helps in avoiding extra work and costs at a later stage.
High-quality Surface Finish
The standard surface finish of the wax patterns used in this method is 125 microns. This produces a part with a precise and smooth surface finish, which is superior to other casting methods. In addition, investment castings have no parting lines because they use only one mold. Therefore, sometimes you do not need to do any finishing work.
Customizable Size Range
Depending on the needs of your project, you can get both small and large castings from this process. Manufacturers can produce products with weights ranging from 0.1 kg to 100 kg. In addition, investment casting does not require a large demand before production can begin. It is possible to produce as few as 10 pieces and still save costs.
What is Die Casting?
Die casting is the process of melting non-ferrous metals and injecting them into a die casting mold. There are two main methods of industrial die casting: hot chamber die casting and cold chamber die casting.
- Hot Chamber Die Casting: This process is a method of melting the metal and then injecting it quickly into the mold using high pressure from a hydraulic system. This method is suitable for metals that melt at low temperatures. Examples include zinc, magnesium, lead, and tin alloys.
- Cold Chamber Die Casting: Unlike hot chamber die casting, in this process, the liquid metal is poured into a cold chamber before it is injected into the mold. The pressures for this process are higher, typically between 2000 and 20,000 psi. This method works well for metals with high melting points, such as aluminum.
Once the liquid metal is poured into the mold, it cools and hardens quickly, resulting in a finished casting. The die casting process produces castings in a variety of sizes and weights for a wide range of applications.
Main Advantages of Die Casting
The die casting process has its advantages and disadvantages. The following are its main advantages:
Strong Mechanical Properties
Castings made by this method have strong mechanical properties. When the hot metal cools and hardens under pressure, it looks strong and smooth. These parts are tough and strong. In addition, they have high electrical conductivity and longevity.
High Dimensional Accuracy
Die castings maintain dimensional accuracy over a long period of time. In addition, they maintain tighter tolerances with very small variations. This process therefore facilitates the manufacture of complex mechanical parts that require great precision. In addition, it eliminates the need for further machining.
Making Fine Thin-walled Parts
Aluminum die casting allows for the manufacture of parts that are lightweight, fine-structured, and strong. This advantage makes it superior to many other forms of metal. In addition, die casting allows for the manufacture of metal parts with a thickness of approximately 0.5 mm. Zinc parts can have wall thicknesses as thin as 0.3 mm.
Smooth Surface Finish
The surface of a die cast part is smooth and flat and has a crystalline appearance. If you use the right shape of the mold in the right situation, you can get a smooth and delicate part. Unless it is a unique project, you may not need any additional post-processing. This can help you reduce the overall time it takes to complete a process.
Detailed Comparison of Investment Casting and Die Casting
Now that you’ve learned about these two methods and their main benefits. So, let’s take a look at the differences between investment casting and die casting. The table below clearly shows the differences for your better understanding.
| Investment Casting | Die Casting | |
| Working Process | Forms molds with liquid ceramic slurry | Forces molten metal into the die cavity at high pressure |
| Casting Material Selection | Ferrous and non-ferrous metals | Non-ferrous metals |
| Design Complexity | High design flexibility | Considerable flexibility |
| Part Size | Small to medium-sized parts | Larger parts |
| Surface Treatment | Best surface finish | Good surface finish |
| Production Volume | Less than 10,000 pcs | Over 10,000 pcs |
| Tolerance | +/-0.005 inches | Standard:+/-0.010 inch
Precision: up to +/-0.002 inch |
| Cycle Time | Hours of casting | Up to 100 shots per minute |
| Applications | Aerospace, firearm, military, automotive, energy, commercial, and beverage industries | Consumer, industrial, and commercial products |
In addition, let’s go through the following aspects for a more in-depth comparison:
Workflow
The investment casting process begins with the creation of a wax mold that will be used to make the final product. The operator ties the wax block to the bottom of the sprue and dips it into the ceramic mold several times. After the ceramic has hardened and taken the shape of the casting, the mold is heated to melt the wax. The operator then injects molten metal liquid into the mold. When the metal has cooled and solidified, the mold is disassembled and the casting is removed.
On the other hand, the die casting process typically injects liquid metal into a cavity under high pressure. Technicians use hardened steel tools to create a mold cavity with the desired product shape. The molten metal is then placed on a sleeve and pushed into the mold with a piston. This piston applies constant pressure as the molten metal fills the mold. When the metal cools, the operator opens the mold and removes the part. The part usually requires additional machining to be fully completed.
Casting Materials
Investment casting is suitable for a wide range of metals, including ferrous and non-ferrous metals. This casting process can be used for metals such as stainless steel, copper, aluminum, and zinc. In addition, it allows for the manufacture of alloys that are difficult to machine.
The die casting process, on the other hand, is suitable for non-ferrous metals. These metals include aluminum, zinc, copper, lead, and magnesium alloys. Therefore, investment casting has more material options than die casting.
Design Complexity
When comparing investment casting and die casting, the shape of the design is very important. Investment casting can produce parts with precise shapes and complex designs. This casting process gives you more design options. It makes it easier to add different features and create complex parts.
Die casting, on the other hand, can create large parts and provide precise shapes. However, it cannot achieve the same level of detail as investment casting.
Part Size
Investment casting can be used for parts weighing from 0.02 kg to about 100 kg. However, this process has some limitations on the size of the part. This is due to the fact that investment casting requires the wax pattern to be firmly fixed to the tool gate for multiple dips in the refractory slurry.
Die casting, on the other hand, allows for larger parts with fewer size limitations. Almost any size part can be obtained by this method. However, larger parts made by the die casting process require larger tools and may have a higher unit cost.
Surface Finishes
When comparing die casting to investment casting, you will find that investment casting produces a higher surface finish than die casting. This process has a standard accuracy of IT5-6 and can achieve a finish of 125 microns. This reduces or eliminates the need for post-treatment operations.
On the other hand, the surface finish of die castings is equally satisfactory. However, products made using this process require additional machining to achieve the desired results.
Production Quantities
Investment casting is best suited for small production runs, usually under 10,000 pieces. Die casting is best suited for larger projects of 10,000 pieces or more. This is because it can produce between 100 and 2,000 parts per hour. While it can be expensive to make a model, a single mold can make up to a million parts. In addition, the die casting process is very reliable and consistent, making it ideal for mass production.
Tolerances
Both investment casting and die casting produce precise and tight dimensions. However, in the casting process, the tolerance capability is highly dependent on the type of material and the shape of the part.
In general, smaller parts have more precise dimensions. As a result, investment casting is better suited for making small parts that need to be very precise, with tolerances of about +/-0.005 inches. Large investment castings, on the other hand, tend to lose some precision in size and shape. In this case, die casting is a better choice for manufacturing large parts. This is because it can provide standard tolerances of +/-0.010 inches and precise tolerances of up to +/-0.002 inches.
Cycle Time
Traditional investment casting takes a lot of time and effort. This is because the process requires a number of operators and hours of casting time. On the other hand, conventional die casting allows up to 3 to 4 castings per minute. Multi-surface die casting, on the other hand, can produce more than 45 castings per minute and, for smaller parts, up to 100 castings per minute. In addition, the die casting process is usually manufactured using a fully automated process that requires minimal labor input.
Investment Casting vs Die Casting: Which is More Cost-effective?
When considering the production costs of investment casting and die casting, the production volume is very important. If you need to produce more than 10,000 pieces, die casting is cheaper than investment casting. Because die casting is more automated, manufacturers can produce more parts faster.
On the other hand, if the production volume is less than 10,000 pieces. Then investment casting will be less expensive. Die casting equipment is expensive, and producing small quantities does not cover these expenses. Investment casting, on the other hand, requires less equipment, which helps reduce manufacturing costs. In addition, investment casting usually requires no additional machining. This means you can save even more on machining costs.
If you are unsure of the best method for your project, it is best to seek professional help. Yonglihao Machinery will provide you with the best and most reliable investment casting and die casting services. Our skilled technicians know these casting methods inside and out. They will provide you with useful advice to make your work a success.
Summary
Die casting and investment casting are both commonly used casting processes, but they are used for different purposes. Which casting method you choose depends on your needs. Die casting allows you to produce large quantities of parts quickly, at low cost, and with high quality. On the other hand, investment casting is suitable for small products with complex designs.
In addition, die casting is only suitable for non-ferrous metals such as aluminum, zinc, and copper. If you need to make parts from hard metals such as stainless steel, then investment casting is the best choice for you. Your production needs will help you decide which process is best to use. If you have any questions about the selection process, please contact Yonglihao Machinery today.