Some of the greatest and most under appreciated technological achievements in the last 40 years have been in materials science and miniaturization.

Early machines were industrial machines with huge price tags, proper linear motion systems, complicated extrusion systems and so on. There is a bit of a mental leap to go from seeing $100k+ machine and dreaming to design something that can be built for $200-500.

The problems were: no "reference designs", no tried and true go-to mechanical parts (like cheap chinese linear motion rails), extruders (they were DIYd!) or heated beds (early models were just PCBs) and so on - imo it just took someone to get this rolling and that may have well taken 30 years.

I think Reprap was first publicly shown around 2005. From then on it was taken on by more and more makers and refined. It culminated in the early 2010s hype with Makerbots and its contemporaries but they still cost > $1500 and were far from set-and-forget appliances, like 50% reliable and slow - we had one at work and I got fascinated but it printed at 5-20mm/s so parts would just take forever and often fail due to bed adhesion, clogs, ...

The last 10-15 years then have seen the popularization of 3d printers through the Prusa i3 and its clones (Ender and other cartesians < $300) and steady refinement of reliability through better materials. Then the last ~5years or so significantly bumped up the speeds through better linear motion components, motion systems and input shaping + firmware and ecosystems like Klipper.

Bambu imo got in at just the right time and refined everything that had culminated up to this point into a solid appliance. Imo their genius was more in the industrial design, making it reliable and affordable manufacturing than anything else.

A complete set of woodworking or metalworking tools was a lot cheaper than a home computer. And there were entire magazines dedicated to proliferating free or easily obtained schematics/designs. Labor was also cheaper, and people had more time for hobbies.

I would also argue the point that it would have been relatively cheap. We are used to the ubiquity of cheap DC motors and precision parts being a click away. But if you were to rummage through a vintage Radio Shack to cobble together a home printer, I think you would struggle to construct anything precise enough with consumer available parts.

> a melting plastic

Don't sleep on the chemistry of filament. It has to be extremely precise and consistent. We benefit from the massive economies of scale today, but this was small batch stuff 20-30 years ago. And if we are talking about the 1970s the plastics were really primitive by today's standards.

1. Cheap stepper motors and electronics from China

2. Expiration of Stratasys patents in 2009

3. Widespread availability of CAD software and desktop computers powerful enough to run it

4. Reprap project made it easy for companies (and individuals!) to develop their own printers