April 2, 2024

The Complete Guide to Micro Injection Molding: Processes, Benefits, and Applications

micro injection molding

Micro injection molding is an extremely accurate production process. Mass-production of small plastic parts is made possible by it. These parts have intricate shapes and are generally small. In contrast to standard molding, micro molding is a process concerned with the production of very small parts. These can be a few millimeters or a few microns in size. They usually get very precise, with tight tolerances in the range of microns.

This is a critical part of the process especially in fields that require small parts but not necessarily with the accuracy or functionality loss. Micro injection molding is developing from the evolution of several areas. The tools include special devices, the designing of molds, and the study of materials. The breakthroughs made it possible to create objects that were considered impossible to craft previously.

What is Micro Molding?

Micro molding is a specific type of plastic injection molding. It’s used to make very small parts with great accuracy. The process works by injecting a small, exact amount of resin into a mold under high pressure. Everything is carefully managed to make sure the parts are accurate and consistent.

Micro molding is known for a few important things. It can make parts that weigh less than a gram. Also, it can create details as tiny as a micron. This makes it perfect for many uses that need complex details and high precision.

Core Processes in Micro Injection Molding

Mold Design and Making

Designing and making molds is very important in micro molding. This step needs very high accuracy. It’s about creating molds that can make very micro parts reliably. To do this, mold makers use advanced computer design software. They also use precise tools, like CNC machines and EDM (Electrical Discharge Machining). These tools help make molds that match the exact needs.

During the design phase, there’s a focus on how the material moves through the mold. They also pay attention to how quickly the part cools down. These factors are key to making sure the final product has the right quality and measurements.

Material Selection for Micro Molding

Choosing the right material for micro molding is very important. The material affects the part’s features, like its strength, flexibility, ability to withstand heat, and resistance to chemicals. Here are some materials often used in micro molding:

  • Thermoplastic Elastomers (TPEs): These are flexible and stretchy. TPEs are great for parts that need to be soft or bendable.
  • Polyoxymethylene (POM): POM is known for being precise, stable in shape, and wear-resistant. It’s perfect for making gears and precise parts.
  • Polycarbonate (PC): PC is strong and clear. It’s used for making medical devices and parts that need to be seen through.
  • Polyether Ether Ketone (PEEK): PEEK can handle high temperatures and has strong mechanical properties. It’s used in car and aerospace parts.
  • Liquid Silicone Rubber (LSR): LSR is very resistant to heat and chemicals. It’s ideal for medical industry and car parts.

When choosing a material, you need to think about what the part will be used for, what properties it needs, and the molding challenges. The material needs to flow easily into the small mold spaces, solidify properly, and come out of the mold without getting damaged.

The Micro Molding Process Step by Step

The micro molding process starts with obtaining the mold and material. A very exact and small amount of pellet of resin is put in a melting process to melt it. Next, it’s fed into the cavity of the mold through a special syringe-sized injection machine. This phase needs the precise control over the pressure, flow rate, and temperature of the injection. To avoid part damage or mold damage, this is to ensure mold fills up properly.

The material solidifies as it cools down and the part is taken out of the mold. Next, the system will begin the cycle all over again. The whole process is observed carefully. This guarantees that all components made are uniform and top quality.

Types of Micro Molding

Micro molding includes different specialized methods. These methods are used to make very small parts. Each method has its own advantages and is good for certain uses. Knowing about these methods can help you choose the best one for your project.

micro injection molding
Source: Pinterest

2-Shot Micro Molding

The second process, which is 2-shot micro molding, is also known as dual-shot or multi-material molding. It is a complicated process that gives a two-material or color parts in one cycle. This is particularly useful in cases where one part needs to be different in different areas. For instance, a medical device might need to be stiff in one part for its strength and have a soft part in another part for comfort.

How It Works:

  • First Shot: The first material is then loaded into a mold section. This is the first step of the item.
  • Mold Rotation/Transfer: Then it is the mold’s turn to open. It is either moved or turned around to a new position in the same mold or it goes to a different mold. Here, the second material will be embedded.
  • Second Shot: Then, the material injection is performed. The glue is put on the first material and then the piece is completed.

This method has a special machine that can manage two materials and move the mold if it is necessary. The main obstacle is gluing them together firmly. Also, the process must be controlled to the last detail in order to achieve the desired features in the final item.

Insert Micro Molding

Insert micro molding is a technique where a previously created part, usually a metal or other plastic, is put into a molded plastic part at the time of molding. This technique is frequently used to incorporate thread, contacts, and reinforcing elements into plastic parts. It enables the parts made of plastic to be more practical and stronger.

How It Works:

  • Insert Placement: An operator or a robot inserts a pre-made tool in the mold space.
  • Molding: The plastic resin is injected into the mold under high pressure. It is the thing that covers and fastens the insert so that it is protected.
  • Cooling and Ejection: The plastic is then cooled and solidified in the insert, and the finished part is taken out of the mold.

The key difficulties in insert molding are putting the insert precisely and selecting materials that are well-suited for the task. Besides, the insert can’t get hurt or move out of its place in the molding process. This calls for concerted and meticulous execution of the process.

micro injection molding
Source: Pinterest


Overmolding is similar to insert molding but the layer is normally a plastic over an existing plastic part. This method is ideal for building soft handles of the tool, multicolored products, or parts that have both hard and soft spots.

How It Works:

  • Base Part Creation: The first part is the main part of the item. This can be achieved with the use of traditional injection molding or micro molding.
  • Overmolding: Thereafter, this part is put into another mold. Here, there is a second plastic layer on top of the first one.
  • Cooling and Ejection: When this new layer is cooled down and hardened, the completed product is taken out of the mold.

Selecting materials that stick to each other well is an important issue for overmolding. In addition, the process should be very well managed. This guarantees that the layer underneath is not harmed and that the two layers are tightly bonded together without any gaps.

Micro molding methods provide the opportunity of making parts with high resolution and multi-materials on a very small scale. They provide new tools for design and application for different purposes. The method to be used depends on the part itself, the part size, shape, materials, and intended use.

Benefits of Micro Injection Molding

Precision and Complexity

Micro injection molding is known for making very accurate parts. It can create parts with very small and precise details. Traditional molding methods can’t do this. This high level of accuracy is perfect for making complex parts. These parts are used in areas where detail and precision are very important. Examples include medical devices, tiny electronic components, and precise measuring tools.


Micro molding may be a complex process, but it is surprisingly cheap for the production of thousands of parts. This is a very effective process. It does not require as much raw material and can create intricate parts simultaneously. This results in less money to be spent on each part. And, last but not least, micro molding molds last for a very long time. They can be used for millions of cycle times. This is the reason why micro molding can be considered as a cost-effective alternative instead of other methods in the long run.

Material Efficiency and Sustainability

Micro molding stands out because it uses materials very efficiently. It only uses the exact amount of plastic needed for each part. This approach reduces waste. The process also focuses on using recyclable and eco-friendly plastics. This makes micro molding more sustainable. It fits well with the environmental goals and rules of many sectors.

micro injection molding
Source: Pinterest

Applications of Micro Injection Molding

Medical Devices and Health Care

Micro injection molding is very important in the medical field. It makes parts with great precision. These small, complex parts are crucial for many medical devices. The technology is used to make surgical tools, drug delivery devices, and diagnostic devices. Examples include tiny pumps, inhalers, and lab-on-a-chip devices.

The materials chosen for these parts are safe for the body. They can be sterilized and have the right mechanical qualities. This ensures that patients are safe and the devices work well. For example, liquid silicone rubber (LSR) is often used. It’s safe for the body and stable. It’s used for medical seals, gaskets, and valves.

This molding technique can create extremely precise features. These are vital for tools used in minimally invasive surgery. Such tools give surgeons better control and lessen harm to patients. Also, making smaller parts means devices can be portable. This improves patients’ lives by letting them receive care at home.

In the medical world, there’s a big need for cleanliness and precision. Micro injection molding meets these high standards. This makes it an essential process for manufacturing in the healthcare industry.

Electronics and Microelectronics

In electronics and microelectronics, micro injection molding is key. It makes very precise and small parts. These parts are essential for the working and trustworthiness of electronic gadgets. This includes things like connectors, tiny switches, and sensors. They’re important for smartphones, computers, wearables, and other gadgets we use every day. This molding method allows gadgets to be made smaller and lighter without losing how well they work.

The plastics used in these gadgets are chosen for their excellent electrical qualities. For example, materials like polyetherimide (PEI) or polyphthalamide (PPA) are used. They can handle the heat and chemicals they’re exposed to when the device is used and put together. Micro molding’s accuracy also lets complex shapes and functions be added to a single part. This cuts down on the time needed to assemble them and makes the devices more reliable.

As electronic gadgets get smaller but do more, micro injection molding is crucial. It helps make this progress possible.

micro injection molding
Source: Pinterest

Automotive Components

The automotive industry, in turn, is a great beneficiary of micro injection molding. This technology is an instrument for making small, complicated parts. These parts play a very crucial role in the car’s functioning, safety and how good the car performs. Among them are connectors for the electric system, which are the sensors’ cases, buttons, and switches that people use inside the car, and also the other precise parts that you can find all over the car.

Such components have to be lightweight, strong, and highly accurate. To cater to these requirements, car manufacturers use various plastics and micro molding techniques. This results in a car that is more efficient and dependable.

The plastics employed in automotive is done because they can endure harsh conditions. This involves high heat, chemicals, and frequent exploitation. This ensures that the parts will work well and for a long time. In cars, if one of the parts malfunction, it can lead to a big problem. Additionally, the auto-electronic parts are becoming more sophisticated as the vehicles become more electric and automated. Micro injection molding is ideal for manufacturing these complex parts in a micro size which can easily be fitted in cars.

Through the development of intricate components on a small scale, micro injection molding is fostering the growth of novel concepts in the way automobiles are engineered and manufactured.

Challenges in Micro Injection Molding

Tooling Complexity

Making molds for micromolding is very complex. It needs advanced technology and experts. The high cost and the long time it takes to make these molds can be difficult for some projects. But, the advantages of micro molding often make these initial costs worth it.

Material Flow and Cooling Issues

It’s very important to have consistent material flow and proper cooling in the micro mold. Because the parts are so small and the molds are complex, this can be hard to achieve. It requires a deep understanding of mold design and how to improve the manufacturing process.

Quality Control Challenges

Quality control in successful micro molding is very strict. It often uses advanced microscopes and measuring tools. The small size of the parts means that any tiny defects can be hard to see. This means special quality control steps are needed to make sure every part is up to standard.

Comparing Micro and Conventional Injection Molding

Key Differences

FeatureMicro Injection MoldingConventional Injection Molding
SizeTiny, precise partsLarger, less precise parts
PrecisionHigh, with complex detailsModerate, for simpler shapes
EquipmentSpecialized for precisionStandard, for volume
MaterialsSpecial formulas for microscaleBroader selection
ProcessAdvanced tech for detailStandard methods
FocusDetail and micrometer accuracyEfficiency and volume

Micro injection molding is different from conventional injection molding in several key ways. It focuses on making very small and precise parts, not larger parts. The equipment and methods used are specialized for these tasks. Micro injection molding is made to produce parts that are too small and detailed for traditional injection molding methods.

These parts need to be very accurate, measured in micrometers. They often have complex shapes like micro holes, thin walls, and detailed textures. The whole process needs to be very precise. This means using advanced technology for making the molds and injecting the plastic. Special machines control the injection pressure, speed, and amount of material very carefully.

The machines and tools in micro molding are different from those in traditional molding. They can handle very small amounts of material with high precision. This precision is crucial for both molding the part and choosing the right materials. The materials must flow and harden in the mold correctly without flaws. This might mean using special formulas or picking materials known to work well at this scale for successful molded components.

When to Choose Micro Molding Over Conventional

It is important for you to figure out if you need micro or conventional injection molding for the parts you’re making so that you can weigh the pros and cons of using each or settle for the other. Sometimes the parts need to be very small and it requires meeting the accuracy. So, there is no doubt, that micro molding is the ideal option for them. The human remains itself contains an aspect which is much more detailed than the normal ones. It becomes significant particularly in areas where you find medical devices, electronics, and aerospace. These areas of the system need to be absolutely accurate and to work in an stable manner.

Besides the flexibility created by the micro molding technology, the emergence of new ideas is another result. It is experiencing businesses growth with, for example, the invention of wearable gadgets and microfluidics. In this way it proves the micro molding condition to be indispensable for making very accurate parts.

Molding by micro injection machine has own tools and approaches; this way it delivers the pieces that are smaller than those. Here lays the next step in the evolution of pressing.

Selecting a Micro Injection Molding Partner

What to Look For

Picking the right partner for micro injection molding is very important. It can really affect how well your project turns out. When looking for a partner, it’s not just about what they can do. You should find a company that really understands micro molding. They should know a lot about making molds and the science behind the materials. This knowledge is key to making parts that fit the strict needs of tiny manufacturing.

The best partner will have a strong history of making high-quality micro-molded parts. Their success in overcoming the special challenges of micro molding shows their skill.

It’s also important that they know about your industry. Different fields have their own rules and standards. A partner who knows your area can handle these details, from choosing the right materials to making sure the parts work well. Being able to stick to deadlines and keep up the quality and assurance even when rushed shows they manage projects well. Also, being able to increase production as needed without losing quality or accuracy is what makes a micro molding partner trustworthy.

Evaluating Technical Capabilities and Experience

When looking at potential micro molding partners, it’s very important to carefully check their equipment, mold making methods, and quality control. Having the latest machines and technology shows that a partner is serious about being a leader in micro molding.

One company to think about is ACO Mold. They have been in the business for over 20 years. ACO Mold is known around the world because they have sent custom molds and parts to more than 20 countries. This shows they are reliable and respected.

Their long experience means they can fully support a project from start to finish. They make sure everything is done very precisely and carefully. Choosing a partner like ACO Mold, known for handling complex projects well, can really improve the quality and speed of your micro molding projects.

Read More: List of Top 11 Plastic Injection Molding Companies in the USA

Frequently Asked Questions

What Are the Limitations of Micro Molding?

Micro molding is great for making very precise and complex parts. But, it has some limits. First, you need to spend a lot of money on special machines and making the molds. This can take a lot of time and be expensive. Also, because the parts are so small, there are limits to the designs you can make and the materials you can use.

Even so, technology and materials are getting better all the time. These improvements are making micro molding even more powerful. They are helping us do more with tiny manufacturing than we could before.


Micro injection molding is a major step forward in making things. It lets us make very tiny parts for different industries. These parts are very precise and complicated. This method is great for making parts that are detailed and work well. It mixes accuracy with being cost-effective and using materials wisely.

Looking to the future, we expect improvements in materials, how molds are designed, and how molding is done. These changes will make micro molding even better. For companies looking into making things on a small scale, choosing the right partners and being open to new ideas are important. These steps will help them get the most out of micro molding.

As time goes on, micro injection molding will become even more important in innovation in making things. It shows us that even the tiniest parts can make a big difference.

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