The Urethane Blog

3D Printed Climbing Hold Molds

Feb 6, 2016 | By Benedict

Instructables user Whitney Potter has published a tutorial for making customized climbing holds with a 3D printer. Following Potter’s method, makers can print their own molds in thermoplastic polyurethane (TPU) before filling them with polyurethane resin to create the finished hold.

Climbing is a great way to exercise whilst having fun. Kids and adults alike can experience the thrill of climbing, be it on natural rock faces, at designated gym climbing walls, or—with the help of 3D printing—in their own back yard. For those who enjoy the rocky ascent but who do not live close to climbing facilities, a homemade climbing wall can provide hours of fun and contribute to a healthy lifestyle. What’s more, with Potter’s Instructables guide, wannabe climbers can create their own unique climbing holds with the help of a 3D printer and a handful of easy-to-source materials.

Over the past few weeks, Potter’s DIY projects have shown up on our 3D printing radar at an impressive frequency. Demonstrating his abilities across a range of applications, the builder recently published an Instructables guide for building an Arduino-powered desktop 3D scanner for just $50. Now, the Instructables Renaissance man has channeled his technical expertise into a project for his kids (mostly). Wanting to build those kids (and himself) a fun and unique climbing wall, Potter was never going to use store-bought equipment. However, determining the best method of construction caused the DIY expert some head-scratching.

Potter’s initial plan was to 3D print a set of climbing holds, but that idea was soon ruled out. “3D printed parts can be weak, especially when stressed across the layer lines,” the maker explains. “They can be made stronger by making them denser up to the point that they are 100% solid, but this adds dramatically to the cost and print time. A fist sized climbing hold printed at 100% infill would take between 12 and 24 hours to print.”

This minor obstacle did not deter the determined Potter. With a clear goal in mind and a perfectly good 3D printer to hand, the maker simply had to adjust his footing and reach in a different direction. After conducting a bit of research into professional methods of climbing hold manufacturing, Potter learned that holds are typically made from polyurethane resin, cast in a silicone rubber mold, itself shaped by a hand-carved or CNC-milled master.

Potter considered 3D printing a master, but realized he could simply skip this step and 3D print the mold in thermoplastic polyurethane (TPU), an extremely flexible 3D printing filament. Although less durable and easy-to-use than silicone, the TPU mold offers several advantages: “In a couple of hours I can print a mold that will produce dozens of copies of a hold,” Potter explains. “The cost of the TPU mold is maybe a dollar which is much better than $10-$20 for a silicone mold.”

The design process for the hold mold will be familiar to all makers. Potter recommends using Meshmixer, Blender, or dedicated sculpting program 3dCoat to create a 3D design for each hold. Once the design is complete—and there are no creative restrictions here!—some boolean handiwork is needed to shell out the solid 3D shape. Add a small socket for the bolt head and the 3D mold is ready for the 3D printer.

Regarding 3D printer settings, Potter says: “Print as few shells and as little infill as you can while still having a decent print as this will make it easier to unmold. All of my molds leak a little, but that's okay. The resin seeps into the mold and seals it the first time you use it.”

Although the holds can be cast in high-strength industrial grout, which looks and feels like real stone, the pro option is polyurethane resin. This can be purchased in a two-part formula, which begins to set a minute after the two parts are mixed. To stop the resin sticking to the mold, a quick spray of urethane mold release applied before casting will do the trick—Potter recommends the imaginatively titled “Stoner” brand. With gloves on hands, the resin can be poured into the mold, then easily removed thanks to the mold release spray. After a little sanding, the holds will be ready for use.

There you have it: Your very own set of climbing holds, fully customized and cheaper than readymade alternatives, made with the help of your 3D printer. Get ready to scale some heights!