If you look around for a little while at new robots coming out, whether they be consumer telepresence robots like Ohmni, stem robots like the LittleBots, or a high performance robot arm like Dexter, they are all 3D printed. This is a trend that has really started gaining ground over the last few years. Robots are heavily utilizing 3D printing to make their plastic components for production. But why? Why are robotics start-ups manufacturing with 3D printers as opposed to injection molding.
Well the first reason is start-up cost. Robots are generally pretty complex machines. They often have dozens, if not hundreds, of individual parts. If a company were to create molds for all of the plastic parts on the robot it could cost hundreds of thousands of dollars.
Lets take an example. Look at the Dexter, open-source, high precision robot arm. They have approximately 50 parts on the robot. Assuming the average cost of a mold for each part was $3000 (though it likely would be higher as the parts are very complex) Then Haddington Dynamics, the company that produces Dexter, would have to produce $150,000 just to get the molds. Then there is the cost of the parts themselves. There is also the time lost in perfecting the molds and the money lost from mistakes in mold design and production. It becomes very expensive very fast before they are even producing a product to sell.
But with 3D printing all they have to do is send over the design files to a production partner like Slant 3D, and pay just for set-up and then practically the cost of materials. It is literally a fraction of the cost of molds, allows them to modify the design anytime, and it lets them to grow organically without having to "bet the farm" on a set of molds.
The other major advantage of 3D printing is how good it is at creating complex parts. In the case of the LittleArm arduino STEM robots they have been designed to be light and very complex in shape so that kids can easily assemble them. It is not possible to make molds for these parts. The parts must have an internal honeycomb and internal channels and holes that molds can't create. It is physically impossible. 3D printing is the only process that can produce these parts. But since LittleBots didn't skimp on the design and embraced the process they have the simplest an most elegant robotic arm kits in the world.
So in short robotics start-ups are using 3D printing to manufacture their machines because the multitude and complexity of parts make them too expensive or just impossible to manufacture any other way. When a company is just starting, large investments, like molds, can really be dangerous.