3D printing is all well and good if you want to produce small quantities, as long as they are small enough to be printed in a reasonable amount of time. But what if you want to make it really big? Does a 35 hour print time sound like fun? Would it even take that long? (Nathan) by Nathan builds robots didn’t feel like waiting and started the project to build a huge parallel 3D printer with four independent print heads. Well, sort of.

The premise seems obvious at first glance: more print heads means more plastic is deposited per unit of time. As long as you can maximize the nozzle diameter and machine speed, it should theoretically be possible to speed things up massively. But that’s not how it works. The custom machine they’ve designed uses a polar coordinate system with a rotating bed (the “theta” axis) and four radial axis gantries arranged at 90 degrees to each other. Each gantry has its own independent extruder, so multilateral printing is also an option. (Nathan) laments that the problem with building such a beast isn’t so much the mechanical aspects, but the limitations of current firmwares. There are also more complex considerations at the slicing level, so getting the machine to work as desired is a pretty big programming task! At the moment, this means that each radial axis has to work in lockstep, which means the objects being printed have to be rotationally symmetric of order four. Another option is to print four copies of a much smaller object in parallel. While this has its uses, it is not the end goal. (Nathan) says he wanted to do a record-breaking 20kg print. However, this first attempt failed due to numerous issues with alignment across height and bed adhesion, not to mention feeding the extruders with fresh filament.

There are some major hurdles in terms of alignment. The four vertical corners can be out of alignment with each other in all sorts of ways, causing the radial axis to shift as the Z axis moves. We suspect this is just a glaring issue and other, more subtle issues are waiting in the wings to cause problems in the future, but we’ll keep an eye on this and see where it goes!

We’ve featured a few projects involving 3D printing lately. Here’s a big printer for big prints, our thoughts on high-speed printing and finally a fascinating machine modification that optimizes color changing through automatic hot-end switching.