With smart manufacturing spreading rapidly, multi-axis industrial robots have become standard equipment in factories. But a standard six-axis robot's reach is limited by its own arm span — once it needs to cover multiple workstations far apart, or continuously process long workpieces such as car bodies, aircraft wings, and wind turbine blades, a single robot simply cannot reach far enough.

The solution is to give the robot a precisely movable "leg." This linear travel mechanism, mounted outside the robot body, is called the robot 7th axis, also known as a robot travel axis, travel track, floor rail, overhead rail, or external axis. The six axes are the arm; the 7th axis lets the arm "walk," stretching a single circular working range into a long strip that can span multiple workstations.

So which industries mainly use this "track"? This article gives a systematic overview.

Five Major Industries Using the 7th Axis

Based on summaries from multiple manufacturers and industry sites, robot travel tracks have penetrated a large number of industrial scenarios. 5 categories are the most representative:

1. Painting Industry

Painting or cleaning large workpieces such as containers, cars, aircraft, and high-speed train carriages is a classic battlefield for the 7th axis. These workpieces are large and have continuous surfaces, making full coverage difficult for fixed robots. With a fully enclosed overhead rail, painting robots can travel long distances along the workpiece to achieve 360° coverage without dead angles. Compared with manual work, robot painting improves paint utilization, ensures uniform coating, and enables 24-hour operation. It is also widely used in automotive, instrumentation, 3C, appliance, ceramics, and furniture processing.

2. Welding Industry

Spot welding, arc welding, laser welding, and other welding tasks can all be performed by welding robots equipped with a 7th axis. Whether it is long body seams, continuous frame welding, or multi-point welding of large components, both overhead and floor rails can adapt. With welding tracking, sensing, positioners, and dust extraction, a single robot can cover long weld seams, significantly reducing equipment investment. In recent years, demand has grown rapidly in new energy battery pack welding, chassis welding, and profile grinding.

3. Grinding Industry

Processes such as car body-in-white grinding, 3C product grinding, and glass cutting and grinding require high surface quality and consistency. A single fixed robot often covers only 2–3 meters of grinding area, but with a 7th axis this can extend to tens of meters, reducing equipment costs and avoiding the fatigue errors of manual grinding. With torque compensation, visual positioning, and floating grinding technologies, the system can flexibly handle multiple workpiece types.

4. Packaging, Palletizing, and Handling Industry

Handling robots can swap end effectors to move workpieces of various shapes, sizes, and states, greatly reducing manual labor. Hundreds of thousands of handling robots worldwide are used in machine tool loading/unloading, stamping lines, assembly lines, palletizing, and case packing. The 7th axis allows one robot to cycle across multiple workstations, upgrading "single-point pick-and-place" to "full-line flow."

5. Automated Storage and Retrieval (AS/RS)

In smart warehousing and multi-station AS/RS scenarios, the combination of floor rail + gantry is particularly common. Robots move along the track between multiple rows of racks and workstations to store, retrieve, sort, and transfer materials — a key link connecting warehousing and production logistics.

Four Typical Workstations

From a "workstation" perspective, 7th axis applications are concentrated in four main scenarios:

  • Handling workstation: Flexible end effector changes, covering machine tool loading/unloading, stamping lines, assembly lines, and palletizing — one of the most widely used scenarios.
  • Welding workstation: Includes robot, welding power source, sensing, positioners, and dust extraction, adapting to spot, arc, and laser welding for high-quality automated welding.
  • Painting workstation: Composed of a six-axis robot, travel track, paint supply system, electrical control, and software. Its core advantage is replacing manual labor, saving paint, and improving coating consistency.
  • Grinding workstation: Integrates grinding tools with vision/floating technology to handle machined parts, casting polishing, and non-metallic deburring, expanding the grinding coverage of a single robot.

In addition, machine tool (continuous loading/unloading of multiple CNCs), new energy (battery and chassis welding, large component transfer), metal processing (long profile cutting, large component welding), automotive manufacturing (body-in-white welding, chassis assembly, parts handling), and large-scale 3D printing (additive manufacturing and repair of large components) are all fast-growing directions for the 7th axis.