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In Focus - Archive October 2010
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EVG: Mit intelligenten Sensoren werden Automationskomponenten zu feinfühligen Helfern
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Inductive proximity switches
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10-11-2010 -
Sensors increase the potentials of Gripping Systems
The figures speak for themselves: SCHUNK, the leading expert for clamping technology and gripping systems has sold thousands of sensors for handling applications. While the status of the actuator has been monitored in the past, modern sensors transform the grippers into intelligent helpers, which can measure, inspect, sort and accelerate the whole process simultaneously. The question on their efficiency potential is answered with an overview of the current sensor systems for handling applications.
Modern sensors for gripping systems are following clear trends. They become more compact and easier to integrate and have become increasingly standardized. Today, SCHUNK offers with its modular gripping system, a vast standardized sensor program, which is adjusted to the individual needs and operational environments, and exploits countless possibilities of interrogation and evaluation.
Monitoring the gripper position
The most significant function of the gripper sensor systems, is the monitoring of the gripper position, which is "open" or "closed". In the past, sensors were error-prone but are now well-engineered and process reliable. Modern inductive proximity switches withstand vibrations, dust, and water without problems. By means of an oscillator coil, they generate a high frequency magnetic alternating field. As soon as a metal object enters this field, it takes energy from the magnetic field. Then the oscillation amplitude diminishes, the change is recognized, and the sensor switches without contact. Modern magnetic switches go one step further. They can be completely integrated into the gripper and interrogate the piston positions from the inside. Inductive proximity switches and magnetic switches are widely used in the meantime.
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SCHUNK RSS
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PA3 with PFH
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ONS with SWG
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Wireless monitoring involves benefits
Depending on the environment and application, cables of such sensors can become a point of failure. Cable wiring of modern highly dynamic machining centers cause many problems. Failures due to cables are the most frequent causes for manufacturing downtime. Trouble-shooting is expensive and time-consuming. For the use on machining centers, lathes, grinding machines and confined handling applications, the use of wireless radio sensor technology is recommended. The sensors of these systems monitor the gripper jaw’s stroke and report the status to a transmitter. Then the information is transmitted via radio to a receiver, which is connected with the control unit. Instead of using comprehensive sealing, cable coatings, strain reliefs, the radio sensors circumvent all mechanical obstacles. They can be actuated quickly and easily, avoid cable breakages, and increase the process reliability of the whole plant.
Position sensors for demanding environments
Even under extreme conditions, the inductive proximity switches and magnetic switches do not reach their limits. Conventional sensor systems are quickly strained by high temperatures, aggressive liquids, extremely large volumes of hot chips or coolant. In such cases, or if no electric components are admissible for explosion protection, an air-controlled monitoring system can make precise and admissible statements on the current gripper position or the process status. For this purpose, the actuator is equipped with two additional pneumatic connections. Via a pneumatic measuring line and an AND-valve the information "open", "gripped" or "closed" can be sent back to the control unit. This is done without any electric sensors or additional cables.
With conventional sensors, position monitoring of miniaturized gripping modules is hardly possible. A camera system or optical sensors are the remedy for this problem. Via an optical fiber, light is sent and due to the reflected light, the distance to the reflection surface and the position of the gripper jaws can be recognized.
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Non-contact teach-in
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FPS-Laptop
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Distinguishing components during gripping
Sensors for monitoring the gripper position provide additional information on the gripped part, go one step further. In case of programmable magnetic switches with many application possibilities, the switching point can be individually defined. An adjustable hysteresis allows a safe position monitoring of very short strokes and therefore the gripper can differentiate workpieces of different sizes. The whole gripping process can be better evaluated and process stability can be optimized. Since modern magnetic switches can be individually programmed, they replace numerous conventional versions. With a teaching tool, the switching points can be quickly programmed. The operator saves up to 90 % of the set-up time. The latest generation of magnetic switches can recognize two instead of one switching points. Moreover, the switching points can be programmed, and in turn process reliability is improved.
For finer work, flexible position sensors are used, which allow the adjustment of three to five independent switching points. They determine the position of the gripper jaws and digitally report in which of the five pre-defined position areas the jaws are located. With their help, the gripper can be used for handling and simultaneously for inspection, sorting and a continuous quality control.
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With the SCHUNK OAS grippers quickly measure distances.
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Recognizing distances
If the distance between the gripper and a part has to be determined, you can use expensive vision systems or trust an optical distance sensor with this task. The sensor quickly transforms the gripping module into a seeing gripper. Therefore, the optical sensor is integrated into the gripper center. It continuously supplies the control unit with information, how far away the part is located, or if a gripped part is located between the gripper fingers. The sensor measures the distance between the gripper and the part. This is done during the running process without any loss of time. With the help of sensors, grippers can differentiate parts and their position, quickly pick them up from the assembly belt, stack them, detect wrongly gripped parts and increases the gripper’s reliability during operation.
The optical distance sensor from SCHUNK works with infrared light of 850 nm wave length. It functions at environmental temperatures between - 10° C and + 55° C, and fulfills the requirements for protection class IP65. The sensor module is an all-rounder and can be combined with other grippers and automation modules too. For analog position monitoring of long-stroke grippers it can be integrated into one of the two base jaws. If they are used for grippers or swivel units, they can be aligned inwards instead of outwards and thus monitor the piston.
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FMS force-measuring system
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SCHUNK SDH-2
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A balanced gripping force prevents the complete
system from damage
Whilst the already introduced sensor systems recognize the individual position of the actuator, force measuring systems are measuring forces, which drift over them. Therefore, the gripper fingers are equipped with force-measuring jaws. They recognize the forces, which are acting onto the fingers. Thanks to this data, unnecessary payloads can be recognized, if for example, a fixed workpiece is permanently gripped from one side by a robot system. Already minimum positions of a gripper of one-hundredth or two-hundredth of a millimeter would affect the robot arm at every single gripping operation with the full gripping force in this direction. In the long run, the system would lose its accuracy and would wear quicker than in case of a force-controlled gripping operation.
With the force-measuring jaws, the static and dynamic gripping force can be precisely measured and controlled. This ensures that components can be safely gripped in the case of highly dynamic movements. In the framework of a preventive maintenance, the force measuring systems can be used for inspecting the gripper on proper function in regular cycles. Both increase the process safety and avoids unexpected and expensive downtimes during the running operation.
Automation components, measuring and control devices become particularly sensitive, if they are combined with force-moment sensors. These sensors precisely evaluate which forces and moments affect all six axes. Positioning inaccuracies of workpieces or tools can be compensated, works at moving workpieces can be carried out, and tools, workpieces and automation systems are protected against overload. Force-moment sensors are used for rigid systems, for instance pressing in components. They are used for quality control in the medical industry for controlling teeth, or for controlling the spinal column load. Moreover, they are used in combination with flexible systems for insertion, chamfering or positioning.
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Tactile sensors measure forces and torques.
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Filling a glass
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The top class: tactile sensors
The tactile sensors belong to the top class of modern sensors for handling applications, and are working more fastidious. They can be used for monitoring the gripping force and the gripping surface independent of their position. Therefore it is possible to identify objects and to grip them sensitively. Even fragile parts with various geometries can be handled securely and reliably with the tactile sensors. Changing objects can also be positioned and then inserted. Due to the manifold application possibilities experts assume that tactile sensors will play an increasing role in the service robotics in future. They convert gripper hands into sensitive helpers, which can also be used in complex and disordered surroundings.
Conclusion:
The current development shows, that sensors belong in an increasing way to the standard equipment of handling systems. They open up many possibilities to shorten manufacturing and assembly processes at a comparably low investment, and make them more flexible and process reliable. In the meantime the sensors became an important key for highly efficient handling processes.
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2010-12
Clamping large turned parts safely
Launched from the energy technology, machining of large parts on lathes has become more important in the past few years. This causes a lot of pressure which has to be absorbed by the clamping device. This factor makes it all the more surprising that many users still use traditional clamping solutions, which are costly to set-up, clean and maintain. Modern clamping devices do more than assuring safe clamping, they increase precision of the workpiece, reduce set-up times, and minimize maintenance efforts. This also applies for chucks and jaw boxes.
 more...
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2010-10
Grippers with additional benefits
The figures speak for themselves: SCHUNK, the leading expert for clamping technology and gripping systems has sold thousands of sensors for handling applications. While the status of the actuator has been monitored in the past, modern sensors transform the grippers into intelligent helpers, which can measure, inspect, sort and accelerate the whole process simultaneously. The question on their efficiency potential is answered with an overview of the current sensor systems for handling applications.
more...
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2010-09
Gripping Technology for Industrial Robots
Industrial robots work quickly, reliably and never stop. The achieved output and quality significantly depends on the individual periphery, particlularly of the gripping sytems. In the hunt of the optimum gripper, engineers and users have to consider a large variety of influencing factors. In addition to efficiency and process-reliability, sustainability of the gripping systems playes an increasing role.
more...
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2010-08
Efficient toolholders for automated tool grinding
For tool grinding the toolholder plays an essential role because microns will decide the quality of the manufactured tool edges. In view of small batch sizes and various tools, a multi-purpose toolholder is needed. The holder would have to be precise for exact cutting edge geometries and surfaces, slim to avoid interference between the grinding wheel, powerful for very short clamping depths, and have a high material removal rate as well. Flexibility is also required for covering many different shaft diameters. All of these requirements are persuading companies to use automated grinding machines in order to reduce their current costs.
more...
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2010-07
Pick & Place Solutions in Comparison
In order to assemble components fast and precisely, operators can choose between many different Pick & Place solutions. The performance features of the systems vary from each other. To find the best solution, the advantages and disadvantages of each system should be compared.
more...
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2010-06
Energy efficient gripping
In the best of case scenario, energy-efficient automation modules should reduce energy consumption of the handling system and increase cycle times and output. It helps conserve the environment and saves money if you focus both measures.
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2010-05
Factor of Success Engineering -
With virtual simulations to the optimum clamping solution
How does a component deform during the clamping process and machining? Which clamping solution assures that the workpiece has the exact dimensions? How can an existing clamping device be ideally used? Virtual simulations are giving valuable answers to these and simular questions. By means of the Finite Elements Method (FEM) deformations and component payloads can be calculated, which allows a comparison of the individual clamping options and how to optimize them. In turn, process and investment reliability are increased, development times shorten, the selection of the suitable clamping device is easier and costs are lowered.
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2010-04
Magnetic Clamping Technology - efficient at a variety of tasks
Magnetism is one of the most fascinating and influential force of our universe. Engineers and technicians use this same force in order to clamp workpieces, or to reliably lift components. Magnetic clamping technology is well-established in various areas, such as grinding, milling, turning, mobile lifting units in production, and for huge crane constructions. Most engineers now know that magnetic clamping solutions reduce set-up times by about 80 percent, that workpieces are clamped without any deformation, and even coils can be reliably transported.
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2010-03
EU-funded project pushes on the service robots
Experts predict an increase in the pursuit of service robotics. This is no surprise: Modern robot applications offer an enormous potential to the economy and society. Pilot applications already show how robots might become more and more the intelligent helpers of humans. In addition to universities and other research institutes, industrial enterprises should focus on development in this sector, and make it a reality. Therefore the European Union has decided to subsidize the transfer of knowledge between research institutes and industry financially support this pursuit as well.
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2010-02
Flexible packing and palletizing
Adaptive handling systems provide dynamics and profitability if comprehensive ranges and frequent changes in assortment are given.
Every week a new product generation replaces the previous one. These products, which provide new impulses in trade, are a real challenge for the packing process. Faster, process reliable, and flexible automated solutions are in constant demand. They help to keep the handling costs under control, even at an increasing product variety.
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2010-01
How operators "play it safe" during turning operation
If a workpiece loosens from the chuck on a lathe, it can be dangerous to those working in the manufacturing hall. Because of this, the Employer’s Liability Insurance Associations, Standards and Safety Commitees, do everything in their power, to avoid accidents.
more...
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In Focus - 2013
In Focus - Archive 2012
In Focus - Archive 2011
In Focus - Archive 2010
In Focus - Archive 2009
In Focus - Archive 2008
In Focus - Archive 2007
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