When investing in new clamping devices, it is therefore worthwhile to look specifically for systems with a quick-change jaw system, since they reduce set-up times to a few seconds and pay off in a short time. In addition: efficient retrofitting sets can convert existing chucks to achieve optimal set-up times.
In view of decreasing batch sizes, reduced inventories, and close margins, many companies are critically examining their idle times, and especially the set-up times of machining centers. No wonder: in two-shift operations the set-up costs for calculated costs per machine hour of € 100 and two jaw changes lasting 10 to 15 minutes per shift easily add up to more than € 10,000 per year. Turning out soft jaw sets causes additional costs.
Retrofitting sets for conventional chucks
SCHUNK, the competence leader for clamping technology and gripping systems, shows that there is a less expensive way. Years ago the innovative family-owned company recognized the efficiency potential of a quick jaw change, and continuously expanded its standard line of clamping technology to include quick-change products for optimizing set-up times. The latest innovation is the SCHUNK quick-change retrofitting system PRONTO, which allows the advantages of quick jaw change on existing chucks. With a change-over time of five seconds per jaw SCHUNK PRONTO achieves enormous savings when used on conventional chucks with a fine serration of 1/16″ x 90° or 1.5 mm x 60°. The high repeat accuracy of 0.02 mm makes the quick-change system suitable also for high-precision applications.
SCHUNK PRONTO consists of supporting and changing jaws. It is suitable for O.D. clamping of rough and finished parts. For jaw change with repeat accuracy, it is only necessary to loosen the locking device with an Allen key, remove the jaw, and replace it with another one. This procedure eliminates the possibility of incorrect positioning. Six-sided form-fit clamping provides for maximum process stability in locked state, and allows high power and torque transfer. Three supporting jaw versions are available for small, medium, and large clamping ranges for a high degree of application versatility. For the top jaw the innovative family-owned company offers four hard claw inserts for different diameters and clamping ranges, as well as soft interchangeable inserts for machining of finished parts. The latter only have to be bored once for repeated use on the system. A special feature: selection of the interchangeable insert allows expansion of the clamping range by up to 16 mm without changing the supporting jaw, which today already means a 300% advantage over conventional chucks. For the AMB, SCHUNK is going even further by introducing PRONTO interchangeable inserts that allow a clamping range extension of up to 45 mm. The clamping depth can be varied by means of workpiece stops.
The SCHUNK quick-change jaw system BWS is already a classic product for minimizing set-up times. It likewise consists of hard supporting jaws and different interchangeable inserts. As opposed to PRONTO, the BWS interchangeable inserts are connected to the supporting jaws by means of an eccentric bolt. The system is standardized for power chucks with diameters of 160 mm, 200 mm, 250 mm and 315 mm. In addition, the interchangeable inserts can be adapted to the individual requirements of the workpiece to be clamped. Similar to PRONTO, the SCHUNK BWS allows the choice of different interchangeable inserts for different clamping ranges. The repeat accuracy amounts between 0.02 and 0.03 mm, depending on the size. Since the inserts are removed upward, the quick-change system is also suitable for small clamping diameters. Large contact and support surfaces ensure optimal stability and repeat accuracy. A built-in pressure bolt secures the interchangeable insert against accidental loosening even if the eccentric bolt is not locked.
Integrated quick-change systems
Lathe chucks with an integrated quick-change system offer even more convenience. They likewise reduce the change-over time for three jaws from 10 – 15 minutes to only a few seconds. In addition, due to the high repeat accuracy of < 0.02 mm soft jaws only have to be turned once, after which they can be re-used repeatedly. Compared to the retrofitting sets described above the jaws are lighter and take up less space vertically. The module serration also makes it possible to change the radial position of the jaws for very fast clamping of different diameters. Changing the jaws could not be easier: with the universal SCHUNK ROTA THW wedge bar power chucks, only a quarter revolution with the jaw change key is needed to unlock the base jaw serration of the opened chuck. After the new jaw has been inserted, and the wedge bar serration has locked securely into the base jaw serration, the key can be turned back. A spring mechanism then ejects the key to prevent it from accidentally being left in the chuck body. This eliminates the possibility of operator errors. The same quick-change principle is used for the ROTA THWB, which is specially equipped for rough machining with especially wide jaw guidance, and for the versatile ROTA THW vario.
In the case of the SCHUNK universal manual chuck ROTA-S plus 2.0, and the straight-serrated precision manual chuck SCHUNK ROTA-G, on the other hand, no tools whatsoever are needed for changing the jaw: a button on the chuck body actuates a plunger pin that unlocks the respective jaw. After changing the jaw, the plunger pin automatically positions the base jaw relative to the wedge bar serration and secures it against falling out. An indicator pin provides for additional safety during turning: the machine cannot start as long as the pin is visible. The chuck must first be correctly closed and the workpiece securely clamped before the pin disappears in the chuck so that machining can start. Even more flexible is the SCHUNK manual chuck ROTA-S flex. It combines the lathe chuck of the ROTA-S plus series with extended guideways and converts them into lightweight and versatile large chucks. Compared with conventional power chucks for large clamping diameters, the ROTA-S flex reduces the weight by up to 60%. For machining of small parts the extended guideways can simply be removed, which significantly improves the accessibility of the workpieces compared to clamping with conventional large chucks. With or without the guideway extension: both versions of the toolless ROTA-S flex quick-change jaw system ensure set-up times of only a few seconds.
The examples illustrate how flexible the capabilities of the quick-change jaw systems have become. Depending on the application, high savings are possible even with comparatively low investments. To facilitate the search for the optimal clamping devices for your application, SCHUNK offers competent advice and detailed cost effectiveness calculations.
Quick change of gripper jaws
With the quick-change jaws for SCHUNK gripper modules, SCHUNK shows how this know-how can also be transferred to other applications: the quick-change system is already integrated in the ABR-BSWS and SBR-BSWS finger blanks. Compared with conventional finger change the new system reduces set-up times up to 90 percent. An easily accessible, form-fit locking mechanism ensures that the finger is changed in a matter of seconds, with perfect repeat accuracy, by turning an Allen key 90 degrees. As opposed to other common solutions that are available, bore holes extending through the entire finger are not necessary, giving users the added benefit of maximum freedom in the design of the finger contour: the fingers can be adapted over their entire length to the respective workpiece, without having to worry about jaw change and the corresponding screw connections. The quick-change fingers are available in aluminum (ABR-BSWS) or steel (SBR-BSWS). They can be used with all SCHUNK premium grippers and with numerous other gripper modules.
Source Schunk GmbH & Co. KG