Schunk introduces PRISMO3 tool grinding toolholder for fully automated grinding processes

5 April 2016

SCHUNK has introduced PRISMO3 tool grinding toolholder, which was developed especially for fully automated grinding processes, company announced. With a high repeat accuracy of ≤ 0.005mm and run-out accuracy of ≤ 0.01mm at an unclamped length of 45mm it steplessly clamps diameters from 3 bis 20mm, without the use of intermediate sleeves or modifications to the toolholder.

During the clamping process the tool shank is automatically centered in the toolholder. Since the X-axis always remains unchanged, regardless of the tool diameter, which means all chuck jaws remain in the identical axial position, it is possible to machine a broad range of drilling, reaming, and milling tools also in small quantities without reprogramming the L1 dimension, in unmanned operation, and in any sequence whatsoever. The expense of additional programming and the danger of a crash due to unnoticed axis misalignment are therefore eliminated. Hard-coated chuck jaws ensure a long life and high process reliability in 24/7 operations. An optimized contour assures that the grinding wheel can run out unimpeded, even in demanding operations. Nevertheless, if the jaw set is ever damaged, it can be replaced as a unit. The engineering design, the base sleeve, and the robust construction give the toolholder its exceptionally high rigidity. Its sturdy jaw guidances prevent the grinding discs from swinging up and almost completely eliminate axial eccentricity. In order to prevent dirt accumulation and to permanently maintain the high precision, the toolholder is flushed with clean oil during the grinding operation. Compact dimensions of 125mm x 125mm leave ample space for the tools, grinding process, and loading. The mechanical high-end toolholder is especially suitable for use in sharpening applications, since it is compatible with virtually all interfaces – from axial clamping cylinders to radial front-end chucks. It is even possible to implement custom machine interfaces.

The SCHUNK PRISMO3 tool grinding toolholder features an impressive clamping range, an optimized interfering contour and an advanced clamping principle.

Resilient polyamide gripper fingers

In developing the toolholder, the engineers utilized the entire range of SCHUNK competence, from the clamping technology to the gripping systems. For the loading process, for example, the innovative family-owned company developed additively manufactured polyamide fingers, which ensure reliable and gentle holding with a simultaneous compensating effect during loading. At the moment when the tool is transferred to the toolholder the fingers prevent over-definition, which ensures exact centering. The resilient fingers were designed for universal use, so that the same pair of fingers can be used for handling of different tool diameters. The fingers are lightweight, extremely wear-resistant and exceptionally adaptable.

In loading of the SCHUNK PRISMO3 tool grinding toolholder the additively manufactured SCHUNK gripper fingers prevent over-definition during the tool transfer.

Hydraulic expansion technology is becoming the standard

There are good reasons why SCHUNK has established a long-standing reputation as a leading supplier of clamping devices for tool grinding applications. The company bundles decades of experience in hydraulic expansion toolholding technology and has developed an extensive range of specialized products for tool grinding. The precision toolholders are available in the TENDO SDF-WZS SK 50 version which is certified to DIN 69871 and also with numerous other interfaces. As opposed to collet-style holders the power-operated hydraulic expansion toolholders have no openings or gaps that are susceptible to dirt accumulation. They are insensitive to grinding particles and therefore require exceptionally little maintenance. The enormous diversity of the product spectrum ensures process stability in use of the toolholders on all relevant grinding machines. They are often recommended and even required by the machine manufacturers. Compared to conventional toolholders the hydraulically clamped SCHUNK TENDO WZS tool grinding toolholders are optimized for the special requirements of tool grinding and they also enable ten times more clamping cycles than conventional tool mountings. The biggest advantage: the tool shank is clamped with no moving parts. Instead it is held evenly and fully by means of pressure build-up in an expansion chamber that extends around the entire shank. The pressure is controlled to ensure precise holding without excessive stress on the hydraulic expansion system. The expansion takes place only in the flexible area of the inner chamber. Changing the tool takes only seconds with an Allen key. One only has to turn the clamping screw to dead stop; over-tightening of the clamping sleeve is not possible.

To enable grinding processes with maximum efficiency, SCHUNK offers the tool grinding toolholders both in a manual version and as power-operated toolholders for automated machine loading. This is achieved by manually inserting the tools in high-precision SCHUNK intermediate sleeves or in special tool extensions with a gripper collar, then placing them in a storage rack, from which the machine automatically changes them into the hydraulic expansion toolholder on the machine spindle. This is where the high repeat accuracy and low susceptibility to dirt accumulation are especially advantageous. In addition, it is possible to use the same toolholder for diverse clamping diameters.