Quentin Harley describes himself as a self-taught hacker from Centurion, just north of Johannesburg in South Africa. He's a softly-spoken engineer for Siemens and a member of a local makers collective, House4Hack.

Harley comes across as jovial and modest, so the first time he tells you that he might have reinvented the homebrew 3D printer — a technology barely old enough to consider itself invented, let alone in need of a makeover — he sounds like he's joking. And yet his proposal for "the next default RepRap design", which features a diamond printhead assembly along the lines of SCARA construction robots, is deadly serious.

Like all the best African inventions, his new design — christened the RepRap Morgan — was born of necessity.

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"I started trying to build a 3D printer around two years ago," Harley says. "But my first designs were really bad. The problem was that in South Africa you couldn't get any 3D printer parts, so you had to make everything yourself.

"So I had to design something from scratch. I wanted to make something that was affordable, because I didn't have much money myself, and I wanted other people could build too."

You can't move on Kickstarter these days without seeing another pitch for a low cost 3D printer. But the original RepRap design — short for "self-replicating rapid prototyper" — upon which most of these fledgling businesses are based was originally created in 2005 by Dr Adrian Bowyer of the University of Bath. It's been refined by both Bowyer and the community since, but while the triangular RepRap "Mendel" and "Huxley" designs have become iconic in their own way, there's been no major revisions for almost three years.

Among the many RepRap spinoffs, Morgan's is almost unique because it mounts the print head (extruder) in a single jointed arm. Most 3D printers mount the extruder assembly on fixed plane, and move it left and right to create the X-axis of a 3D print. The print bed itself then moves forward and backwards to create the Y dimensions. The entire X-axis is then lifted or lowered to create height.

In the Morgan design, Harley says, the print bed drops in order to create a model's height, while the arm brackets holding the extruder pivot around a fixed head and expand and contract to create the other two dimensions.

Harley is so confident that his printer is easier and cheaper to build than previous attempts, that he's entering it for the $20,000 Gada Prize for Interim Personal Manufacturing. The prize has been established to encourage people like Harley, because, the entry page says: "As the printers become more efficient at printing, this need for assembly becomes an increasingly restraining bottleneck to their spread. This could be addressed by some form of automated assembly, or it could be addressed by making the printers easier for people to put together (or both)."

The primary advantage is to reduce the overall bill of materials — and Harley is aiming for under $100 by the time the design is fully refined — and to make the whole thing easier for novices to build. Most printers require a dozen or so threaded rods to be coupled together at various angles using pre-printed brackets, with precise spacing between each one and it can take a newcomer months to assemble one, even with all the parts provided. Morgan, on the other hand, uses a simple stand made out of any stiff plastic tubing and offcuts of wood. Pre-printed parts are required for the arms and holding the print bed in place, but overall it's a much more straightforward construction.

"RepRap Morgan looks like a most interesting design," says Bowyer, the father of RepRap. "The problem with most lever-arm/SCARA-type mechanisms is that they can suffer loss of precision, particularly at the extremes of their movement. But that is not fatal — if it were, IBM would never have developed the SCARA."

The specific problem with SCARA arms, Harley says, is that the print head moves in a slight parabola rather than on a flat plane, which can lead to poor quality printing. Harley's solution has been to adjust the standard RepRap firmware so that the print bed is constantly moving up and down to compensate for this curve.

Harley plans to start selling Morgan in kit form via the printer specialists Open Hardware in Durban, but says he hopes people will use his designs from maker community site Thingiverse.

"I've got two printers in my study and have all the printers I'll ever need. So if anyone else wants to build their own Morgans, they're very economical and cheap to build."

As an afterthought he adds, in his characteristic style: "And from what I've seen, the print quality is quite passable."

Like many, Harley believes that 3D printers have suffered from a touch of overhype in the past, but are now getting to the stage where they can be genuinely useful for innovation in countries like South Africa.

"We're just building the tools," he says, "What's really exciting is the thought of putting these things in the hands of people who live in the townships and seeing what they can do with them."