Is 3D printing a viable technology for end-user/consumer products? The short answer is yes, of course! It is ultimately the end-user/customer that decides what is or isn't a viable product, and the marketplace for 3D printed items is growing. Even in our little niche of magfed paintball, many people are utilizing their creativity and technological know-how to introduce new and exciting products that expand our sport. I don't know if it's ok to name names here, but I assume most of you will know the major players that offer 3D printed products as fully usable items. Magfed Maker is new to the scene, so time and experience will tell of our own acceptance by players, but the trailblazers already out there and putting mag adapters, mag winders and other accessories out there and in games seem to have a mostly positive review history.
There is a dark side, of course. I've even seen 3D printing mentioned as the "dark side" of machining/manufacturing. It's really important to choose the right tools for the job, as is true with any method of fabrication. What makes 3D printing a little more prone to fallacy is that it's more accessible to people without having prerequisite engineering or mechanical knowledge and/or experience. Meaning, anybody can pick up a $300 printer, dabble in sketchup for a weekend and start pumping out rails or speed loaders without worrying too much about structural integrity, design theory, tensile stress points or glass transition temperatures. I readily admit that I do not have an engineering background, and basically did exactly what I described above, teaching myself CAD and how to use 3D printers.
An example of the above situation can be seen with the initial use of PLA as the most common polymer used in 3d printed offerings. The reason for using PLA is simple, it's a safe, biodegradable polymer that is easy to print, readily available and relatively cheap with the slightest learning curve. The problem is that PLA is brittle and prone to snap if designed with thin walls, cannot be mended easily (ABS can be bonded to itself with acetone, nylon bonds very well with super glue), and the most significant trait: a low glass transition temperature. This means that a printed part will start to warp and even melt if exposed to moderate heat such as a sunny day at the paintball field. This condition is worsened when the part is a dark color, such as the tactical black we love so much for our guns. However, this only applies to a few polymers that are used in 3D printing, as ABS can be left in the sun all day. Polycarbonate and some nylons can be exposed to boiling water without losing shape.
Magfed Maker can't speak for other companies, but we only use ABS, PETG, TPU (rubber-like), nylon and polycarbonate in our products. These are all very strong materials that can withstand the abuse of the paintball player, and even direct paintball impacts. These materials have been tested to endure most common temperatures where we play. Our northern comrades may have some troubles with ABS and TPU on the below-30 centigrade days, but I've yet to see any evidence of part failure in the cold. This means our products are designed to be used just like any other part you can buy. We utilize design theory to try and make up for 3D printing's shortcomings such as weak stress points on the axis that was printed up from the print bed. The idea is to not just make something that works, but to design a part that lasts.
Another critique is that 3D printing is best left to it's origin, that is: rapid prototyping. The idea is that 3D printing is great for pumping out a functional prototype of an item that will later be machined or manufactured using more traditional methods, such as CNC, casting or injection molding. While this is incredibly valid, the advances in 3D printing materials that have been made, along with where the technology is headed, make this a moot point (as in, debatable to no end). 3D printing was for the longest time an industrial best-practice, and materials used in their operation were purpose-driven to accomplish the task of pushing out a tangible object. Durability wasn't an issue, nor was surface finish. Modern 3D printing materials and methods now offer substantially increased durability and aesthetics similar to a manufactured item. <citation needed>
The greatest argument for 3D printing as a product is the availability and potential. With traditional manufacturing methods, there is so much investment made that only the most viable options can be produced. CNC and casting only become economically sensible when there will be plenty of demand. Injection molding requires tens of thousands of dollars to make the tooling. With 3D printing, we can offer a single part or mod kit for just one customer and have it still make sense financially. By harnessing this technology, Magfed Maker hopes to offer a complete digital armory to satisfy every deep and dark desire of the magfed player, one gun at a time.
In closing, 3D printed products as products are already out there, being used and abused. They may not be as strong as their injection molded and CNC'ed brethren, but they are certainly being proven to be plenty durable enough to fulfill their purpose. A bonus: The selection of available products can only grow tremendously as the technology is adopted and mastered, and it is the player that is taking control of what is possible.