Making the Case for Rapid Manufacturing

The promise of mass customization – specifically, of a world filled with perfect-fitting, custom fabricated, low-environmental impact parts created on a per-user basis – excites the imagination of those technology-minded designers and visionaries privy to an inside view of rapid prototyping technologies. Beyond prototyping, this technology is potentially suited for rapid manufacturing. While mass manufacturing means a limited number of types and sizes of any given object, rapid manufacturing means that objects can be specifically tailored to the tasks—even to the extent of making products for specific users.

Consider, for example, a fireman’s back-mounted pack. It exemplifies the need for optimal design. The human factors demands are extreme: the heavy pack must fit the body perfectly and distribute the weight evenly in order to minimize the feeling of bulk and mass. The current backpack typifies the ‘one size fits all, adjust to individual fit’ resulting from traditional manufacturing. Taking this to the next step in performance necessitates a fundamentally new approach to the design process. It requires a process where the body of the individual firefighter is actually designed into the pack itself from the first stage in the process.

The backpack I developed has a slipstream design that fits tightly against the firefighter’s back. Additionally, articulated plates of “armor” extend down the arms to protect from falling objects. A dry-chem nozzle is located at the wrist to spray out spot fires. All of this is predicated on a specific body shape. Consequently, where as in the traditional design process the user is taken into account at the last stage of the process, the rapid manufacturing approach actually puts the body of the user at the very first stage, and builds from that point forward.

Developing the model

During the development of the pack, users put on body stockings and were scanned by CyberFX, using a Cyberware laser scanner (www.cyberware.com). Once surfaced, the now-digital body is introduced into a Pro/Engineer model (www.ptc.com) comprising both fixed geometric entities, which remain unchanged per instantiation, and trimming surfaces, which serve to define portions of the body serve as body-mating contours for the production of the backpack. The body surface is offset, sliced, and joined with the existing CAD geometry, and a user-specific pack is instantly, automatically created. The user’s individual bone structure, body asymmetries, and spine curvature are all used to drive the final resulting geometry. The design compensates for flexure in spinal areas that need to twist or adjust to body movement. Anticipated shape changes, particularly around the waist, are designed to be especially flexible, so that the geometry never confines the user should they gain weight. The design incorporates captive parts, hinges that connect the arm components, as well as a ball-and-socket connecting hip belt to pack frame. This allows the hips to move in their “figure 8” motion as the user walks, while still supporting the weight from the pack.

Making it

At this stage, all of this is in a digital format. The shape needs to be actualized. Traditional CNC machining cannot create the thin walls, the extensive undercuts, the interlocking mechanisms, or the hollow cable and hose conduits that the PyroPack requires, at least not in the context of reasonable time and budgetary requirements. Selective Laser Sintering was selected for the process, and a flame-retardant polyamide was the chosen material. An EOS P730 laser-sintering machine (http://www.eos.info/en/home.html) is able to handle the large physical size of the backpack. Once the polyamide has been processed, the resulting parts are dusted off and ready for final assembly with the internal components. The arm “armor” is similarly fabricated with interlocking upper and lower arm parts, with an integral hose extending from elbow to wrist, allowing the firefighter to spray dry-chem “Spiderman style.” Like the backpack, this is designed based on trimmed offsets of the user’s arm scan.

Completing the product suite is a headset, comprising a sintered clamshell case housing electronics and thermal imaging camera. A water-clear SLA slider component allows the user to deploy a heads-up display in smoky environments. This was achieved by mounting a display into a spherical gimbal, fabricated of 17-4 stainless using DMLS.

The case for rapid manufacturing

This project demonstrates a hypothetical example of just how rapid manufacturing can impact a high-performance, human-factors dependent product. And although this product was created for demonstration purposes only (and it did perform as anticipated), the CAD model and process could easily be adopted for mass digital manufacture, with the following benefits:

• Cost. Each pack would cost around $7,000. Costs would likely be reduced as the speed and resolution of machines improved. This is comparable to the cost of a current pack, which comprises many welded parts and low-quantity fabrication runs.
• Weight. Sintered polyamide is inherently light, strong and flexible, offering every attribute needed to create a high-performance pack of this sort. With proper FEA optimization, it can be assumed that this pack would be comparable in weight to its current counterpart
• Performance. The integrated, ball-and-socket mounted waist belt and back suspension allow a perfect fit, thereby minimizing the likelihood of back problems, fatigue, and discomfort during use. Even the best “one-size-fits-all” product cannot reach this level of user centricity.
• Adaptability. Rapid manufacturing, by its very nature, invites on-the-fly design changes. As new technologies arise, problems are discovered, or niche specialty components come about, the parametric CAD model can be immediately adapted to implement needed enhancements.