in Vol. 18 - September Issue - Year 2017
Modular RWT Shot Peening System - Maximum Process Stability And High Cost Efficiency
The blast chamber of the swing table blast machine RWT 13/4 S is especially equipped to be wear-resistant and walkable for maintenance work
While in one 180° segment, two work pieces can be processed and two work pieces can be loaded/unloaded in the other 180° segment. The RWT design is based on a modular concept that was specifically developed for the peening of transmission components
A comprehensive monitoring and control system, which monitors the air volume (orange control unit), ensures the high process safety and consistency required for any shot peening operation
The nozzles can be moved vertically, horizontally and can be pivoted at an angle from 0 to 90°. This guarantees complete coverage of all work piece surface areas. The high efficiency of the pressure blast system results in significant savings in compressed air consumption.
As international market leader, Rösler Oberflächentechnik GmbH offers total solutions in the field of mass finishing and shot blasting, painting & preservation systems, and mass finishing consumables. In addition, Rösler offers a broad spectrum of surface finishing technologies (deburring, descaling, desanding, polishing, surface grinding,…) for work pieces made from metal and other materials. Headquartered in Germany with plants in Untermerzbach/Memmelsdorf and Bad Staffelstein/Hausen, the Rösler group also maintains sales and manufacturing branches in Great Britain, France, Italy, the Netherlands, Belgium, Austria, Serbia, Switzerland, Spain, Romania, Russia, Brazil, India, China and the United States.
For transmission components like gears and shafts, shot peening has become an indispensable step in the overall manufacturing process. With this in mind, Rösler developed the RWT swing table blast machine, featuring a modular equipment concept that can be easily adapted to different technical requirements and offers maximum process stability paired with repeatable peening results and high cost efficiency. In addition being used by numerous customers, the RWT is also successfully running at an Asian automotive supplier.
As part of a capacity expansion project for minivan transmissions, which increased capacity to 40,000 units per year, this customer decided to carry out the required shot peening operation in-house instead of subcontracting it to an external job shop. The specifications called for a system that can handle approximately 560,000 single work pieces per year. The work pieces consist of 15 different types of gears and shafts, for which peening programs had to be developed for. Tight control of the entire peening process was required by the customer, which led them to choose the Rösler RWT 13/4 S shot peening system, for fully automatic processing of gears and shafts with diameters of 300 mm (12”), heights of 500 mm (20”) and weights of up to 25 kg. The pressure blast system includes a table with two 180° segments, each equipped with two satellite stations. This concept allows processing of two parts in one segment, while another pair of parts can be loaded/unloaded in the other segment. Since some work pieces are already completely finished, special wear-resistant masking had to be integrated into the work piece fixtures to protect the finished surface areas. For complete coverage of the work pieces the RWT is equipped with four blast nozzles – two for vertical and two for vertical movement.
A concept that can be easily adapted to specific customer requirements
Rösler conducted a detailed study of current and future requirements for manufacturing of automotive transmissions, which led to the modular concept of the swing table design. Based on this study numerous equipment components could be standardized and design improvements could be implemented. This includes the blast chamber, which when compared to other peening systems on the market, contains considerably more wear protection and is easier to access for maintenance work. The pressure blast system was also optimized by requiring a considerably lower amount of compressed air, which significantly improved its efficiency. All swing table blast machines are equipped with a satellite rotation control device mounted on the outside of the blast chamber ceiling. This device monitors the actual rotation of the work pieces while in the blast zone. To meet all customer requirements the system design allows the parallel use of two different blast media types or one type with different shot sizes. The RWT can be equipped with a spiral separator for discharging any broken-down blast media. For controlling the overall peening process, Rösler leverages the use of standard components. These include the automatic control of the blast media throughput and the precise measurement of the media throwing speed directly at the nozzle exit. Magna valves are used for monitoring the precise dosage of blast media as well as all media hoses.
Measuring of compressive stresses with a X-ray diffractometer
During the course of the project, the Asian customer provided various work pieces for testing at Rösler. After peening trials with the specified parameters, x-ray diffraction of the treated components at the Rösler test lab showed that the achieved compressive stress values were twice as high as the values stipulated by the customer.
The X-ray diffractometer allows an accelerated process development not only for transmission components but also for a wide variety of different parts. These can include valve and chassis springs, other chassis components, airplane turbines and components for the energy generating industry. Rösler also offers x-ray diffraction measurements as a service.