What is Micro Injection Molding?
Micro injection molding refers to the production of highly precise plastic components where the molded products typically weigh less than 0.01 grams to several grams. In other words, it encompasses plastic parts that may not be exceptionally small in overall size but exhibit extremely fine details and demanding dimensional accuracy. Such plastic items can be categorized as micro injection molding products.
When compared to standard injection molding, micro injection molding imposes greater demands on both the injection mold and the injection molding machine.
Applications of Micro Injection Molding
Requirements for Injection Molds in Micro Injection Molding
The creation of molds for micro injection molding demands high precision and expertise, given the advanced machining equipment involved and the intricate nature of the molds.
- High-Precision Machining Equipment: Modern machining equipment, such as high-speed milling machines and mirror EDM (Electrical Discharge Machining) machines, offers the necessary precision. However, the successful utilization of these tools requires experienced and responsible mold engineers.
- Challenges in Detailing and Accuracy: Some mold details need to be completed using EDM. A common challenge encountered during this process is the wearing off of the tool radius at sharp corners, which can cause these corners to become less defined and larger than intended. Traditional methods alone might not suffice to guarantee the dimensional accuracy in such scenarios.
- Innovative Solutions for Precision: For instance, in one of the products, an insert structure was used for making the slider to maintain the sharpness of the inner recess’s corners. This kind of innovative solution is often necessary to meet the stringent requirements of micro injection molding.
- Dimensional Inspection of Molds: When inspecting the dimensions of these molds, a projector is preferred over a three-dimensional coordinate detector. The reason for this choice is that the probe fillet of the latter is typically too large to accurately measure the fine features of these molds.
Conclusion: The production of precision injection molds for tiny parts necessitates not only high-precision processing equipment but also highly skilled engineers. Both elements are critical and cannot be substituted. This combination of advanced technology and expert craftsmanship is essential to meet the exacting standards of micro injection molding.
Requirements for Tiny Injection Molded Parts
When it comes to the production of tiny injection molded parts, there are three critical requirements to ensure quality and precision:
Precise Detailing: Precision is key. Every aspect of the original design must be accurately replicated. For instance, if the design specifies clear corners with an arc radius of 0.05mm, it’s crucial that this measurement is met. Deviations, such as an increase to 0.1-0.2mm, can lead to a loss of detail and a blurred appearance in the final product.
Dimensional Accuracy: The standard dimensional accuracy for ordinary injection molded parts is typically within the range of 0.1-0.2mm. However, for small precision parts, this accuracy needs to be less than 0.05mm. Maintaining this level of precision is vital for the functionality and fit of the component.
Weight Accuracy: The accuracy of weight in ordinary injection molding can achieve ±1% of the product’s weight. In precision injection molding, this accuracy tightens to ±0.5%, and for ultra-precision molding, it goes below ±0.3%. This parameter is crucial as it not only reflects the accuracy of the molding process but also indirectly indicates the overall precision of the part.
In some cases, tiny injection molded parts may primarily require precise detailing without as stringent demands for dimensional and weight accuracy. A classic example is the helmets of Lego toys, where the focus is on replicating exact appearance details.
Measuring dimensional accuracy in plastic parts can be challenging due to the material’s elasticity. Typically, pass-and-stop gauges are used for this purpose. On the other hand, weight accuracy is relatively easier and quicker to measure. It’s a useful indicator of the molding process’s precision and is often used as a key testing parameter.
Requirements for Injection Molding Machines
When addressing the requirements for injection molding machines in the realm of micro injection molding, a few key factors come into play, especially depending on the size of the product and the volume of production.
Option 1 一 Adaptation of Standard Machines: For products that are not extremely small, it’s possible to use an ordinary injection molding machine, one that is designed for smaller gram numbers. However, a critical modification is needed: changing the screw to reduce the single injection volume. This is important because if the molten plastic remains in the barrel for an extended period, it can lead to molecular chain breakage, adversely affecting the material’s properties.
Option 2 一 Specialized Machines for Very Light Products: For high-volume production or when the product is exceptionally light, it’s advisable to opt for a dedicated small precision injection molding machine. These specialized machines are designed to handle the nuances of micro injection molding more effectively.
Notable Brands and Machine Specifications: Some of the more well-known brands in this domain include Sodick, Fanuc, and Toyo. These machines typically have a tonnage of only 40 tons or even as low as 15 tons. To put this in perspective, a common injection molding machine with a tonnage of 80 tons is considered relatively small for standard applications.
Advanced Machine Features:
- All Electric mode: Most high-precision injection molding machines use all-electric mode, eliminating the need for a hydraulic system and using a private server system to control movement. This improves accuracy and reduces energy consumption.
- Screw-Plunger Hybrid Structure: This is adopted by some machines to ensure consistent plasticization, crucial for maintaining the quality of the final product.
- PID (Proportional Integral Differential) Temperature Control: This mechanism is vital for maintaining optimal temperatures throughout the injection molding process.
- Screw and Nut Mechanism for Mold Operations: These machines use a screw and nut mechanism for mold opening, closing, and ejection pin ejection. The precision of this mechanism is remarkable, with a transmission accuracy of up to 0.01mm.
- New Type of Force Sensor: This technology is employed to accurately control the injection back pressure, ensuring stable dimensional accuracy of the molded parts.
In summary, the choice of injection molding machine and its specifications play a pivotal role in the successful implementation of micro injection molding, especially when striving for high precision and quality in small-scale production.
Note: Confusion of micro injection molding machine.
On the internet, there’s often confusion between micro injection molding products and micro injection molding machines. However, these two are distinctly different.
Micro injection molding machines typically refer to smaller, simpler injection molding machines that offer a cost-effective solution. These machines usually have basic structures, limited automation, and relatively lower production precision.
As a result, while they’re suitable for manufacturing simple, small-sized products, they’re not designed for extremely small or highly detailed plastic parts. Such limitations make them unsuitable for producing the tiny, intricate components often associated with micro injection molding products.
Precautions to Consider in the Micro Injection Molding Process
The injection molding process for micro plastic products has distinct requirements compared to ordinary plastic products, especially in terms of temperature, pressure, and injection speed.
Temperature: Micro plastic products typically require a higher injection temperature to ensure the material’s fluidity and complete filling of the mold. Precise temperature control is crucial. This includes accurately adjusting the barrel temperature, mold temperature, and hot runner temperature. Such control is necessary to prevent issues like thermal degradation, thermal stress, and thermal deformation.
Pressure: Both injection pressure and holding pressure for micro plastic products are generally higher than those for standard plastic products. This is to overcome the increased resistance and high shrinkage rate in micro mold cavities. High-pressure control is essential, including precise management of the injection pressure’s size, segmentation, and switching points. Proper control helps avoid defects like short shots, flashes, shrinkage cavities, and warpage.
Injection Speed: Micro plastic products are usually injected faster than their regular counterparts to achieve rapid filling and even cooling. Controlling the injection speed is vital, including precise management of its size, segmentation, and switching points. This helps prevent issues like jets, burn marks, flow marks, and welding lines.
In summary, the injection molding parameters for micro plastic products demand high precision, efficiency, and stability. Achieving this requires the use of dedicated precision injection molding machines and specialized micro molds. These tools and techniques are essential for the successful production of high-quality micro plastic components.
Reverse Engineering of Tiny Injection Molded Products
Reverse engineering tiny plastic products presents a unique set of challenges. This process involves creating three-dimensional drawings from physical samples, a task that becomes significantly more complex with small-sized products.
Challenges with Scanning Technology: Typically, scanners are employed for three-dimensional modeling of products. However, when dealing with tiny items, the effectiveness of scanning technology diminishes. The issue lies in the size of the product relative to the distance between adjacent points in the scanner’s point file. For small products, this distance is often too large to generate a clear and detailed 3D file.
Designer Expertise and Additional Tools: To circumvent these limitations, designers must rely heavily on their experience and expertise. This involves manual three-dimensional modeling, supplemented by tools like projectors and vernier calipers, to accurately determine the size of key features.
Practical Example – LEGO Toy Helmets: A practical example of this process can be seen in the reverse engineering of LEGO toy helmets. Our designers utilized their personal experience and collective suggestions for improvement to recreate these helmets. While achieving a 100% accurate replica is challenging, the final design closely resembles the original. This example illustrates the blend of technology, manual skill, and collaborative effort required in the reverse engineering of tiny injection molded products.
In conclusion, micro injection molding demands precision in machinery, mold design, and process control, blending advanced technology with expert craftsmanship to create intricate, high-quality plastic components.