As a result of the success of complete machining on 5-axis machines, workpiece accessibility is an aspect of growing importance in clamping technology. While in the past it was necessary to use long projecting special tools or multiple setups to machine workpieces over clamping claws or chuck jaws, intelligently designed clamping devices of today allow significantly better access by the tools, in addition to processes that are much more efficient.
With respect to clamping devices for machining of complex workpieces, the trend is clearly away from simply solving problems toward boosting efficiency. As a response to the challenge of confined spaces, slim toolholders or tool extensions had initially experienced a boom. Today, the user focus is not only on slim contours, but also on the machining process as a whole. The goal: more efficiency, more output, and maximum system availability, as well as optimum accessibility.
Slim hydraulic expansion toolholders
For example, the SCHUNK TENDO Slim 4ax hydraulic expansion toolholder recently made it possible to combine the complete outer geometry of heat shrinking mountings in accordance with DIN 69882-8 with the convincing qualities of SCHUNK hydraulic expansion technology. With this symbiosis, the slim precision mounting creates entirely new possibilities for drilling, countersinking, reaming and thread cutting in the vicinity of interfering contours in 5-axis machining centers and also in prototype, die and mold construction. Tests confirm that the vibration damping properties of hydraulic expansion technology significantly improve drilling processes. In spot drilling, for example, it is possible to cut the maximum amplitude of the course of the forces in the X/Y direction – the deflection of the tool – in half. Reducing the loads of the chisel edge and the cutting corner lengthens the tool life significantly. Users additionally benefit from exact borehole gauges and maximum workpiece precision. The work needed for the conversion is minimal: the precision plug & work mountings can replace conventional heat shrinking toolholders without having to program a new external contour.
The main reason why special tools are no longer necessary even in very confined spaces is the use of standardized tool extensions. The efficient SCHUNK TENDO-SVL extensions can turn virtually every standard toolholder, regardless of the spindle interface, into a highly flexible special toolholder for hard-to-access areas. The unusually high torque of the oil-clamped 150 mm and 200 mm slim extensions holds the tools reliably during drilling, reaming and finish milling operations. Instead of special tools or heat shrinking systems, a single TENDO tool extension equipped with different standard tools for the particular requirement is often sufficient.
Direct clamping without interfering contours
In the field of workpiece clamping, developments in magnetic clamping and especially direct workpiece clamping are considered insider solutions for avoiding interfering contours and improving process efficiency. The basic principle is deceptively simple: Threads are tapped into the workpieces for mounting standard quick-change clamping pins so they can be clamped in SCHUNK VERO-S quick-change pallet modules with no additional clamping devices. As with MAGNOS magnetic clamping technology, this makes the workpieces freely accessible on all five sides. In addition, the zero point is precisely defined. Direct clamping is therefore superior to many other clamping solutions especially in one-off production and small series. Standardized raised modules ensure full spindle access. On the basis of extensive experience from individual projects SCHUNK has developed a modular system for direct workpiece clamping. It consists of various basic modules for mounting on the machine table and grid plates, in addition to the clamping modules and freely combinable stacking modules. The latter are variable in very fine gradations of 10 mm starting at a height of 80 mm, which eliminates the need for special solutions. Height differences can be compensated by the use of compensating modules and borehole gauges by means of compensating bolts. All interfaces feature zero-play taper centering, which ensures a repeat accuracy of < 0.005 mm between the single components.
High 5-axis vises
Accessibility is also an issue of increasing importance for manually operated NC clamping vises. In the high-performance SCHUNK KONTEC KSX 5-axis clamping vise, for example, a support surface at a height of 211 mm ensures virtually unhindered access to the workpiece on all sides. A single lever movement clamps the workpiece in a vibration-proof clamping set-up with perfect repeat accuracy, in less than one second. Adjustment of the clamping force requires no tools and a range of 4 to 40 kN ensures safe holding even in the case of minimal clamping faces. Clamping by tension prevents the base body from lifting. In addition, the long guiding system and the configuration of the clamping mechanism ensure a rigid, dimensionally stable clamping set-up. Both the drive and the adjusting mechanism of the 5-axis clamping vise are completely encapsulated, and protect them from chips, dirt, and cooling lubricants.
Accessible lathe chucks
Advancements with respect to accessibility are also evident for solutions in the lathe chuck technology. The highly flexible SCHUNK ROTA-S flex, for example, combines time-proven lathe chucks of the ROTA-S plus series with extended guideways to create lightweight and versatile large chucks. Compared to conventional lathe chucks for large diameters, the weight of the ROTA-S flex is reduced by up to 60%. In addition, the low height leaves plenty of room for the workpiece and the tools. The guideway extensions can easily be removed for machining smaller parts, significantly improving accessibility to the workpieces as compared with conventional large chucks.