How a Claw Machine Gantry Works
Direct Answer
A claw machine gantry is the overhead mechanical framework that moves the claw unit along the X (left-right), Y (forward-backward), and Z (up-down) axes inside the cabinet. The gantry receives position commands from the mainboard, drives the claw to the player-selected position, lowers it to grab a prize, and returns it to the drop chute. Understanding how the gantry works is essential for installation, calibration, and troubleshooting.
Gantry Components
- X-axis rail — Horizontal rail running left to right across the top of the cabinet
- Y-axis rail — Horizontal rail running front to back, mounted perpendicular to the X-axis
- Z-axis assembly — Vertical mechanism that lowers and raises the claw unit
- Drive motors — DC motors mounted on each axis, controlled by the mainboard
- Limit switches — Sensors at each end of the rails that define the home position and movement boundaries
- Cable carrier — Flexible conduit that routes power and signal cables along the moving axes
- Claw unit — The grabbing mechanism suspended from the Z-axis
How the Gantry Moves
When a player inserts a coin and operates the joystick or buttons, the mainboard sends directional signals to the X and Y axis motors. The motors drive the gantry carriage along the rails using a belt or rack-and-pinion system. When the player presses the drop button, the Z-axis motor lowers the claw to the prize field, activates the claw grab sequence, then raises the claw and returns it to the drop chute position.
X / Y / Z Axis Sequence
- Player moves joystick — X and Y motors position the gantry over the target prize
- Player presses drop — Z motor lowers the claw to the programmed depth
- Claw opens and closes — Claw strength (grip force) is applied per mainboard settings
- Z motor raises — Claw lifts with prize (or without)
- Gantry returns to home — X and Y motors drive back to the drop chute position
- Claw releases — Prize drops into the chute
Home Position and Limit Switches
Every gantry has a defined home position — typically the front-left corner or the drop chute location. Limit switches at each axis endpoint tell the mainboard when the carriage has reached the boundary. On power-up, the gantry performs a homing sequence: it moves each axis until it triggers the limit switch, then resets its position counter to zero. If a limit switch fails, the gantry may over-travel and jam.
Common Gantry Problems and Causes
- Gantry not moving on one axis — Motor failure, broken belt, or disconnected motor cable
- Gantry moving in one direction only — Limit switch fault or mainboard output failure
- Gantry jerking or stalling — Rail obstruction, worn bearings, or insufficient motor voltage
- Gantry not homing correctly — Dirty or misaligned limit switch
- Z-axis not lowering to correct depth — Z-depth parameter requires recalibration in mainboard settings
Frequently Asked Questions
Q: What motors are used in a claw machine gantry?
A: Most claw machine gantries use 12V or 24V DC gear motors for the X and Y axes, and a separate DC motor for the Z-axis. Motor specifications vary by cabinet size and manufacturer.
Q: How do I calibrate the gantry home position?
A: Access the mainboard service menu, select the axis calibration or home position setting, and run the homing sequence. Refer to your specific mainboard parameter guide for exact steps.
Q: Why does my gantry stop moving mid-travel?
A: Common causes include a triggered limit switch, motor overheating, belt slippage, or a mainboard fault. Check each axis individually to isolate the cause.
Q: Can I replace a single axis motor without replacing the whole gantry?
A: Yes. X, Y, and Z axis motors are individually replaceable components. Match the voltage, RPM, and shaft size of the original motor when ordering a replacement.
Related Resources
- How X/Y/Z Claw Mechanisms Work in a Claw Machine
- How to Troubleshoot a Claw Machine Gantry
- How Claw Machine Mainboards Work
- How Claw Strength Is Controlled in a Claw Machine
- Arcade Glossary — Gantry, X/Z Axis, Limit Switch definitions
- Knowledge Center — Installation and Wiring Guides
- Arcade Spare Parts — Motors, Limit Switches, Cable Carriers
- DIY Claw Machine Kits