Pack-out room ergonomics: benches, heights and repetitive strain

Twenty-eight first-aid reports in eleven months, twenty-two of them shoulder and lower back, all from a room where nobody had lifted anything heavier than a 4.8 kg crate. The plant manager had already bought lifting aids nobody used and run a manual handling course that everyone passed and nobody changed. The actual cause was a bench at 900 mm, a crate stack on the floor beside it, and a pack-out motion that required every operator to reach down and forward 1,100 times a shift.

Repetitive strain in a pack-out room rarely comes from a single heavy lift. It comes from a small awkward movement repeated at a rate the body was not designed for, and it is entirely fixable with a tape measure.

The geometry of one pack

Watch an operator build a carton and count the movements: reach for the pack, reach for the product, place, fold, tape, lift the carton to the roller, return. That is six movements, and at 1,100 cartons a shift it is 6,600. If the pack is stored 300 mm below the bench surface, every one of those reaches includes a downward flex of the spine and a stretch at the shoulder.

The fix is a bench height that puts the working surface 50 to 100 mm below the operator’s elbow, with the pack supply at the same height as the bench, not below it. For a standing operator of average height that lands around 850 to 950 mm; for a seated operator it is lower and needs an adjustable chair more than an adjustable bench. Get this wrong and everything downstream is compensation.

Reach zones, not comfort

Divide the bench into three zones. The primary zone is within 400 mm of the body, where both hands work without turning. The secondary zone extends to 600 mm with a reach, for things picked up occasionally. The outer zone is anything that requires a step or a twist, and nothing that happens 1,100 times a shift belongs there.

Tape the zones on the bench in three colours and put the pack supply in the primary zone. This costs a roll of tape and it is the single most effective change we have seen in a pack-out room, because it makes the wrong layout visible to everyone, including the supervisor who set it up.

The roller is not a luxury

A gravity roller conveyor at bench height, running to the pallet, removes the lift-and-turn that puts most strain on the lower back. The carton leaves the bench by sliding, not by lifting, and the operator’s feet stay planted. Where a full roller run is not possible, a simple skate-wheel section of 1.2 m at the end of the bench captures most of the benefit.

The trap is putting the roller too high. A roller set at 1,000 mm makes the operator lift the carton to shoulder height to place it, which is worse than the floor stack it replaced. Set the roller 20 mm below the bench surface so a carton slides across rather than being lifted onto it.

Rotation that people believe in

Job rotation works when it changes the movement, not just the product. Moving an operator from packing cartons to packing cartons of a different size changes nothing. Moving them from a standing pack bench to a seated labelling task for ninety minutes changes the load on the shoulder and the spine, and that is what the body needs.

Build a rotation on paper with the movements written next to each task, and rotate on the movements. Ninety minutes is a reasonable block; two hours is common and usually too long for the highest-repetition station. Put a clock in the room that everyone can see, because a rotation nobody can track is a rotation that stops happening in week three.

What to measure, and what it will tell you

Track three things monthly: first-aid reports by body area, the number of cartons packed per operator per hour, and absenteeism on the pack-out line. When the bench height is corrected, the first-aid reports fall within a quarter and the throughput usually rises by 4 to 8%, because the operator is no longer spending a fraction of each cycle recovering position.

That throughput gain is the argument that gets the bench rebuilt. Safety cases stall in budget meetings; a 6% throughput gain with a payback under five months does not.

If you are laying out a new pack-out room, the carton and pack handling dimensions in our logistics ice pack user guide are given as working heights rather than product sizes, which is the way a bench layout should be drawn.

Take a tape measure to your worst station this week, measure the bench, the pack supply and the operator’s elbow, and take a photograph from the side. The gap between those numbers is your injury rate.