To further optimize product quality, productivity and manufacturing capacity, a leading supplier of injection-molded plastic components decided to decommission its existing shot blast machines and replace them with new ones. The company chose de-flashing solutions from Rösler: A RWS 1200 system that can be easily integrated into manufacturing cells and allows the consistent, automatic de-flashing of single work pieces. For processing complete batches of work pieces produced in bulk, a tumble belt blast machine, model RMBC 1.1-S, was selected. Since this machine allows surprisingly high batch volumes and short cycle times, it replaced three shot blast machines, which were previously used for the same de-flashing operation.
The Helvoet Rubber & Plastic Technologies B.V., located in Tilburg, Netherlands, is a globally operating manufacturer and development partner for high-precision components and assemblies. The rubber, thermoplastic and duroplast work pieces are produced with the injection-molding technology. Among these materials duroplast is one of the most challenging. It is used for producing highly wear-resistant components with a precision in the micrometer range. Duroplast parts are frequently used as replacement for metal components. A downside of the injection-molding process is that it creates more or less pronounced flashes on the work pieces that must be removed to ensure the work piece quality and functionality.
High demands regarding the de-flashing quality and dimensional precision of the work pieces
Helvoet’s customers from the automotive, medical engineering and many other industries are demanding excellent quality and a high dimensional accuracy for their products. To fulfill these demands in a cost-efficient manner the company has been using Rösler de-flashing equipment and blast media for quite a while. Important aspects of this dynamic cooperation are Rösler’s strong commitment towards continuous process improvement and to adapt its shot blasting solutions to the specific requirements at Helvoet. This allows the company to sell high-quality products in a very competitive market environment. Moreover, the strong global presence of Rösler allows Helvoet to always have quick access to a Rösler de-flashing expert. For all these reasons it was obvious that Rösler will be the supplier of the new shot blasting equipment.
A complete solution for the fully automatic processing of single components
For de-flashing of single, delicate components the swing satellite table RWS 1200 was chosen. About 25 units of this machine type are successfully running in the field. The RWS machines can be equipped with extremely precise blast nozzles or energy-saving blast turbines. They can also be supplied with a combination of these two blast systems.
The new Rösler de-flashing machine is part of a fully automatic manufacturing cell. Precisely defined interfaces in the RWS control panel ensure a quick and precise communication with the higher level controls of the manufacturing cell. Work piece loading and unloading takes place with a special handling system. It places the work pieces onto the work piece fixtures, which were also designed and supplied by Rösler.
The clever design of the RWS 1200 with two satellite stations placed opposite from each other, allows the loading/unloading of one satellite station, while components in the other satellite station undergo a de-flashing process. Compared to other shot blasting machines available in the market, the RWS concept reduces the unproductive equipment times by up to 85 percent.
During the de-flashing operation all relevant process parameters, such as blast pressure, RPM and dust collector air flow, are monitored by sensors and automatically kept at their preset levels. The blast media recycling and cleaning operation with screen and air wash separator, as well as media replenishment, also take place fully automatically. The blast media operating mix is always maintained at an optimal quality. All this ensures that, irrespective of the production volume, the plastic components are leaving the machine perfectly de-flashed and without any residual dust on their surface.
Reliable and economic batch processing
For the de-flashing of its mass produced injection-molded work pieces in batch mode Helvoet chose the new RMBC 1.1-S. This machine represents the latest equipment and control technology for batch de-flashing of large volumes of small plastic components. The tumble belt blast machine can handle work piece batches of up to 70 liters. Special design features and the high processing capacity helped not only to reduce manual loading and unloading operations but also allowed replacing three existing shot blast machines. This freed up valuable manufacturing space.
Another significant contribution towards a more effective and efficient blast de-flashing operation is the modern blast turbine: Instead of employing an expensive compressed air injection system Rösler is utilizing the much more economical blast turbine technology. The blast media is accelerated and thrown at the work pieces by an electrically driven rotating turbine, while the work pieces are continuously tumbling over each other in a chamber formed by an endless belt. This guarantees all-around, even de-flashing results on the components. At the same time, the de-flashing effect is accelerated by the work pieces tumbling over each other.
Critical process parameters like the turbine RPM and the media consumption are monitored by sensors. For example, when the sensor signals a low media level in the machine, new media is automatically added. The RMBC 1.1-S is also equipped with an air extraction system for the blast chamber and a vibratory screening unit for removing larger burs and flashes, before the media is passing through a cleaning device. An antistatic feature is also included to prevent blast media and flashes from sticking to the work pieces. All these technical features ensure an optimal media operating mix, a high process stability and perfectly de-flashed and clean work pieces.