Stack ‘em high, sell ‘em cheap was once a palletising tactic confined to wholesale outlets. Yet nowadays, it’s not uncommon to see pallet loads, especially around busy seasonal periods, carefully positioned on supermarket floors. More complex patterns, combined with revisions by the Health & Safety Executive (HSE) to the L23 manual handling guidance (Manual Handling Operations; Regulations 1992), is proving to be catalyst for automating palletising operations.
It might seem like a giant game of Jenga, but given that back injuries from manual handling are a major cause of occupational ill health, palletising is no game. Well over a third of injuries lasting 3 days or more reported annually to the HSE are caused by manual handling. Switching from stacking pallets by hand to automated systems is far less risk averse. It can also significantly increase your production output and save on transport and labour costs.
If you are currently stacking pallets by hand, it is important to give consideration to a number of factors. Manual handling hazards are wide ranging. Although application driven, unusually shaped or unstable loads, excessive weights, stooping and twisting in cramped workspaces can increase the likelihood of a workforce injury.
When assessing risks, palletising operations are advised to study first the weight of what is being lifted and the frequency and distance that the load is being carried. For lifting, it can be helpful to use the 5×5×5 equation – does the load mass weigh more than 5kg, is it carried further than 5m and does the person do this activity more than 5 times a month? If the answer is yes, this could imply a significant lifting activity.
In terms of manual weight-handling limits, even with the new HSE guidance there are no hard and fast rules. The recent revisions suggest that when lifting at waist height, it’s around 25kg for men and 16kg for women. The trouble is, pallet layers start at ankle height and often reach above shoulder height, and the advisable weight limits drop significantly to around 10kg for men and 7kg for women. Many bulk loads, from sacks of rice to cases of beverages, exceed these advised limits. And if you look at bulk animal supplies, such as bedding hay, stacks can reach up to 2.4m, which is impossible to manually stack safely.
The art of creating stable stacks
Whether you are palletising bags, pouches, cartons, boxes, pails, buckets or drums, the ultimate stability of your stack is paramount. Of course, you want to be an efficient operation and getting as much product onto the pallet as possible within the appropriate weight and height limits plays a part in this, but not at the detriment of other people’s safety. Outside of these primary aims, other factors to consider are barcode scanning or the ease of picking or de-packing the stack by the customer.
Leaving gaps between boxes can help to create a stable stack, and an automated program can do this repetitive task consistently. Retailers are also calling for more mixed pallet loads in an effort to pare down stockroom inventories. A robot can be configured to differentiate light from heavy packages, which means they can palletise a variety of case sizes of products on one pallet without compromising the stability.
There is also an emerging trend for the double stacking of palletised loads. Although this technique increases your storage capacity, to do double stacking successfully depends upon the base pallet load being sufficiently strong to carry the load of the pallet above. The weight of the upper pallet must be evenly shared by all sides of the bottom stack, which articulated robotic arms can successfully accomplish.
Different strokes for different stacks
There are a whole host of stacking patterns. The actual design will ultimately depend on the where the pallet is destined for; for example, shipping container patterns would be different to a wholesaler like Costco. Again, stability is vital and in most pallets you won’t see the same pattern repeated layer upon layer. Like building a brick wall, most cases are arranged to interlock. One exception tends to when stacking rigid cardboard boxes of similar size. Here, it can actually increase the rigidity of the overall pallet if each row is mirrored. For those heading to the retail stores, packaging labels are also orientated to face outwards on all four sides.
When programming the required pattern, you also need to consider the pallet type and size. The most common standard pallet remains the 1 × 1.2 m, yet there are even variations within this. Do the straps run parallel to the long or short edge? Are all four sides fitted with skid bases and is the pallet configured for 4-way or 2-way entry?
Be mindful of tricky products
Sacks tend to be lumpy compared with plastic crates or cardboard boxes. Also, plastic sacks can be more slippery than paper. In many cases, a person building a pallet can compensate for slight variations in outer package shape and pallet stability. Nevertheless, a strong pallet binding with wrap or strapping may be advisable to avert potential disaster.
Palletising location and climate can also have an effect. For example, when stacking bags of frozen product condensation can form and even ice up, which can make packs and sacks slippery.
Systems today can also be surprisingly compact. The Cartesian options on the market today can be installed into tight spaces at the end of line packing process where the lack of space previously eliminated the idea of automating palletising.
Many complaints about automated palletising systems can be attributed to incorrect fill level of products being stacked, how the product has been settled prior to picking up, programming or end of arm tooling. Like any readily available commodity, a palletising robot ‘out of the box’ will accomplish very little. It is the ancillaries, applications knowledge, software and set-up you apply to it that make all the difference.
While there are many free pallet load calculators available on the Internet, Pacepacker always recommends speaking to a well-proven palletiser system provider who can demonstrate how they can handle your products and palletise them. The company’s award-winning, Essex-based ‘Try Before You Buy’ facility enables customers to complete pallet stack trials, giving 100 per cent confidence that the chosen palletising technique won’t topple their efficiency ambitions.
For more information about automated palletising systems please go to www.pacepacker.com.