Gantry robots usually run around the clock, and power interruptions from maintenance or grid disturbances are unavoidable. How quickly and safely a machine returns to service after a power loss depends on homing and reference-point management — an often overlooked but fundamental part of stable line operation.

Homing rebuilds the coordinate reference of each axis. Servo axes with incremental encoders lose position data once power is cut and must relocate their home switches, while absolute encoders keep data on battery power and recover coordinates at start-up. Mechanical origin, soft limits and station coordinates must all share one reference frame.

The common method pairs a home switch with a deceleration dog: the axis searches for the switch signal, slows down on the dog, then creeps to the encoder Z pulse to lock the origin. Simple and inexpensive, with proper search and creep speeds it meets the repeatability needs of most gantry stations.

On dual-drive gantries the homing sequence matters. If each servo on the two rack-driven axes homes independently, a synchronisation offset can trigger alarms. The standard practice is to home the master axis first and let the slave follow the same logic, or use a single linear scale as the shared datum so both beam ends stay aligned.

Homing restores the machine coordinate system only; station coordinates also need management. Pick stations, machine tables and loading positions should be mechanically located with datum pins or stops, taught once during commissioning and recorded. First-article checks in daily running catch any offset caused by collision or loosening.

Abnormal axis positions at the moment of power loss need special care. If an axis stops mid-travel, do not restart the automatic program at full speed; first jog it through one stroke at low speed, manually or step by step, to confirm clearance. After an e-stop reset, check every axis and re-home when necessary.

Reference management should also live in procedures. Homing steps belong in the operation manual and the daily checklist; absolute encoder batteries need a scheduled replacement plan to prevent data loss; and homing alarms should be logged so switch drift, loose dogs or electrical noise can be told apart.

In projects covering truss manipulators, gantry robots, truck loading, AS/RS and seventh-axis systems, Truman treats homing strategy and reference management as fixed parts of electrical design and operator training, turning shutdown recovery into a repeatable procedure and reducing the impact of unplanned stops.