Flexible, fast, precise shop fabrication

The hard-fine machining of small to medium-sized batches of components for chucking tools requires tool machines which guarantee the user a maximum degree of flexibility, speed and precision, because the challenges involved are enormous: the different components in a wide range of sizes, weights and geometries need to work perfectly and be produced quickly at low cost and according to customers' individual requirements. For this reason, the chucking device manufacturer SWS Spannwerkzeuge GmbH decided in favour of a specially designed machine from the DVS UGrind series, which has been demonstrating its outstanding performance in practical use for some time now.

In the context of the hard-fine machining of large series, continual tool, machine and process innovations are still leading to steady increases in efficiency. In the field of grinding, for example, tool service lives were significantly increased by the use of CBN high-performance cutting materials – despite the pure process times being drastically reduced at the same time. At SWS Spannwerkzeuge GmbH in Schlüchtern in eastern Hesse/Germany, the focus is less on the optimisation of process and tool service lives, because the company manufactures standard and custom chucking devices for a wide range of different branches and industries, from the automotive sector through medical technology, the optics industry to the machine tool industry. This extremely diverse range of applications and customers results in a wide range of different individual orders, all of which present highly specified requirements and challenges to the manufacturer, which is why day-to-day business focuses on the shop fabrication of small to at most medium-sized component batches. In this type of manufacturing, the majority of time and work effort is spent on set-up and preparation, such as the customised programming of adequate machining processes for numerous workpieces of different sizes, weights and geometries, as well as on productivity-decreasing process steps such as clamping, continual remeasuring and repeated feeding until the necessary final dimension has been achieved. SWS Spannwerkzeuge GmbH has found a way to reduce these efforts and thus to ensure more efficient production – the solution is the DVS UGrind series of machines, the introduction of which is successfully transferring the expertise of the DVS TECHNOLOGY GROUP in the field of hard-fine machining of large series to shop fabrication. Within the DVS group of companies, this field of competence and its continued development is in the capable hands of DVS Universal Grinding GmbH based in Dietzenbach near Frankfurt am Main, a company formed specifically for this purpose in the year 2016.

DVS expertise for shop fabrication

Initially SWS Spannwerkzeuge faced the choice between a hard-turning machine, which can be used for the precise and economic production of a large number of the required geometrical tolerances yet reaches its limits where extremely high manufacturing tolerance and surface requirements are necessary, or a grinding machine, which makes even extremely demanding manufacturing qualities possible yet involves both higher investment costs and longer machining times. The company also debated the capital-intensive procurement of both of these machine types in order to guarantee maximum machining and component flexibility. In the end, the chucking device manufacturer decided not to put up with any compromises and chose a machine from the DVS UGrind series. Thanks to the innovative multi-function turret, this solution allows the integrated execution of grinding and hard-turning as well as milling and measuring applications in a single machine and just one clamping – a first in the field of shop fabrication. In close cooperation with the Schlüchtern-based customer, the DVS UGrind machine was designed and specially constructed for the production of a large number of different chucking device components. The extremely compact machine with a footprint of just 7 m² provides the added bonus of intuitive operability using an in-house developed user interface, thus significantly reducing the overall machining time during component production – yet at the same time guaranteeing maximum manufacturing precision and workpiece variability.

Non-productive times are reduced with DVS UCee

The user-friendly user interface, which goes by the name of DVS UCee, makes simple and safe operation via a multi-touch display possible for the clamping tool manufacturer. The logical structure guarantees that machine operators will always have all the relevant information they need within their field of vision. For machining, the operator first defines the given workpiece geometry, the required machining surfaces and respective tool parameters. Then all that is necessary is the selection of a suitable machining cycle before the manufacturing process is started at the push of a button. Thanks to DVS UCee, standard machining cycles no longer have to be continually re-programmed, rather they can be saved permanently with the aid of the integrated workpiece management feature and retrieved again specifically in the concrete application case. The transfer of geometry data and tool allocation which has been prepared externally, at a PC for example, is also possible via USB. For shop fabrication by the clamping device specialist, these functionalities all result in a considerable reduction of the usual set-up and preparation effort, and thus of the non-productive times. Within the context of the production of clamping device components, a precision of less than one micrometer is mostly required for various position and shape tolerances. In order to guarantee the constant reproducibility of manufacturing qualities to this standard, the DVS UGrind has a vibration-damping machine bed made of granite that ensures maximum thermal and dynamic machine stability. The optimised lever arm ratios of the multi-functional turret also have a positive effect on the dimensional accuracy of the machine series. It has a radius of action of 270° and is equipped with six tools in line with the specific SWS Spannwerkzeuge requirements. One CBN grinding disc for machining outer diameters and flat surfaces, two inner grinding tools for the grinding of bore holes, two turning tools for external, internal and face turning as well as one measuring probe which controls and monitors the entire machining process until the required target dimension is reached.

Hard-turning, grinding and measuring operations in one clamping

Thanks to this tool concept, the metal cutting of even high dimensions, such as is required for a majority of the components produced by the clamping device manufacturer, is realised in an economic and reliable process. To achieve this, each of those clamping device component is hard-turned at a high feed speed and cutting depth first, and then – checked by the integrated measuring probe – ground in the same clamping and thus without reclamping errors to its respective final dimension. Time-consuming manual processes such as continual remeasuring and repeated feeding are no longer necessary and contribute to a further reduction of non-productive times. The magnetic chuck used and the optimum accessibility of the work chamber permits SWS Spannwerkzeuge GmbH ergonomic loading and unloading as well as the precise and flexible clamping of tools with widely different characteristics. Practical innovation with an explicit focus on the context of shop fabrication was key to the development of the DVS UGrind machine series. Its use allows SWS Spannwerkzeuge GmbH to increase productivity many times over with regard to speed, flexibility and precision – an outstanding advantage which many other users in the field of hard-fine machining small and medium-sized batches will be able to benefit from in future.