Standard GRBL firmware is built to drive three stepper motors (X, Y, and Z axes). However, many "2.5D" machines—like drawing robots—benefit from the lightweight, simple nature of a servo motor to lift and lower a pen. The MI-GRBL ecosystem provides the necessary modified firmware and software extensions to make this hardware setup functional.
MI-GRBL Inkscape Extension on GitHub – This plugin converts designs into servo-compatible G-code.
This "hacked" version of GRBL redirects the Z-axis step/direction signals to a PWM (Pulse Width Modulation) signal compatible with hobby servos. mi grbl z-axis servo controller download
Setting up an MI-GRBL system requires flashing the Arduino and configuring the hardware. MI GRBL Z-AXIS Servo Controller for Inkscape 0.92 - GitHub
For pen plotters, you need a way to generate G-code that specifically tells the servo when to go "up" and "down." Standard GRBL firmware is built to drive three
is a specialized, open-source firmware and extension ecosystem designed to control hobbyist CNC machines, particularly pen plotters and laser engravers, by using a servo motor for the Z-axis instead of a standard stepper motor.
To get your Z-axis servo running, you typically need two main components: the modified firmware for your Arduino and an extension for your design software. MI-GRBL Inkscape Extension on GitHub – This plugin
MI-GRBL GitHub Repository – The primary source for the modified code.