Development of gantry robot

1 Introduction

In the modern automobile manufacturing industry, achieving full automation of the entire production process—from raw materials to finished packaging—has become a key trend in international automotive manufacturing. Many developed countries have already implemented successful automated systems. Recently, our factory has successfully integrated 13 gantry robots for automatic loading, unloading, indexing, and inverting transportation at Xiangfan Automobile Co., Ltd. This system enables complete automation of car body and cylinder head processing, significantly improving productivity and working conditions. The implementation of this technology has transformed traditional logistics methods, ensuring product quality, reducing physical labor, and elevating the overall level of automobile manufacturing. Our gantry robot is the first of its kind in the domestic automotive industry and was part of the "National Key Scientific and Technological Project of the Ninth Five-Year Plan" under the Ministry of Machinery Industry. After two years of operation, it has proven to be at the forefront of technological development in China.

2 How the Gantry Robot Works

The appearance of the gantry robot is shown in Figure 1:

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Figure 1: Appearance of the robot

2.1 Main Technical Parameters:

  • Rated load: 250kg, transporting parts weighing up to 40kg
  • X-axis maximum stroke: 2500mm
  • X-axis maximum speed: 36m/min
  • X-axis maximum acceleration: 0.6m/s²
  • X-axis positioning accuracy: ±0.25mm
  • Z-axis maximum stroke: 500mm
  • Z-axis maximum speed: 24m/min
  • Z-axis maximum acceleration: 0.4m/s²
  • Z-axis positioning accuracy: ±0.25mm
  • A-axis rotation angle: 0°–180°
  • A-axis rotation speed: 45°/s
  • C-axis rotation angle: 0°–270°
  • C-axis rotation speed: 120°/s

2.2 X and Z Axis Linear Drive System:

The X and Z axes are driven by motors through reducers, gears, and linear rails. The precision and stability of movement are critical for the robot's performance. To ensure smooth operation, we use imported motor reducers and elastic coupling to minimize vibration and impact. Aluminum roller brackets reduce weight, while eccentric shaft adjustment ensures proper clearance between rollers and rails. These measures enhance accuracy and reliability.

2.3 A and C Axis Rotation System:

The A-axis rotates around the Z-axis using a rack and gear mechanism, while the C-axis rotates around the X-axis via a belt-driven pulley system (see Figure 2). The 270° rotation helps remove dust and maintain cleanliness on the raceway.

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Figure 2: C-axis transmission diagram

2.4 Gripper System:

The gripper uses two cylinders to clamp the workpiece. It includes limit blocks to prevent rotation and ensure stability. The center of gravity is determined using CAD to avoid imbalance during rotation.

2.5 Z-Axis Balancing Device:

A balancing cylinder ensures smooth Z-axis movement and prevents drift. Air pressure is maintained at 0.4–0.5MPa, and the system is designed for high rigidity and low weight.

2.6 Electrical System:

The system uses common motor speed reducers and pulse encoders. French TE’s TS X47 series PLC controls the system, with AXM182 axis modules and variable frequency motors forming a semi-closed loop for accurate positioning.

3 Key Manufacturing Technologies

3.1 Beam Manufacturing:

The beam is a critical component of the robot. It is made from square tubes and plates, with rails and racks installed. The beam must meet strict accuracy requirements, including linearity and parallelism within 0.06mm over 3500mm. Welding, heat treatment, and grinding are essential processes to ensure structural integrity and minimal deformation.

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Figure 3: Beam diagram

Welding uses COâ‚‚ gas shielded welding with precise parameters to minimize distortion. Heat treatment is performed in a deep well furnace to eliminate residual stress. Grinding ensures high straightness and parallelism, with special techniques used to manage thermal deformation.

3.2 Screw Loosening Solution:

To address screw loosening during high-speed operation, we applied Loctite 242 adhesive, which has effectively prevented loosening and improved system reliability.

4 Conclusion

The future of gantry robots lies in serialization and the development of more advanced models, such as three-dimensional robots with crossbeams longer than 6 meters. This represents a new challenge and opportunity for the automotive manufacturing industry.

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