A turnover box moves parts from one process to another inside a factory – from machining to assembly, from goods-in to the line, from one building to another. It is one of the least glamorous items in a plant and one of the most used. Most of the problems with them come from one thing.
Load, which is nearly always the issue
Metal parts are dense. A turnover box that looks half full can be carrying three times what the same box carries of anything else, and the box is rated by weight, not by volume.
The failure is gradual and therefore missed: the base deforms, the box becomes slightly out of square, it stops stacking properly, and then it cracks. Specifying to the actual weight of your heaviest part in a full box prevents all of it.
What a turnover box is and what it is for generally is set out in what a turnover box is used for.
Stacking and nesting
The two states matter equally. Boxes stack when full and nest when empty, and the ratio between the two determines how much space empty boxes take – which in a plant with limited floor area is the binding constraint.
Ask for both numbers. A box that nests well and stacks badly is a problem on the line; one that stacks well and nests badly is a problem in the store.
What they get carried on
Whatever it is, check compatibility before ordering. Boxes that go onto roller conveyor need a base that runs on rollers; boxes that get carried by hand need handles that take the load; boxes that go into racking need the right footprint.
Conveyor compatibility is a common surprise and it is covered in do PP crates run on roller conveyors.
Identification
Most plants mark boxes by destination or by part family, and a simple colour split is often enough. Cards or labels in a holder on the box end work well and can be changed – which matters because what a box carries changes far more often than the box needs replacing.
What wears
The base, from being dragged. The rim, from being caught. And the stacking lugs, if the box has them and they are misused. Most of that is handling rather than specification, and it is worth saying plainly: the largest single cause of premature turnover box failure is dragging rather than lifting.
Standardise on two sizes
Most plants end up with a dozen box sizes through accretion, and consolidating to two – a small and a large – makes stacking, racking and ordering simpler and reduces the total fleet needed, because boxes are interchangeable.
The cost of consolidation is that some loads do not fit perfectly. In practice that is a smaller cost than a fragmented fleet, and it is worth doing once.
Cost per trip
A turnover box in internal logistics makes hundreds of trips a year, which means the purchase price is almost irrelevant and durability is everything. Specify for the trip count rather than for the price, and it will be cheaper over a year.
What we can do
We supply PP turnover boxes and will specify to your actual heaviest load rather than to a nominal size. Tell us the part weight and how the box moves – that is enough to get it right, and we will tell you when a crate would serve better.