TIPS WITH TONY: 3D Printing Living Hinges

Did you know that living hinges are possible with 3D printing? Here are a few things areas to keep in mind when designing hinge functions so your part’s functionality and integrity remain intact.

We offer two processes for 3D printing thermoplastic or thermoplastic-like materials: selective laser sintering (SLS) and stereolithography (SL). But only SLS will produce parts with the functionality required for a living hinge.

An SLS part with living hinge functionality.

Anytime we see the potential for a living hinge in a 3D-printed part, we will strongly guide you to SLS. SLS uses nylon thermoplastic, primarily PA 850 Black, which is a nylon 11 material. PA 850 has an increased EB of 14-51% followed by ALM PA 650 with an EB of 24%.

However, you can’t take a part that was produced in PA 850 or ALM PA 650 and expect it to function as a living hinge without a secondary process first. When you have a living hinge, we need to know what direction or the range of motion in which the hinge may function. This is critical as we anneal the part by heating it to 250-275°F and flex the hinge in the intended range of motion. This extends the life of the living hinge by stretching the material instead of fracturing the links of resin.

SL offers thermoplastic-like materials, but they are not be recommended for living hinge applications. Somos 9120 is our most flexible material of all SL resins with an elongation at break (EB) of 15-25%.

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WEBINAR: Rapid Manufacturing Methods for Plastic Parts

Tony Holtz, Tech Specialist.

You’re invited to join Proto Labs’ live webinar presentation on rapid manufacturing. The free webinar will be hosted by our technical specialist Tony Holtz and last around 45 minutes with a Q+A to follow.

You’ll hear about the different industrial 3D printing, CNC machining and injection molding processes at Proto Labs, and learn which one is best suited for your next project, based on the project’s material requirements, quantities and lead times.

TITLE: Choosing the Right Rapid Manufacturing Method for Plastic Parts

DATE: Thursday, April 21 at 1 p.m. CDT


Unable to attend? Register anyway and we’ll email you the recording afterward!

3D-Printed Molds vs. Aluminum Tooling

Industrial 3D printing has made a tremendous impact on the manufacturing world. Rapid prototypes are possible within a day, material selection continues to grow stronger and parts with un-manufacturable designs have found their happy place. Recently, some companies have begun using this important technology to produce injection molds.

Molds made with thermoplastics-based 3D printing are kind of like the plastic storage sheds some of us put in our back yards. They’re a little cheaper than metal sheds. They go up quickly and are fine under light loads. Pile too much snow on them, however, and they’ll collapse like a house of cards.

A 3D-printed Digital ABS mold built in an Objet Connex machine.

Still, printed molds have their place, and some shops have had good success with them. Proponents argue that 3D printing produces molds up to 90 percent faster and 70 percent cheaper than using traditional moldmaking processes. And while this may be true in some circumstances, it’s important to understand the pros and cons of printed plastic molds compared to those machined from metal.

Quality is king. 3D printing builds parts in layers. Because of this, printed parts can exhibit a stair-step effect on any angled surface or wall. Printed molds are no different, and require machining or sanding to remove these small, jagged edges. Holes smaller than 0.039 in. (1mm) must be drilled, larger holes reamed or bored, and threaded features tapped or milled. All of these secondary operations eliminate much of the “print-to-press” speed advantage associated with printed molds.

Size matters. Part volumes are limited to 10 cubic inches (164 cm3), roughly the size of a grapefruit. And although modern additive machines have impressive accuracy, they cannot compete with the machining centers and EDM equipment at Proto Labs, which routinely machine mold cavities to +/- 0.003 in. (0.076mm) and part volumes up to approximately 59 cubic inches, about six times larger than parts made with 3D printing.

The heat is on. To make material flow properly, injection molding requires very high temperatures. Aluminum and steel molds are routinely subjected to temperatures 500°F (260°C) or greater, especially when processing high-temperature plastics such as PEEK and PEI (Ultem). Aluminum tools can easily produce many thousands of parts, and can also serve as bridge tooling until a production mold is available. Molds produced with SL and similar 3D printing technologies use either photoreactive or thermoset resin, which is cured by ultraviolet or laser light respectively. These plastic molds, though relatively hard, break down fairly quickly when subjected to the demanding thermal cycles of injection molding. In fact, printed molds typically become ineffective within 100 shots of soft, hot plastic such as polyethylene or styrene, and may produce only a handful of parts from glass-filled polycarbonate and other tough thermoplastics.

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WHITE PAPER: Choosing the Right Material for 3D Printing

We have a saying here at Proto Labs, “Materials Matter.”

To learn more about selecting the right material for 3D printing, download our free white paper.

Indeed, material properties are an especially key piece to consider in the case of industrial 3D printing, or additive manufacturing, which is different from traditional manufacturing methods.

To help you sort through the properties — from tensile strength to yield strength, elongation at break to hardness — we’ve published a comprehensive new white paper, “Selecting the Right Material for 3D Printing.” The paper explores recent improvements and advancements in materials used in 3D printing, and then goes in depth to cover materials that work best for three frequently used technologies: direct metal laser sintering, selective laser sintering and stereolithography.

This new white paper is part of a range of resources in our online library of 3D printing content that includes design tips, case studies, videos and other white papers. We also have a staff of experienced customer service engineers who can discuss design questions that may arise. Find us at or call us at 877-479-3680.


TIPS WITH TONY: Replace Metal with Plastic to Save Weight, Cost

To decrease weight and potentially cost, you can replace metal with plastic on certain parts through 3D printing and injection molding. At Proto Labs, we use industrial 3D printing process stereolithography (SL) to produce thermoplastic-like parts that have a nickel coating on the surface. This offers the increased strength of aluminum die-cast components, without the weight. With injection molding, the introduction of thermally conductive plastics has broken new ground when looking for heat dissipation of expensive heat sinks.

Stereolithography parts built with SLArmor have a metal coating applied over a thermoplastic-like base.

SLArmor involves a ceramic-filled DSM Somos material, which has a metal coating applied to achieve the look, feel and, most importantly, comparable strength of aluminum without added weight. SL is a cost-effective prototyping method for initial parts that mimic metal before moving to higher volumes of die-casted parts.

The material properties of SLArmor are greatly improved in regards to heat deflection, tensile strength, elongation at break and elasticity. The chart below shows exactly how the material relates to die-cast aluminum in three different thicknesses that can be applied based on geometry of SL parts. Note that the thickness of the nickel plating may vary on each part due to the ability to apply the coatings.

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