Modular clamping systems for more rational production of wooden parts with maximum flexibility

Any company which produces special solid-wood products such as shaped strips, flat strips, covers, decorative elements for furniture fronts or doors is often confronted with orders for varying batch sizes from one-off jobs to large quantities. Such companies must therefore pay great attention to efficient and economic operations throughout the production process. A decisive factor in this respect is the flexible and, above all, best-possible use of the complex and expensive CNC machining centres.

Today, no manufacturer can afford to keep large stocks of manufactured goods, which means that the entire production process must be geared for the manufacture of any batch size from one upwards and for the just-in-time production of orders with any desired quantities. This places correspondingly high demands for flexibility in use on the CNC woodworking machines and, of course, on the operating personnel. In addition, the woodworking machines must be equipped with highly flexible workpiece clamping systems in order to ensure that the non-productive times which result from setting up and converting the machines for new workpieces do not excessively reduce the overall performance of the machines. Such problems frequently confront the specialists responsible for production at Messrs. Reichert Holztechnik GmbH & Co. KG in 72285 Pfalzgrafenweiler, a company with 95 employees which is recognised as one of the largest companies in Germany for the development, manufacture and marketing of the above-mentioned solid-wood elements for kitchen and bathroom furniture, for doors and for interiors. The technical manager Helmut Bross says: "We are recognised for our competence in the manufacture of furniture fronts in high quality and also take on small to medium-sized orders. Our strong points are our advanced product development, our reliability as a supplier and our flexible response to customer requirements". All well and good, but Jochen Nübel, responsible for the production equipment, says that the services and flexibility offered by the company present a great challenge to the production department, where 85 of the company's staff of 95 persons work. Nübel is a trained mechanic and has many years of experience, which means that he knows what is involved in converting the CNC woodworking centres to handle several different workpieces per hour.

Machine performance is only part of the productivity

In this respect, Jochen Nübel said: "In order to achieve the necessary productivity, flexibility and economic operations, we regularly invest in the latest machine tools. The same applies to the periphery of these machines in the form of workpiece clamping technology and parts handling systems. For this reason, we have equipped our new CNC woodworking centre with a vacuum clamping system and have upgraded one of our older CNC machine with the same system". The vacuum clamping systems used here are complete solutions from the "Innospann" series made by the vacuum specialists J. Schmalz GmbH in 72239 Glatten.

The first woodworking centre was purchased in 1993 and was later upgraded with an Innospann vacuum clamping system. The second woodworking centre was installed in 1999 and equipped from the start with an Innospann vacuum clamping system. Both woodworking centres are used today in single- or double-shift operation and each produces about 95,000 workpieces per year. The older centre, a so-called double-position, double-spindle machine is used primarily for the manufacture of standard products, while the newer centre is used more for the production of one-off parts and small batches. The company produces strips with 53 different profiles in many different lengths and widths (in increments of 1 mm), resulting in a very large number of different products. This, in turn, means that it must be possible to convert the vacuum clamping devices flexibly and quickly. According to Jochen Nübel this can be done very easily and quickly by the machine operators with the aid of the Innospann system. One of the problems is that the workpieces have to be clamped by their "good" sides and that they have to be machined with a resulting flatness of less than 0.1 mm, since the transitions between individual door elements would otherwise be visible.

Precise machining requires precise clamping

It is thus clear that the machining precision can only be as good as the mechanical accuracy of the machine table and of the clamping consoles, adapter plates, clamping blocks and suction cups mounted on the table for setting up the clamping system to match the workpieces. Jochen Nübel said: "With the standardised vacuum clamping system Innospann from Schmalz, we have an extremely precise, highly flexible and easily handled basis for the rational and efficient production of orders of all sizes, including one-off jobs. The quick and exact conversion to other workpieces helps to reduce the idle times and thus the non-productive times to a minimum. Even in cases where we have to convert the machines several times a day, we can still manufacture parts efficiently and economically".