When buying a car, we assess various factors that help us to make a decision. Similarly, selecting the right industrial robot requires a good evaluation of key specifications crucial for its applications. In this article, we explore essential factors to consider before investing in an industrial robot.

Payload Capacity

Payload capacity refers to the maximum weight a robot can handle, including both the workpiece and the EOAT (End of Arm Tooling). It is important to account for the weight of the tool when determining the robot’s payload capacity.

Some manufacturers specify two payload capacities:

• Maximum Payload: The highest weight a robot can handle within its optimal working envelope
• Safe-to-Handle Payload: The weight a robot can manage when fully extended

Avoiding overload is crucial as it can lead to reduced performance, excessive wear, or even mechanical failure.

Reach and Workspace

The reach of a robot, or its working radius, is the maximum distance it can extend the end-effector from its base. For a 6-axis robot, this is measured as the maximum distance between the robot’s wrist centre point and its first axis.

The workspace, or working envelope, is the 3D area within which a robot can operate. More precisely, it is a collection of all targets the robot can reach. For a 6-axis robot, this is a collective space formed by the movement ranges of all axes, creating a sphere-like shape in 3D space.

Using a robot simulation tool can help evaluate whether a robot’s reach and workspace are sufficient for the required tasks. It allows for 3D visualisation of the operation space, making it easier to plan compared to using 2D drawings produced by the manufacturer.

Speed and Acceleration

Robots are generally designed to operate faster than humans. The speed and acceleration of a robot determine the cycle time, that is the time it takes to complete a task. Knowing the estimated cycle time is valuable for production planning so make sure to check the robot’s maximum speed and acceleration if high productivity is required.

The specifications of speed and acceleration include:

• Linear Speed: Measured in millimetres or metres per second
• Joint Speed: Measured in degrees or radians per second
• Linear Acceleration/Deceleration: Measured in millimetres or metres per second squared
• Joint Acceleration/Deceleration: Measured in degrees or radians per second squared

Understanding the difference between a robot’s linear and joint movements is essential to make sense of the speed and acceleration specifications. We will cover these details in future articles.

Repeatability and Precision

Repeatability and precision are key indicators of a robot’s displacement performance. Repeatability refers to the robot’s ability to return to the same position consistently, while precision (or absolute accuracy) indicates the robot’s ability to move to a specific position within a fixed coordinate system.

High repeatability and precision are achieved through robust construction and high-quality components, such as motors, gears, and drives. Industrial robots generally exhibit good repeatability to ensure consistent operations. On the other hand, achieving high precision is proven to be challenging and requires careful calibration. This is easier to understand if we compare the design of a precise CNC machine and a 6-axis robot arm.

The International Organisation for Standardisation (ISO) sets testing standards for robot repeatability and precision (ISO 9283). However, most manufacturers do not provide this level of detailed information but a repeatability specification.

Interface and Ease of Programming

If a robot needs to integrate into an existing automation system, consider its controller capabilities, including support for external axes, available communication protocols, I/O interfaces for EOAT and peripheral devices, and user-friendliness for control and programming.

It is worth evaluating the robot’s programming options, especially if in-house staff will handle programming and if the robot will be repurposed for future processes. Ease of programming can reduce system downtime, setup time, and product turnaround time, making a robot more cost-effective.

Conclusion

Other aspects to consider include the operating environment, energy consumption, and safety features. When evaluating potential suppliers, consider the training, support, and maintenance they offer, as well as the overall cost-effectiveness of the package.

It is essential to analyse the factors that are important for meeting your needs. We hope this article will help you make an informed decision about purchasing an industrial robot.