Scoping a Robot Cell: Payload, Reach and Cycle Time
Measure payload honestly
Rated payload is not usable payload. Add the end effector, the workpiece, any fixture carried by the robot and a margin for tooling changes. A robot quoted at its rated payload will run slow and wear out early; the practical rule is to stay near 60-70% of the rated figure for a cycle that repeats all day.
Reach includes the gripper
Reach is measured to the tool flange. Subtract the tool length, then check the worst-case position in the cell — not the average one. Robots lose accuracy near the edge of their envelope, so plan the motion path to keep the critical operations inside the middle of the working volume.
| Parameter | How to measure | Common mistake |
|---|---|---|
| Payload | Workpiece + gripper + cabling + margin | Using the workpiece weight alone |
| Reach | Flange-to-target at the furthest point | Forgetting the gripper length |
| Cycle time | Sum of moves + grip + process + settle | Ignoring I/O and handshake delay |
Cycle time is a system number
Add the time the machine spends waiting for a signal, the time the operator needs to present a part, and the settle time after a fast move. Simulation is useful for the robot motion; the handshakes are usually what break the takt time in the real cell.