Productivity and economical operation in the production of wooden parts cannot be achieved simply by using a modern CNC machining centre. The desired results can be achieved only by perfect interaction of the machine, the tools, the controller, the software and, above all, suitable clamping technology for the workpieces. 
 

It is a basic fact that the clamping of workpieces on CNC machining centres is one of the most important activities. Now that all other processes are partially or fully automated, the workpieces are still in many cases handled manually, and this is responsible for most of the idle times. This is particularly true for small and medium batches and one-off jobs. The same applies to the setting up and changing of the clamping devices for wooden parts, since fitting and positioning these devices takes a lot of time during which the machine cannot be used productively. And this is not the only problem: depending on the shape and design of the workpieces, it is often necessary to construct special clamping devices in order to clamp the workpieces with reproducible accuracy. In the past few years, vacuum clamping systems have become increasingly popular as an alternative to the complex and costly mechanical/pneumatic clamping devices. However, depending on their system concept, such systems vary widely with respect to the modularity of the system components, the available flexibility for differing applications, the design flexibility for the construction of simple to complex clamping devices and the compatibility with the basic clamping systems and machine tables which are in most cases already available. With the aid of the vacuum clamping systems INNOSPANN from the vacuum specialist J. Schmalz GmbH in D-72293 Glatten, for example, almost all existing woodworking centres can be utilised far more economically and flexibly. With this system, a machine can be converted for the precise positioning of a different workpiece in a matter of seconds, compared with the several minutes needed for the same task on a machine with conventional, mechanical positioning and clamping devices.

Not every vacuum clamping system
offers the necessary flexibility

In all cases, the various workpieces must be positioned and clamped quickly and reproducibly on the machine table and, after machining, removed without damage. Thanks to the modular concept of the INNOSPANN system, individual, complete solutions can be created for any machining centre and any application. This solution also does away with the costs for special clamping devices and templates, or at least reduces them considerably. This vacuum clamping system offers specially designed clamping elements for the clamping of large or small, narrow and/or curved workpieces and also doors and frame elements. The basis for upgrading machines with smooth, grooved or console tables which are not already equipped with a Schmalz clamping system is the so-called Steel Plates (made of magnetised stainless steel), which can be mounted easily on the machine table. These serve to transfer the vacuum to the so-called Suction Blocks without the need for vacuum hoses or other elements which could get in the way. In addition, elements such as the INNOSPANN Adapter Plates can, depending on the machine type, be used either together with or instead of the standard suction blocks on the consoles or on the suction-pad mountings. It is thus possible to use a mixture of the two or to position the workpieces directly on the consoles or suction-pad mountings, resulting in even more flexibility. Up to four identical or different suction pads, the so-called Mono Bases, or a single Quad Base (with four positions) can be mounted on each adapter plate. The suction cups to match the properties and dimensions of the workpiece are then placed on the bases and the workpiece clamping system is ready for use. Since, for example, the four mono bases can be positioned freely on each adapter plate, it is possible to ensure optimal and safe clamping of even critical workpieces. The available clamping area on the workpiece can be fully used to ensure secure clamping, which in turn permits higher feed rates and cutting speeds and thus increases productivity. The adapter plates can be adapted easily to many different woodworking centres and can be retrofitted without major modifications.

Rationalisation of clamping systems
with standard modular components

Messrs. Kaiser Möbelwerkstätten GmbH in D-94107 Untergriesbach planned to rationalise their woodworking activities and were quickly impressed by the possibilities of this system. The company was founded in 1948 and originally produced carts. When the next generation of the family took over the management in 1972, cabinet-making and joinery were added to the company's activities. Today, the company employs 25 persons and manufactures acoustical products and high-quality interior fittings for public, private and industrial objects. It also supplies the automotive industry with interior fittings for motor vehicles and mobile homes. It purchased its first CNC machine tool in 1993 and, in 2004, a CNC machining centre. Although this centre was equipped with a vacuum clamping system as standard, this proved to be far too inflexible with respect to the positioning of the suction pads to match the differing workpieces. Furthermore, the suction pads were too heavy and unwieldy, and displayed shortcomings with respect to their holding forces. For this reason, the company started to look for an alternative and found this in the vacuum clamping system INNOSPANN from Schmalz. After a through analysis and consultation carried out by a system engineer from Schmalz, Kaiser decided, in the spring of 2006, to convert the machine and purchased the following vacuum clamping systems components: 2 base plates Steel-Plate-T, 3 mm thick, with the dimensions 1,495 x 1,260 mm (with laser-cut grooves), 16 suction-pad mountings Quad-Base-T with 175 x 175 x 22 mm (L x W x H), 40 standard suction cups Cup 1 with 80 x 80 x 30 mm, 12 suction cups 2 with 80 x 40 x 30 mm, 12 suction cups 3 with 80 x 28 x 30 mm, 64 spacer rings for standard suction pads and various mounting and installation accessories. The INNOSPANN system was installed by the Kaiser employees. But before this could be done, the machine table had to be milled flat and the grooves for the vacuum supply had to be milled into it. After a production period of about three weeks, the complete vacuum system was delivered to Kaiser ready for installation on the machine table.

All requirements fulfilled, or
a resounding success!

In the meantime, the clamping system has proved its suitability in tow- and three-shift operation and all employees who use the machine are very pleased with this practical solution. Since the work load of the machining centre varies widely, depending on the orders received and the batch sizes, and because the company produces both small batches and one-off jobs, the vacuum clamping system has to be converted or modified frequently. Thanks to the flexible INNOSPANN concept, the company was able to reduce the set-up, workpiece changing and workpiece handling times drastically. A further benefit is that the suction pads can be positioned freely. The Quad-Base-T suction blocks are placed directly on the Steel-Plate-T and can be positioned anywhere in the area where there are valves for the vacuum supply. The suction blocks are initially held in position magnetically; the actual clamping of the blocks and the workpiece is done by the vacuum. The use of two base plates Steel-Plate-T on the machine table has the advantage that finished workpieces can be removed from the one plate, and new raw parts mounted there, while other workpieces are being machined on the second plate. Since the overall height of the INNOSPANN components is only low, there is no reduction in the vertical machining range, which means that all previously manufactured parts can still be produced. And this can now be done more rationally and with a higher productivity. On the one hand, the innovative vacuum clamping technology fully complied with the demand for flexible use and conversion. On the other hand, this resulted in considerably shorter set-up times and thus in longer effective machine times. This is clearly demonstrated by the fact that the CNC machining centre is used by five specially trained employees who have to coordinate their activities optimally in order to meet the machining schedules. A further highlight is the extremely short amortisation period of the investment – about 12 months. The productivity increases achieved to date indicate that this period is absolutely feasible.