Time to read: 5 min
If you’ve worked with consumer electronics, you’ll have come across living hinges. They are found in a wide variety of components – clamshell packaging, attached bottle caps, and electronic cases, just to name a few.
They are low cost, easy to manufacture, and have little wear or friction involved in operation — understandably a popular choice! The idea is about as simple as you can get: a thin, flexible section of the same material used to build connecting parts of your product. But while the idea is simple, the execution can be more complicated.
让我们看一下一些最重要的设计，过程和物质注意事项，以帮助您开始。
Dimensions and Design
Since its introduction in the 1960s, the actual dimensions in living hinge design have changed very little.图。1shows the standard polypropylene design used for injection molding.
6 Living Hinge Design Best Practices
1. Add Generous Radii
宽敞的半径在成型过程中改善了通过铰链的流动，并在使用过程中降低应力浓度。
2.包括“肩膀”
‘Shoulders’ on the part creates a flat recess. This both serves to make sure the hinge will bend in the center and that the part can deform enough for the hinge to have room to close.
3. Thin and Flexible is Best
A thicker hinge may appear more robust, but the greater elongation on the surface can cause the material to exceed its yield point, shortening the lifespan of the hinge. A thinner hinge is more flexible.
4. Divide Long Hinges
Hinges longer than 6 inches should be designed in two or more parts to improve hinge life.
5. Experiment with Thickness
The thickness of the hinge will change how stiff or sloppy the hinge feels to operate. You may have to experiment with more than one thickness to find what best fits your design.
6.方向影响力量
塑料分子的方向高度影响关节的强度和铰链强度。长塑料分子应尽可能垂直于铰链。如果您的设计需要，则可以以平行方向制作可行的铰链（例如，例如挤压），但您不会最大程度地发挥材料的强度。
While it’s helpful to use the typical polypropylene design as a starting point, make sure to tailor this foundational design to your product’s specific needs.
Production Methods
Living hinges can be created in final production parts through injection molding and extrusion, with injection molding as the strongest method. For prototyping, 3D printing or urethane casting are both great options.
我们将研究每种生产方法，并涵盖每个生产方法的最佳材料选项和重要的设计注意事项。
For quick-turn prototypes (3D printed parts in 24 hours), you can simply upload your files below for instant quotes in 3D printing and urethane casting.
用于注塑成型的铰链设计
Injection molding is the strongest way to build living hinges and great for production parts.
Best Material Option
Due to its toughness and ductility,polypropyleneis the best material choice and a well designed, injection molded PP hinge can have an almost infinite service life reaching several million flexes.
聚乙烯is the second most common living hinge material with similar properties to polypropylene.
Design Tips
One of the most important design rules in injection molding is to maintain uniform wall thickness. In uneven walls, the different rates of contraction during cooling can cause residual stresses, warping and even breaking in your design.
However, when designing a living hinge you actually need to do the opposite by creating non-uniform walls, because for the hinge to be flexible it needs to be much thinner than the connecting rigid part.
Potential issues can be reduced or resolved entirely if you think carefully about where the gates in the mold will be placed. The full method for optimal gate placement can be found in the麻省理工学院设计生活铰链指南.
请注意，在成型后立即将铰链弯曲几次。这将使塑料绘制，从而大大提高其使用寿命。简化工具修改的交易技巧是从铰链上方的平坦部分开始，其深度至少为.015英寸，铰链厚度为.006英寸”。
Living Hinge Design for Urethane Casting
聚氨酯铸造是一个很好的选择bridging the gap between prototype and production.
Best Material Option
尿电烷树脂是一个巨大的家庭，有数百种不同的物业。不同国家和州的制造商手头上有不同的树脂，其中包括类似于聚丙烯，这是最佳的生活铰链材料。
Within the family of these PP-like materials, there is a tradeoff related to the durometer of the material — you can have rigid parts with a short-lived hinge or a flexible hinge and soft part walls. Some recommended materials are theHapflex ™ 600 series, andBCCplastics BC8160 resin, specifically formulated for living hinge applications.
您的制造商可能有其他合适的树脂，并且应该能够帮助您为设计选择一种。
Design Tips
当您用聚氨酯施放时，流动压力远低于注射成型，因此必须进行权衡。减小的压力意味着树脂的流量较低，因此在仍可生产可靠的零件的同时，铰链不能像薄一样薄。
Because of this, we recommend starting with a thickness slightly thicker than your injection molding design and choose a urethane in the low Shore D range.BJB FD-45是一个很好的起点 - 岸45A，735％的伸长率和可铸造。
As mentioned earlier, high durometer resins will retain part rigidity but give the hinge a limited life, while low durometer resins result in a more flexible hinge and softer part.
Living Hinge Design for 3D Printing
对于具有3D打印的原型铰链，有很多不错的选择，可以测试不同的厚度，位置和形状。所得部分不会像注射模制的部分那样强，但应承受足够的弯曲以正确测试组件。
Best Material Option
When selecting the best 3D printing materials for living hinges, you should look for plastics with good elongation and flexibility.尼龙is a great option, for example.
Another great option is to prototype your part as a multi-material piece with a combination of VeroWhite and Rubber-like. Here’s a resource to help you prepare files forprinting in two materials，如果这对您的表现至关重要，则可以为您提供铰链的功能，而不会牺牲体内的力量和抵抗力。
Design Tips
When creating hinges in 3D parts, build orientation is very important. For the hinge to have maximum strength, the horizontal build plane should be perpendicular to the hinge direction.
当铰链厚度至少是印刷分辨率的两倍时，就会出现最佳结果。鉴于尼龙的分辨率为0.254mm，我们建议以0.5mm的速度从最小厚度开始。
遵循这些说明应确保您的打印在其测试周期中至少有100个弹性。
主要要点
Designing living hinges can seem complicated at first, but once mastered can result in huge cost savings.
如果传统的铰链可能需要多个成型操作，组装操作，增加的零件以及导致磨损的零件之间的摩擦，则可以将铰链铰链制成，并将其包含在您的设计中，仅一项操作，而摩擦却一无所有。
Invest in thoughtful design at the prototyping stage and you’ll save time, effort, and money when ready for higher volume production.
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