7th Axis Robot Systems – Linear Tracks for More Reach

When Does a Robot Need a 7th Axis?

A 7th axis is useful when the reach of a fixed robot is not enough.

Instead of installing a separate robot at every workstation, one robot can travel between several positions. This can make better use of the robot and create a more flexible automation layout.

Typical applications include:

• Machine tending at two or more machines

• Material handling between workstations

• Pick and place over longer distances

• Palletizing and depalletizing

• Assembly at several stations

• Inspection of large components

• Gluing, welding, or processing along long workpieces

• Flexible workcells with changing robot positions

A robot linear axis is particularly useful when tasks can be completed one after another. When two operations must run at the same time, two separate robots may be the better choice.

Which 7th Axis Fits Your Robot?

Start with the exact robot manufacturer and model.

The robot mount, moving capacity, motor, controller, and software connection must fit the robot. A linear rail designed for a lightweight cobot is different from a track intended for a larger industrial robot.

RBTX offers preconfigured solutions for robot families including:

• igus robolink DP

• igus ReBeL

• Epson SCARA robots

• Epson VT6

• Universal Robots in different size ranges

Solutions for ABB robots and other robot brands are also possible. The correct setup depends on the exact robot model and application.

How Much Weight Must the Track Move?

A robot 7th axis does not move only the workpiece. It carries the complete robot setup.

The moving load may include:

• Robot

• Robot mounting plate

• Gripper or process tool

• Workpiece

• Cameras and sensors

• Cables and hoses

• Additional equipment mounted on the robot

A simple way to estimate the load is:

Moving load = robot + tool + workpiece + moving accessories

The robot payload alone is not enough for selecting the track.

The position of the weight also matters. A long tool that extends far from the robot can place more stress on the track than a compact tool of the same weight.

Before selecting a robot transfer unit, collect both the weight and basic dimensions of the complete moving setup.

How Much Travel Does the Robot Need?

The travel length describes how far the robot can move along the track.

Do not measure only the distance between two machines. Also consider the reach of the robot and the exact location of each pick, place, loading, or process point.

Important measurements include:

• Distance between workstations

• Position of the robot base on the carriage

• Robot reach

• Pick and drop-off positions

• Space at both ends of the track

• Distance from walls and surrounding equipment

• Space required for cables and the energy chain

• Possible future workstations

A longer robot rail system is not automatically better. It requires more floor space and may increase the effort needed for support, alignment, cable management, and installation.

Select the travel length the process actually needs, with enough reserve for realistic adjustments.

How Fast Should the 7th Axis Be?

The required speed depends on how often the robot changes position.

For machine tending, the travel time between machines may directly affect production output. For a slower inspection or assembly process, maximum track speed may be less important.

Ask three questions:

1. How far does the robot move during each cycle?

2. How often does it move between positions?

3. How much time is available for each move?

Maximum speed is only part of the answer. Acceleration, deceleration, and final positioning also take time.

A faster external robot axis may not improve the overall process when the robot spends most of the cycle waiting for a machine, conveyor, or operator.

Compare the full cycle rather than only the maximum track speed.

How Accurate Does the Track Need to Be?

The required positioning accuracy depends on the task.

For basic material movement, the robot may only need to reach the correct general workstation. For assembly, inspection, or handling small parts, more consistent positioning may be required.

Do not evaluate the robot linear track alone. The robot, track support, tool, fixture, and workpiece location all affect the final result.

How Is a Robot 7th Axis Controlled?

The track needs a motor and a suitable control system.

Depending on the solution, it may connect through:

• Robot controller

• Digital inputs and outputs

• PLC

• Separate motor controller

• Manufacturer-specific software

• Prepared programming modules

There are two common ways to use the track.

Moving Between Fixed Positions

The track moves to a defined location such as Machine 1, Machine 2, a pallet position, or a home position. Once the position is reached, the robot begins its task.

This approach is suitable for:

• Machine tending

• Several fixed workstations

• Pallet changes

• Simple pick-and-place applications

Coordinated Robot and Track Motion

In more advanced applications, the robot and track move as part of one coordinated process.

This can be useful for:

• Long welding paths

• Gluing along large components

• Inspection of long workpieces

• Processes that require continuous motion

Coordinated movement requires more planning and programming than moving between fixed positions. ABB, for example, describes track motion as an external axis that can be coordinated with the robot’s main axes.

Before selecting a track, decide whether it only needs to move between stations or whether it must move during the robot process.

What Is Included in a Complete Robot Linear Track?

A linear rail alone is not always a complete 7th-axis solution.

Depending on the product, the following components may be included or required separately:

• Linear track

• Moving carriage

• Motor

• Motor controller

• Robot mounting plate

• Cables and connectors

• Energy chain

• Home or limit sensors

• Mounting hardware

• Software or programming modules

Two products that look similar may include very different components. Compare the complete package rather than only the rail.

Why Is Cable Management Important?

When the robot moves, its cables and hoses move with it.

These may include:

• Robot power cables

• Control and data cables

• Gripper cables

• Camera cables

• Pneumatic hoses

• Other process lines

An energy chain guides these lines along the robot linear track and helps prevent them from hanging loose, bending too sharply, or becoming damaged.

Before purchasing, check:

• Which cables and hoses must move?

• How long do they need to be?

• Which connectors are used?

• Is pneumatic supply required?

• Is an energy chain included?

• Is there room for future cables?

Cable management can have a significant effect on both installation effort and total cost.

7th Axis for ABB Robots and Other Brands

An ABB 7th axis allows an ABB robot to move between machines, pallets, stations, or positions along a large workpiece.

The exact ABB robot model is important. A track for a compact robot has different requirements than one for a large industrial robot.

The same applies to other manufacturers. A brand-compatible solution is selected using information such as:

• Robot manufacturer and model

• Robot weight

• Tool and workpiece weight

• Required travel length

• Required travel speed

• Existing controller

• Installation orientation

• Cables and hoses

• Available installation space

ABB refers to this type of equipment as track motion and uses it to extend the robot’s working area so that one robot can serve several machines.

Even when a ready-made version is not shown for a specific robot, a suitable external robot axis may still be possible after the application and robot model have been reviewed.

7th Axis, Larger Robot, or Two Robots?

A 7th axis is not the only way to increase coverage.

A 7th axis allows one robot to perform several tasks, but the robot needs time to travel between them.

When two machines must be loaded at the same time, two robots may be more suitable. When each machine has enough waiting time, one robot on a linear track may serve both.

Which Setup Fits Which Application?

What Does a 7th Axis Robot System Cost?

The total cost depends on the robot model, travel length, moving load, speed, controller, and included components.

A lower-priced rail may require additional spending when the motor, controller, adapter, or energy chain is not included.

A preconfigured system may have a higher purchase price but require less engineering and assembly. Compare the complete scope of supply.

How to Select a 7th Axis for Robots

Answer these questions in order:

1. Which robot model will be moved?

2. Which machines or stations must it reach?

3. How much travel is required?

4. What is the total weight of the robot, tool, and workpiece?

5. How quickly must the robot change positions?

6. Will the track move to fixed positions or move with the robot?

7. Which controller or PLC is already available?

8. Which cables and hoses need to move?

9. Which components are included with the track?

These details usually narrow the selection to a small number of suitable systems.

Frequently Asked Questions About 7th Axis Robots

What Is a 7th Axis on a Robot?

A 7th axis is an additional linear motion system that moves the complete robot. It extends the robot’s working area along a track.

Is a 7th Axis the Same as a Robot Linear Track?

The terms are often used for the same basic concept. A complete robot linear track includes the rail and may also include the carriage, motor, controller, adapter, and cable management.

Can Any Robot Be Installed on a 7th Axis?

Not automatically. The track capacity, robot adapter, dimensions, motor, and control system must fit the exact robot model.

Is a 7th Axis Available for ABB Robots?

Yes. 7th-axis systems can be configured for ABB robots. The exact model, total moving load, travel length, and control connection are needed for selection.

Are Linear Tracks Available for Other Robot Brands?

Yes. In addition to preconfigured products, systems may be developed for many cobots and industrial robots from other manufacturers.

How Is the Required Load Capacity Calculated?

Include the robot, mounting plate, gripper, workpiece, sensors, and other moving equipment. Do not use only the payload rating of the robot.

How Much Travel Length Do I Need?

The required travel is based on the work positions the robot must reach. Robot reach, mounting position, track ends, and cable management should also be included.

Does a 7th Axis Need Its Own Controller?

That depends on the product. Some tracks connect through the robot controller or digital signals, while others require a separate motor controller.

Can the Robot and Track Move at the Same Time?

Yes, when the control system supports coordinated motion. For simpler applications, the track can move to a fixed position before the robot begins its task.

Is the Energy Chain Always Included?

No. Check whether the energy chain, cables, hoses, and connectors are included with the selected system.

When Are Two Robots Better Than One Robot on a Track?

Two robots may be better when tasks must happen at the same time. A robot rail system is useful when one robot can serve several stations in sequence.