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Overview of Micro Injection Molding
There is an increasing demand for precise and intricate plastic components in plastic manufacturing. Many product designers and engineers are turning to a groundbreaking technique known as micro injection molding to address this need. Traditional injection molding may not be suitable for producing small plastic parts that measure only a few millimeters in size.
Unlike conventional molding processes, micro molding produces tiny components with delicate features, thin walls, micro-holes, and tight tolerances. This technique enables manufacturers to fulfill the demand for small, precise components while ensuring scalability for high-volume production.
This blog will explore micro molding and examine how it differs from traditional molding processes. We will also discuss its advantages and challenges.
What Is Micro Injection Molding?
Micro molding is a specialized injection molding that focuses on producing extremely small components. The process involves creating a cavity that accurately matches the desired shape of the part. Molds made of micro-structured steel or aluminum are meticulously machined using CNC and EDM techniques, achieving tolerances at the micron or even submicron level. This precision allows for the production of components that weigh less than a gram and have sizes in the range of just a few millimeters.
What Is a Micron?
When working with extremely small components, precision is essential, which is why they are often measured in microns. A micron, also known as a micrometer, is a unit of length equal to one thousandth of a millimeter or one twenty-five thousandth of an inch. For perspective, the average diameter of a human hair is approximately 60 microns. In industries such as telecommunications, optical fibers need to be shaped to a diameter of 500 microns, and in the medical field, surgical plastics must be manufactured with precision levels within just a few microns.
Source: How big is 1 micrometre?
Principles of Micro Molding
To start the micro molding process, factories create a mold with small cavities shaped according to the desired component. In liquid injection molding (LIM), liquid silicone rubber (LSR) is quickly injected into the heated cavity. Inside the cavity, the material undergoes vulcanization and forms the final part. Some micro-molding techniques utilize runners, which are channels that guide the material into the cavities. In contrast, direct gating methods inject material directly into the part, eliminating runners and significantly reducing material waste.
There are three key aspects to consider regarding this technique. Firstly, “micro” refers to the size of the part itself, with an emphasis on small-scale manufacturing. Secondly, “microfeatures” refer to small components within a larger part. While the overall part may be sizable, specific features within it are considered micro-sized. Lastly, “micro tolerance” involves the precision and accuracy needed for part measurements. Micro-molded parts must meet strict injection molding tolerances, even as small as a thousandth of an inch, so that ensuring they adhere to the required needs.
The principle of micro injection molding relies on several factors, including tooling, mold design, and fabrication. Access to top machining capabilities and experienced professionals is crucial for achieving sub-micron tooling precision. Additionally, advanced metrology techniques are used to validate the capabilities of molded parts and automated sub-assemblies.
One important factor influencing the use of micro injection molding is “micro tolerance,” which denotes the narrow margin of error allowed in a part’s measurements. Tolerances can be as precise as 1/100th of an inch, in some instances, as small as 1/1000th of an inch. Conversely, smaller components that do not require such tight tolerances can usually be produced using traditional injection molding methods.
Difference Between Micromolding and Injection Molding
The process of micro molding is similar to traditional injection molding. First, a piece is designed and prototyped, followed by the fabrication of a double-sided mold. Thermoplastic materials are then melted and injected into the mold using a highly pressurized injection tool. Once the plastic cools and hardens, the finished piece is ejected from the mold. While the fundamental steps remain the same, micro molding requires a specialized injection unit to accommodate the small-sized components.
Advantages of Micro Injection Molding
The micro molding technique provides several advantages in precision, machining, and cost. Among the many benefits of this process, here are some significant ones:
Complexity and Precision
This advanced injection molding technique is highly effective in achieving high levels of accuracy and creating intricate geometries. That process allows for the production of extremely small parts with tight tolerances. Advanced machining methods, such as CNC (Computer Numerical Control) and EDM (Electrical Discharge Machining), enable the fabrication of micro-sized cores, cavities, and features with exceptional precision.
This level of precision is crucial in the medical device, electronics, and micro-optics industries, where even minor deviations can significantly affect performance. The technique ensures consistent replication of complex designs, allowing for the production of precise and reliable plastic parts.
Various Material Options
The procedure supports a variety of material selections, including high-performance polymers and engineered thermoplastics. These materials provide excellent chemical resistance, mechanical properties, and thermal stability.
The compatibility of various materials allows for the creation of components tailored to specific applications. Material selection can be optimized for various properties such as biocompatibility, electrical conductivity, and heat resistance. This versatility in material choice ensures that micro-molded parts meet the desired functional requirements.
Efficiency and Cost-Saving
Unlike conventional injection molding, this technique offers significant cost advantages. The tools required are smaller and more affordable, leading to cost savings. For example, the reduced clamping force necessary allows for the use of smaller, less expensive machines. Consequently, the cost of micro-molding can be roughly 40% lower compared to traditional full-scale tooling costs.
Additionally, this technique can integrate multiple steps, such as overmolding or assembly, into a single production cycle. This consolidation of processes boosts efficiency and shortens overall manufacturing time. With optimized micro-molding tooling and automation capabilities, this technology achieves faster cycle times, ultimately improving productivity and cost-effectiveness.
Furthermore, this process greatly reduces production expenses through shorter cycle times. It typically uses micro molds made from aluminum, which allows for faster and more cost-effective machining. The incorporation of compact barrels, fewer mold cavities, and smaller runners further contributes to cost reduction. These factors collectively enhance the overall cost-effectiveness of the micro-molding process. The small size of micro components also enables efficient use of materials, thus minimizing waste.
Challenges in Micro Molding
Tool design for injection molding is one of the most difficult aspects of the process. The double-sided mold made from materials that can withstand high-pressure injection without bending, even after thousands of uses, is crucial for ensuring quality. In micro molding, the challenges of tooling design are even greater. The tolerances for steel must often be within just a few microns, and very few suppliers are capable of meeting this requirement.
Additionally, this can lead to the formation of “parting lines.” A parting line is the thin line of separation on a plastic part where the two sides of the mold meet. In most plastics, this seamless line is typically not an issue since it is only a few microns wide and can often be shaved down. However, in micro molding, parting lines can significantly impact assembly and proper fit.
Gate location, which is the opening in the mold plastic is injected into the cavity, also affects the overall strength and accuracy of the part. Choosing the right location for the gate is critical for ensuring uniform flow and maintaining quality. After the plastic cools, the gate may leave a small piece of plastic known as a vestige, which needs to be trimmed. Finishing and trimming are the gate vestige must be done with caution and precision because accuracy is vital.
Applications of Micro Molding
This procedure is valuable in numerous applications, particularly where size and precision are critical. Its capability to create small, intricate plastic components with exceptional accuracy enables innovative progress in various industries:
Automotive Industry
The importance of this molding technique is clear in automotive manufacturing, where lightweight and compact designs are often required.
Medical Industry
The healthcare sector requires a high level of accuracy in its processes, often relying on complex instruments. This advanced methodology is crucial in the manufacturing of medical devices, which include drug delivery systems, diagnostic tools, catheters, and components for optical and hearing aids.
This technique is especially well-suited for instruments used in minimally invasive surgical procedures, such aortic and neurosurgeries treatments. Additionally, microfluidic systems are becoming increasingly important in medical applications, which is further driving the adoption of this technique within the medical industry.
Electronics Industry
As electronic devices continue to shrink in size, the electronics industry demands higher precision in manufacturing. Micro injection molding offers significant advantages for producing various electronic components. For instance, it is used in producing micro-optics, including laser-based devices, smartphones, lenses, and prisms.
Additionally, micro injection molding is essential for manufacturing microelectronic components such as plugs, connectors, and switches. These components are crucial for applications in computing, communication technology, musical instruments, and other areas of microelectronics.
This micro-molding technique also benefits microelectromechanical systems. There is a growing need for advanced molding methods in manufacturing processes. In particular, research into Biomedical micro-electrical systems and the application of NNext-Generation Sequencing have significantly increased the demand for microelectromechanical systems.
Conclusion
While conventional injection molding has its advantages, it may not be suitable for all applications. This limitation has led to the development of a more accurate and compact solution known as micro injection molding. This process offers numerous advantages and versatile applications, making it essential across various industries and effectively addressing emerging market challenges.
To succeed in micro molding, it is crucial to have precision mold tooling, advanced technologies, and optimized manufacturing processes. Enze, a reliable partner, provides comprehensive injection molding services utilizing cutting-edge technologies to turn your concepts into reality. Our experienced team instills confidence, ensuring that you receive the best manufacturing solutions for your projects.
