T he packaging industry has for decades used manual labour for picking and packing products into boxes, trays and blisters. A typical application is packing mixed chocolate pralines into blisters, a repetitive task that is performed at very high speed. This type of work is tedious and generally poorly paid, which makes it increasingly difficult to find and retain labour. Additionally, growing concerns about food safety have encouraged the industry to seek alternative ways to pick and pack food, so that human contact is minimised. For these reasons, the industry has shown a great deal of interest in automation.
The ABB FlexPicker
Launched in 1998, ABB’s FlexPicker, IRB 340 was uniquely designed for the picking industry, to pick and pack small lightweight objects, such as chocolates. Although the robot had a simple design and was easy to build, controlling was altogether more difficult. Far more challenging was moving the robot at such speeds without causing jerky movements or destroying the manipulator. Hence, ABB overcame such a challenge with the development of its highly successful IRB 360, which can pick and place products quicker and more gently than any other robot.
IRB 360 provided solutions for new applications, creating new markets, which in turn boosted sales.
Improvements in the design and strength of components created a more durable and robust robot that required minimal maintenance to achieve maximal operating time. Additional design features have made the new generation delta robots more versatile; a smaller version taking up less space on the factory floor and a new version for the food industry that allows thorough cleaning using standard industrial methods. One of the most important features of the ABB delta robot is its advanced motion control, which is fundamental to the overall performance of the machine. It is easy to build a delta design robot and incorporate a high torque motor to move it very quickly. The challenge is to make it fast and accurate, while maintaining a long lifespan. The problem is that it is not possible to compensate for poor motion control with a ‘stronger’ mechanical design, since the weight of the robot slows its movement. High performance comes from advanced motion control. The control loop in the ABB robot controller plans the movement of the manipulator, taking account of its dynamic behaviour to reduce mechanical stress. Inevitably, during the picking and packing process, products occasionally appear on a picking line in unexpected places. Sometimes frozen products, for example, can be frozen together and then separate during movement, or products can be repositioned during a sudden conveyor belt shutdown. Such product relocation can cause problems for a robot, resulting in unexpected collisions. With the FlexPicker the lightweight arm system detaches during a heavy collision. The arm system is held in place by a spring unit that protects the arm from damage during a mechanical impact, even when fully accelerating. This safety feature protects the robot, but a robot that stops moving when the arm system falls off would further protect the product and the conveyor. The new QuickMove and TrueMove motion controller can detect a malfunctioning arm system and automatically stop the robot.
A robust robot
A high-speed picking robot can typically make 130 pick-and-place operations a minute. In a production line made up of eight robots, this equates to over one million cycles a day, and over 200 million cycles a year. Even with a low failure rate of one in a million, the probability of a malfunction becomes a daily event. Such a failure rate is unacceptable and can be reduced only by making the robots extremely robust. Universal joints, theta axes and fixation screws are critical elements that had to be improved. Components have been made stronger so that they last longer and require less maintenance. Improved design features have ensured that parts can be replaced easily, even by relatively unskilled technicians. Such features include enlarged screw dimensions and guiding sections so that service and repairs can be made easily and cannot be made incorrectly.
Robot for food industry
The new generation IRB 360 has an improved sanitation design, which although heavier, can be more easily cleaned. It has all stainless metal components, including the theta axis, delta plate and arm end caps, as well as a watertight casing (IP 69K), which allows to be cleaned with hot, high-pressure water at close range. This means that no special time-consuming arrangements need be made to clean the robot. It can be treated just like any other equipment in the plant.
Saving floor space
Floor space is always at a premium in industry and the food industry is no exception. Increasing productivity within a given area is one of the frequent demands made of robots. The standard ABB robot controller is, however, too large for most food and pharmaceutical industry applications, which is why a modified controller was developed several years ago. A smaller footprint was achieved by packing the components more densely and increasing the unit’s height. This new controller rapidly gained popularity among picking customers, saving crucial floor space and reducing costs, since the new controller was housed within the customers’ existing control cabinets. When developing a new robot, reducing the size of the footprint is a neutral requirement for the development team; however, keeping the number of parts to a minimum is, for cost reasons, a high priority.
By shortening the upper arms and decreasing the work envelope, the new IRB 360 requires less floor space, even without changing the base box (a floor space reduction up to 30 per cent). The width of a Flexpicker cell was decreased from 965 to 810 mm and its length reduced from 980 to 820 mm. Even greater space savings can be imagined, when the increased cycle speed of the IRB 360 is considered. Higher performance means that seven new IRB 360 robots can replace eight old IRB 340 robots, providing total floor-space savings of as much as 40 per cent.
From picking to packing
IRB 360 was developed to allow an increased payload by increasing the torque on the fourth (theta) axis in the middle, so that the robot would be more versatile, increasing its scope for new applications without reducing the lifespan of the robot. Case packing with a Flexpicker is a very common application, yet by expanding the payload from 2 to 3 kg, the number of packing applications was dramatically increased. The IRB 360 robot can pick up heavier products, handling sausage packs of 2 kg with a 1 kg gripper, as compared to the IRB 340 robot, which can only pick up 1.3 kg sausage packs with a 0.7 kg gripper. This improved performance presents the possibility of doubling production throughput.
By separating the parallel arm, the new robot could be made stronger, but would also affect its weight. A further drawback would be an increase in the number of required components, since different arm systems would be needed for different payloads. Again these problems were solved by the new motion controller. The improvements made in robot movement control actually made it possible to handle 3 kg payloads using the same arm system as before with even shorter cycle times. Smoother robot movement and a greater understanding of the robot’s limitations have given the IRB 360 a 30 per cent performance improvement with a 2 kg payload as compared with the IRB 340 model. Throughput can be increased from 30 to 50 per cent in case of packing applications.
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