Vibratory grinding devices – Made in Germany


BY CHRISTIAN THIEME, DÜSSELDORF

In many branches of industry, the company Spaleck Oberflächentechnik GmbH & Co. KG is an established name when it comes to vibratory grinding. Since 1992, the Bocholt company has been offering the complete performance spectrum, ranging from machine and plant engineering, construction through to the manufacture and sale of process materials, as an independent organisation. The medium-sized company presents itself as a full-service provider for the surface treatment of metal, synthetic or wooden parts with numerous partners, including on the international market.

Embedded in idyllic scenery on the western edge of the Münsterland is the town of Bocholt. For centuries, the small town was closely associated with the German textile industry. However, after the world wars, this branch of industry declined more and more; today, there are only a few reminders of this past. After the war, large parts of the town lay in ruins but were quickly rebuilt thanks to the economic boom of the 50s and 60s. Nevertheless, the town was unable to develop its full potential as an economic location over the coming decades. Economies in terms of infrastructure and traffic links meant that the location became less attractive for many companies.

One company that experienced the developments of the post-war period was Spaleck Oberflächentechnik. Originally formed in Greiz (Thuringia) near Zwickau, the owners fled to West Germany in 1949 and started rebuilding the company. Initially still anchored in the textile industry, the company division specialising in vibratory grinding technology developed into an independent company that was formed in 1992. “As a consequence of the independence of the business area as well as for strategic reasons, Spaleck Oberflächentechnik  was later divested from the Spaleck Group and sold”, explains the Managing Director of Spaleck Oberflächentechnik , Alwin Keiten-Schmitz. “As a result, we are now separated from the original Spaleck company both legally and physically.” The Bocholt Industrial Park in the southwest of the town was chosen as the new site. This is the largest integrated and fully developed business park in the whole of NRW.  Nevertheless, it is not only at the NRW site, with its almost 80 employees, that the company is well positioned. It is also present on the international market via numerous partnerships. “We have sold vibratory grinding devices to countries ranging from Holland to New Zealand”, comments Keiten-Schmitz. “Nevertheless, a person from Bocholt is always present at the negotiating table”, adds sales engineer Ingo Löken with a smile (picture 1). With its extensive sales network, the company achieves annual sales of approx. 12 million euros and sells over 100 machines throughout the world. In addition to metal processing, the company also offers its customers further special solutions for synthetics, ceramics and wood.

Achieving objectives with the right concept

The company’s entire know-how in vibratory grinding is bundled at the plant site, with the demonstration centre as the most important area for customers. This area features all devices from the range offered by the medium-sized company. There, customers can, on the one hand, obtain an overview of the range of machines; on the other hand, farming-out work is also performed here and new device concepts and process materials tested under real conditions. The premises also take on additional importance during the quotation phase as each quotation is preceded by an extensive trial period. “As a rule, customers come to us with a workpiece that is to be processed”, explains Löken. As a next step, the suitable process materials such as chips and compounds (picture 2) are chosen from the extensive range. The chips act as grinding wheels during the vibratory grinding process, while compounds, mainly liquid additives, perform additional functions. In this way, for example, they can degrease the work pieces, protect them against corrosion or etch the surfaces of the workpieces so as to further optimise the grinding process. “Particularly important, however, is the geometry and size of the grinding wheels” emphasises Löken. “They must fit the respective workpiece precisely and fulfil the process requirements.”  When a suitable combination of device and process materials has been found, a complete batch of the workpieces is processed in the demonstration centre during a trial run.

“Only once the desired effect for the customer has been determined can a precise quotation be prepared”, explains Keiten-Schmitz. If the customer order is subsequently concluded, the device is assembled ready for operation and then commissioned in the plant under the supervision of the customer. “Only when the customer is satisfied with the work of the machine ordered and accepts it will the machine be delivered to the customer”, comments Löken.

The right type of device for every form of use

The typical areas of use for vibratory grinding devices are the deburring, polishing, edge diffraction, smoothing and cleaning of metal, synthetic or wooden parts. Principally speaking, three basic concepts exist for this: rotation, vibration and centrifugal force. “All machines from Spaleck Oberflächentechnik draw on these basic concepts in differing manners”, explains Löken.

Rotation devices (picture 3) constitute the simplest and most cost-effective device variant for vibratory grinding. The workpieces are placed in a drum together with the process materials. The drum then rotates and the rotation ensures the correct vibratory grinding result after a certain time. In contrast to the other concepts, however, this variant is the slowest and is therefore mainly found in smaller companies without high throughput of parts.

On the other hand, the vibration devices that are also suitable for larger workpieces are faster by a factor of 5 (picture 4). The machine is vibrated by an unbalance motor. In the trough, the workpieces are then set in horizontal worm-shaped movement together with the grinding wheels, thus triggering the grinding process. The process materials and the time factor can then be used to set the desired grinding result. Round trough vibrators are designed solely for the batch processing of workpieces, i.e. the devices must be loaded and unloaded with bulk material by an employee; complete automation is possible to a limited extent only.

The last type of device works on the basis of centrifugal force and is ten times faster than the vibration devices. A rotating plate is located in a fixed upper part (picture 5). During the vibratory grinding process, this is accelerated up to a high speed. Adding process materials also sets the workpieces in rotating worm-shaped movement within the grinding wheels. As this vibratory grinding process is only suitable for small workpieces, this type of device is found, for example, in the production of coins.

Vibratory grinding is mainly interlinked with several process stages. After the grinding process, the grinding wheels must again be separated from the bulk material, used chips are filtered out and new ones added. As vibratory grinding normally involves the use of liquids, the workpieces must subsequently be dried using hot air or granulate. The process water used is treated and purified. The company also offers proven solutions in these areas that can be included directly in the device concept (picture 6).

Surface treatment in diecasting

“In some industrial applications there was a desire to integrate vibratory grinding into the manufacturing process as an automated solution”, explains Löken. “This idea resulted in the development of the throughfeed devices of the DL series. With this type of device, the workpieces are continuously processed and separated in contrast to the batch processing in the classical round trough vibrator. The DL devices use the vibration technology to generate the relative movement. Unlike competitor systems, we do not convey the workpieces linearly or in worm shape on one level but rather upwards in screw form. This enables us to achieve a very space-economising device configuration and homogenous vibratory grinding movement at all points of the device.”

Following repeated requests by customers, we have developed a smaller variant of the DL 1000 – the DL 600 (picture 7). This machine enables throughfeed processing in the smallest of spaces and is therefore ideally suited to the diecasting industry. The diameter of the work container is 1600 mm and ensures perfect all-round running of the workpieces despite the compact form.  The stretched length of the work container is approx. 9 m and thus enables flexible throughfeed times of approx. 8 minutes with a greatly reduced space requirement of less than 4 m². Thanks to the small dimensions, the DL600 can be optimally coupled to an existing diecasting machine. Process interlinking makes it possible for the workpieces to pass directly to the vibratory grinding process following casting, before passing through a drying process. This eliminates the transport of the workpieces from the diecasting machine to the vibratory grinding device, thus saving time and storage capacity.

Everything from a single source

During processing of a customer order, all work is carried out at the plant site in Bocholt. Here, the company bundles not only its sales expertise but also the research, development and assembly of the devices. In the plant, the steel components, delivered finished and annealed at low voltage, are put together expertly before being lacquered and coated. In addition, all necessary SPC (stored programmable control) programming is carried out on site as well as the electrical assembly of the machine. Machines from Spaleck Oberflächentechnik are exposed to the strongest of influences, be these through vibration or contact with the workpieces. Experience has resulted in improved construction at particularly critical points so as to ensure the longest possible service life on the customer’s premises.

Looking beyond the horizon

With an eye on the future, the company continues to focus strongly on international markets. “The know-how of Spaleck Oberflächentechnik is in international demand”, explains Keiten-Schmitz. The high level of expertise in the treatment of process water has ultimately also resulted in an order from Russia involving the development of a device for process water separation. This device is intended for use in the dismantling of old atomic submarines in the Russian north sea. Although this order is far removed from the normal day-to-day business of the Bocholt company, it demonstrates what development potential can be hidden in individual business areas and how this can result in new focal points for a company. The company’s past is evidence of this.