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In Focus - Archive July 2009
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Compared to conventional collet chucks, the hydraulic expansion toolholder, TENDO achieves brilliant surfaces and at the same time protects the tools against damage, thanks to its vibration dampening characteristics.
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01.07.2009 -
For many years, collet chucks have been popular because of their low pricing and have been the established toolholders for many machining applications. Unfortunately, the same scenario happens in many companies: Because of worry over loose tools, many machine operators are tightening the coolant tube nut of the collet mountings with oversized extensions. They also have to repeatedly clean the dirty components of the multi-part toolholders and be aware of how fast the tools wear in the collet mountings.
Because of this, experts agree that precision toolholders offer enormous potential concerning quality, performance, process reliability, and lower costs. Investments in modern toolholders generally pay for themselves in a very short time and ensure future competitiveness in metal-cutting manufacturing.
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SINO-R from SCHUNK allows in the die and mold production an economic rough machining and provides perfect surfaces.
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Two strong arguments for precision toolholders:
Quality demands of customers and cost calculation
On one hand, tolerance allowances of modern workpieces become better, on the other hand, cost is increasing which makes it necessary to maximize profit in all areas of productivity. At the very least, when the operator is thinking about automated manufacturing, a higher efficiency or the use of high-quality tools, the toolholding equipment has to be critically analyzed.
"Compared to conventional universal clamping solutions, sophisticated and proven precision toolholders have enormous benefits", says Michael Kraft, Product Manager of SCHUNK Germany. "They reduce tool and machine costs, the number of tool changes and adjustments, as well as the costs for maintenance works at the toolholder. Moreover, they provide higher efficiency and improved machining quality."
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Compared to conventional collet chucks, the hydraulic expansion toolholder, TENDO achieves brilliant surfaces and at the same time protects the tools against damage, thanks to its vibration dampening characteristics.
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Collet chucks are restricted in efficiency
A collet chuck consists of three components: A base body with a cone, a collet chuck and a coolant tube nut. All three in combination ensure clamping of the tools. At the same time, the chuck is composed of three pieces, which affects run-out quality. As long as the mountings are merely used for simple tasks, this weakness is not essential. With increasing spindle speed and metal removal and increasing demands on precision, the collet mounting has become a critical factor. An uneven cut affects precision, as well as a high wear of the cutting edge of the tool. Collet chucks are also very sensitive to dirt and the process reliability is not exacting.
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With TENDO the tool can be adjusted quickly.
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Tool change within seconds...
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Shorter production times per piece require a safe hold within seconds
Many operators know that tools could fall out during machining because they are drawn out of the collet mounting. With oversized hook wrenches, operators try to minimize this risk. However, the collet chucks wear out very quickly if this method is applied. The true-running accuracy of the mountings is reduced and the quality of the workpiece surface and tools are damaged.
If the tools have smaller diameters, there is the risk of the tool breaking because it was exposed to high forces and squashes in the collet chuck. Such a mistake is very expensive because even small tools are costly.
In contrast to collet chucks, the clamping operation of modern precision mountings is simple. Hydraulic expansion toolholders should be always equipped with a stop for the clamping pressure. This ensures that the toolholders always generate the same optimum clamping force. One turn with a hexagon socket key to the end stop sets the machine up and prevents the chance of over-clamping.
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The all-rounder type SINO-R demonstrates its abilities: With a 0,8 mm micro end milling cutter, defined slots are milled into a prototype.
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Length adjustment is maintained during clamping operation
When the collet chuck is closed, an unintentional axial movement occurs, which causes a misalignment in the tool, whereby it loses its exact position of the pre-adjustment. This misalignment may be up to 0.6mm. This could not happen with hydraulic expansion toolholders or elastomer expansion toolholders. The expansion sleeve carries out an absolutely radial expansion. The tool is neither pressed out of the toolholder nor is it drawn into it.
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Used on lathes/ and milling centers, TENDOturn scores: Highest precision, excellent surface quality, low tool wear and minimum set-up times.
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Symptom of fatigue
The sliding surfaces of the collet chuck between the collet and the base body are heavily loaded since they are moving towards each other, while a high surface pressure also exerts force. This causes high wear, which can occur after 1,000 clamping cycles and causes a significant decrease in the run-out accuracy. Expansion sleeves in turn are basically wear-free and no loss of the clamping accuracy can be measured before 10.000 clamping cycles.
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The excellent vibration dampening provides smoother surfaces. Here is a comparison of threads. The right thread was machined with a TENDOturn. The surface shows considerably less chatter marks.
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Advantage of the damped expansion toolholders
In case of rough machining, not only a tight and safe hold of the tool is important, but also are the dampening characteristics of the toolholder. When the tool edges are immerging, vibrations of the tool are generated, which can spread out over the whole machine tool. If these vibrations occur in the right frequency, the frequency of the machine, the vibration can become very strong and damage the tool.
Expansion toolholders have a tight hold and excellent dampening characteristics. The oscillation amplitude considerably reduces vibration and the surface becomes smoother instead of rough and bumpy.
By avoiding high oscillation amplitude, the load of the tool’s cutting edge is considerably lowered. Thus the service life is increased and the tool‘s cost rates are reduced. The noise exposure is also lowered and the spindle‘s seat is protected from damage.
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Expansion toolholder SINO-R from SCHUNK disposes of high radial forces and at the same time provides vibration damping for a safe hold of the tools.
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Design of the expansion toolholder
Expansion toolholders have many advantages, such as the length adjustment, vibration dampening, and low symptoms of fatigue. Hydraulic expansion toolholders, generate pressure by expanding the sleeve and by compressing oil, and elastomer expansion toolholders, compress the volume-stable elastomer mechanically.
Hydraulic expansion toolholders have their strength in true-running accuracy, which especially distinguishes them for the applications such as high-precision drilling and milling.
Elastomer expansion toolholders dispose of high transmissible torques in connection with strong dampening characteristics, which make them excellent for rough machining and high material removal rates.
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The one which is attractive in price and is extremely short. TENDO-ES: Ideal for narrow machining areas.
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The economic point of view
By using expansion toolholders, higher feed rates are achieved and in contrast to collet chucks, they are almost maintenance-free. Expansion toolholders are very attractive in price since a considerable reduction in price has been taken in the last few years.
SCHUNK GmbH & Co. KG offers you a vast program of toolholders with the product lines TENDO and SINO-R.
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11.2009
Straightaway micron-precise
In addition to a high repeat accuracy, in modern machine tools, positioning-, measuring- and handling the accuracy of the axial movement is now playing an important role. In this way, precise parts for the production or electronic industry, can be designed with a micron-precise guidance along the complete axis.
 more...
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10.2009
How Machines Can Learn To See
More and more industries tap the full potential of machine vision systems. Whether in the supermarket, on the highway, at the airport, or in the factory; pictures are being taken by a camera system and are evaluated with a computer, in order to make a fully-automatic, quick and safe decision.
more...
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09.2009
Hydraulic expansion technology for workpiece clamping
Hydraulic expansion toolholders for tool clamping (milling cutter, drills, taps and reamers) are known on the market for a long time and are appreciated for their technical advantages. They combine powerful, centric clamping with a high internal dampening. The result is an excellent surface at high machining speeds.
more...
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08.2009
Gripping - checking - measuring - preventing from damage
Intelligent sensors transform actuators to sensitive helpers in automation
Sensors used in automation are essential organs of machines and plants. While gripping modules and other actuators performed pre-defined tasks in the past, today, they are intelligent and flexible helpers in the manufacturing process due to the use of intelligent sensors. They provide the plant with important information on the process, products or components as well as plant functions. This increases flexibility, shortens manufacturing time, ensures product quality, avoids plant failures, and prevents the automation systems from damage.
more...
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07.2009
The trend towards precision toolholders
For many years, collet chucks have been popular because of their low pricing and have been the established toolholders for many machining applications. Unfortunately, the same scenario happens in many companies: Because of worry over loose tools, many machine operators are tightening the coolant tube nut of the collet mountings with oversized extensions.
more...
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06.2009
Always up-to-date with the standards - The new machinery directive in the EC
The safety of products and systems traditionally tops the priority list at SCHUNK. Since we want to partner with our customers, we are exclusively offering top-of-the-line products in quality and safety.
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05.2009
Highly economical due to performance in toolholding and workholding
5-axis machines offer an enormous potential for efficiency in modern production. With sturdy machine kinematics, high axis accelerations, short chip-to-chip times, fast tool magazines and finely tuned controllers, you have all kinds of production power in a very small space.
more...
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04.2009
Microvalve Technology
- Small component handling and assembly
Anyone who wants to handle or assemble small, light parts can really get a move on with electromagnetic microvalves. These energy-efficient valves are screwed directly onto the pneumatic actuator and thus eliminate the need for long wires. They make the tempo significantly faster and thus save compressed air, complicated wiring, and a lot of assembly time.
more...
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03.2009
Reliable precision for the most well-hidden corners
Regardless of their design sophistication, it is sometimes impossible to avoid cre-ating hard-to-reach points on workpieces. All of these cases require slim toolholder systems with minimized interference contours. They have to penetrate into the most well-hidden corners, transmit sufficient torque and guarantee high precision at the same time.
more...
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02.2009
The foundry sector: a red-hot key industry
With 87,000 employees and sales of around €14 billion in 2007, the foundry sector is one of German industry's smaller branches. Its economic significance is large.
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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