Nano-injection molding: principles, technology, advantages and applications
- Nano-injection molding: principles, technology, advantages and applications
- What is nano-injection molding?
- The Development History of Nano-Injection Molding
- The principle and process of nano-injection molding
- NMT Nanocore Processing Technology Classification
- Advantages of nano-injection molding
- The difference between nano-injection molding and insert injection molding
- Common problems in nano-injection molding process
- Design Guidelines for Nano-Injection Molding
- How do engineering plastics bond with metals in nano-injection molding?
- The Future Prospects of Nano-Injection Molding
- Summarize
Nano-injection molding is an advanced technology that enables assembly without a single screw. In various industries such as mobile phones, home appliances, and automobiles, this NMT (non-metallic metal-plastic) technology, which integrates metal and plastic, makes it possible to lightweight components that are impossible to achieve with traditional techniques. In the future, as nano-injection molding technology matures, it will be applied to more industries, replacing many traditional technologies and bringing more conceptual products to life.
This article will explain the principles, technology types, advantages, and application areas of nano-injection molding. You can gain a comprehensive understanding of this process.
What is nano-injection molding?
The term “nano injection molding” gives a general idea of the process’s principle. However, from a technical perspective, “nano injection molding” is not easy to understand. People who are not familiar with it may mistakenly believe that it is a process of using nano resin or nano-sized resin to injection mold into corresponding plastic products.
In fact, nano-injection molding is a type of injection molding process, but it’s not simply used to mold single plastic products. Nano-injection molding is actually a bonding process, currently most commonly used for bonding metals and plastics. Nano-injection molding usually refers to Nano Molding Technology (NMT), a process that combines metals and plastics using nanotechnology. First, the metal surface is nano-treated, and then plastic is directly injection molded onto the metal surface, allowing the metal and plastic to be integrally formed into a single product. The “nano” here refers to a microporous process, where a specific solution is used to create nanoscale micropores on the metal surface. The main purpose is to improve the bonding strength between the metal and plastic surfaces.
The Development History of Nano-Injection Molding
Nano-injection molding technology was developed by Taisei Plas Co., Ltd. of Japan and commercialized in 2004.
JSR Corporation of Japan developed a coating that allows TPE to be injection molded onto any polymer. JSR then transferred this technology to Taisei Corporation, which further developed a coating capable of bonding TPE to stainless steel. Taisei hopes to develop even more practical technologies to bond a wider range of thermoplastics and metals.
Therefore, Taisei Plus Corporation of Japan developed a plastic thermal fusion bonding technology. This technology requires alternating molding within a mold, where the heat from the second flow of resin melts the previous resin into a single unit. Initially, it involved bonding soft resins together, but later it expanded to bonding hard plastics with soft plastics. They successfully developed a technology for bonding low-hardness elastomers to PC, ABS, acrylic resin, and PBT, which is now widely used in the molding of components such as switches and waterproof seals.
The principle and process of nano-injection molding
The key to nano-injection molding lies in the nano-sizing of metal materials. Nano-sizing is arguably the most crucial step in the entire injection molding process; if this step is not performed correctly, everything else is meaningless. Therefore, its principles and process flow mainly include:
| alkaline washing | Soaking metal workpieces in an alkaline liquid removes grease from their surface. |
| pickling | The acidic solution is used to remove the metal oxide layer and activate it. Then, the larger nanopores of the “coral reef” structure on the surface are treated. At the same time, the acidic solution can neutralize the alkalinity after the alkali treatment, so that the workpiece is in a neutral state. |
| T processing | This is an important step: by immersing the working surface in a T-treatment agent (weakly acidic), smaller nanoscale pores are formed on the metal surface. |
| Clean and dry | Remove excess liquid T by immersing in clean water, ensuring the nanopores are filled with liquid T, and expel any air inside. Then, dry the surface of the metal parts. |
| Injection molding | The workpiece is placed into the mold for injection molding, where the resin and metal form a tight bond, thus completing the injection molding process. |
NMT Nanocore Processing Technology Classification
The main difference in NMT nanoprocessing technology lies in the different methods of pore formation. T-processing is a purely chemical reaction, while E-processing, PMH-processing, and TRI-processing combine chemical and electrochemical reactions . The core of nano-injection molding technology is the treatment of metal materials, known as pretreatment processes or technologies. With continuous development and innovation in technology and processes, several pretreatment techniques for metals are currently available, each with its own advantages and disadvantages.
T-processing technology
The T-treatment is named so because the first letter of the English name of Taisei Plas Co., Ltd. of Japan is “T”. The principle of T-treatment is chemical corrosion. The T-treatment invented by Taisei mainly involves four steps: alkaline washing, acid washing, T-treatment solution, and water washing, as shown in the figure.
E-processing technology
The combination of chemical corrosion and electrochemical technology specifically employs the principles of aluminum alloy anodic oxidation film formation, chemical pore expansion technology, and chemical bonding technology; it is particularly suitable for micro-nano surface treatment and nano-injection molding of aluminum alloy structural parts .
HK processing technology
With superior bonding strength, the HK process is easy to control, ensuring safe and environmentally friendly manufacturing. A variety of plastic options are available, and the metal-plastic composite exhibits stable anodizing properties. Suitable for profile aluminum and die-cast aluminum, with an aging period of over one week. Not suitable for stainless steel and MIM .
TRI processing technology
The mechanism of TRI treatment is a combination of nanoscale physical bonding and chemical reaction chain. The treatment agent used contains triazine thiol. The nanoscale physical bonding is consistent with the principle of T treatment, with the aim of obtaining larger nanopores. After TRI treatment (electrochemical treatment), an oxide film with a thickness of 70-1500nm is formed on the aluminum alloy. That is, small nanopores are created in the large nanopores. The nanopores on the oxide film contain substances such as triazine thiol, which can react with resin and bond with metal. Under high temperature and pressure, a chemical reaction occurs, which makes the resin and metal firmly bonded and produce a high sealing state, with good waterproof performance.
Advantages of nano-injection molding
In summary, the advantage of NMT (Non-Metallic Metallurgy) lies in its ability to combine the texture of a metallic appearance with simplified structural design, allowing for greater design freedom and enabling solutions to many previously impossible applications. It’s important to note that nano-injection molding is only advantageous in certain areas. In traditional applications, conventional methods are still preferable for joining metal and plastic, as nano-injection molding would be too costly. Specifically, its main advantages include:
| Higher freedom in product design | By overcoming many technological limitations, product design ideas become broader, reducing concerns about the future. |
| Simplified process | For example, processes that originally required two or more steps can be completely simplified in a single injection molding process; |
| shortened working hours | Products that previously required extensive secondary CNC machining and a significant amount of processing time can now be completed in a single injection molding process, greatly shortening the production cycle. |
| Higher and stronger mechanical properties | Because the metal and plastic are nested together at the nanoscale, the bonding strength is greatly improved and the mechanical properties are also increased by several levels, enabling many applications that were previously impossible. |
| Cost advantage | The reduction in working hours, simplification of procedures, and decrease in processing difficulty have led to a series of cost reductions, thereby enhancing the competitiveness of the products. |
| Product Appearance Advantages | Nano-injection molding can achieve both a metallic appearance and a more robust structural component. |
| Product Structure Advantages | It can simplify the design of product components, making the product lighter, thinner, shorter, and smaller. |
| Environmental advantages | Because NMT is a safe and recyclable technology with minimal environmental impact. |
The difference between nano-injection molding and insert injection molding
When discussing nano-injection molding, one must mention another similar but already mature insert injection molding process. Insert injection molding refers to a molding method in which pre-prepared inserts of dissimilar materials are placed into a mold, followed by resin injection. The molten material bonds and solidifies with the insert to create a one-piece product. If nano-injection molding is divided into three stages—pretreatment, injection molding, and post-treatment—the injection molding stage is essentially insert injection molding. However, traditional insert injection molding typically uses smaller inserts; the plastic part is the main component, and the insert only forms a localized structural feature on it. Because the plastic raw materials used in nano-injection molding are relatively expensive, hot runner systems are often used to save on runner costs and achieve better filling effects. An extended process is secondary injection molding, also known as overmolding, such as soft plastic overlaying hard plastic.
Common problems in nano-injection molding process
In the production and processing of nano-injection molding, several problems can easily arise if the technology and materials are not handled properly. Common issues include poor adhesion between the plastic and metal, peeling off of the plastic body after CNC machining, cracks in the plastic, and the whitening of black plastic after anodizing. When these problems occur, it is necessary to carefully analyze their causes and find targeted solutions and measures to avoid cost waste and various losses.
Design Guidelines for Nano-Injection Molding
The mold needs to adopt a hot runner design, and attention should be paid to the design of the injection point, runner, and thickness of the glue area, as well as the rationality and standardization of cold material and venting;
Nanomolding allows for appropriate increases in plastic thickness based on structural strength, and nanoplastics are less prone to shrinkage.
When designing the hook and the groove for removing glue, it is necessary to make a radius (R). The diameter of the radius directly affects the diameter of the tool used in CNC milling, which in turn affects the CNC milling time. The coarser the tool, the faster the milling.
When designing the ribs, you can follow the structural methods of ordinary plastics, which can reduce the amount of material used.
How do engineering plastics bond with metals in nano-injection molding?
Today, nano-injection molding can bond a variety of metals, including aluminum, magnesium, copper, stainless steel, titanium, iron, and brass. Available resins include PBT, PPS (such as FORTRON®), nylon-6, and nylon-66. Because the linear coefficients of thermal expansion of metals and resins differ, glass fibers and fillers are added to the resin to match the plastic’s thermal expansion rate with that of the metal, thus preventing peeling or damage to the bonded interface. This bonding method is neither adhesive bonding nor chemical bonding, but rather a physical fusion. Nano-injection molding machines have slightly smaller and more precise barrels than traditional machines.
Therefore, in actual production, after nano-treatment of the metal surface, nanoplastics are typically injected into the treated aluminum alloy to fill the tiny pits in the alloy, forming a tightly bonded structure with high adhesive strength and effective resistance to the penetration of liquids and gases. If you observe this under an electron microscope, you will find that the treated metal surface not only retains its metallic texture but also simplifies product design, making products lighter, thinner, shorter, and smaller. Compared to CNC machining, nano-injection molding offers greater cost-effectiveness.
The Future Prospects of Nano-Injection Molding
Nano-injection molding technology is a process that combines metal and plastic using nanotechnology. It eliminates the need for drilling holes in metal, satisfying aesthetic requirements while maintaining mechanical properties. Furthermore, NMT (nano-molding technology) simplifies and shortens the manufacturing process, bonding materials like magnesium alloys without adhesives, reducing unnecessary surface treatments. In addition, this technology is recyclable, safe, and has minimal environmental impact. Therefore, with the booming global electronics market, the nano-injection molding industry is also developing rapidly. In China, nano-injection molding went from commercialization to widespread use in less than five years. It’s conceivable that in the next few years, this advanced technology, which enables assembly without a single screw, will gradually expand from mobile phone applications to fields such as automobiles and home appliances. Currently, nano-injection molding is gradually becoming a popular choice in the manufacturing industry. Industry leaders such as Foxconn, BYD, and Rilong Mould are investing heavily in NMT research, highlighting its importance.
Summarize
By reading this article, you can learn everything about nano-injection molding. Although it was first applied in the mobile phone manufacturing industry, nano-injection molding is a process that combines metal and plastic using nanotechnology. It not only maintains the metallic appearance and texture but also simplifies the design of product components, making products lighter, thinner, shorter, and smaller. It is believed that in the near future, it will be applied to a wider range of industries and applications.
If you have a need for manufacturing plastic parts, please contact Elimold, a professional injection molding service provider. With extensive experience and a fully equipped factory, we can meet your needs from product analysis and mold design and manufacturing to high-volume production of plastic products. Contact us now for a free quote.