Brain Climbing Hold

myminifactory

I'm exploring the use of 3D printing to create holds for a climbing wall I'm building. Directly printing holds is possible but not optimal due to several reasons. To be strong enough, most holds would need to be printed from high-strength materials like ABS, nylon, or PET at 100% infill. However, high-strength materials are notoriously difficult to print in large blocks with high infills. Even if the print could be accomplished, it would be extremely time-consuming and very expensive. Climbing walls require a lot of holds, making direct printing one at a time not the best solution. Climbing hold producers cast their holds from resin, typically polyurethane. It's possible to print a master and make a mold from it, but mold rubber is quite expensive and the mold-making process is time-consuming. With a little 3D printed cleverness, this can be avoided. It's easier to turn the master into a mold digitally and then print the mold in a flexible material like Ninjaflex. However, its stretchy and flexy characteristics make it difficult to print reliably. Additionally, it's proprietary and quite expensive. TPU filament is slightly stiffer, making it much easier to print, and it's available from multiple suppliers, making it much cheaper. The socket in the middle of the mold forms the countersink for the mounting bolt. The socket holds a stub of 3/8" round rod that forms the bolt hole. While it's possible to print this part of the mold, in practice, it doesn't work well due to the 3/8" round rod tearing off on the first cast. The example shown is based on a model of a human brain made from a medical scan and somewhat simplified to make a usable mold. The photo shows a hold cast in high-strength fiber-reinforced industrial grout, which is very inexpensive and works great for large holds where its lack of tensile strength isn't an issue. Smaller holds and designs where part of the hold must resist tension are better cast in polyurethane resin like Alumilite RC-3. RC-3 sets so quickly that you can mix, pour, and unmold a cast every 10-15 minutes. For comparison, printing this hold at 100% infill would take 48 hours if it could be done at all. We discussed this topic and more on the 3D Printing Today podcast available on iTunes or Stitcher Radio; learn more at http://www.threedprintingtoday.com/.