Preparing the published article.
Payload, Reach and Cycle Time Must Be Read Together
The three parameters constrain each other; reading any one alone can lead to an unworkable design.
Cover image is an AI-generated illustration of a robotics application, not a photograph of the equipment described.
The first three terms anyone meets in robot selection are payload, reach and cycle time. They are not independent figures. They constrain each other and have to be assessed inside one and the same task.
Payload is more than the weight of the part
Payload usually refers to the total mass the wrist can carry, which includes the gripper, cabling and vision components in addition to the workpiece. The further the centre of gravity sits from the mounting flange, the lower the usable capacity tends to be. Checking payload therefore means describing the end-of-arm configuration and the centre of gravity, not quoting a single weight.
Check reach at the worst working point
Reach describes the reachable envelope, but being able to arrive at a position does not mean the rated payload and accuracy still hold there. The furthest, highest or otherwise least favourable posture on the path is what matters. Plotting the working points and checking each one is more practical than remembering a maximum radius.
Cycle time depends on the motion path
Cycle time is related to path length, lifting height, positioning tolerance and whether the robot waits for peripheral equipment. The same model can show large differences between tasks. When assessing cycle time, write out the full sequence of motions and the waiting time that is permitted, then compare with manufacturer data obtained under similar conditions.
When the three conflict, change the task
If payload, reach and cycle time cannot be satisfied at the same time, the first option is to adjust the task split, the cell layout or the process sequence rather than forcing an oversized machine into the design.
This article covers selection fundamentals and recommends no specific model. Actual designs should be assessed by an integrator together with the site conditions.