endstop

An endstop, in motion control systems such as CNC machines and 3D printers, is a sensor or switch that detects the end of travel of a moving axis. Endstops provide a reference point for calibration and a safety limit to prevent components from overtraveling or colliding. When triggered, the controller can stop movement or initiate a homing sequence to establish a known origin.

Endstops come in several types. Mechanical limit switches use a lever or pushbutton activated by contact. Optical endstops use a light beam interrupted by a flag or tab. Inductive or capacitive sensors detect a target without contact and are common where metal parts or non-metal targets are involved. Hall-effect sensors sense a magnetic field. Each type has tradeoffs in cost, reliability, and environmental tolerance.

Wiring and electronics: In many systems, endstops are normally closed (NC) devices wired to a digital input with a pull-up resistor. This produces an active-low signal when triggered. Firmware monitors the endstop state during movement, and the homing routine relies on it to establish origin. Debouncing and filter settings help prevent false triggers; some systems use opto-isolated or shielded wiring for noise immunity.

Placement and usage: Endstops are typically located at the minimum end of an axis (X, Y, Z). The machine moves toward the endstop to perform a home operation and define the origin of its coordinate system. Some machines employ multiple endstops for redundancy or alternative homing strategies, while others use non-contact sensors for wear-free operation.

Related terms include limit switch. Endstops are integral to safe and predictable motion control, but miswiring, misalignment, or mechanical binding can cause false triggers or missed homing and should be diagnosed with status reports or diagnostic routines provided by the controller firmware.