What is the Difference Between Metal Injection Molding and Die Casting?

Table of Contents

I. Introduction

Die casting, and Metal Injection Molding (MIM) are two of the most widely utilized technologies in the manufacturing sector, and they are frequently combined to create precise parts and components. The Metal Injection Molding process is a net shape process that forms and uses metal powder to produce high-strength components. It is a cost-effective process when components require high strength and wear characteristics that other processes cannot achieve. Even if both the MIM and die casting processes involve injecting metal into a die, this is where the similarity ends. Die casting has several economic advantages, which in the right circumstance and component, may offer large cost savings opportunities for the component designer.

Understanding the differences between MIM and die casting is essential for manufacturers because they can make conscious decisions on the most reliable and effective process to use during manufacturing. This guide will help you understand the key differences between MIM and Die casting. 

II. Fundamental Concepts

Metal Injection Molding and Die Casting

A. Definition of Metal Injection Molding

Metal Injection Molding (MIM) is a manufacturing process that combines powder metallurgy and plastic injection molding to create complicated, precise metal components. Metal powder and a binder material are combined to make a feedstock, which is then injected into a mold cavity at high pressure to form a net-shaped part. Debinding is the process of removing the binder following molding; this can be done using heat or chemicals. After the binder has been removed and the metal particles have been fused together in a high-temperature furnace, or sintered, the resulting green portion is a dense, high-strength metal component. Aerospace, automotive, medical, and consumer product manufacturers all rely on MIM because of the material’s ability to produce complex geometries, fine details, and tight tolerances. In addition, the MIM process enables mass manufacture of parts at a cheaper per-part cost than is possible with conventional machining or casting.

To sum up, the MIM process is a significant resource for the production of high-quality metal components since it is adaptable, cost-effective, and provides a wide range of design possibilities and material options.

Materials used in MIM

MIM components can be constructed from a variety of materials, depending on their intended purpose. Metal injection molding (MIM) is commonly employed to manufacture components from stainless steel, low alloy steel, tool steel and copper alloys; magnetic alloys, tungsten alloys and titanium alloys as well. thermoplastic polymers such as polyethylene, polypropylene or wax serve as binders in MIM projects so that metal powder mixes smoothly with them for stability when injected into molds.

B. Definition of Die Casting

Die casting is a manufacturing process used to create complicated and accurate metal pieces with a smooth surface finish by injecting molten metal under high pressure into a metal mold, also known as a die. High pressure is used to force the molten metal into the mold cavity, where it fills all the nooks and crannies before being cooled and solidified into the finished product. This method is frequently employed in the manufacturing of automobile components, home appliances, and electrical equipment due to the high dimensional accuracy, smooth surface finish, and outstanding mechanical qualities that the parts generate.

The die casting process can be analyzed in various stages as shown below:

  1. Preparation: The metal surface is cleaned and coated with a lubricant to prevent it from sticking to the die.
  2. Injection: A high pressure, usually between 1,500 and 25,000 psi, (10-170 MPa) is used to feed molten metal into the die. The pressure aids in the speed with which the mold cavity is filled and the uniformity with which the metal is dispersed.
  3. Cooling: As the molten metal cools in the mold, it solidifies rapidly. Water-cooled pathways in the die or cooling the die itself can speed up this procedure. The die is opened and the part is evacuated once it has hardened.
  4. Trimming: Trimming is the process of removing extra metal or fixing other flaws in the part. 

Materials Used in Die Casting

Die casting is the process of pumping liquid metal under high pressure into a die or mold, where it solidifies quickly to form the desired shape or part. This typically involves one of two materials:

Aluminum – Aluminum is widely used for applications where cost and strength are crucial. It’s the most widely used die casting material due to its abundance and low price point.

Zinc – Zinc has been used as a die casting material for years due to its low density (one-half that of aluminum), ease of fabrication, good workability before solidification, and smooth surface finish after solidification.

Magnesium – Magnesium can be an ideal structural metal, though it does have a slight reduction in surface finish after casting. It has excellent mechanical properties.

Other Alloys – Die casting alloys such as lead and tin-based alloys can also be utilized for special applications requiring low friction or corrosion resistance. These materials may be ideal for applications requiring unusual properties like low friction or corrosion resistance.

III. Key Differences

A. Materials Compatibility

Materials suitable for MIM

Metal powder for metal injection molding (MIM) can be produced from a wide range of metals and alloys. When selecting the binder system, parameters like viscosity, curing temperature and chemical composition must be taken into consideration; compatibility between them must then be ensured in order to achieve optimal mixing and flow during injection molding. MIM requires a variety of metals and alloys, such as:

  1. Stainless Steel – Due to its strength, hardness, and resistance to corrosion, stainless steel has become an ideal material for MIM applications. Popular stainless steel alloys used in MIM include 17-4 PH, 316L, and 420.
  2. Low alloy Steel – Low alloy steels can be used in place of high alloy when great strength and hardness are not essential. Complexly shaped parts made of low alloy steel, such as gears or bearings, lend themselves well to the MIM manufacturing process.
  3. Nickel-Based Alloys – High temperature industries such as aircraft and power generation rely on nickel-based alloys. Inconel 625 and Hastelloy C-276 are two popular nickel-based alloys used in metal injection molding.
  4. Titanium – Titanium is a lightweight, high-strength metal used in aerospace, medical and military applications. MIM (metallurgical melting process) is an ideal method for producing small complex titanium parts such as dental implants and surgical instruments.
  5. Cobalt-Chrom – Cobalt-chromium alloys boast superior biocompatibility, corrosion resistance, and wear resistance that make them ideal for use in medical and dental fields.
  6. Copper – Due to its excellent conductivity, copper is widely used in these fields. Small, intricate copper items such as electrical connectors can be precisely manufactured using the MIM technique.

Metals suitable for Die Casting

Metal ingots are forced under extreme pressure into a steel die during die casting. The desired quality, complexity of the part and volume of production all influence which metal works best in this process.

Some of the metals and materials commonly used in die casting include:

  1. Aluminum: Aluminum is the most popular choice due to its excellent mechanical qualities, lightweight nature, and resistance to corrosion. It has excellent electrical and thermal conductivity which make it ideal for use in electronics applications.
  2.   Zinc: Zinc’s superior strength, dimensional stability and castability make it the metal of choice for die casting. Furthermore, its low melting point makes it suitable for casting lightweight components.
  3. Magnesium: Thanks to its low density and exceptional mechanical strength, magnesium is an ideal material for crafting a wide variety of useful components.
  4. Copper: Die casting often utilizes this metal due to its excellent electrical and thermal conductivity, making it perfect for applications such as electrical connectors and heat sinks..
  5. Tin: Due to its relatively low melting point, tin is perfect for die casting intricately shaped small items like jewelry and home decor.

B. Production Speed and Efficiency

Metal Injection Molding and Die Casting

MIM production rates

Metal Injection Molding (MIM) production rates shift based on many variables, such as the part’s complexity, the size of the manufacturing run, and the materials employed. Depending on the criteria mentioned above, MIM can produce anything from several hundred to several thousand pieces each day. Higher manufacturing speeds are possible for smaller parts with simpler designs than larger ones with more complex designs. The ideal part weight range for MIM manufacturing is between a few grams and several hundred grams.

Die Casting Production Rates

Die casting is a highly efficient and cost-effective manufacturing technique, as die casting machines can rapidly produce large numbers of parts in short amounts of time. On average, die casting machines produce between several hundred to several thousand components per hour; however, this rate may vary depending on the application or circumstances. When selecting a production method, speed of production should not be the only factor considered; other elements like tooling costs, materials costs, quality assurance standards must also be taken into account when making any decision.

C. Complexity and Precision

Geometries Achievable with MIM

MIM can create parts with complex geometries that would be impossible to make with more traditional techniques. Injection molding and sintering work together in MIM to produce intricate details like microscopic holes, undercuts, and thin walls – features impossible to replicate using other methods like machining or casting. This makes it possible to produce intricate components with intricate shapes and features not possible with other manufacturing processes like machining or casting alone.

Complex geometries, undercuts, and thin walls are all possible with MIM’s part production capabilities. Injection molding is well suited for manufacturing small metal components because it permits the creation of parts with high levels of detail and accuracy. Polished, textured, and matte surface finishes are all possible when manufacturing with MIM.

Geometries achievable with Die Casting

The die casting machine’s capabilities and the intricacy of the part design determine the range of possible geometries. Die casting allows for the creation of a variety of standard geometries, including.

Die casting allows for the production of components with complicated shapes and thin walls, characteristics that would be challenging, if not impossible, to achieve with other manufacturing methods.

Die casting allows for the production of components with a clean surface finish, making them useful in settings where visual appeal is paramount.

Die casting’s rapid production rates make it well suited for mass production runs of a variety of components.

D. Tooling and Mold Costs

The intricacy of the component affects costs. Although metal injection molding is less expensive than die casting, the process costs are higher. Depending on the application, die casting might be less expensive than MIM. The labor and the equipment that go into die casting make up the entire cost. Since the procedure requires minimal labor, the cost primarily depends on the instruments and equipment required to do the task such as CNC machining and rapid prototyping. The expense of the tooling is significant for high-precision die casting. They have some of the best rankings of any excellent mold manufacturing technique. Die erosion, which manifests as the steel parts of the die losing their sharp edges, is a risk during production. All of these result in higher tooling expenses. Your merchandise should be in flawless condition. Cutting tooling costs can be accomplished by simplifying the mold designs. On the other side, injection molding is comparatively less expensive. The complexity of the item and the raw material both have an impact on injection molding prices.

E. Surface Finish and Post-Processing

The final product manufactured due to die casting tends to have a better surface finish. This is one of the perks of this process. The extra finishing is just done so that it can increase the aesthetics. Finishes in injection molding are not compulsory, but it is done more frequently than in die casting. Surface finishing options for die casting include anodizing, powder coat, chem film, gold plating, and impregnation. These finishes are primarily for increasing the beauty, durability, thickness, and mechanical and chemical resistance. Finishes for injection molding can be grouped into four major categories, namely:

  • Degating
  • Deflashing
  • cleaning
  • Decorating

Post-processing requirements

High-quality metal parts with complicated geometries and tight tolerances can be made using a cutting-edge manufacturing process called metal injection molding (MIM).However, to attain the needed characteristics and final product quality, MIM necessitates several post-processing procedures that are not present in conventional production. Debinding, or removing the binder material from the molded part, is the first step in the post-processing of MIM. This is necessary to preserve the part’s form during sintering and prevent flaws. Thermal or solvent extraction techniques can accomplish debinding. To increase the density of the MIM component, sintering is performed after debinding. Sintering is typically carried out in a furnace with the variables of time, temperature, and atmosphere strictly controlled.

Additional surface treatments are often necessary for MIM parts to achieve the desired finish or to improve their corrosion resistance. Shot blasting, anodizing, and electroplating are all examples of such processes. Machining may be necessary to get the required dimensional accuracy or to add features that cannot be made with MIM.

IV. Applications and Industries

Industries Utilizing MIM

Metal injection molding is an excellent production method because it permits the creation of small, complex, and intricate parts with close tolerances and thin walls. A few uses for MIM are:

  1. Firearms industry: triggers, sights, bolts, ejectors, barrel release
  2. Medical industry: joint replacement parts, surgical instruments, drug delivery systems
  3. Automotive industry: electrical connectors, system controllers, shift levers
  4. Industrial industry: drone parts, micro gears, machinery components
  5. Aerospace industry: engine components, flap screws, valve holders
  6. Electronics industry: mobile phone componentry, smart wear, cable accessories

Industries Utilizing Die Casting

Die casting is extremely versatile, allowing it to be used for customers in various industries. A few of these industries include the following:

  1. Firearms industry: triggers, trigger guards, safeties
  2. Medical industry: surgical devices, peristaltic pumps, blood analysis machines
  3. Automotive industry: gear housings, powertrain systems, engine components
  4. Industrial industry: outboard gear case, hydrostatic axles, steel liner inserts
  5. Electronics industry: electrical housings, antenna mounts, RF filters

V. Choosing the Right Process

Factors to consider when selecting MIM or Die Casting

MIM and die casting offer numerous advantages, making a decision between them difficult. Consider the part’s design, the materials you would like to use, and the application you have in mind before settling on a manufacturing technique. The decision between plastic injection molding and die casting is very important. Before beginning fabrication, evaluating the part’s intended purpose is important. It makes choosing much easier to do. The next step is to compare each approach’s benefits and drawbacks with the component’s function. If you do that, picking the best method will be a breeze. Fluidity issues under high pressure are a problem for die casting. Injection molding is also useful for making large parts. However, it is a logical conclusion when making complex parts that call for great care and attention to detail in their production. It would be best if you used die-casting. It is the superior option for items like that. For some applications, either of these methods will do just fine. Cost-cutting measures and budgetary restraints will be next on the agenda. Remember that the costs of injection molding and die casting are drastically different. As the manufacturer, you have the final say, as both options are viable.

VI. Conclusion

Die casting and injection molding have been compared extensively, and both processes are viable options for producing high-quality products. After all, these are two of the most common processes used by global manufacturers. Neither approach is without merit. Insight into the procedures involved and the benefits and drawbacks of each approach facilitates the selection of appropriate methods. The answer to this question is heavily dependent on your intended output. The results of die casting, according to some, are superior. Plastic injection molding, on the other hand, produces plastic goods of the highest quality. It is up to the manufacturer to specify their preferences. The die casting method is not best for materials with high fluidity under high pressure. 

When manufacturing large-sized parts, you should use the injection molding method. However, when manufacturing high-complexity parts that require high precision and accuracy, use a die casting method. In addition, there are times when both methods are good for any intended product. In this case, we, therefore, focus on the budget, especially on how to minimize it. Finally, remember that injection molding is much cheaper than the die casting method, however, the choice is entirely yours as the manufacturer, as both methods are good.


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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