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In Focus - Archive May 2010
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The red areas of this drive laterns of ALLWEILER AG are especially loaded during the clamping operation. In a further simulation, the clamping solution and the machining parameters can be varied.
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05-01-2010 -
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.
Simulation avoids expensive trouble shooting
In the past, many components were made with the wrong dimensions because design engineers worked with extreme safety margins. Today safety itself is not a sufficient criterion for a good design. In order to survive on the global competitive market, developers and design engineers face constant challanges. They have to cut down time on project planning, manufacturing and be prepared to reduce energy consumption of their projects. On the other hand, precision, robustness and longevity of components and complete systems have to be increased, while future maintenance works have to be decreased. Because of this, simulations provide invaluable results! During the design phase, long before the first prototypes are built, simulations on a computer can determine, how the components will behave during maching, if accuracies can be assured after machining, and if due to the high clamping forces, structural changes at the workpiece might occur, which may weaken the material.
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In case of large workpieces enormous clamping forces occur, which makes a simulation very worthwhile.
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Simulations pay off in particular where large and complex workpieces are concerned
Precise machining of large, thin-walled or particularly complex components is often a challenge. Certain limits of clamping forces should not be exceeded, so that the workpiece will not deform or be damaged. On the other hand though, clamping must be sure enough that cutting forces can be absorbed. With the FEM method it becomes clear how the workpiece will behave during the clamping process and machining. The simulation is the basis for developing the optimum combination of clamping units, jaw design, clamping height, clamping force and speed. It supplies knowledge on fracture mechanics, rigidity, lifetime and vibration behavior of the components. Particularly in case of complex geometries and high precision requirements, as for bearings, gear wheels, turbo housings, cylinder heads or brake rings an early simulation offer enormous advantages.
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In order to control the behavior of components, a grid is put over the workpiece after having defined that the workpiece will be clamped in a 6-jaw chuck.
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Thin-walled, ring-shaped workpieces are especially sensitive towards deformation. The simulation shortens the search for a suitable clamping unit.
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Sequence of simulation
In order to simulate the workpiece behaviour in the clamping unit and during the machining process, some data is required:
- 3D-solids of the workpiece, e.g. CAD data as a STEP file
- Details of the material
- Metal cutting parameter and maximum machining speeds
- Sketch of set-up with clamping and supporting points
- Specifications on holding forces/ jaw clamping forces
- Geometry of the chuck jaws, e. g. smooth, claw jaws, diamond serration
- Machine data, particularly specifications of the clamping cylinder and spindle arrangement
This data is entered in the CAD program and a three dimensional model is created for the clamping application. Then the FEM programs the material and the contact surfaces of the set-up are defined and a first grid of individual elements with start and end notes are put over the solution. In subsequent loading steps, the individual edge conditions are defined. In a first loading step it can be simulated how the workpiece will behave, if a defined clamping force is transfered to certain points. In a second step it can be examined for example how the payload will change, if the component is turned in a lathe chuck. Finally in a third step the behavior during machining is simulated.
After a first rough calculation, the grid can be reworked at extremely critical areas which improves the statement quality of the simulation. A three dimensional view or animation points out for each individual loading step, which radial or axial deformation occurs. This makes the three dimensional deformations above the so-called yield point relevant, since they do not achieve their initial shapes again. The simulation can also show, if with a certain clamping solution a defined run-out accuracy will be achieved.
With the FEM method effects, caused by various set-ups, machining parameters, and various points of force transmission at the workpiece, can be simulated. Even clamping solutions can be simulated, where the clamping pin of a quick-change pallet system is directly screw connected with the workpiece. Here the FEM method provides statements on stability of the pin and the screw, and also on permanent deformations at the workpiece.
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How must a ring be clamped in order to maintain the required tolerances even after machining? The FEM method quickly provides the appropriate answer.
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Example: Clamping solution for drive laterns
An example shows the possibilities of the FEM method. ALLWEILER AG is European-wide market and technology leader for pumps in the shipbuilding, power generation and special industry applications. By means of simulations the company tests the set-up of drive laterns made of cast iron GG25: They test if a component from the drive section of the pumps, which has been manufactured in three operations until now, can be machined in just two operations. In this case, the radial clamping behavior is tested in a 6-jaw compensation chuck.
The first simulation shows that the untrue-running at the fitting Ø 218 f7 (tolerance 0.048 mm) after clamping, winding up and machining amounts to 0.054 mm and consequently is beyond the tolerated range. In a second simulation speed is increased, and the cutting data is adjusted, making the operation successful. By way of a pure variation of the machining parameter, ALLWEILER AG can machine the drive laterns with an existing standard clamping unit - an enormous cost savings, which could not have been achieveable without a detailed FEM analysis.
Since the FEM method is always a theoretical calculation, it is advisable to carry out a practical test after the simulation. In most cases, the actual results hardly deviate from the calculated results. In case of hardened components or cast parts with casting skin, the internal stress of the material can sometimes cause major differences.
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Even axis combinations in automated solutions can be simulated by SCHUNK. The payloads of the components, the limit loads as well as the lifetime of the module can be evaluated at the virtuel model.
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SCHUNK offers simulations by call off
SCHUNK disposes of an internal network of experts, who coordinate the modern computer-assisted development technologies (CAE) cross-project, using effective methods of calculation, prepare results and make them re-usable. This efficient instrument is used for toolholding, workholding, and automation.
Since many operators do not have their own resources to carry out such a simulation, SCHUNK offers the know-how of theoretic basics and software with the competence in handling of the system and the knowledge of how to implement ideas. Operators can profit from this in many ways. They already know of possible weak points in advance, and on the basis of this simulation they can create precise engineering specifications and requirements or define well-directed clamping equipment and the type of set-up. This makes unnecessary investments or over-dimensioned systems a thing of the past. The simulation makes an important contribution to a higher efficiency for developing and manufacturing new products.
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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.
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.
more...
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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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