3D Printing

Your guide to additive post-processing inserts

By November 23, 2022
Gold inserts

By Genevieve Lee, Senior Additive Manufacturing Engineer

Many 3D printed parts aren’t 100% ready straight out of the printer, which is where additive post-processing comes in. Post-processing techniques like sanding and smoothing can improve the look and feel of your part, but other post-processing techniques such as the application of metal inserts, enhance its mechanical properties or geometric accuracy. In some cases, post-processing inserts may need to be added to ensure that a part functions as intended, meets its design specifications, and is ready for customer use.

Additive post-processing inserts serve different purposes, including allowing for printed parts to be fastened to other components, eliminating the need for rivets or adhesives, and helping to streamline the manufacturing process. Since metal is more durable than plastic, certain inserts can even increase part durability, meaning that 3D printed plastic products can be repeatedly assembled and disassembled without damage.

Three are three general types of additive post-processing inserts available: press-fit inserts, heat-staked inserts, and Helicoil inserts. Each insert type is better suited to different 3D printing processes and use-cases: with that in mind, we’re here to help you understand which is the right fit for your project.

Additive post-processing inserts

Press-fit inserts

Press-fit is the most common additive post-processing insert type, and is best suited to Carbon Digital Light Synthesis (DLS), HP Multi Jet Fusion (MJF), and stereolithography (SLA) parts. While tapping a part or integrating threads into its design may be an option for 3D-printing projects, plastic threads will wear or break down relatively quickly compared to metal press-fit insert threads. With that issue in mind, press-fit inserts are often used in cases that require high load-carrying capabilities and durability, such as 3D-printed plastic housings, casings, consumer electronics, and other parts that need to accept screws for assembly.

To use a press-fit insert, you’ll need to design your part with a hole, or drill one after the print is complete. Adding the insert will be relatively easy once you have your hole: press-fit inserts are tapered, so they will self-align as they are pressed in. Instead of tapping the hole or melting the plastic before installing an insert into a 3D-printed part, you can simply use a hammer or arbor press to set it into place. Since press-fit inserts often have knurled outer surfaces, they will stay in place once inserted.

Heat staked inserts

It’s also possible to use heat-staked inserts with additive parts. Best suited for MJF and FDM printing projects, heat staking involves heating the insert to melt the plastic, and pushing it into place as it cools. Raising and cooling the temperature of 3D plastic components will enable the material to re-form around the insert, creating a strong bond with the printed part. You’ll need to pay attention to how much heat and pressure you apply when installing heat-staked inserts in order to achieve the best results. 

Heat staking not only reduces a part’s complexity by eliminating the need for CAD thread design or rivets, but increases its durability and improves cosmetic appearance. Threaded inserts that have been heat-staked (rather than 3D printed or tapped) will also have greater pull-out strength and be able to better resist stripping, pull-out loads, and torque-out loads. As a result, using heat staking to fix metal inserts and fasteners into 3D printed parts is a common practice in many industries, including the automotive, telecom, and appliance industries, and the process is used on everything from electronic enclosures to appliance dials.

Helicoil inserts

Helicoil inserts are traditionally used in metal parts but can also be used in FDM 3D prints, regardless of whether a part has a 3D printed thread or a traditionally drilled and tapped hole. Also known as helical inserts and screw thread inserts (STI), Helicoil inserts are coiled wire inserts with coils that are wider than the hole into which they are inserted. To install a Helicoil insert, you’ll need to drill and tap, or 3D print, a threaded hole, before screwing the insert onto an installation tool and installing it. The coil will then expand, forming a tight seal against the existing threads.

There are several types of Helicoil inserts available. Stanley Engineering, for example, offers HeliCoil threaded wire inserts that provide internal threads for standard-sized fasteners and screw locking wire inserts that offer permanent conventional screw threads. Stanley Engineering also produces free-running wire inserts with threads that can be used from both ends, and tangless threaded inserts that are wear-resistant and eliminate the need for tang retrieval.

Metal Helicoil inserts are strong, durable, and resistant to heat. They also prevent threaded holes from wearing out, and so can lengthen a 3D printed part’s lifespan. Helicoil inserts are commonly used in the aerospace, defense, automotive, medical, and telecom industries.

Creating strong, durable parts with Fast Radius

Press-fit inserts, heat-staked inserts, and Helicoil inserts offer everything from increased part durability to the possibility of a more streamlined manufacturing process. However, since each insert type is best suited to different project requirements, incorrect installation can damage plastic parts and end up increasing production times and costs. Given the importance of inserts to certain projects, and their associated challenges, it makes sense to work with an experienced manufacturer like Fast Radius to ensure that you select the right insert for your needs. 

When you work with Fast Radius, you won’t need to be a manufacturing expert to add inserts to your 3D-printed parts, or to navigate any aspect of production. Our team of experts will guide you through the manufacturing process, helping you refine your designs to ensure that your parts are optimized for quality and cost at every stage, and meet your expectations on completion. It’s easy to get your project started: simply create an account and upload your design, and we’ll generate an instant quote for your parts. Prior to generating a quote, you’ll be able to adjust part materials and manufacturing methods, and run automated design for manufacturing (DFM) checks to identify issues with your part. To learn more about post-processing inserts, or any of our manufacturing services, contact us today

Visit our resource center to learn about what to expect during the additive manufacturing process, manufacturing design tips, and more.


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