Step into any modern machine shop and you’ll see CNC mills and lathes the size of minivans. A CNC mill operates a lot like a 3D printer, so you may wonder why they’re so much bigger—even when the working area is roughly the same size. The reason is that they’re precision machines that are built to be incredibly rigid in order to avoid any flex under fairly substantial forces. Even a thousandth of an inch of deflection on the end mill can make a difference. Roetz 4.0 used a vintage air bearing-equipped machine to build a 3D printer that meets similar standards.
The machine used for this project is a massive 1.3 ton coordinate measuring machine (CMM) built by C.E. Johansson. That CMM was designed for taking incredibly precise measurements from various points on a part and each of the three axes rides on air bearings for virtually frictionless movement. While those don’t provide quite as much rigidity as a CNC mill’s ways, the setup is perfect for a 3D printer that only has to compensate for the weight of the extruder and hot end. The machine can move with almost no resistance or flex at all, which means it is capable of printing incredibly high quality parts. This is the textbook definition of “over-engineered,” but it’s hard not to drool at the precision of this CMM.
Roetz 4.0 has spent years working on this project, but it is finally coming together. He retained the machine’s original table and those amazing air bearings, but needed to add a lot of more conventional machine parts for movement. Beefy stepper motors and ball screws are used for actuation on each axis. Mounting those required a number of custom-machined parts, but luckily Roetz 4.0 had a well-equipped machine shop to fabricate those. A standard BigTreeTech SKR V1.4 Turbo board is used to control the printer’s movement just like any other 3D printer.
It took quite a lot of experimenting and tuning to get the machine printing properly, but the results are spectacular. Not only can this machine maintain unbelievable levels of precision, it also has a massive working area. The use of ball screws somewhat limits the movement speed, but it can almost certainly be pushed further than what Roetz 4.0 demonstrates in the video. Regardless, it is hard to imagine a more overbuilt 3D printer than this one.