Metal Injection Molding (MIM): Precise Metal Parts Manufacturing

Table of Contents

Metal Injection Molding Pusher furnace
Metal Injection Molding Pusher furnace

I. Introduction

Injection molding might be very popular with plastic injection molding, but it’s never limited to that. The transformative capacities of this ingenious technique transcend beyond just the plastics. This is where we introduce to you the realm of metal injection molding commonly known as (MIM).

Metal injection molding employs the innovative method of part production by combining powdered metal material and injection molding techniques. This in turn births groundbreaking marvels of metal injection molded parts that cut across diverse industries.

As we explore the world of metal injection molding, we aim to decipher how this inventive manufacturing genius shapes precision in metal parts production. So, tag along on this exciting journey.

Metal Injection Molding Design
Metal Injection Molding Design

II. What Is Metal Injection Molding (MIM)?

It should interest you to note that metal injection molding is predicted to have a compound annual growth rate (CAGR) of 7.4 between 20021 and 2026 as projected by Market Research Future. Metal injection molding is a marriage between metallurgic powder material and injection molding, with the aid of a binding agent.

The result of this combination is a precisely engineered metal part that serves its purposes in numerous industries. Before we end this adventure, we shall surely delve into the various industries where MIM components are applicable, but for now, let’s tell you more about this remarkable technique.

Metal injection molding is like a perfectly conducted orchestra that begins with the mixture of a meticulously selected metal material with a binding agent. The binder is usually a thermoplastic material that becomes the feedstock when combined with the metal powder. The symphony is then injected at high pressure into carefully fabricated molds that hold the intended design of the component.

Furthermore, the molded part is allowed to pass through a debinding process where the binder is separated from the molded mixture, and what we’re left with is the green part. This green part further undergoes a sintering process where the metal part is solidified. And voila, there you have your precision-engineered component with extraordinary density. It is no wonder it has had a significant growth rate of eight percent yearly over the past decade.

III. Advantages of Metal Injection Molding

The metal injection molding in its uniqueness offers a plethora of beneficial attributes. These attributes are the reasons it is different from the rest. Especially in a world where cost-effectiveness, precision, and design flexibility cannot be compromised, metal injection molding addresses all these factors with ease and poise.

When you speak of complex geometries and design flexibilities, metal injection molding smiles in the face of difficult angles and dimensions. This is because the attention to detail and the finesse employed in crafting these metal components do not permit any margin for error. Hence, what was once impossible is now made possible with this style of part manufacturing. Design flexibility allows even designers to reach for traditionally unattainable design heights.

In addition to that, if there’s one thing MIM can do effortlessly, it is to create near-net-shape components. This ensures that there’s limited or zero material wastage, which translates to reduced lead time and cost efficiency.

Again, material diversity is a huge advantage metal injection molding offers. Imagine a phenomenal manufacturing innovation being limited by material options. Various materials such as stainless steel, titanium, super alloys, and ceramics, to mention a few are available to be deployed.

To crown it all, cost-effectiveness is a benefit both manufacturers and clients alike want to enjoy in every production run. The same applies to parts with minimal intricate parts, and this is due to its adaptive nature.

Different Metal Powder for MIM
Different Metal Powder for MIM

IV. Materials Used in Metal Injection Molding

Having mentioned material diversity as a benefit in metal injection molding, it is however essential to carefully consider material properties before selection is made. And that is what we’re about to examine. The application of metal injection molded parts in different industries varies. As a result, the quality of the material will differ. That means we need to understand project requirements before we can choose a material to deploy based on its properties. Failure to do that means we are already shooting ourselves in the foot.

The choice of material is the first step to reaching a successful metal injection molding process. With that said what types of materials are available for selection? We have stainless steel, which possesses great corrosion resistance, has enormous strength, and is preferred in the aerospace and medical industries. It is also a suitable material for high-quality mold manufacturing. On top of that, the electronics industry will typically go for tungsten materials for their heat resistance and outstanding density capabilities. 

Besides, all of these impressive qualities, the final step in the metal injection molding process ensures the metal materials take the solid desired shape when sintering is done. Sintering assists the parts to take form in the last stages of the process. Material selection goes far beyond mechanical properties but further into alignment with the manufacturing process itself.

V. The Metal Injection Molding Process

At this juncture, it is time to examine the metal injection molding process itself to unravel the key players involved in this masterpiece. A proper understanding of the process will broaden our scope of the manufacturing technique. As briefly mentioned when defining MIM, the process is preceded by the mixing of two materials. The finely ground metal powder and the binding agent which is usually a thermoplastic material are mixed to form a feedstock. The feedstock is then injected into the mold at high pressures to form the intended shape of the manufactured part.

Once the shape is formed, it is time for debinding. Debinding represents the separation of the molded material from the binding agent. What’s left after debinding is a permeable molded part, and this part is the part that goes through the sintering process. Like a sculptor administering finishing touches to their work of art, sintering marks the final part of the metal injection molding process. Like a final piece of the puzzle, sintering is done at a high temperature.

The suitable temperature for sintering is regulated between 10930C and 15380C for proper fusion. The heat needed for sintering must be adequately regulated to avoid the complete melting of the molded metal. For this reason, at the right temperature, the metal combines to form a thick and completely strong metal fit for its intended application.

VI. Mold Design and Tooling

For every part manufactured via injection molding whether plastic or metal, complete reliance is on the mold. When we talk about mold design and tooling, what we’re getting at is how the complexities of the design could be achieved by designing the intricate parts of the mold. In addition, the mold is the lifeblood of the project. It determines what shape the component takes, and how precise its dimensions are. That is why in MIM, considerations must be given to the corners and edges of the mold as it must make provisions for the shrinking of the metal during sintering.

As we already know that material behavior matters in injection molding, it is for that reason factors such as gate placement, venting systems, and cooling channels are paramount to the mold. In the same vein, temperature control within the mold contributes to the evenness of the component when undergoing sintering. Moreover, tooling plays its part in metal injection molding, especially with computer-based manufacturing methods like high-quality CNC machining. To attain ultimate mold design Electrical Discharge Machining (EDM), flow patterns, and thermal expansion are factors that must come under examination with precise calculation to yield the appropriate result.

Innovative ways were then thought of to eliminate these obstacles, and hence the introduction of simulation technologies. This software imitates the mold design process, examines the possible obstacles, and provides solutions on how to navigate around them.

Metal Injection Molding Quality Control
Metal Injection Molding Quality Control

VII. Quality Control and Inspection in MIM

It is common knowledge that the absence of quality control and inspection leads to disaster and low-quality standards. This knowledge has also prompted researchers such as Transparency Market Research to research the growth that emerges from effecting a robust quality control exercise. This has led to a revelation that non-destructive testing equipment utilized in quality control exercises is to grow up approximately to a whooping three point two billion US Dollars by twenty-twenty-four.

In essence, maintaining quality depends on the potency of quality control measures. In metal injection molding, non-destructive testing procedures are the popular quality control measures put in place to monitor every stage of the process. A typical example is ultrasonic testing which is employed for examining internal defects.

Additionally, quality control must be strictly complied with not just for quality reasons, but for safety reasons as well. Take, for instance, the medical and healthcare professionals who make use of metal rods in surgeries. If the component doesn’t meet industry standards, the patient’s life is at stake. Or the automobile industry where over eighty percent of the vehicle structure is metallic, drivers face a high risk of accidents. Do we need say to more?

VIII. Common Challenges and Troubleshooting in MIM

When you deal with complexities, there are bound to be challenges. Taking on high-risk projects often comes with setbacks. In case you’re feeling lost, let’s help you understand. Metal injection molding can handle complex designs, nonetheless, it faces several risks of defects and internal flaws which may compromise the integrity of the component.

Regardless, designers and engineers with technical know-how often find ways around such drawbacks. This is what makes them experts in the trade. One such common challenge is the problem of porosity in manufactured components. Correcting this setback is to go back to the foundation and begin a trace to where it started. It could be temperature control, debinding exercises, or pressure. Once traced, correcting and fine-tuning the problem gets easier.

What’s more? Quality control can also be administered in feedstock mixing and sintering processes as well. The goal is for the component to attain industry-regulated standards, and these could likewise help with that. Another one is accomplishing tight tolerances. This can be helped by employing process optimization practices such as Electrical Discharge machining. Meanwhile, other factors such as crafting a perfect mold, selecting the appropriate material, and monitoring the process steps could mitigate the challenges posed by tight tolerances.

IX. Applications of Metal Injection Molding

After exhaustively dissecting the theoretical part, diving into real-world applications of metal injection molding in the high-quality mold manufacturing industry and across different industries is the next step.

Our first example of a real-world application of metal injection molding is the medical and healthcare industry. This is a dynamic industry charged with the responsibility of dispensing medical care to the public. Surgical instruments, devices such as pacemakers, brackets, etc., are all beneficiaries of the revolutionizing part manufacturing method in metal injection molding. With that, you should understand the reason why this industry cannot compromise on quality and precision. Not to mention the meticulous selection of materials that must be used in producing these gadgets and instruments.

 Our next stop is the aerospace industry. This is yet another important industry that cannot joke with the safety of lives and properties. In the aerospace industry, metal injection molding has left an indelible impact by crafting delicate components of the aircraft. And just like the medical industry, stringent standards are expected in the quality of the components. But none can stop the effectiveness of MIM in the industry.

In the automotive industry, the manufacturing of engine parts, and transmission systems have been transformed by the advent of metal injection molding. It has provided an opportunity to create fuel-efficient automobiles that perform excellently. The consumer goods industry is not left out. The adaptability of MIM in crafting delicate yet strong components that assist our daily living cannot be overlooked.

MIM Arranger
MIM Arranger

X. Advancements and Innovations in Metal Injection Molding

Metal injection molding might be a transformative manufacturing method, but the world of manufacturing innovation never stops. Developing technologies capable of taking metal injection molding to the next level are constantly gearing up. One such innovative development is the combination of 3D printing technology with metal injection molding. This would greatly impact the designing of molds and help attain tight tolerances that seem difficult. Another developing technology is the introduction of automation into the production process. This minimizes the occurrence of errors and maximizes quality through precision.

Let’s mention a few more before we conclude. In the medical industry, surface treatment that boosts device safety has been adopted. Patient safety is guaranteed with such innovations. Not only that, metal materials are recycled into powdered metals to be reused in production. This reduces carbon footprints and is eco-friendly. As earlier mentioned, for every challenge that rears its head in confronting the capabilities of metal injection molding, several solutions are deployed to counter them.

In years to come other reformative techniques will be in play. A very close one is the use of nanotechnology, robotics, and AI to shift the barriers of metal injection molding to unimaginable heights.

XI. Conclusion

As we round up this informative journey, noting a few cogent points is crucial. One such point is that metal injection molding is a carefully organized process done by mixing a metal powder material with a binding agent before it is injected into the mold. Then debinding takes place and sintering concludes the process. In addition, its benefits are enormous, but cost-effectiveness, material diversity, and design flexibility lead the pack.

Metal injection molding also permits the use of different material options, all you need to do is understand your project requirements and select your material accordingly. Nevertheless, it can be confronted by certain challenges. But if carefully handled, they can be easily dealt with and corrected.

Conclusively, watch out for various innovations that aim to make this technique even better than it already is. Furthermore, sustainable ways that help save the planet and reduce energy and carbon footprints are already in motion and are being adopted to increase environmental awareness and safety.


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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