Palletising: robotic or manual

The primary concern for all companies relying on manual palletising has to be occupational health and safety. Manual and repetitive lifting and carrying is fraught with danger. The inherent risk of injury to employees is high and job satisfaction is low resulting in frequent turnover of staff that affects the quality and consistency of the end product. And, as the manager of every production critical facility knows, speed of throughput, quality control and full-time use of manufacturing systems are just a few of the factors that can have detrimental effects on overall competitiveness.

Early solutions

Since the late 1960s, dedicated automatic palletising equipment has been available in Australia and New Zealand, and plants with high product volumes have benefited hugely from this technology. Unfortunately, in Australia, for the large number of plants that were producing lower volumes due to the inherent lower demand in the marketplace, these dedicated sys-tems just didn't work. They were too expensive, not feasible or simply too imprac-tical to implement.

Flexible palletising

Since the 1980s, standard robot manipulators have been used to perform the palletising of cartons, bags, trays, pails and containers.

Initially, the system components such as grippers, controls, safety components and human machine interfaces required for a reliable system were not available. As a result many systems were installed with components specially converted by the system integrator, often requiring replacement within a matter of months.

As the robotics industry emerged worldwide throughout the 1980s and early 1990s, many manufacturers of robot systems experimented with emerging technology, much of which, sadly, failed. Large SCARA-style palletising robots and 'Bubble Memory' modules, for example, are just two technologies that never made it through to the new millennium.

More effective solutions

The 1990s saw an overall reduction in the number of robot system manufacturers worldwide. With the advent of more standardised designs in robot manipulators and controllers came a market boom in the use of robots away from the automotive industry and robot systems became one of the most reliable machines within a plant.

This is certainly the case in Australia and New Zealand where a significant proportion of robots sold today replaces those machines installed over 15 years ago, which have been operating non-stop over multiple shifts ever since.

Robot accessories

The boom in robot sales throughout the 1990s has been the impetus for progress among manufacturers of specialised robotic tooling such as grippers, flexible cable sets and tool change systems.

The robot system manufacturers today also provide standard palletising robots and software to minimise programming time, which is often a significant portion of the system investment.

Designing and building a system

When designing and building a new system there are many factors to be taken into consideration. Space, product variations, environmental issues, size, required temperatures, hygiene issues, warehousing and shipping all need to be taken into account by the engineer when designing the most suitable robotic palletising system for your requirements.

Who do you talk to?

Look for a System Integrator. A company specialising in system integration tends to be independent of any one brand of hardware and is able to work with and combine a variety of software and hard-ware solutions to ensure you are getting the best design possible for your needs.

Make sure your system integrator has considerable knowledge of the current products and operational flow of your plant, while using their experience to ensure that the system design is flexible enough to meet future pack-aging changes, and is safe to use and easy to operate with minimal training.

What does it cost?

As a general rule of thumb, if your plant has more than one person involved in manual palletising, then a system can be engineered to your require-ments to give your company a return on investment within two years based on labour savings alone. This does not take into account possible injury claims and other losses suffered over the same period attributable to manual systems.

Where to start

To understand the products in this example we will concentrate on finished cartons, known as shippers.

• Identification of products including alignment and flow

  Listing all the products and defining which line number they run from provide an indication of how many carton infeeds and completed pallet outfeeds are required. Specifying carton dimensions and the orientation of flow from the packing systems determine the infeed conveyor design and influence the gripper design.

• Weights

  The weights and rates of the cartons, combined with knowledge of the board quality and contents of the carton, guide the system integrator to select the optimum gripper design. The most common gripper in use today has rows of vacuum cups that can be individually switched to allow efficient gripping of different sized cartons.

  While common, this method is typically suitable for cartons that weigh less than 10 kg containing unbreakable products. For cartons holding glass containers, for example, a mechanical gripper supporting the carton from the sides and below offers security during transfer with the trade-off of a slightly longer cycle time.

• Rates

  Determining the rates that the robotic palletising system can achieve requires an understanding of the pallet patterns. As a rule, the more simple the pallet pattern the greater the number of cartons that can be transferred per cycle. With a typical cycle time of six seconds, a robotic palletising system can transfer from one to six cartons per cycle, providing rates of over 3000 cartons per hour.

• Other criteria

  Other criteria such as available floor space and whether multiple pallet types, slip sheets, automatic stretch wrapping and automatic pallet transfers are required also determine the optimum robotic palletising system for your plant.

Robotic palletising offers a cost-efficient solution where medium production volumes are produced from one or more lines.

System integrators within Australia have the experience to produce a design and costing estimate within several weeks, with manufacture, installation and commissioning typically completed within just 26 weeks.