Hinges are integral to our daily routines, delivering unparalleled convenience in many situations. From the moment you glance at your front door or the cabinets in your home, it becomes evident how hinges play a crucial role in ensuring the seamless operation of doors.
These ingenious mechanisms work behind the scenes, enabling doors to open and close smoothly, effortlessly fitting into the rhythm of our lives.
Living hinges serve the purpose of connecting doors with their frames, securely holding them in place. Unlike conventional hinges, which are typically made from various materials, such as metals, living hinges take a unique approach. They are made from the same material as the doors and frames, showcasing a seamless integration.
While wooden doors generally don’t incorporate living hinges, you’ll find this ingenious technology employed in many everyday items.
The functioning of numerous objects is improved by these living hinges, which easily blend into the materials themselves. Now, let’s dive deep into the essential details about living hinges and uncover the reasons behind their significance.
What is Living Hinge?
A living hinge differs from a traditional hinge in that it comprises individual components attached to surfaces to allow for stable opening and closing mechanisms.
The material’s hinged portion is purposefully thinner than the connected parts, allowing for flexibility while maintaining overall strength and stability. The seamless transition allows for this continuous flow from the base to the moving part.
Typically, these hinges are designed with precision and efficiency in mind. Injection molding, a common manufacturing method, makes living hinges for everyday products. In contrast, alternative manufacturing techniques may be used.
Although 3D printing has made production more cost-effective, potential trade-offs must be considered, as quality may vary when compared to injection molding methods.
Types of Living Hinge
There are several living hinge designs available, each with a unique set of features, such as:
The flat hinge is one of the most basic and widely used among the various living hinges. It consists of a landing area on each side of the hinge and a thin section designed specifically to serve as the pivotal hinge point.
This useful flat hinge is commonly found in electronics packaging or plastic injection-molded packaging. Notably, it is widely used in power tools and associated accessories, demonstrating its versatility and dependability in everyday applications.
The double hinge has a one-of-a-kind design with two hinges separated by a thin landing material. This innovative design allows the hinge to move beyond the traditional 180 degrees.
Furthermore, the double hinge can accommodate packaging designs that require a gap or space between the two hinged parts. This adaptability makes it ideal for applications requiring extended movement and flexibility while providing optimal functionality and convenience.
Butterfly living hinges, which are commonly used on dispensing caps, provide a good solution for flip-top caps. These hinges’ clever design allows for smooth and effortless opening and closing.
When the hinge reaches a certain angle, it completes the rotation and remains securely in the fully open or closed position. Say goodbye to cap fumbling and hello to the convenience of these butterflies living hinges.
The bi-stable hinge is a step forward from the butterfly hinge design, with supplementary hinges strategically placed behind or on the sides of the primary thin plastic web forming the main hinges.
Although smaller and thicker than the main hinge, these additional hinges act as springs, effectively securing the hinge in either the open or closed position.
The addition of these extra hinges ensures the cap’s stability, both when fully open and when securely closed, giving it the name “bi-stable.”
Bi-stable hinges are used in situations similar to butterfly hinges. They are, however, especially useful when the cap must remain open continuously. For example, keeping the cap from accidentally snapping shut is critical when dispensing corrosive or hazardous cleaning liquids.
Because of their increased stability, bi-stable hinges are an excellent choice for ensuring safety and convenience in critical situations.
Why Are Living Hinges Important?
Here are some compelling reasons to incorporate a living hinge into your product design.
Molded living hinges are extremely durable. Their frictionless operation and lack of intricate parts contribute to less wear and tear, even after many cycles. This makes them an excellent choice for clip-close applications such as enclosure door latches, ensuring long-lasting performance throughout the product’s lifespan.
Living hinges are substantially more cost-effective in mass production than conventional hinges. While custom living hinges may necessitate an initial investment in molds and specialized tooling, the economies of scale realized during mass production easily offset this cost.
Living hinges provide exceptional flexibility, frequently exceeding 180 degrees in standard straight designs. They can be configured to provide 360-degree rotation or to restrict rotation at specific angles as needed.
This increased flexibility is useful in applications where lids such as electrical enclosure door hinges must rotate 180 degrees or more and move completely out of the way.
Unlike traditional metal hinges, which require separate assembly and screw fastening, living hinges integrate seamlessly into the product because they are made of the same material. This eliminates the need for additional assembly steps, resulting in a more efficient manufacturing process.
Living hinges don’t rust because they are made of plastic. They are highly resistant to environmental factors, require no maintenance, and provide long-term performance without degradation and even oiling.
Living hinges are resistant to many chemicals. This makes them ideal for laboratories using boxes, electrical enclosures, and telecom equipment cabinets, where corrosion resistance is critical.
What Are the Processes of Making Hinges?
There are many approaches to making living hinges but injection molding is still the best way to make living hinge. CNC machining and 3D printing are options for prototype live hinge designs.
The Kemal platform provides a fantastic opportunity to connect with top-tier additive and subtractive manufacturers worldwide to go deeper into the world of living hinges and gain valuable insights into your designs.
Engage with experts, get real-time feedback, and expand your knowledge of living hinge production techniques.
Living Hinge Manufacturing Through Injection Molding
Injection molding is the most common and cost-effective technology for mass-producing live hinges. Polypropylene is the most commonly used plastic material with good durability when placed perpendicular to the hinge’s central axis.
To maximize these properties, the injection mold design must direct polymer flow across rather than along the hinge.
While mold design should consider pressure dips and potential issues with mating between product halves, maintaining high melt temperatures and velocities ensures uniform flow.
Furthermore, bending the hinge improves molecular orientation immediately after molding, increasing its strength and longevity.
Living Hinge Manufacturing Through CNC Machining
Living hinges can now be CNC-machined with accuracy because of cutting-edge technical breakthroughs. This method enables polypropylene to be cut to very thin thicknesses as thin as 0.005 inches.
However, due to the lack of the characteristic molecular orientation in injection-molded hinges, CNC-machined hinges may not be as durable as injection-molded equivalents.
In contrast, CNC machining provides significant advantages for quick prototyping.
Living Hinge Manufacturing Through Urethane Casting
Urethane casting is rarely used to make things because it isn’t very strong and can break easily. It works well for developing prototypes before mass production. Low-durometer urethane resins cast a rubber mold, resulting in prototypes that may not withstand heavy use.
Because polyurethane casting flow pressures are lower than injection molding, hinge designs must be significantly thicker to ensure reliable products. Low Shore D urethane resins balance part stiffness and hinge flexibility.
Living Hinge Manufacturing Through 3D Printing
3D printing allows for small batch production and rapid iteration, making design changes simple. 3D printed hinges, like CNC machining, may not be as durable or long-lasting as polypropylene injection-molded hinges.
When designing hinges for 3D-printed items, the horizontal build plane should be perpendicular to the hinge’s direction.
A minimum thickness of at least twice the print resolution is required during testing cycles to ensure acceptable flexing performance.
Living Hinge Manufacturing Through a Laser Cutter
Laser cutting is becoming more and more popular for making hinges in thicker sheet materials like MDF, even though it isn’t a standard way to make living hinges. These hinges are utilized in high-end commercial items such as folders, laptop cases, and notebook covers because they favor aesthetics over endurance.
What Are the Best Practices for Living Hinge Design?
Incorporate Smooth Curves
To ensure optimal performance and longevity of your living hinges, consider incorporating smooth and generous curves in the design. These curved features improve the material flow during molding and reduce stress concentration while the hinge is in use, promoting its overall durability.
Additionally, integrating ‘shoulders’ into the part design creates a flat recess, allowing the hinge to bend precisely at the center and ensuring sufficient deformation for proper closure. This clever addition enhances the hinge’s functionality and contributes to its seamless operation.
Opt for Thin and Flexible
Thinner is often better when it comes to the hinge’s thickness. While a thicker hinge might seem more robust, it can lead to excessive elongation on the surface, pushing the material beyond its yield point and ultimately shortening the hinge’s lifespan.
Opting for a thinner, more flexible hinge offers superior performance and extended usability.
Divide Lengthy Hinges
For lengthy hinges that exceed 6 inches, dividing them into multiple parts is a smart strategy to enhance their overall durability over time. This approach helps distribute stress more effectively, preventing potential weaknesses along the hinge’s length and ensuring a longer-lasting hinge solution.
As you fine-tune your living hinge design, don’t hesitate to experiment with various thicknesses. Finding the ideal balance between stiffness and flexibility is crucial for achieving the desired performance in your specific design application.
You can refine your design by testing different thickness options to achieve the perfect fit for your unique project.
Choice of Material
The choice of resin significantly impacts the efficiency of the living hinge. It should have good flow properties through thin sections in the mold and exhibit resistance to stress cracks when flexed after cooling.
Placing the gate in the middle of the hinge ensures even resin distribution throughout the mold, resulting in consistent formation and optimal cooling of the hinge design. As a result, the living hinges are stronger and more durable. The gate also contributes to the molecular alignment that enhances the hinge life.
Orientation of Plastic Chains
The orientation of plastic chains significantly impacts joint strength and, as a result, hinge durability. When possible, align the long plastic molecules perpendicular to the hinge for maximum strength and performance.
While functional hinges can be made with a parallel orientation, such as in extrusion processes, this alignment may not fully maximize the material’s inherent strength.
By ensuring that the long plastic molecules are perpendicular to the hinge, you will be able to take advantage of the material’s natural properties to create a more robust and durable hinge.
This orientation allows the plastic molecules to distribute stress and pressure more effectively, increasing the hinge’s overall strength and longevity.
What Are the Limitations of Living Hinge
While living hinges offer unique advantages, it’s important to acknowledge their limitations. Conventional hinges are the way to choose if your design focuses on the following features:
Living hinges aren’t known for being strong, so they might not be good for joining big or heavy-weight pieces. While they can be used in certain industrial settings, they are not robust enough to match the capabilities of traditional heavy-duty hinges.
Living hinges are fragile because of their very flexible central part, which can break under unequal or severe stress.
Because of their elasticity and low cost, living hinges, which are frequently made of plastic, are popular. However, remember that plastics frequently have a low melting point, rendering live hinges unsuitable for high-temperature applications. Plastics can become brittle and breakable when exposed to extreme cold, limiting their use in freezing conditions.
It is recommended that live hinges be used primarily in items suitable for moderate temperature conditions to maintain their longevity and efficacy.
This cautious approach will help avoid any problems caused by temperature fluctuations and ensure that the hinges work optimally for the duration of their lifespan.
Limited Material Options
Living hinges’ unique, flexible components are often constructed of plastic materials such as polypropylene or polyethylene. These polymers offer the ideal balance of flexibility and durability for a dependable living hinge.
Though additives can be used to change specific properties of the plastic, it is vital to understand the restrictions in order to avoid any negative effects on the overall performance and efficacy of the hinge.
It is crucial to examine these variables when determining if the proposed use is consistent with the capabilities and limitations of living hinges. If you understand the trade-offs, you may make informed selections when picking the proper hinge type for your design.
Kemal Tooling and Injection Molding Services
Kemal is your one-stop shop for all of your Plastic Injection Molding requirements. Our highly skilled engineering staff, armed with cutting-edge software, is dedicated to creating high-quality products that match your specific requirements.
We take great satisfaction in adhering to industry best practices, assuring the greatest quality in every product we manufacture.
Our competent operators continuously deliver great goods, including a wide selection of hinges, thanks to our competence in modern machining procedures.
Contact us to learn more about the many services and solutions that Kemal provides. We look forward to being your trusted partner in bringing your ideas to life.
The living hinge design enhances product functioning in a new and adaptable way. Living hinges enable manufacturers to develop flexible, robust, and efficient items.
In this article, we’ve covered all sorts of live hinges, from flat to bi-stable, as well as their purposes and benefits. We’ve talked about how important smooth curves, “shoulders,” and proper thickness are for performance.
We also discussed how materials affect hinge durability and thermal stability, which will assist you in selecting the proper material for your application.
CNC machining and 3D printing for rapid prototype and injection molding for large manufacturing, with a focus on process improvement.
Accept the art of live hinge design to transform your product manufacturing method. By leveraging the knowledge and strategies offered in this guide, you can build goods that stand out for their flexibility, durability, and originality, impacting consumers and distinguishing your brand in a competitive market. Living hinges will transform your products!