CNC glass processing with 2-axis backlash compensation sets new standards
The 5-axis horizontal CNC machining center for glass processing is the high-end model from Chinese specialist Ge‘en Intelligent Technology. It uses Beckhoff TwinCAT as an open CNC platform and integrates flexible interfaces and CAM nesting software to enable efficient and convenient operation. The gap elimination function for two motors improved the dynamic stability and control precision of the C-axis and enabled the original direct drive structure to be replaced cost-effectively.
Ge‘en Intelligent Technology is a manufacturer of intelligent glass cold processing machines. The company produces various systems such as vertical drilling and milling centers, vertical machining centers with suction cups, 3-axis horizontal machining centers, 5-axis horizontal machining centers, and their automatic production lines. These products are widely used in the glass processing industry and have been exported to numerous countries and regions around the world.
The AIR 3015.5 5-axis horizontal machining center is a high-end horizontal CNC machine for glass processing with three linear axes (X, Y, Z) and two rotary axes (A, C). It enables multi-axis simultaneous control for a variety of glass processing operations, including drilling, milling, grinding, polishing, grinding and polishing beveled edges at any angle, as well as precise positioning with a touch probe. Various tools can be used for special glass processing as an option. The machine uses TwinCAT 3 CNC for precise control of each servo axis and features automatic tool compensation, which continuously tracks the tool during machining. An independently developed control interface ensures simple operation, supports the recognition of CAD graphics, and automatically generates optimized tool paths to ensure the efficiency and quality of processing.
Main functions and structure of the machining center
The 5-axis horizontal machining center is a versatile glass processing machine that can automatically process even irregular glass shapes such as circles, ellipses, and polygons. Beveled edges can also be ground and polished at any angle. In addition, a touch enables optimal positioning and machining by precisely capturing the workpiece.
The machining functions include:
- Drilling: A drill can be used to make holes of various diameters
- Milling: quick and easy milling of various shapes
- Chamfering: features the option of a drill bit with a chamfer sleeve or a chamfering disk
- Edge grinding: of internal and external contours, including safety corners
- Polishing: of internal and external contours, including safety corners
When it comes to processing beveled edges, the 5-axis machining head can automatically select tools such as diamond, resin, and wool disks to grind and polish the edges at any angle according to process requirements.
According to Ge‘en Intelligent Technology, the main components of the machine tool – such as the machine bed, crossbeam, X-axis slide plate, and Z-axis slide plate – have optimized structures to ensure the machine’s rigidity and to dampen resonance frequencies. The work platform consists of aluminum profiles that are manufactured using custom-made molds. The left and right grooves of the aluminum profiles ensure the overall integrity and rigidity of the table, guaranteeing that glass products are processed accurately.
The transmission structures of the X, Y, and Z axes combine a high-precision rack-and-pinion transmission with a ball screw. The Y-axis uses a gantry structure with two motors to move the crossbeam synchronously back and forth on the machine bed. The machine is equipped with a fixed tool magazine with multiple stations for easy tool changing.
Backlash elimination with two motors
The electric double-oscillating screw of the C-axis is one of the most important components of the machine. The A and C double-oscillating screws are high-speed electric screws with a central water outlet. The A and C axes use toothed belt or girth gear units to achieve rotary motion. Precision gears and the double gear backlash elimination structure are used to eliminate backlash in motion, ensuring high machining quality of irregular shapes and curved surfaces.
Due to the high structural load on the swivel head two motors of the C-axis drive a large peripheral ring gear via corresponding pinions. A planetary gear unit with a transmission ratio of 200 is arranged between them. However, the backlash compensation function of the two motors greatly reduces mechanical backlash during forward and reverse movements of axes C1 and C2. After extensive testing, the final backlash is around 0.01 mm.
This software function block generates a mechanical preload between the master and slave motors in a dual-motor drive system. Through PID adjustment, it optimizes the dynamic response characteristics of the entire control function, eliminating mechanical transmission backlash, increasing system rigidity, and improving operational stability.
Universal control platform and servo control
A cost-effective and compact C6015 ultra-compact Industrial PC, EtherCAT I/Os, and AX5000 Servo Drives from Beckhoff are used for the machine’s control technology. The TwinCAT 3 CNC software is used on the software side. Control is handled by the standard version of the CNC software, consisting of one CNC channel and eight interpolated axes. The system offers a tool wear compensation function that allows fixed or dynamic compensation settings to compensate for wear caused by prolonged tool use, thereby improving machining accuracy. The dual-motor C-axis is controlled by the AX5203 Servo Drive and has a function to eliminate backlash between the two motors, which ensures a fast response and high positioning repeatability during the machining process.
The user interface was programmed in the C# programming language. Glass processing recipe management, manual operation, online hardware monitoring, and other functions are integrated into a single platform via ADS communication, enabling user-friendly human-machine interaction and convenient process programming. The unit offers multiple processing mode options at different scales, enabling stand-alone operation or integration into an automatic loading and unloading system for automated processing.