The large-area vacuum gripper systems from J. Schmalz GmbH, D-72293 Glatten, are widely used for automation of many different woodworking processes. The range of large-area vacuum grippers comprises three basic series which differ in their design and applications. The FX and FM series are used for the safe and precise handling of workpieces which have already been machined and thus have smooth surfaces. These parts may be solid or have apertures. The VacuBox is used for handling long, heavy and possibly warped beams and boards and is thus intended for rougher use. The SBX series is a highly flexible large-area vacuum gripper system which is suitable for handling rough-sawn wooden parts, for handling beams, boards and planks, and handling partially finished wooden parts with easily damaged surfaces.

As the following example demonstrates, these systems are suitable for many different handling tasks in the woodworking industry. An Italian manufacturer of high-quality designer doors planned to rationalise the order-driven individual production and was initially faced with the question of which machining system would be the best solution. Logically, the next question was how this system could be utilised optimally. The answer to this question was: if possible, fully automatically in multi-shift operation, although most of the doors and frames are manufactured individually to meet the customers' specifications.

Automation with vacuum handling

The answer to the first question was provided by a large German manufacturer of woodworking machines in the form of a fully automatic edge-machining system. The second question was answered the special engineering company "MM - Mutz Maschinenbau GmbH" in Dornstetten - which offered a suitable handling system. The only remaining question was how the gripper system for doors and other wooden parts should be designed to meet the widely varying requirements, namely the careful and safe handling of doors of various sizes up to 1.300 x 2.700 mm, different weights, solid doors and doors with apertures, door frames with frieze widths up to 100 mm and, above all, the high-quality finish of the door element. This problem was solved by the vacuum specialists J. Schmalz with their large-area vacuum gripper systems of the SBX series. These large-area vacuum grippers have very high holding forces, adapt themselves very well to various rough or uneven surfaces and are ideal for handling long wooden workpieces with different widths and weights.

Thanks to an intelligent system which disables unused suction areas, these grippers are extremely economical, consuming only the minimum necessary amount of energy.
Their low intrinsic weight means that they have no major effects on the maximum possible loads and the dynamic movements of the handling device. They are also easy to install because they are delivered as complete systems: an SBX large-area vacuum gripper always comes complete with an integrated vacuum generator. In most cases, this is a multi-stage ejector mounted inside the gripper housing. For the application being considered here, however, the vacuum is provided by an external vacuum pump of the type EVE.

Flexibility thanks to universal large-area vacuum grippers

The automatic production process is as follows: the "rough" doors are first inserted into the edge-machining system, where they are completely machined in up to four steps. Depending on the number and the sequence of the machining steps, the doors or frames may pass several times through the system. For this, they are stacked at the end of each step and then returned automatically to the input side of the machining line. Since the doors and frames are individual designer jobs, which means that the shape, size, weight, surface finish, colour and machining vary widely, the related data are read by a barcode reader at the inlet to the edge-machining line. The entire production process is then executed fully automatically and the handling devices, which are equipped with two flexible SBX large-area vacuum gripper systems, control the entire flow of materials.

Each large-area vacuum gripper consists of SBX beams and is mounted as a complete gripper on the scissor-type lifting device of one of the portal handling devices. One vacuum pump EVE is sufficient for each gripper (two SBX beams), thus saving weight, installation time and costs. The gripper systems are mounted such that they can be turned, permitting them to handle the wooden parts flexibly and as required, including placing them in the edge-machining system with the correct orientation. For careful handling of the parts, the gripper systems are mounted flexibly on spring elements, and the 25 mm thick layer of special foam material used as suction mats ensures the necessary damping.

According to the users, the handling of doors and frames with the SBX large-area vacuum gripper systems functions very well and without problems. To date, it has not been necessary to replace any of the foam sealing mats.

Summary

At the moment, the edge-machining system is running in single-shift operation, although it is designed for two-shift operation. The factory can produce about 600 doors per day, which means that the cycle times in the edge-machining system are correspondingly short. Not only the Italian customer, but also the engineering company Mutz Maschinenbau, praised the SBX large-area vacuum gripper system from Schmalz: the solution with the SBX grippers operates very reliably, and is also far cheaper than an alternative solution with additional axes.