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In Focus - Archive June 2012
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A lot of chips in a short space of time - in volume cutting, a wide diversity of factors determine success.
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02.06.2012 -
The times when brachial roughing was normal are over. Those who want to produce a lot of chips in a short space of time now take advantage of high-quality cutting and intelligent toolholding systems that transmit high torques and, at the same time, reliably absorb any occurring vibrations. Modern toolholders protect the cutting edges, the machine spindle, and the workpiece surface and allow you to work with high metal removal rates even when using challenging materials.
With large volume cutting, you need maximum productivity; that is to say high feeding and infeed rates. As much material as possible needs to be cut within a short period of time. At the same time, the whole system consisting of the headstock, spindle, toolholder, tool and workpiece is subjected to very high loads. Cutting materials specially designed for the procedure such as carbide, cermet or cubic boron nitride withstand the enormous alternating loads on the cutting edge particularly well. In some cases, fiber-reinforced tools are also used to minimize the risk of fracture.
Toolholders are also exposed to extreme loads. When dismantling from the front side, very high radial forces can develop which can cause the toolholder and tool system to be deflected. The deflection behaviors are influenced by the toolholder's design, by the toolholder and tool system's projecting length and by the cutting parameters. Also having an effect - depending on the angle of twist on the cutting edge of the tool - are, in some cases, enormous axial pull-out forces which will pull the tool out of the toolholder in the worst-case scenario.
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Precise concentricity pays off for high-performance cutting, too.
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The clamping force has a significant influence on the process stability in volume cutting.
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Four factors are decisive when selecting a toolholder suitable for volume cutting:
Run-out accuracy:
If the clamped tool does not turn centrically to the toolholder axis, then the tools start to bang during machining, which leads to micro blowouts on the cutting edge and accelerates wear on it. The run-out accuracy also crucially affects whether the dimensions and tolerances are observed. The combination of these factors is the reason why - even in volume cutting - precision toolholders with run-out accuracies of less than 0.003 mm, measured at 2.5 x D, are being used more and more frequently.
Clamping force:
This decides whether the torque at the interface between toolholder and tool can be controlled. If the clamping force is suffient, the tool’s cutting edge cuts evenly into the material. If the clamping force is sufficient, the tool begins to turn in the holder and the cut will be unsteady. In extreme cases, the tool may even be pulled completely out of the toolholder. In order to prevent this from happening, toolholding systems with form-fit clamping, which frequently exhibited deficiencies in concentricity however, were mostly used in the past for volume cutting. Owing to technological progress, toolholders with force-fit gripping today also ensure high clamping forces, which means process-stable volume cutting is possible when using them.
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High cutting forces require a high radial rigidity
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Vibration-damping toolholders protect both the cutting-edge and the spindle.
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Radial stiffness:
This determines how high the cutting forces may be. Important factors here are the material properties of the toolholder (E-module), the geometry of the toolholder (size and shape, wall thickness) and the integration of the toolholder in the overall system for the machine tool. As the radial stiffness increases, the shorter the toolholder, the greater its diameter; the more homogenous the unit consisting of tool and tool mounting the thicker the wall of the tool mounting and the more extensive the support for the holder on the machine spindle.
Vibration damping:
Vibrations will inevitably occur during milling, and will not only result in the varying chip thicknesses during the machining process and from the interrupted cut of the individual teeth due to the process, but also from imbalances, for example. Toolholders can absorb vibrations in a similar way as the shock absorber and ensure a smooth and even cutting action. This allows noise emissions to be minimized, the quality of the workpiece surface is improved, tool life is prolonged, and the spindle can be protected.
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In comparison to collet chucks and heat shrinking toolholders, the powerful TENDO E compact hydraulic expansion toolholder offers clear benefits.
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Only very few tool clamping systems meet all the requirements
Marked differences are revealed if one compares the tool clamping technologies currently on the market with regard to these four characteristics. Weldon chucks exhibit deficiencies in the run-out accuracy and have a tendency to judder. Conventional collet-style holders have shortcomings in the run-out and repeat accuracy as well as in the clamping force. Heat shrinking holders have a good run-out accuracy, high clamping forces, and high radial stiffness. However, due to the one-piece clamping system, they can hardly absorb vibrations occurring during volume cutting. So precision holders specially designed for volume cutting were viewed for a long time as the first choice in the field of volume cutting on the basis of a polygonal clamping technology. A framework-like chamber design guarantees you an especially high rigidity. In addition, cast inserts made of a copper alloy ensure excellent vibration damping that is around four times higher than of heat shrinking toolholders.
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Neck-and-neck race
The two market leaders for large volume cutting come from SCHUNK, the competence leader for clamping technology and gripping systems, and were optimized particularly for volume cutting:
TRIBOS-R:
- Precision toolholder basedon polygonal clamping technology
- Rotationally symmetric design
- Run-out accuracy of less than 0.003 mm measured at 2.5 x D
- Balancing grade of G 2.5 at 25,000 rpm
- Interfaces: HSK-A63, HSK-A100, SK40, SK50, JIS-BT30, JIS-BT40, JIS-BT50
TENDO E compact:
- Precision toolholder based on hydraulic expansion technology
- For universal use in milling, boring, reaming, and thread-cutting
- Run-out accuracy of less than 0.003 mm measured at 2.5 x D
- Balancing grade of G 2.5 at 25,000 rpm for HSK mountings
- Interfaces: HSK-A63, HSK-A100, SK40, SK50, JIS-BT30, JIS-BT40, JIS-BT50
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12.2012
New application possibilities for square pole technology
The electro-permanent square pole technology is a part of the magnetic clamping technology, and represents an ideal clamping solution for machining centers. It offers numerous advantages: Workpieces are easily accessible, and can be machined in one set-up from five different sides. It is no longer necessary to spend time on the fine adjustment of clamping elements. Multiple clamping operations of workpieces during the machining process are no longer necessary as well. In addition to milling applications, square pole technology also covers flat grinding applications. Moreover, special display modules increase process reliability and create optimum preconditions for automated loading.
 more...
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11.2012
High-performance automation from the modular system
Those who plan high-performance assembly plants for electronics, medical technology, automotive, or consumer goods industry, know of the challenges, if individual modules and assembly groups need to be linked to an entire system. Missing mechanical joining elements, incompatible controller concepts, or insufficient planning tools influence the planning and implementation processes as well as during the process itself. The variety of combinable system programs can be an efficient alternative - provided they are well thought out in terms of performance, volume, compatibility, and configuration.
more...
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10.2012
Applying strengths in a targeted way
Stationary clamping systems have enormous hidden efficiency and quality potentials for production. Those who want to utilize them, should question, where the strengths of the individual clamping technologies are. If they are selected and combined in a targeted manner, their investment costs can be amortized very quickly.
more...
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09.2012
The underestimated collaborators
In view of sophisticated lathe chucks, clamping blocks with compact performance, and highly engineered devices, the technological possibilities of chuck jaws may seem at the first glance rather limited. In reality, however, these direct interfaces to the workpiece open up enormous potentials: Beside conventionally hard and soft top jaws, a broad range of established chuck jaws ensure that even tricky clamping tasks can be economically solved. An overview shows what is potentially possible.
more...
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08.2012
Efficient concepts for automated machine loading
In the past, automated loading and unloading was restricted to large series, today though, small batches and individual pieces are now standard. The ultimate aim is to reduce set-up involved downtimes and to have as few workers possible manning production around the clock. What is needed, is the sophisticated interaction of innovative clamping equipment and automated components which lead to utmost precision and ensures reliable processes all at the same time.
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07.2012
Consistent maintenance increases precision, process reliability,
and safety of the clamping vises in the long run
Vises used for workpiece clamping in today’s production environments are exposed to extreme conditions. This significantly influences the precision of the workpiece, process stability, and safety for both operator and machine. In order to ensure optimum clamping force, users normally follow the manufacturer’s information on lubrication intervals. Moreover, many more companies are choosing preventive maintenance programs, where the clamping vise is thoroughly tested in defined cycles. This ensures longtime accuracy, minimum wear, and high process reliability.
more...
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06.2012
High performance without chatter
The times when brachial roughing was normal are over. Those who want to produce a lot of chips in a short space of time now take advantage of high-quality cutting and intelligent toolholding systems that transmit high torques and, at the same time, reliably absorb any occurring vibrations. Modern toolholders protect the cutting edges, the machine spindle, and the workpiece surface and allow you to work with high metal removal rates even when using challenging materials.
more...
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05.2012
Pneumatic or mechatronic gripping?
In many industries, the increasingly wide range of product variants, the ever-shorter cycle of innovation, and the increasing comparability among products are leading to an enormous pressure on costs. Experts believe that production automation will be one of the keys to business success in the coming years. These issues also apply to gripping systems: the precision, flexibility, speed and reliability of a gripping system has a significant impact on the profit margin which they can achieve. Although pneumatic gripping systems were long considered the state of the art, mechatronic solutions have since made significant strides. As a result, users and system planners are increasingly faced with the question of which drive concept is more advantageous to handling and assembly processes: pneumatics or mechatronics?
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04.2012
Vacuum clamping technology: an ideal addition to the standard clamping devices
In comparison to clamping brackets, clamping blocks, jaw chucks, quick-change pallet systems, or magnetic clamping technology, vacuum clamping technology is mostly unknown in the metal cutting industry. Nevertheless, vacuum clamping technology can perform a valuable service here, especially when machining thin parts that are susceptible to deformation, or workpieces made of aluminum and other non-ferromagnetic materials. Particularly when they are in the form of versatile matrix plates, they are a useful and easy to handle addition to clamping devices already in use.
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03.2012
Gripping Systems of the future
Mechatronic handling systems offer distinct advantages: They are very flexible, offer numerous intelligent functions, and despite higher acquisition prices, they quickly pay off. Therefore, it is no surprise that the handling issue is becoming increasingly important in the pneumatics dominating world. This particularly applies, since more and more mechatronic components can be easily operated by average users.
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02.2012
Tool extensions with minimal interfering contours
Due to the success of modern 5-axis machines, tool mountings with slim interfering contours have experienced a real boom. With sufficient torque, and high run-out accuracy they allow a deep, collision-free tool path into the workpiece, and thus ensure precision machining, even in areas which are difficult to access. These slim tool extensions are economic, flexible, and can be assembled between tool and toolholder on request. They can be combined with various machine tapers.
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01.2012
Up-to-date support for all gripping tasks
Gripping systems in handling and assembly are often in operation around the clock, seven days a week. Many components have to withstand external influences such as chips, dust, aggressive media or heat. In addition, tight margins and deadlines due to just-in-time production often result in enormous scheduling and planning pressure, usually starting well before the initial commissioning. In view of these challenges, many purchasing decisions are increasingly made based not only on the quality and performance of the modules, but also on the range of services offered. Services increase planning reliability, facilitate commissioning and ensure maximum cost effectiveness during operation.
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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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