Aluminum Vacuum Blocks from Schmalz: A Strong Hold on Shear Forces

The machining of solid core plastic sheets and hardwood workpieces requires high cutting forces. This posed a challenge for the Eibl joinery firm, who found that workpieces kept slipping during the clamping process, thereby jeopardizing a safe machining process. Help finally came in the form of a solution provided by vacuum specialist Schmalz. Efficient aluminum vacuum blocks ensure the sheets are held securely in place and control the shear forces that are at play, allowing rapid and reliable processing.

Eibl uses aluminum vacuum blocks from Schmalz to process HPL sheets.
The vacuum blocks are equipped with a special friction pad.
The aluminum vacuum blocks from Schmalz can also be used to securely clamp complex free-form surfaces.
Front face of a Slackdeck
Final product and blank side by side – this is what a finished Slackdeck looks like.
Josef Eibl and his employees are thrilled with the reliable clamping solution from J. Schmalz GmbH.

Josef Eibl GmbH, located in Aham in Bavaria in Germany, specializes in wood processing for shopfitting and interior fitting. On an area covering around 5000 square meters, the company and its 26 employees also manufacture products made from high temperature laminate (HPL) and the solid surface material Varicor. HPL is a solid core plastic. High pressure is used to compress individual layers into sheets of different thicknesses and dimensions. These are then turned into kitchen worktops, doors or partition walls. Varicor starts out as a liquid but then hardens to form ceramic-like washing stations for hotels, hospitals or kindergartens. Eibl has gained considerable experience of working with these materials in recent years. “These materials are in great demand,” says Managing Director Josef Eibl junior.

In practical terms, the modern materials offer many advantages. For example, HPL sheets are extremely hard, while at the same time offering high bending and tensile strength. They are resistant to abrasion as well as being shock and scratch-resistant. However, they are more complex to process than the simple pressed particle boards. Machining requires lower feed rates, which in turn lengthens the processing time. The material properties place greater demands on the tools, causing them to wear more quickly. Making bores on the face of the workpiece is the most demanding load case in CNC machining. Almost exclusively shear forces act on the clamping system during this process, which can lead to displacement of the workpiece on the vacuum block. These forces are particularly strong in the case of HPL sheets. Eibl found that efficient processing could no longer be guaranteed using conventional vacuum blocks.

The CNC specialists therefore had to dig into their bag of tricks: To prevent slipping, employees applied double-sided adhesive tapes to the table and the workpiece. They also used mechanical clamps. However, there were disadvantages to both methods. In the case of the adhesive tape, the tolerance and the subsequent removal of the tape proved problematic. Mechanical clamps clamp the workpiece but in doing so, prevent continuous processing of the surface because the clamping disc is in the way. The clamping system piston prevents a continuous machining process on the face. This meant that the employees had to clamp the workpiece several times to enable it to be machined from all sides – a time-consuming process.

The state-of-the-art Eibl machinery processes an increasing number of HPL sheets and solid surface materials. However, this only intensified the problem of unnecessary loss of time due to having to clamp workpieces multiple times. So the company managers set about looking for alternatives. Intensive discussions with suppliers, Internet research and visits to trade shows failed to turn up a suitable solution. The company finally made a breakthrough at the Ligna trade show for the timber industry. At the Schmalz stand, they discovered solid wood suction cups made from aluminum. The vacuum experts attended to the task and explained that the suction cups were also suitable for the reliable processing of HPL sheets and Varicor. Their arguments were convincing and Eibl purchased eight suction cups there and then at the Schmalz booth.

Schmalz provides special VCBL-K1/2 vacuum blocks for single-circuit and two-circuit systems. Both the main body and suction plates are made from aluminum. In the two-circuit version, the first vacuum circuit is used to hold the suction cup on the table and the second to fix the workpiece. In the single-circuit version, the vacuum blocks are fitted with a mechanical clamping lever for prefastening the suction cup on the console. In order to counteract the powerful shear forces, the vacuum blocks are fitted with a special friction cup. This is particularly effective in combination with the protective film that is applied as standard to the HPL sheets. This film protects the sheets against damage, and meshes to optimum effect with the friction cup material, effectively absorbing the shear forces.

Vacuum Blocks Also Effective for a New Piece of Sporting Equipment

The innovative product from Schmalz has also found favor in a totally different application. Almighty Boards GbR from Egenhofen in Bavaria have developed a new piece of sports equipment – the Slackdeck. A combination of a longboard and a snowboard, the Slackdeck enables you to balance on a slackline and train your sense of balance. The young entrepreneurs commissioned Eibl to produce blanks for the boards and to process them. The Slackdeck is made up of several layers of wood and composite materials, making the board strong and resilient.

This robustness and the special waveform of the Slackdeck pose a real challenge for the machining process. There are only a few suitable places in which the boards can be secured reliably. Conventional suction cups are unable to absorb the high machining forces on the small clamping areas. This is where the solution from Schmalz comes in. Thanks to their outstanding holding force, the solid wood suction cups are able to clamp the workpieces securely. “Without this development from Schmalz, we would have had to make elaborate templates to securely clamp and machine the boards. Using the aluminum suction cups lowers costs and enables us to deliver high quality,” says Josef Eibl junior.

The use of the vacuum blocks at Eibl is a complete success. “The workpieces are perfectly secured to the machine table. There is absolutely no slipping even when we are using high forces on the workpiece face,” says the Managing Director enthusiastically. The use of the Schmalz solution has simplified processes. “We don’t need any expensive auxiliary equipment and no longer have to clamp the workpiece multiple times, which proved extremely cumbersome. The machining process runs smoothly and safely, saving us time and money.” Schmalz provided the optimum solution for machining HPL sheets, solid surface materials as well as solid wood boards.

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