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In Focus - July 2010
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07-01-2010 -
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.
In the past, rotating cam shafts were the exclusive means of actuation for Pick & Place units. In fact, mechanic solutions with ground cam disks are still in use, which carry out defined motions in a defined cycle time. In modern manufacturing concepts though, they are replaced by pneumatic or electrically driven solutions, which offer more freedom to the operator. Because of the increasing variety of options, miniaturization, and the growing cost pressure, precise, fast and process reliable solutions are now in great demand.
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Pneumatically or electrically driven?
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Ideal for easy applications: the modular designed pneumatic Pick & Place Unit.
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Engineers are now becoming more aware of the advantages of mechatronic solutions. Their high flexibility and dynamics, and the low operating costs are very attractive. However, compared with a pneumatic system, the price of an electrically driven solution is still 2 - 3 times higher. If the same components are to be repeatedly assembled, and mechatronic knowledge is not available, a pneumatic solutions is still the best choice.
For easy Pick & Place applications, the combination of two pneumatically driven linear modules is ideal. By combining the corresponding sizes, design models and built-up systems, and by adjusting the end positions, such solutions can be individually adjusted for every application. In the area of assembly automation, current strokes of 200 mm in horizontal and 100 mm in vertical direction can be achieved at a cycle time of 1.2 seconds. In case of modular set-up pneumatic solutions, strokes of up to 1500 mm can be achieved.
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Compact pneumatic units for high cycle times
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The PPU-P from SCHUNK is a compact pneumatic unit for high speed applications.
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In the meantime, pneumatic solutions for high speed precise applications are now available, which achieve up to 120 picks per minute. This compact pace-maker has repeat accuracies of up to 0.01 mm. In contrast to conventional pneumatic solutions, the horizontal and vertical motions overlap and are positively driven by a curved roller. They can be actuated faster compared to conventional pneumatic Pick & Place solutions, reducing cycle times by 50 %.
Such a solution is ideal for operators, who do not have mechatronic knowledge, but wish to achieve high cycle times. These units are comparabily low-priced and can be set-up quickly. Strokes can be adjusted via end positions. In order to increase energy efficiency, an optional valve box minimizes the compressed air consumption which increases energy supply and cycle times. The maintenance requirements of the pneumatic units is low, with the shock absorbers having to be exchanged every four to five million cycles.
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Conventional electrical solutions
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Flexibility for Pick & Place tasks with large components resulting from units with spindle/ belt drives.
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While pneumatic solutions normally do not offer more than two intermediate positions, solutions with electric drives offer more freedom to the operator. Conventional modular set-up Pick & Place solutions mostly work in Z-direction with a spindle drive, and in Y-direction with a belt drive, which is comparably lower in price and achieves respectable speeds of 8 m/s. Conventional electrically driven Pick & Place solutions achieve constantly high forces and allow payloads of up to 800 kg, and large stokes of up to eight meters. Although both values never play an important role in the classic assembly automation, it shows the broad spectrum for possible applications. Due to the self-locking effect of the spindle drive, this kind of conventional solutions can be also used without an additional safety device for safety-relevant applications.
For automated assembly of small components, conventinal solution can be applied to some extent, since the spindle and belt drive are not that rigid, and repeat accuracies of less than 0,1 mm can be assured for such solutions. Due to the comprehensive mechanics, wear parts must be regularly exchanged, which causes additional maintenance costs. When assembling small components, the conventional electrically driven solutions reach their limits, even when needing low strokes. In both cases it is better to change over to axes with linear direct drives.
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Flexible module solutions with linear direct drive
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Modular designed units with linear direct drives are maintenance-free, precise and flexible.
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Linear direct drives have considerably less interfaces in the drive train than at the spindel or belt drive. Therefore there is less scope.
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The low-maintenance linear direct drives are more precise and faster. There is only one interface between the motor and the slide. Modular designed solutions with linear direct drives offer maximum precision, flexibility, speed and comfort. They provide reliable repeat accuracies of less than 0.01 mm. However, the purchase price of the solutions are higher than of pneumatic or conventional electrical solutions, and are even more expensive when larger axes are needed.
In addition to the build-up of the directly driven linear modules, the stroke and driving forces can be individually defined and controlled. This flexibility particularly pays off if components have to be changed often. In case of insertion processes, the individual forces can be measured by a control system. With linear direct drive, strokes of up to 3.800 mm are possible. When using high speed applications, this is a disadvantage, since the motor of the vertical axis is also moving in the same direction and at high speeds increases the danger of a cable break. Due to the motor, a relatively high mass has to be moved, which in turn reduces efficiency.
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Variable unit for a rapid Pick & Place
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At a cycle time of 0.58 seconds, and a repeat accuracy of less than 0.01 millimeters, the linear directly driven Pick & Place Unit PPU-E30 from SCHUNK is setting standards in assembly automation.
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As for the pneumatic solutions, in the field of linear directly driven Pick & Place Units there is a very compact solution available now, which combines the most essential advantages. The fastest Pick & Place Unit, PPU-E from SCHUNK comes on the market, which does not require a moving motor cable, since the motor of the vertical axis is also fixed. With rapid cycle times and an excellent repeat accuracy of less than 0.01 mm, it is setting standards in assembly of small components. The cycle time amounts to just 0.58 seconds, which includes switching and gripping times at a vertial stroke of 40 mm, a horizontal stroke of 120 mm and a moving mass of 2 kilograms.
All the feed lines for power supply, control, sensor system and pneumatics of the compact unit are plugged in at the rearward stationary connection. Cable breaks and plant disturbances are excluded. The freely programmable unit is designed for a 100 mm vertical stroke, a 270 mm horizontal stroke and a moving mass of 3 kilograms. It carries out high speed assembly tasks with high precision, and due to the force control, it is also suitable for insertion processes, pressing in and force measuring. For using all the numerous options, the operators should have knowledge in handling mechatronic solutions and can be trained if necessary.
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An individual analysis makes sense
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Pick & Place Solutions in Comparison
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These examples show that every Pick & Place solution has its strengths and weaknesses. While modular designed solutions cover all imaginable requirements, compact Pick & Place Units mostly score at high speed applications. It is the very important to work out an optimum combination from the given application data.
SCHUNK, the competence leader for clamping technology and gripping systems offers a vast module program for every thinkable Pick & Place application. A neutral analysis proves that the operator will receive a customized and time-effective solution. For a rough evaluation, data on strokes, masses and required cycle times are needed. The SCHUNK experts will then quickly work out the details for an optimum solution. Moreover, SCHUNK works out solutions with different drives, 3-axis system or planar gantries for sophisticated tasks. The comprehensive modular program proves that from the gripper, to the rotary module, to the linear axis, all components are individually adjusted to each other.
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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.
more...
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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.
more...
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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.
more...
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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 - 2010
In Focus - Archive 2009
In Focus - Archive 2008
In Focus - Archive 2007
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