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Robots clean up their act

20 May 2018

A combination of economic drivers and concerns over long-term labour resources has resulted in an increasing interest in the use of robots. Laurence Wood considers the hygienic implications of their use in food production applications. 

As robots continue to move further upstream in the food manufacturing processes, the requirements for cleanliness, hygiene and food safety become more stringent and consideration needs to be given to adhering to current food safety directives and to ensuring that the type of robot used and its design characteristics are appropriate for the specific application.

Robots first found their way into the food-manufacturing sector through end-of-line packaging and palletising applications. Their high payload capacity and large work envelopes made them the ideal fit for these relatively simple applications. Safety considerations focused entirely on protecting operators through the use of fencing and / or light-guard systems. Other than maintaining the integrity of the cartons and populated pallet there are minimal requirements and few considerations in relation to hygiene in this environment.

However, integrating robots further upstream in the food manufacturing process brings additional complications, including the variability of products, the fragile and often perishable characteristics of the products being handled, high production speeds and a much greater emphasis on cleanliness and hygiene.

Robots have addressed the issues of high speed, and deal with product variability and positioning through the use of sensors and machine vision systems. In addition, innovative gripper concepts have made it possible for robots to handle a wide variety of different food products.

From a hygiene and cleanliness perspective, using robots does eliminate the potential opportunities for human-borne sources of contamination during food handling. However, the type of robot used, and its design characteristics, need to be given careful consideration if the highest standards of cleanliness and food safety are to be maintained within hygienically sensitive environments. Little will be achieved if the potential human sources of contamination are replaced by others resulting from the use of robots of an inappropriate design or standard.

Collaborative study
A collaborative study between the European Hygienic Engineering & Design Group (EHEDG), ECOLAB (Minneapolis, MN) and Stäubli Robotics, known as the Humid Environment (HE) Project, set out with the goal of achieving technological advances that would elevate the standards of hygiene for robots used in sensitive environments to the highest level.

The project brought together dairy manufacturers, freezing and thermoforming equipment manufacturers and robot manufacturers familiar with EHEDG guidelines and specifications and over a number of years it has resulted in the development of a consistent, high-performance and cleanable robot designed specifically for sensitive food production applications.

A primary objective of the project was to consider the potential sources of contamination, and how best to eliminate them. This encompassed a detailed review of the mechanical elements of the robot and how the working environment and temperatures could influence the generation of contaminates.

Of the three main types of robot used within the food-manufacturing sector: Delta, four-axis and six-axis, the Delta configuration holds the greatest potential for contamination. The architecture of this type of robot means that its motors, transmission oils, retention zones and the overhead mounting frame itself, are all located directly above the food product.

Another factor which is not always considered carefully enough, is that during operation a robot can heat up to 70°C, especially when installed within a high-speed line.

In sensitive environments, where operating temperatures range between 4°C and 10°C, condensation, oil expansion and cooling off occur within a few minutes. The effect of the heat generated by the robot is most noticeable when the robot reaches the end of the production cycle.

Bacterial growth
The ideal conditions for bacterial growth inside a robot include: medium temperatures between 15°C and 40°C; water presence and activity; vapour condensation drawn from the environment directly into the robot (including bacteria); neutral pH; and most significantly, lack of access for cleaning the inner parts of the equipment.

The collaboration and study, took into account multiple factors including robot arm design, potential for bacterial contamination, retention zones, dielectric exchanges between cleaning solutions and the various metals used in the arm construction and surface treatments.

Ultimately, the study showed that ‘HE grade’ can be considered as a recommended standard for use in the design and engineering of both four-axis and six-axis robots. To achieve enhanced hygienic features a HE robot should be used. Parallel (or Delta) architecture robot design is not recommended and any Delta robots used in sensitive food production areas should be covered to prevent possible contamination.

The exterior arm of the ‘HE grade’ robots from Staubi are designed to comply with EHEDG recommendations on minimising water retention to prevent bacteria such as salmonella and listeria from developing.

Further, its connectors are integrated into the body of the robot so that all of the equipment can be cleaned. The equipment is smooth (with rounded edges), and pressurised arms eliminate the risk of contamination. The robot arms are water-tight, and designed to allow water to drain away. To make sure the robots can withstand frequent wash down cycles, Staubli worked with a manufacturer of detergents and sterilization products to make the outside surface of the arm chemically compatible with the cleaning products commonly used within the food industry.

Laurence Wood is sales manager at Staubli (UK) Ltd.

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