Whether your manufacturing operation is small and low-speed, or a highly-automated high-speed concern, the question of how to efficiently and safely palletise your products is an important one to answer.

Phillip Biggs outlines the factors to consider. 

No matter the size or scale of your manufacturing plant, safety and efficiency in end-of-line function would be a priority. Not surprisingly, there’s no ‘silver-bullet’ solution that solves all current and future application problems.

There are numerous factors to consider, starting with the shipper:

• What’s your shipper production rate?
• What form does your shipper take? (Case, tray/shrink, tray only, shrink only, shelf ready?)
• How rigid is stand how heavy is it?
• And how many different shippers would you like to palletise on the same machine?

And then:

• How many pallet sizes do you have?
• Do you want interleaving sheets?
• How much space do you have available?
• How much extra capacity or flexibility do you need for the future?

And, of course, what’s your budget?

There are a very wide range of potential palletising solutions and technologies available. Is a robot the perfect solution? Would a conventional technical solution be more suited to your factory environment, or possibly a hybrid robotic/conventional palletiser?

And what are the implications of choosing a high-level palletiser rather than a low-level solution?

HIGH LEVEL OR LOW-LEVEL CASE ENTRY HEIGHT

Both high and low-level palletisers are similar in that they form each of layers of the pallet prior to positioning the layer on the pallet.

The product is delivered via an infeed conveyor, turned to the correct orientation and conveyed forward to form a row. A completed row is then pushed into the layer forming zone, which can be a sliding plate, an opening apron or even a robot gripper head.

In a low-level palletiser, the layer is hoisted to be placed on top of the partially built pallet, known as upstacking.

For a high-level palletiser, the pallet is lowered layer by layer as the formed layers are stripped onto the preceding layer (down-stacking), resulting in faster throughput than low-level machines.

High-level palletisers have the advantage of having higher throughputs, even greater than 10 layers per minute. That equates to 100 cases per minute with 24 pack cartons of beer, and much faster on small packs.

They also have a smaller footprint, as the layer-forming section is immediately above the pallet. High-level case delivery can also provide greater flexibility in plant layouts, allowing movements of fork trucks below the conveyor, for example.

Owing to the platforms required, high-level solutions can be seen to be more expensive.

Low-level solutions typically have easier access for maintenance duties. Forklift operators are also able to monitor case in-feed as they remove or place pallets. Low-level case infeed makes them ideal for close coupling with case packers or case sealers.

Generally, low-level machines take up more floor space because all pallet infrastructure, case conveying and layer forming are on one level. Access around the low-level machines often requires personnel conveyor crossovers.

With capital costs ranging from $100k for a cobot palletiser to approximately $1 million for high-speed high-level solutions, the decision-making process for purchasing the correct technology for your factory needs to be considered very closely.

MECHANICAL OR ROBOTIC AUTOMATION

Robots are increasingly being deployed in palletising applications. In the simplest case, they are used to pick up single cases, or a number of cases aligned the same way, to place them in the correct location on a layer.

This solution has the advantage of occupying a small footprint and also has the flexibility to easily change layer patterns from one product to the next, particularly if a simple layer pattern program is used.

A further advantage of robotic palletising is that a single robot is potentially able to assemble multiple pallets simultaneously. They are also able to assemble mixed pallets, particularly if a vision system is incorporated into the solution. A potential drawback of pick and place solutions is the cycle time constraint may limit speeds to approximately 10 cycles per minute, dependent on layer patterns and product suitability. Safety fencing and interlock requirements for robots also add to the cost and footprint of robotic solutions.

An alternative use for robots in palletising is to dynamically orientate the cartons as they move along a pattern-forming conveyor towards the mechanical layer sweeper. Widely deployed in high-speed beverage applications, these hybrid robot/conventional palletisers can operate at speeds of up to 80-120 cartons per minute. It has the dual benefits of speed and flexibility.

Mechanical palletisers have the advantage of typically being lower cost than robotic palletisers, though they have less flexibility and generally require increased maintenance. However, owing to their mechanical nature, they are simpler to maintain than a robotic solution. For specific high-speed applications with rigid, cube-based shapes, they can perform at very high speeds, up to 100 cases per minute or more.

FLEXIBLE COBOTS

In recent times, collaborative robots (cobots) are being deployed for palletising.

Cobots operate in the same way as conventional industrial robots, though they have the advantage of requiring less safety fencing and guarding, significantly reducing footprint and cost. However, with a low payload (<10kg) and lower speeds, they are limited to approximately 10 units per minute. They have their place though, as a highly flexible, low cost and safe solution, typically for a plant moving from a fully manual to an automated process.

CAPITAL COSTS

With capital costs ranging from $100k for a cobot palletiser, to approximately $1 million for high-speed high-level solutions, the decision-making process for purchasing the correct technology for your factory needs to be considered very closely.

As with most capital purchases, several other factors must also be considered, including maintenance costs, ease-of-operation, OEE, local support, software integration capability (i.e. PackML), flexibility and reference sites.

An experienced provider of robotic solutions should be able to guide you through the process of selecting the correct palletising technology for your application.

Phillip Biggs is a director at Packaging Partners, a firm investing in Australian packaging machinery organisations, one of which is Foodmach.

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This article first appeared in PKN Packaging News May-June 2017