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The future of advanced handling

The future of advanced handling With increased demands in the food manufacturing and packaging industry to improve energy efficiency and reduce operational costs, plant managers are reviewing their automation systems. Nigel Dawson of Festo reviews the next generation of handling systems and discusses the advantages of systems that operate using parallel kinematics.

Industrial robot manufacturers have designed and developed a variety of robots to automate manufacturing applications and the six-axis robot is the most commonly integrated industrial robot on the market today. These traditional robotics are built using serial kinematic principles, whereby larger axis are used to move smaller axis. Each axis is driven by an individual motor, which in turn is attached to the next axis, similar to a human's arm. These systems are accurate, relatively dynamic, and have been carrying out reliable handling tasks for many years.  

Recently however, parallel kinematic systems have been developed which are more efficient, enabling manufacturers to reduce operational costs and make significant savings. In parallel kinematic systems each motor acts directly on the load and by sharing the load in this way, the motors can work more efficiently and the robotics can achieve higher dynamics. Parallel kinematic systems have many advantages over traditional systems including higher dynamics, higher payloads, reduced cable management and they are more compact.

As the mass is shared equally between the motors, smaller motors can be used to deliver the same high performance, therefore improving energy efficiency, reducing current consumption and reducing the purchase cost. Conversely, the same sized motors can be used to give a higher performance. There are also benefits for ease of installation and cable management. As the motors remain static, the cable management design is simplified and cable failure breakdowns are reduced.

Festo has developed three systems based on parallel kinematics: the H-gantry, the T-gantry and the Tripod.  They deliver a highly dynamic response at lower costs and are 30% faster than conventional handling systems, heralding a new era in packaging technology. The H and T gantries combine the dynamic response of a linear motor handling system with the cost of a toothed belt handling solution - which is precisely what is needed for the fast transfer to boxes at the end of the form-fill-seal process, for example.  

The H-gantry features two stationary motors with one dynamic toothed belt and low moving mass, and has a high dynamic response of 70 picks per minute. It covers a rectangular working area that is significantly larger than that of robot systems with delta kinematics, which can only work in round or kidney-shaped areas, and the 3D/planar surface gantry can easily distribute packaged foodstuffs such as chocolate bars to boxes. The high-speed H-gantry can be scaled to any stroke, has a very low profile, a low centre of gravity and a simpler frame than high-speed delta robots. Its optimised acceleration and braking characteristics enable strokes of 2m and 1m along the X and Y axis, with an repeatability of ±0.1mm.

The rotary/lifting module of the high-speed H-gantry is ingenious too. It consists of a hollow shaft with integrated energy through-feed for the end effector and forms the Z-axis to which the gripper unit is attached. The rotary/lifting module accelerates to a speed of 1.5m/s at a rate of 20m/s2. Vacuum and mechanical grippers with workpiece loads ranging from zero to two kilograms can be utilised.

The T-gantry works in a similar way to the H-gantry with one dynamic toothed belt. It is more suitable for Y-Z applications and has a high dynamic response rate of over 90 picks per minute. The high-speed T-gantry can easily achieve cycle times of 670 milliseconds. It is a high-speed pick and place unit with a higher dynamic response than a conventional linear gantry and can be scaled to any stroke. It can thus keep up with the cycle times required in the form-fill-seal process.

The gantry has a maximum speed of 4m/s and achieves acceleration rates of 50m/s2 over the entire working area thanks to a clever design that connects both toothed belt axes to the cross member with a single dynamic toothed belt around the drive shafts. The belt is driven by two servo motors. An added benefit is the fact that the motors are not moved within the X/Y area. With its two degrees of freedom, reduced mass and high performance servo drives, the system facilitates fast, dynamic motion and results in less wear.

The Tripod handling system is unique in the field of delta robots in that the rotation movement of the motor is transferred into linear motion of the axis before the carbon fibre arms. Other delta type robots exist, however these use rotational movement, which is not as robust.   

The Tripod provides operating speeds of 150 picks/sec, greater precision and can carry heavier payloads, yet is available at a competitive cost as the products that make up the Tripod are standard Festo axes, motors and drives which are readily available. This results in delivery of a complete Tripod robot in just 15 days. The pyramid construction means the structure is sturdy and there is high stability due to the mechanical axis. It features very low vibration, and as a result operates quietly. In particular, the system can accelerate at 110m/s2, with speeds of 7m/s, and carry loads of up to 5kg.

The Tripod has rotational accuracy with exceptional precision and path accuracy for applications that need accurate motion profiles. Traditional delta robot systems based on rotational movement are not as strong or precise and as a result, do not perform as well in assembly tasks. Further, Festo has designed an innovative patent-pending collision observer safety function to prevent expensive and dangerous damage to the robot. In alternative robotic systems that use delta construction, the knuckle joints holding the carbon fibre rods can, on high acceleration or impact, come apart. Festo's system pressurises the joint with low pressure air and monitors that pressure. If the knuckle comes away by a minute fraction, the whole system goes into E Stop.

All of these high-speed handling systems come as complete packages consisting of a controller and mechanical components for fast transfer and positioning, and are delivered ready to install. Often, advanced handling systems such as these require additional integration such as conveyors, guarding and handshaking with additional machinery. In order to facilitate this requirement Festo is working with automation supplier Autarky Automation.

The new generation of handling systems represents a significant step forward in automation. They are real alternatives to expensive and complex systems such as robots with delta kinematics and SCARAs, providing manufacturers with increased energy efficiency and a substantial increase in productivity.
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