3D printing frames?

3D printing have many disadvantages:

1. Materials cost and strength: although new materials has been made over the years to reduce the cost, it is still quite expensive for mass production. In our department, a good material would cost £10/g, and the cheapest is around £1/g (very porous and fragile).
2. Labour cost: it takes time to CAD a small part, but it takes even more time to clean/wash/polish the final parts. For complex part(s), there is a need for filler which could be dissolve at the later stage. This filler dissolution process would take a day and is expensive for mass production (effective time for one part).
3. Replaceable parts: without an established market, the cost for parts would be sky-high.

So far, 3D printing is very successful in prototyping/customizing. This is because the price has been driven down to the point it is the same as if you make a prototype with conventional materials (metal, plastic). Simple and readily-available materials, zero skill requirements for machining contribute to this lower cost. This does not apply in larger scale (where machines replace human labour) and so 3D printing loses advantages.

In the end, it is still much easier and cheaper to CNC parts from conventional materials than to 3D-print a part, given the technology and market right now. If one has to produce a prototype, I always advise the person to try CNC machining before 3D-printing

Five years later, it turns out it was just a matter of time until 3D-printed (additive printing) titanium frames showed up:

https://www.pinkbike.com/news/the-3d-printed-moorhuhn-is-now-available-in-full-titanium.html

In the article above, Huhn Cycles announces their 3D-printed titanium bike, the Moorhuhn. There is also a 3D-printed steel version available that was announced in June of 2020 (https://huhncycles.com/Homepage).

Additionally, brands like Atherton Bikes are using additive manufacturing to create lugs for (semi-)custom carbon frames.

According to their technology page, the basic process for Atherton is the following:

1. The customer submits their custom geometry
2. Atherton develops designs for the lugs
3. The lugs are manufactured
4. Tubes are bonded into the lugs, bike is assembled.

Both of these companies produce full suspension mountain bike frames.