Shot blasting of work pieces made from aluminum must meet certain technical requirements. For example, non-ferrous blast media, such as aluminum, must be used because ferrous deposits on the work piece surface would cause corrosion. Because of its relatively low bulk density, aluminum media requires higher throwing speeds and a higher media throughput to achieve good shot blast results. For these reasons, a renowned automotive supplier replaced the conventional blast wheels on their shot blast machine with the high performance Gamma G turbines from Rösler. This resulted not only in significantly improved shot blast results but also a marked capacity increase as well as lower energy consumption and reduced maintenance costs.
With its light metal castings division, the Handtmann group of companies is a strategic partner in the automotive industry, producing aluminum and magnesium die-castings for components like drive trains, chassis and car bodies. In factories at the company headquarters in Biberach, Annaberg, Kosice (Slovakia), and Tianjin (China), Handtmann is utilizing more than 80 fully automatic cold chamber die-casting machines with locking forces of up to 4,000 metric tons for a wide range of aluminum and magnesium alloys.
The goal: Higher blast performance and process stability
At the Annaberg factory, in the state of Saxonia, aluminum die-castings like oil pans, transmission supports, and engine cradles are made. After casting, the work pieces undergo a shot blast process for removing material overflow in the form of flashes, for slightly breaking sharp edges and to create a homogeneous, isotropic surface structure. The continuous spinner hanger shot blast machine used for this task could not provide the required work piece throughput and consumed too much energy.
“The aluminum cut wire media we use has a relatively low weight and, subsequently, a low impact energy. That is why we could only achieve acceptable shot blast results by running the shot blast machine at maximum load and extremely long cycle times. Moreover, the blast media was frequently plugging the turbines causing expensive downtimes”, explains Raffael Schaarschmidt, manager of the machine shop in Annaberg.
To resolve this problem with a comprehensive retrofit of the blast machine the customer contacted “TuneUp”, a department at Rösler Oberflächentechnik exclusively dealing with the modernization and optimization of existing shot blast equipment made by different manufacturers. The scope of the “TuneUp” services extends from improving the overall machine performance, the adaptation to changing technical requirements up to improving the energy efficiency of the equipment. A key element of this service package is the installation of high performance turbines adapted to the customer needs.
Better shot blast results with shorter cycle times and reduced energy consumption
Raffael Schaarschmidt continues: „Rösler informed us extensively about the retrofit possibilities with new turbines and provided us with a detailed operating cost analysis. Subsequently, we decided to exchange the two conventional blast wheels with Gamma 400 G turbines.” These high performance turbines are equipped with curved throwing blades in “Y” shape allowing the use of both blade sides. Compared to straight throwing blades the curved design allows a highly fluid, unimpeded media flow. Compared to conventional blast wheels with the same diameter and the same RPM the result is a more effective acceleration of the blast media with higher throwing speeds, the result is up to 25 % higher blast performance. For this reason the installed power could be reduced from 11 to 9 kW per turbine.
“Despite the lower power input, which resulted in considerable energy savings for our company, with the Gamma turbines we achieve a much higher overall blast performance. Actually, even at reduced cycle times our shot blast quality has improved dramatically. Last but not least, this provides us with additional, urgently needed shot blasting capacity”, explains Mr. Schaarschmidt.
The special turbine design also reduces media turbulences on the throwing blades producing a much more precise and stable blast pattern. This results in a highly focused blast media impact on the work pieces contributing to shorter cycle times and reduced equipment wear and tear.
Lower maintenance costs and higher equipment uptimes
Another benefit of the special “Y” blade design is that both sides of the throwing blades can be used by simply turning them. Such a blade exchange requires less than 10 minutes per turbine: The blade mounting mechanism can be loosened after simply removing the maintenance cover on the turbine, thus allowing the quick blade removal, turn and re-installation. Mr. Schaarschmidt explains: “Ever since we started using the Gamma turbines, our maintenance and repair costs have gone down. Moreover, we have no problems any more with plugged turbines. And with the retrofit the overall equipment availability has significantly improved.”
Surprisingly quick amortization
At Handtmann light metal casting in Annaberg, the modernization of the shot blast machine contributed to a significant optimization of the manufacturing process. For example, the lower bulk weight of the non-ferrous aluminum blast media is more than offset by the higher blast performance of the Gamma G turbines. In addition, not only could the shot blast results and process stability could be improved, but also the overall productivity. Because of the savings in maintenance costs, spare parts and energy consumption, the investment was also a financial success with an amortization period of less than 2 years. Concludes Raffael Schaarschmidt: “Our blast machine retrofit was a full success. We are very satisfied with the overall results”.
As supplier of complete surface treatment systems Rösler Oberflächentechnik GmbH is global market leader in the field of mass finishing and shot blast equipment, paint and preservation lines as well as consumables and process technologies for the optimum surface treatment (deburring, descaling, de-sanding, polishing, surface grinding,….) of work pieces made from metal and other materials. Besides the German manufacturing locations in Untermerzbach/Memmelsdorf and Bad Staffelstein/Hausen the Rösler group has branches in Great Britain, France, Italy, Netherlands, Belgium, Austria, Switzerland, Spain, Romania, Russia, Serbia, Brazil, India, China and USA.