Metal Injection Molding (MIM) is the most efficient way to produce huge quantities of strong and complex metal parts. It involves mixing fine metal powder with a binder which results in the creation of a mingled material that behaves like plastic, hence can be injected into a mold. This process is ideal for large-scale production of tiny, intricate metal components at a fraction of the cost.
What metal injection molding is all about is what this guide is to you. The guide will literally take you through all the steps involved starting from the very first and going all the way to the last. Besides that, you will also have a comparative reference of this method to other ones. Additionally, we will take you to its pros and cons. After you have gone through this guide. You will get an idea of whether MIM is suitable for your project.
The 4-Step MIM Process
The metal injection molding process is a complete cycle from fine metal powder to high quality. It is a sophisticated and multi-stage process that should be performed with precision. It is very hard to find a person who can do it well. Learning these four steps is the first thing to do if you want to find out what is metal injection molding.
(We suggest that you use a flow chart to help your team visualize these four steps.)
Step 1: Feedstock Compounding
The first step that is taken is to make a specific material called feedstock. This is a careful mix of such fine metal powder and a binder. The binder is made mainly from wax and other plastic-like materials. The Metal Powder Industries Federation states that the metal powder particles are, on average, smaller than 20 micrometers. That’s thinner than a human hair.
The mixture is then heated and mixed together until it is uniform. It is then cooled and formed into small pellets which are the raw material for the next step.
Step 2: Injection Molding
Next, the feedstock pellets go into an injection molding machine. The machine heats the pellets until the binder melts. This creates a thick, paste-like fluid. This fluid is then injected under high pressure into a steel mold. The mold is the exact shape of the final part. This part of the process is very similar to литье пластмасс под давлением.
The part cools down and hardens inside the mold. After it becomes hard, it is taken away. At this moment, the part is referred to as green part. It is an absolutely similar shape to that created by the mold. It is mostly 20% bigger than the final part. This extra size will allow for the shrinkage that occurs later.
Step 3: Debinding
Сайт green part is firm enough to handle it, yet some binder is still left in it. The following step is debinding. The purpose of this step is to remove most of the binder. This is a critical stage of the process. The binder is only a temporary carrier for the metal powder.
There are some ways to achieve this. You can use a special solvent, a low-temperature furnace, or a catalyst. After most of the binder is gone, the part is fragile. It is now called the brown part. The brown part is a metal skeleton that formed from the particles of metal. A little bit of a binder that remains holds them all together.
Step 4: Sintering
The last stage is sintering. The delicate brown part is dunked in a furnace that reaches a high temperature. The furnace is heated just below the melting point of the metal. In this step, the metal particles join together.
The part shrinks to its final size and becomes very dense. It can achieve 95-99% of the same density as solid metal. This step is the one that gives the part its final strength and hardness. It also provides the part with other essential metal properties. After sintering, the part is a finished solid metal part.
MIM vs. Other Methods
The decision on what process to use is critical for the project to be successful. It includes how much time, cost, and quality you are willing to take. In specific use cases, metal injection molding has certain advantages over methods including CNC machining.
The table below shows how MIM compares to CNC Machining and Die Casting, which are other metalworking methods.
| Feature / Factor | Metal Injection Molding (MIM) | Обработка с ЧПУ | Литье под давлением |
|---|---|---|---|
| Сложность деталей | Очень высокий | Высокий | Средний |
| Подходящий объем | High to Very High | Low to Medium | High to Very High |
| Tooling Cost | Высокий | Нет | Высокий |
| Cost-per-Part (High Vol.) | Very Low | Высокий | Низкий |
| Материальные отходы | Минимум | Высокий | Низкий |
| Допуски | Превосходно | Превосходно | Хорошо |
| Время выполнения | От среднего до высокого | Low to Medium | От среднего до высокого |
Based on the comparison, it is obvious that what is metal injection molding is a very effective choice for producing complex parts in high quantity. It is the most effective method used when the cost per part is low is prioritized. In the case of prototypes or small runs, Китай CNC обработки услуг are often a better choice.
Key Advantages and Limitations
As is the case with all technologies, metal injection molding has both merits and demerits. Knowing these helps you in deciding whether it is a good fit for what you need.
Advantages of MIM
- Design Freedom & Complexity: MIM promotes the idea of making complex shapes and fine details very easy. Features like undercuts, thin walls, or internal channels are among the designs that are hard or impossible to make with other methods.
- High-Volume Production: The production of the parts can happen very fast and consistently, once the mold is made. As a result of this, the cost per part becomes extremely low for the large production runs.
- Excellent Material Properties: The sintered MIM parts are not only strong but also very dense. Their mechanical properties are similar to parts developed from solid metal blocks.
- Minimal Waste: MIM is a “net-shape” process. This means it creates the final shape with very little material scrap. This is a cost-cutting measure, especially when one is dealing with metals that are expensive.
- Excellent Surface Finish: Parts are taken from the mold with a smooth surface. Consequently, sometimes it is unnecessary to perform any further polishing or finishing operations.
Limitations to Consider
- High Initial Tooling Cost: The steel mold that is required for injection is very intricate and may become expensive to fabricate. Thus, this initial investment can have a substantial impact on the bottom line.
- Longer Lead Times for Tooling: The process of obtaining a quality mold often requires weeks or even months. Therefore, MIM is not a suitable choice for projects that require the parts to be manufactured quickly.
- Size and Weight Constraints: The MIM process is best suited for small parts that weigh usually less than 100 grams. For parts that are larger in size and weight, it becomes impractical and costly to use this method.
- Not Cost-Effective for Low Volumes: Due to the high tooling costs, MIM is not a viable option for manufacturing only a few prototypes. It is also not cost-effective for a small batch of parts.
Is MIM the Right Choice?
How can you determine whether your project suits this technology? Before making any commitments to MIM, we always ask our partners to reflect on the following questions. This checklist is useful to clearly define whether or not what is metal injection molding is the answer to your problem.
- How complex is your part’s geometry? MIM is a very strong candidate if your design consists of intricate features. This can include several components that could be combined into one or shapes that are hard to machine.
- What is your required production volume? Are you thinking about producing tens of thousands of parts every year? What of hundreds of thousands or even millions? If that’s the case, then it would be worth it in the long run to get MIM at a lower per-part price.
- What are your material and strength requirements? Does your part require real metal’s high strength? Does it have to stand up to wear or corrosion? If other materials such as plastics are not ideal for, MIM is a great choice.
- What is your part’s size and weight? Is your component fairly small? Does it fit in your palm? MIM will be rescued from waste if the parts are under 100 grams.
- Can you accommodate the upfront tooling investment? Your financials must allow for the initial cost of изготовление пресс-форм для литья под давлением. The per-part price is cheap, but the tool is a big investment. It enables the savings.
If you answered “yes” to most of these questions, metal injection molding is probably a great choice for your project.
Common Materials and Applications
MIM technology can be applied to several metals which makes it useful for a variety of industries. One of the main advantages of the metal injection molding process is that it can produce parts using these materials.
Common MIM Materials
- Stainless Steels (e.g., 316L, 17-4 PH): Applied for the making of parts that require considerable strength and rust prevention. They are common in medical equipment and marine hardware.
- Low Alloy Steels (e.g., FN02, 4140): Selected when the need for strong structural parts is paramount. They can be found in automotive and firearms components.
- Инструментальные стали: Are used in applications that require high hardness and resistance to wear.
- Titanium Alloys: Are used for parts that must be lightweight and very strong. They are also biocompatible. Aerospace and medical implants are some of the applications in which they are found.
- Медь: Chosen for parts that must have high conductivity to heat or electricity.
Where is MIM Used?
MIM parts are in almost all products we encounter daily. Here are some of the examples we have in our experience:
- Medical & Dental: Tiny, complex parts like surgical tools are made with MIM. This includes brackets for braces and components for implantable devices. The process creates sterile, strong, and precise parts.
- Автомобиль: The injection molding of small parts like in the car engine and valve often uses MIM. This includes turbocharger vanes, sensor housings, and parts for the valve system.
- Потребительская электроника: Durable and stylish metal cases for smartphones, smartwatches, and laptops are made with the help of MIM. For instance, watch cases, SIM card trays, and charging port connectors are examples of MIM applications.
- Aerospace & Defense: MIM is used in the defense, for components of guns, like triggers, hammers, and sights. It is for small parts in drones and latching systems on aircraft.
Finding the Right MIM Partner
A successful MIM project is not only about technology but the other aspect is having a manufacturing partner who is an expert. It involves material science, mold design, and process control. The best partners will work with you from the early stages of the design. They will ensure the part is made in such a way that it is easy to manufacture.
Being with a knowledgeable team is very important. It will help you to meet your quality and cost targets for the product. For overall manufacturing solutions, you can consider partnering with a recognized expert like Mekalite.
Часто задаваемые вопросы
1. How strong are metal injection molded parts?
The MIM parts are quite strong. They can reach a level of density that is 95-99% of the wrought solid metal. That means they will have excellent mechanical properties. Their tensile strength and hardness are high. The strength of MIM parts is frequently more than that of die-cast ones. Their strength is similar to machined parts.
2. What is the typical cost of metal injection molding?
The cost can be split into two sections. There is an initial, high tooling cost that is one time, and the cost for each part is low. Costs for the mold can range from about $10,000 to above $100,000. This is the reason why MIM is such an excellent choice for mass production. It is, however, still costly for producing low quantities.
3. What are the size limitations for MIM?
MIM is best suited to manufacture small, complex parts. The preferred weight is generally under 100 grams. Although larger parts can be made, the process will be less cost-effective as the part size increases. This is due to higher material costs and longer processing times.
4. How does MIM compare to metal 3D printing?
MIM and metal 3D printing have different purposes to meet the needs of clients. The MIM process is designed for high-volume production. It gives a very good surface and has low per-part costs. However, it requires a large initial investment in tools. 3D printing is ideal for prototypes, tailors made parts, and low-volume runs. It has no tooling costs, but the cost per part is much higher. Production is also slower.
5. What is the difference between a “green” part and a “brown” part?
The “green part” is the initial part that still has the binder material attached. It becomes a “brown” part after the majority of the binder has been removed.
