The crossbeam of a large gantry milling machine must remain level during operation; any deviation will affect accuracy, and excessive deviation can damage the mechanical components. Therefore, in the process of developing and manufacturing our own large CNC gantry milling machine, we adopted the GANTRY function from the German SIEMENS CNC system to achieve bilateral synchronous drive of the crossbeam. I. Overview of the GANTRY Function The GANTRY function is a fully synchronous drive control function. It defines the two sides of the large-span component requiring synchronous drive as two completely independent coordinates, each with its own independent position loop, speed loop, and current loop. These two coordinates are linked into a "synchronous coordinate pair" through the GANTRY function in the CNC system, implementing synchronous drive control (its principle is shown in Figure 1). The two coordinates linked by the GANTRY function are completely independent coordinates in the CNC system, with independent addresses, independent machine data management, and independent servo drive systems. After forming a "synchronous coordinate pair," motion commands can only be given to the leader axis (LA), and the commanded motion process is exactly the same as the normal motion coordinate. The motion command for the following axis (FA) is generated by combining the motion command setpoint of the LA with the deviation compensation value. This is the main function of the GANTRY function. It accepts the actual coordinate values ​​of LA and FA, compares them, and adds the deviation value of FA from LA to the motion command of LA as the motion command of FA. This operation is performed in real time during motion. Another important function of the GANTRY function is monitoring. First, it monitors the synchronization accuracy of LA and FA. When the deviation exceeds the limit, an alarm signal is generated, and necessary logic processing can be performed on this signal to ensure normal synchronization. Furthermore, when the deviation is too large, GANTRY is shut down, coordinate motion is stopped, and processing is pending. [b]II. Implementation Method 1. Mechanical Structure[/b] The output shaft of the drive motor drives the worm gear to rotate after being reduced in speed by two sets of gears in the gearbox. The ball nut on the worm gear rotates together with it, while the lead screw is fixed. The rotation of the nut drives the crossbeam. [b][align=center]For details, please click: CNC Moving Beam Gantry Milling Machine Crossbeam Drive[/align][/b]