So we’re planning to use a 3 independent z-axis setup on the SolidCore 3D Printer. I’m not an engineer but I think that the belt and pulley ratio gives the steppers more torque and increases resolution. The belt to lead screw arrangement also minimizes and vibrations that might be transfered from the motors to the z-axis. Each lead screw will be constrained by an MGN12 linear rail. With the Duet Wifi we can drive 3 steppers and run an auto bed leveling routine using a proximity sensor or probe.
The typical corexy 3d printer parts arrangement has a single NEMA 17 stepper motor with the belt routing to all two or three lead screws which move together in sync. Originally we were working on a design that used this single z-axis motor configuration. But after having trouble sourcing the belt that was the perfect length I decided to just go with three stepper motors similar to the HeVort printer or Jubilee tool changing core xy platform.
Single Z-Axis vs Triple Z-Axis
Many 3d printer users frown upon the idea of multiple steppers for independent z motors due to syncing issues. But with a good electronics setup like the 32 bit Duet board and the RepRap Firmware keeping the three lead screws in sync should be fie. When powered up stepper motors tend to jump to the four steps that match the phase current. Some will jump forwards or backward after a number of power cycles.
Duet Wifi Firmware
While a single nema 17 motor could use a continuous closed loop belt routing to all three lead screws in sync. This can be avoided by adding code in RepRap Firmware to detect a power down moing the motors to the correct position ready for power up. The Duet WiFi has two power monitor circuits on board but it doesn’t matter because the machine will run an auto levelling at start up.
While there are many open source 3d printer designs to pick from on Thingiverse. And when it comes to corexy printer designs there are a few that raise the bar. Here are some of the best designs that we would like to talk about.