Size for peak, not average

The single most common way a palletizing or packing cell disappoints is that somebody sized it against the number on the production report instead of the number the line actually hits at four in the afternoon.

Every plant has two rates. There is the average, which is what the monthly report says, and there is the peak, which is what happens when the filler runs clean, the crew is caught up, and product comes down the line as fast as the equipment allows. The average is a comfortable number. The peak is the number your cell has to survive.

A robot cell that keeps up with the average and falls behind the peak does not fail gracefully. It backs up. Cases pile at the infeed, somebody steps in to hand stack the overflow, and within a month you have a robot and a person doing the job the robot was bought to do. The cell did exactly what it was specified to do. The specification was wrong.

There is a second trap underneath the first. The rate on a robot datasheet is a laboratory figure, measured under conditions your cell will not have. It assumes a short move, a light payload and no waiting. Your actual cycle includes the gripper opening, closing and settling, the arm moving to a real pick point and a real place point, and any pause while a pallet is swapped or a conveyor indexes. It is not unusual for a real cycle to run a third longer than the headline number, and if you are running collaboratively near people, the risk assessment may slow the arm further.

So the arithmetic is not peak rate versus datasheet rate. It is peak rate versus achievable rate with derates, and then some margin on top, because a cell running at ninety eight percent of its capability has no room to recover from anything. One jam, one bad pallet, one slow changeover, and it never catches up. We would rather quote you a cell with visible headroom than one that looks cheaper on paper and disappoints on a Tuesday.

The practical version of this is simple and costs nothing. Before anyone quotes you, stand at the station with a stopwatch during your busiest hour of your busiest day and count. Not what the report says. Not what the line is rated for. What actually arrives. That number, plus honest derates, plus margin, is the specification.

If the peak number frightens you because it pushes the cell into a bigger arm or a fenced industrial machine, that is useful information rather than bad news. It is much cheaper to learn it before purchase than after.