Palletising automation: stable stacks, pattern changes and awkward products

The pattern is a stability problem, not a packing puzzle

Software will happily generate a pattern that fits the maximum number of cases on a pallet footprint. Whether that stack survives a forklift, a lorry and a distribution centre is a different question, governed by interlocking between layers, alignment of vertical case walls that carry the load, overhang beyond the pallet edge, and the strength of the packaging once it has absorbed humidity. A dense pattern that collapses in transit costs more than a slightly less efficient one that arrives intact. Test patterns on real product, ideally including a transport trial, rather than accepting the highest count the software offers.

Product consistency at the end of the line is worse than expected

Automated stacking assumes cases arrive square, closed, upright and within dimension. Real end-of-line output includes bulging cartons from over-filled product, flaps that did not fold, cases damp from a chilled process, sacks whose contents have settled unevenly, and shrink-wrapped bundles that vary in tension. Each defeats a gripper that was set up on clean samples. Before specifying, watch what actually leaves the packing operation over a full shift including start-up and changeover, and be prepared to fix the upstream packing before the stacker will run unattended.

Changeover decides whether it fits a mixed plant

A dedicated line running one product changes pattern rarely. A plant running many products and pack formats may change several times a shift, and then the relevant figure is how long a change takes and who can perform it. If a pattern change means calling an engineer to edit a program, the machine becomes a constraint on scheduling and the plant starts batching to avoid it, which is a hidden inventory cost. Insist on pattern selection from a stored library, chosen by a production operator from the panel, with new patterns creatable through a graphical tool rather than by programming.

Slip sheets, layer pads and everything the stack needs besides cases

Real palletising involves more than cases: layer pads for stability, slip sheets between products, corner boards on heavy loads, a top frame, labels applied at a defined position, and a pallet that must itself be fed from a magazine. Each of these is a separate mechanism with its own faults, and collectively they cause more stoppages than the stacking motion. Include them in the specification and in the acceptance test, and check the pallet supply: variation in pallet quality, particularly with reused wooden pallets, jams magazines and produces stacks built on an uneven base.

The safety case is usually the reason it gets funded

Manual stacking combines repeated lifting, awkward postures and often twisting under time pressure, and it is a recognised source of musculoskeletal injury that occupational safety authorities in most countries publish guidance on. That exposure has a cost in absence, claims and turnover which rarely appears in an automation appraisal but is frequently the strongest argument for it. Where full automation is not justified, partial measures such as a lift assist, a pallet positioner that keeps work at a sensible height, or a semi-automatic stacker capture a large part of the benefit for a much smaller commitment.

Frequently asked questions

What makes a palletised load fail in transit?

Usually a pattern that looks efficient and does not align the case walls that actually carry vertical load, combined with overhang past the pallet edge which removes support from the outer cases. Packaging strength falls as board absorbs moisture, so a stack that is sound leaving a dry factory can settle in a humid trailer. Wrapping technique matters too: insufficient containment force, or wrap that does not tie the top layers to the pallet, allows the load to shear under braking.

How quickly should a pattern change be possible?

Quickly enough that scheduling never avoids it, which in a mixed plant means a production operator selecting a stored pattern from the panel in a few minutes without tools. If creating a new pattern requires the supplier or an engineer, you have introduced a dependency into your product introduction process. Specify a graphical pattern tool the plant can use, confirm during acceptance that your own staff can create and run a new pattern, and make sure that training is delivered before handover.

Is a robot or a dedicated layer-forming machine the better choice?

It depends on rate and variety. A dedicated machine that forms whole layers and deposits them is fast and well suited to steady, high-volume output of consistent cases. An articulated arm placing individual cases is slower but far more flexible about product type, pattern, multiple line inputs and awkward items such as sacks or trays. Plants with wide product ranges and moderate rates usually favour the arm; single-product high-speed lines usually favour the layer-forming approach.