[Marius Hornberger] has been busy hacking his “Hammer” CNC router again, and now it sports a much desired feature — an automatic tool-changer. Having wanted one for a while, [Marius] was unhappy sacrificing a big chunk of useable bed area just to park the tool-changer magazine. An obvious solution would be to have the magazine retract away from the bed, outside of the working area. Sadly, the CNC controller had only enough spare outputs to drive the pneumatic tool changer (mounted on the spindle) leaving none spare to control the magazine assembly. So, there was only one obvious route to take, use some simple spring-loaded mechanics to move the magazine into tool-picking range with the Y axis motion instead.

Obviously, the whole thing is CNC machined on the machine itself, taking only a couple of iterations and smidge of table-saw action to get everything to fit well and operate smoothly without binding or colliding with the moving gantry. A cunning pair of levers on each end of the magazine allow it to move much further than the advancing gantry, swinging it quickly into position when the Y axis is at the extreme of its travel, and retracting away when the gantry moves back. Another nice addition to the build was a tool depth sensor (AKA: a switch) mounted off to one side, which allows the machine to find the bottom of each tool, if it is not known, so the Z axis can compensate. When combined with the automatically retracting dust shoe, this is a definitely a CNC build we’d love to see in a shop near us!

We’ve had a fair few CNC hacks over the years, including tool changers, like this one, but 3D printers can use some tool changer love too!