Do you work with living hinges? If you’re in the consumer products space, it's likely that’s a “yes.” A living hinge is simply a one-piece hinge—just a thin, flexible piece made from the same material as the rigid components it connects. Living hinges are found in plastic packaging, dispensing caps, thermoformed clam shell packaging and more. Manufacturing guidelines are easy to obtain for a variety of use cases.
Living Hinge Prototypes
Prototyping living hinges typically prove to be much more complex than the simple nature of their deign. There are plenty of traditional approaches—you probably have your own—ranging from using industrial tape to bonding sheets of polypropylene to act as a living hinge insert. Building a hinge that closely mimics the real molded part is challenging and often labor-intensive.
This is where 3D printing can help. It is possible to 3D print parts with living hinges already in the design but you have to use the right materials and techniques.
The Right Printers for the Job
To be clear though, not every 3D printer is suited for functional prototyping of living hinges. So let’s look at a few printer/material combos that work well:
PolyJet Lowest Cost: Objet30 Pro/Prime Using Rigur (RGD450) Material
The Rigur (RGD450) material is available on the Stratasys Objet 30 Pro/Prime and higher 3D printers with PolyJet technology. With Rigur (RGD450), a simulated polypropylene material, you’re getting good durability for living hinges and snap-fit components.PolyJet Highest Performance: Stratasys Connex3 Using Rigur + Agilus30 Black Digital Materials
On Stratasys PolyJet printers using multi-material jetting technology, Agilus30 Black (Shore 30A Rubber-like) can be mixed with rigid materials to create a blend called a Digital Material. Mixing Agilus30 Black + Rigur (RGD450) results in superior living hinge performance, plus the ability to have parts with rubber over-molding, transparency or other effects (depending on specific printer capability).
FDM Lowest Cost: MakerBot Method Using Tough PLA
Using MakerBot’s Tough PLA on the MakerBot Method allows for producing living hinges that are able to withstand many flexing cycles before failure. Please check out this existing blog post that talks about the process and settings used to produce living hinges using MakerBot Tough PLA.
FDM High Performance: Fortus Using Nylon-12 Material
While not as robust as using an Agilus30 material blend on the PolyJet prints, this solution is still very useful and is the best FDM-based solution. Running Nylon12 requires a Fortus 380mc/450mc (or the Legacy Fortus 360mc/400mc), and results in a well-performing hinge using a single material. This solution requires more focus on the design of the hinge and is what we will focus on in this post.
The part shown in the image was printed on the Stratasys Fortus 450mc (a commercial high-performance FDM 3D printer) using the Nylon12 material. It was designed in SOLIDWORKS and the native ‘.SLDPRT’ files were opened directly in GrabCAD Print to be set up for printing to the Fortus 450mc.
The Nylon12 parts result in a great performing hinge that allows for many bends before failure and prove to be a very close match to the final part look and feel.
One of the biggest advantages of using 3D printing for prototyping is the ease of testing multiple design iterations! In fact, you could easily print two or more variations of a design at once and choose the best after functional testing.
Tips for Best Living Hinge Prototype Results
At TriMech, we regularly print sample benchmarks for all sorts of applications. We applied our expertise here to give a few simple guidelines for getting the best result.
- Hinge design: The basics from traditional living hinge design apply even with 3D printed parts. Use a generous radius at the bottom of the hinge and a tight recess at the top to enable easy folding-over and prevent excess stress during folding.
- Hinge thickness: Hinges work best when a maximum of 2 contours are used to print the majority of the hinge. Using default Nylon12 settings this means the thinnest part of the hinge should be (007” Slice – Hinge thickness of .026”, .010” Slice – Hinge thickness of .040”, .013” Slice – Hinge thickness of .046”.
- Choose the right build orientation: FDM printers tend to have parts with more strength in the horizontal build plane; however, we are actually breaking that run with living hinges. We want a part to flex only on contours – not in areas with rasters.
- Choose the right material: The Nylon12 material we used is ideal for applications that demand high fatigue endurance, flexibility in thin cross sections, and high impact strength – all attributes needed for repetitive snap fits and living hinges.
With 3D printing using Stratasys Fortus 3D printers with high-performance materials, design proofs and verification that can be tested and in your hands within hours. This means that design faults can be found early and fixed long before investing in full-scale production, reducing time to market, reducing development costs, and improving innovation.
Do you have more questions on designing for 3D printing applications? Reach out to us!