Gearpods – EPICS

Students

Leonard Merkin

Matthew Kolodzik

Project Description

This impulse behind this project came from two things we love most: Music and Wrestling. Our project goal was to combine a wrestling headgear with Apple Airpods so that athletes can listen to their own music during practice and warm up. To do this, we aimed to place the Airpods in an encasement which could fit safely and securely inside of the headgear. The case needed to be non-intrusive, easily accessible, and sound amplifying. Plastic was the initial candidate; however, plastic is difficult to secure to the headgear shell, which has no flat surfaces for mounting. Additionally, had plastic was potentially hazardous due to its proximity to the ear. We considered a softer, more elastic material and came to two equally viable candidates: Silicone and the 3D Printing filament Thermoplastic Polyurethane (TPU), often referred to by its trade name, ‘Ninjaflex’. Lastly, we considered creating an injection molded silicone “sleeve” around the Airpods, however, designing and manufacturing with silicone proved slow, unwieldy, and unfavorable to modifications. TPU is extremely favorable in comparison to silicone injection molding. Its elasticity allows for easy adhesion to the inside of the headgear. This flexibility eliminates the need to secure the case via wire tethers or toleranced buttonholes, as was originally brainstormed. Most importantly, by using adhesive at the base of the flexible encasement, no design modifications are necessary for various brands of headgear and placement can be customized to the athlete’s preference. Ninjaflex proved to be perfectly suited to prototyping and fabrication, and we are extremely pleased with our final product.

Technical Background

3D printing starts with a digital design created on a computational CAD software. After modeling, a different software slices the object into thin layers which enables the printer to understand and interact with the object. 3D printing allows for rapid prototyping and material testing of 3D printable materials. One such material is Thermoplastic Polyurethane, or TPU, a 3D printing extrusion material that is both elastic and durable. Often referred to by its trade name, ‘Ninjaflex’, TPU is incredibly apt to rapid prototyping flexible products like phone cases and other impact resistant encasements. Unfortunately, there is a learning curve associated with printing flexible filament. Normally, 3D printers heat up and extrude hard plastic like PLA or ABS onto a print bed, which is also maintained at a high temperature. TPU requires an even higher extrusion temperature than both these plastics, and a low print bed temperature to ensure proper layer adhesion. Furthermore, an extremely low extrusion speed is used in keep filament from bunching up or clogging the extruder. Navigating these parameters requires lots of trial and error, as print profiles vary from machine to machine, however, once these parameters are discovered for any particular machine, TPU provides a wonderful, and flexible product.

Silicone molding was another method used to produce impact resistant cases and molds. Silicone usually comes in LSR (liquid) or HCR (pliable rubber) form. Like 3D Printing, both halves of a silicone mold are created in CAD software. When making a mold, it is important to pay close attention to how it will be removed after it has set. Improper decision making may lead to destruction of the part. The best method for HCR silicone is usually to slice it long ways in two halves, but this is not always possible. The mold may need to be played with until a suitable orientation and slicing is found. These techniques are good for prototypes; however, injection molding is usually done with LSR silicone. While Silicone Molding does not favor itself to rapid prototyping; it’s an incredibly efficient means of producing final products in large quantities.

No references “What Is 3D Printing? How Does a 3D Printer Work? Learn 3D Printing.” 3D Printing. Accessed March 14, 2019. https://3dprinting.com/what-is-3d-printing/#How-Does-3D-Printing-Work.

“Silicone Micro Molding, Manufacturing & Production | Albright Technologies.” Albright Technologies | Silicone Molding, Medical Silicone Prototyping, Injection Molding & More. Accessed March 14, 2019. https://albrightsilicone.com/silicone-micro-molding

Design Drawings

Fabrication Process

A wrestling headgear has three main components: A rigid plastic shell over the ear, a foam covering for the shell, and straps which secure the right shell to the left shell. We began by considering placement of the Airpods inside the headgear, as this would determine the overall geometry and shape of the attachment. After modeling the headgear shell and Airpods in CREO, a CAD software used universally by engineers, we started to brainstorm the best placement for the attachment. Given the tight space between the headgear shell and the athlete’s ears, we opted to place the Airpod as far away from the ear as possible. We created a rough encasement by hand using putty like Silicone, then modeled our first prototype in CREO. We 3D printed a mold for this model, as well as copies of the Airpods themselves. With these we expected to make a silicone injection mold, however this proved more laborious and time consuming than we initially thought.

Mold making in CREO is a lengthy and tedious process because it requires three additional steps to the fabrication process. Instead of simply modeling a part in CREO, and 3D printing that part, one must also model, and 3D print the negative and Positive molds of the part, in addition to a model of the part itself. The part model is then sandwiched in between the negative and positive halves of the mold, then silicone is injected into holes between the two halves. Once completed, the final product is a ‘sleeve’ of silicone around the part. After grappling with the difficulties of this process over several design iterations, we opted to split our efforts to search for more efficient fabrication techniques, namely, Ninjaflex 3D print filament. This was a gamble because 3D printing with Ninjaflex could turn out to be just as time consuming as silicone injection molding if the 3D printer is not suited to print with this flexible filament.

While half of the team continued to work on Injection molding, the other half worked on using the available printers to reliably print prototypes using Ninjaflex. Initially, we turned to the Makerbot Replicator and Makerbot Replicator Z-18 XL printers, both of which are well known and reliable printers. However, every attempt to print using Ninjaflex yielded poor results. After successfully laying down one or two layers of Ninjaflex, both printers would unpredictably extrude in droplets instead of a smooth and consistent flow. Furthermore, the printer filament would begin to bunch up as it was fed into the extruder, causing the Ninjaflex fillment to loop around the print head before it even had a chance to heat up and extrude. On our third and final printer, a CraftBot 2, we were able to obtain a reliable print. We discovered that once this printer accepted Ninjaflex filament, the key to reliable and clean prints lay in the extrusion settings for the printer. The three most important settings are extrusion speed, extrusion temperature, and print bed temperature. The first keeps the filament from bunching up and looping around the filament head by pushing it into the nozzle at very slow speeds. While regular PLA or ABS extrudes at 50 – 55 mm/ second, Ninjaflex prints at only 25-30 mm/sec. Extrusion temperature melts the filament at the desired rate, in this case about 250 degrees compared with 185 – 205 degrees for PLA. Print bed temperature ensures secure adhesion onto the print bed and all subsequent layers of the print. Ninjaflex requires the print bed to be at 50 Degrees Celsius while PLA and ABS are usually upwards of 70 degrees Celsius. Once we achieved clean and functioning prints of our designs, rapid prototyping was quick and easy. Ultimately, we arrived at a final model, and we couldn’t be happier with the result.

Students

Project Description

Technical Background

Design Drawings

Fabrication Process

Final Result