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In Focus - Archives Juin 2011
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Precision rings
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09.06.2011 -
In case of rings, housings and other workpieces which are highly deformable during processing, conventional 3-jaw chucks quickly reach their limits. If the clamping forces are too low, there is no secure hold. If they are increased, workpieces deform, and precision is reduced. A comparison shows the alternatives, the difference between them, and how users can achieve an optimum result.
The variety of clamping tools and devices for deformation-free workpiece clamping is great. It ranges from a comparatively low-priced plastic chuck jaws and pendulum jaws to special jaws and oscillating compensation multi-jaw chucks, up to self-centering magnetic chucks. Users who are looking for the best solution should first define the importance of each individual application: Which components are to be machined in which lot size? Are the workpieces manually or automatically loaded? How flexibly can the machine be used? Which form and positional tolerances have to be met? Based on these criteria an optimum solution can be worked out, which combines the demands on efficiency, precision and processes.
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QUENTES plastic jaws from SCHUNK
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6-point pendulum
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Plastic jaws: the low-priced alternative
Special jaws made of glass fiber reinforced plastic are still considered to be an insider’s tip in the field of workpiece clamping with low deformation. Their high friction coefficient of 0.3 to 0.4, and a wrap angle ensure that high machining forces are transmitted, even in case of low clamping forces. The support structure of the aluminum support jaw provides for stability. Due to the low weight of the clamping solution made of an aluminum support jaw and plastic top jaw, low centrifugal forces occur at the jaws during the turning operation. Therefore the plastic jaws are also suitable for high machining speeds of up to 6.000
rpm. Moreover, on ground or surface-treated components, no clamping marks will occur. In terms of cost the exchangeable clamping inserts make this solution affordable as well.
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This workpiece is fixed via 24 clamping points.
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Pendulum jaws: efficient and low-priced
While the high friction coefficient of plastic jaws is used for clamping the workpieces with low deformation, the number of clamping points is important for pendulum jaws. The basic version of the pendulum jaws is equipped with two clamping inserts, by which the clamping points of a 3-jaw chuck double. They are available for I.D. and O.D. clamping, are supported movably, and are mounted like top jaws onto the base jaws of the 3-jaw chuck. The contact points are evenly distributed over the O.D. or I.D. at a 60° angle. As a result, pendulum jaws can be used for a conventional 3-point clamping application and transforms it to an optimally compensating 6-point clamping application.
What is the effect of 6-point clamping?
At an identical clamping force and a twofold increase of the clamping points, the achievable mathematical true-running accuracy is increasing by factor 17. Example: if a tube section of 50 mm length, made of aluminum, with an O.D. 60 mm and an I.D. of 50 mm is clamped with 100 kN in a conventional 3-jaw chuck, the mathematical deformation amounts to 0.497 mm. Clamping over 6-point pendulums improve the value to 0.029 mm. Due to the pendulum motion, the chuck jaws optimally adjust to the workpiece, and compensate the form tolerances within a certain range in case of cast iron bodies for example. It would be ideal, if pendulum jaws can be fixed for finish machining, or for clamping pre-turned surfaces, as it is done at SCHUNK. In order to provide for higher speeds, they should be light-weighted. With the help of calculation programs, the necessary pendulum motion can be determined, in order to meet the predefined true-running tolerances. For example, the mathematical deformation of the workpiece from the above-mentioned example amounts to 0.002 mm with a 12-point-pendulum - it should be stressed at this point that this is a calculated, not an exact value.
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24-point pendulum special solution
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In case of conical components, it can be necessary to use a 24-point pendulum solution in order to achieve the required precision. The workpiece will be radially clamped on two levels with 12 clamping points, which are rotatably mounted. In turn, both clamping levels are arranged in an oscillating manner, so that all the clamping points lie flat at the workpiece, and form errors of the component can be compensated.
SCHUNK standardized the first chuck jaws in 1964 and, is still the manufacturer with the world’s largest product range of chuck jaws. Modular systems consist of support jaws, pendulum jaws, and clamping inserts, offering excellent conditions for configurating individual clamping solutions, and to adjust them to the workpiece.
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ROTA NCR 6-jaw compensation chuck
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ROTA NCR from SCHUNK is an expert in workpieces which are highly deformable.
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6-jaw chucks: high-precision and flexible
Even if pendulum jaws lead to the desired result, they can reach their limits if high repeat accuracies and the last nanometer of precision at the workpiece are concerned. In these cases, users should better decide for a 6-jaw chuck. The ROTA NCR from SCHUNK for example is the ideal solution, since it is rotatably mounted and compensating. For finish machining or clamping of pre-turned surfaces, the pendulum should be clampable in its center position, so that all six jaws can move concentrically.
The ROTA NCR chuck consists of a central chuck piston, which supports three inner pendulums which are evenly arranged at a 120° angle. Each pendulum jaw is connected with two base jaws. The result is a workpiece centering between six contact points, which are pairwise centered. Since the clamping forces are aligned with the chuck center, even raw parts are optimally centered without being aligned with the workpiece. With its oscillating jaws, the chuck perfectly adjusts to the raw part. In case of conventional jaw clamping this configuration allows maximum roundness of the workpieces, and also provides for optimum centering. Instead of costly system jaws and special solutions, conventional standard jaws can be used on the jaw interface. Therefore no cost and time-intensive special solutions are necessary, and flexibility is ensured. Moreover, the top jaws are considerably lighter than pendulum jaws, and the influences of the centrifugal forces are minimized. In contrast to applications with face plates, the complete clamping operation of the ROTA NCR runs quickly and precisely. Due to the high precision, some complete manufacturing steps can be eliminated, if e.g. during the finishing work the tolerances are already achieved, for which costly grinding operations are necessary.
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Radial pole technology
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Standardized MAGNOS radial pole plates are available in 17 sizes up to 2.000 mm.
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Magnetic chucks with radial pole technology:
There is no deformation
The chucks with electrically activated permanent magnets are working even more efficient. Their variable pole extensions ensure safe and deformation-free workpiece clamping. Without any additional set-up effort, workpieces of various sizes can be alternately, precisely machined on the magnetic chucks. Due to a multi-stage adjustment of the holding force, the parts can be easily aligned with the chuck, and are quickly clamped without deformation. Magnetic chucks allow 3-sided turning operations in one set-up, or milling operations from five sides. Comparative measurements at users on-site have shown that set-up times can be cut by 30- 50% by using magnetic clamping technology. When machine downtimes decrease, and workpiece machining becomes more efficient, investment costs for a magnetic clamping solution normally pays back very quickly. Moreover, surface clamping minimizes vibrations, and prevents the tool’s cutting edge from wear. In case of high-quality tools the magnetic clamping technology reduces the tool costs and improves the surface quality, too. Depending on the application, magnetic chucks with automatic demagnetization, or with particularly high magnetic forces should be used.
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Deformation aluminum ring
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Virtual simulation paves the way for optimum clamping solutions
The virtual simulation can be very useful for selecting the clamping tool or -device. It helps to develop the optimum combination of clamping tools and devices, the type of jaw design, clamping height, clamping force and speed. In cases of complex geometries and high precision requirements, such as bearings, gears, turbo housings, cylinder heads or brake rings, magnetic clamping technology show impressive results. The result of a virtual simulation at SCHUNK shows that a component of a pump’s power-train, which had been manufactured in three operations, can now be machined in 2 operations on a ROTA NCR 6-jaw compensation chuck from SCHUNK. Although the roundness error at the fitting Ø 218 f7 (tolerance 0.048 mm) after clamping, turning and machining amounted to 0.054 mm and was outside the tolerated range. However in a second simulation, the speed was increased, and the cutting data were adjusted, and the operation was successful. The highly efficient combination of virtual simulation and 6-jaw compensation chuck provides an enormous cost savings of the customer.
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Workpiece clamping with low deformation
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Full range of products, advice and service
SCHUNK is considered by most to be the worldwide competence leader for clamping technology and gripping systems. No other manufacturer is offering such a diverse program for workpiece clamping at low deformation. The standardized modular system for multi-point clamping from SCHUNK already covers the clamping ranges from 200 and 630 mm and everything is immediately available from stock. It comprises a wide range of clamping bridges, and their center of rotation is perfectly adjusted to the clamping range. In addition, there is a unique spectrum of clamping inserts. It ranges from plastic inserts, by which the workpieces can be clamped on the ready machined surfaces, to clamping inserts which are made of 16 MnCr 5 steel, and are extremely wear resistant.
Even the high-end chuck program of the innovate family- owned company is convincing: The ROTA NCR 6-jaw compensation chuck is available in the standard sizes 165 to 1.200 mm. SCHUNK offers the MAGNOS magnetic chucks with radial pole plates in 17 standardized diameters between 400 and 2000 mm. A comprehensive service program completes the user’s possibilities. During the planning phase, you can virtually simulate the clamping operations at SCHUNK. Even before the first chip is cut, it can be recognized, how the workpiece will behave during the clamping operation and machining process. And after the purchase SCHUNK will provide great technical support to their customers. Pendulum jaws for example, can be tested for two weeks free of charge. Moreover, experienced service technicians all around the globe ensure that precision tools and devices will be professionally commissioned and maintained.
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12.2011
Clamping solutions for automated mass production
Efficient manufacturing means automated manufacturing. This particularly applies if large series are machined. This is when the clamping vises, which are the direct interface to the workpiece, playing an important role. In only a few seconds, they have to mount the components, safely and precisely align them, clamp them with-out deformation, and after machining they have to be reliably released. In view of the several million clamping cycles, which have to be carried out by many clamping vises being exposed to chips and coolant, process reliability is one of the decisive factors of success.
 Pour en savoir plus…
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11.2011
Modularity the factor of success
When designing gripping systems for handling and assembly applications, standardized modular systems will play an increasingly important role in the future. They reduce the necessary time for project planning and commissioning, and lower the investment costs. Due to the standardization, they offer optimum preconditions for stable processes. Since modular designed units can be flexibly modified and enlarged, they can be re-configurated for any changes that come up in the future.
Pour en savoir plus…
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10.2011
Producing more efficient
For a number of years, everybody was talking about the energy efficiency issue. Increasing energy costs, a growing environmental awareness, and the political guidance were all triggers for many companies to highlight the energy consumption of machines and components in their communication with the public. Efficiency is much more than simple energy efficiency now, especially when considering the
time- and cost aspects in regards to efficiency. When all these factors have been considered in a holistic way, the full potentials for modern machining and production become visible. The modern clamping devices and gripping systems make it clear how complex the possibilities are.
Pour en savoir plus…
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09.2011
Welding demanding materials crack- and pore-free
Laser welding technology is second-to-none, regardless of whether you are dealing with gears and injection molds or delicate and challenging welding works. When conventional cw lasers and many Nd:YAG-lasers reach their limits, modern process strategies can help to machine demanding welding metallurgies, different types of materials, or micro components process reliably and efficiently. Laser welding is particularly used if components have to be joined at a high welding speed, because slim welding seams, and a low thermal distortion are required. Compared with other welding techniques, the energy during laser welding fully penetrates into the material.
Pour en savoir plus…
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08.2011
More than a "Stopgap":
Intermediate sleeves ensure safe clamping and precision
They appear to be unimposing - but they are located at a decisive interface in the chain of the metal cutting process. Between toolholder and workpiece, the intermediate sleeves influence reliability and precision of the clamping operation. The thin-walled, mostly slotted precision sleeves cover the difference between the clamping diameter of the toolholder, and the workpiece which has to be clamped. Functioning like reduction inserts, they multiply the fields of application of the toolholders or arbors, compensate tolerances, and ensure safe and gentle clamping of gear wheels. The newest sleeve design can do even more. Intermediate sleeves with nozzle effect extend the tool service life and increase the volume machining.
Pour en savoir plus…
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07.2011
Changing, machining, compensating -
current trends in robot accessories
In dealing with industrial robot efficiency cycle rate and process reliabilty largely depend on their front ends, the grippers and other tools, but also from the effectors’ interfaces to the robot arm. Robot accessories have a great influence on the robot’s performance, flexibility and fields of application. Latest developments of quick-change systems, driven tools, compensation units, and power sensors show that the potentials of modern accessory components are enormous. Experts assume that their importance for handling, assembly and manufacturing will continuously increase.
Pour en savoir plus…
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06.2011
Deformation-free clamping:
From the plastic chuck jaw to the hybrid chuck
In case of rings, housings and other workpieces which are highly deformable dur-ing processing, conventional 3-jaw chucks quickly reach their limits. If the clamping forces are too low, there is no secure hold. If they are increased, workpieces de-form, and precision is reduced. A comparison shows the alternatives, the differ-ence between them, and how users can achieve an optimum result.
Pour en savoir plus…
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05.2011
Service robotics is the future key market
Insiders are convinced that golden times lie ahead for service robotics. Around the world companies and institutes have recognized the potential of robots as helpers for humans, and are working on everyday solutions. All different kinds of businesses are interested in service robotics, from large companies, to innovative startups, and also conventional manufacturers of industrial robots, electronic and automation components.
Pour en savoir plus…
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04.2011
Having set-up times under control
You cannot earn money with a turned off machine. However, in many companies the workpieces are still set-up in a complicated and time-consuming way on a grooved table while the plant is turned off. But solutions exist, which optimize the machine tool load. Modern quick-change pallet systems demonstrably accelerate the machining process, and at the same time, ramp up the precision and process reliability score. This leads to a reduction of set-up costs of up to 90%.
Pour en savoir plus…
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03.2011
Toolholders for micro cutting
Clamping tools used for micro cutting have their own rules. The subtle tools, the high spindle speeds, and the extreme precision requirements are a challenge for every tool manufacturer and user. Those who want to achieve continuously precise results, need mountings with a high run-out accuracy and balancing grade. Moreover, they should be as slim as possible and resistant to dirt. Furthermore, they have to assure that even small tools can be precisely adjusted and exchanged.
Pour en savoir plus…
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02.2011
Leight-weight design increases efficiency of Gripping Systems
Light-weight modules are now playing an increasing role in the area of gripping systems. Integrated into the system, they are saving energy at the same efficiency, or achieve a considerably higher efficiency at the indentical energy consumption. In both cases, the efficiency of the whole system is increasing. This is why the lightweights are so interesting for plant manufacturers, system integrators, and users. Since light-weight solutions had the reputation of being overly expensive in the past, recent developments now show that efficiency and cost control can go hand-in-hand. Modern designs, materials and techniques are paving the way to lighter solutions, which are rigid and robust, too. This also offer many more advantages.
Pour en savoir plus…
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In Focus - 2013
In Focus - Archives 2012
In Focus - Archives 2011
In Focus - Archives 2010
In Focus - Archives 2009
In Focus - Archives 2008
In Focus - Archives 2007
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