An absolutely consistent and repeatable finishing process for high value castings
Rösler offers specially engineered rotary vibrators for finishing the surface of large castings that are typically produced as single pieces or in small batches for aerospace applications as well as for manufacturing of large turbines and pumps. Even with highly complex part geometries these special rotary vibrators produce excellent and absolutely repeatable finishing results with a minimum of labor input.
Even in today’s highly technological age many large high value parts with complex geometrical shapes, like blisks, disks, stators, impellors and other turbine components, are still finished by hand. Usually, this finishing method is characterized by high personnel costs and high variations in the finishing quality.
For these challenging applications Rösler has designed the DL range of rotary vibrators without inner dome along with specially developed media and compounds. The parts to be finished are mounted onto the vibrating work bowl. This enhances the intensity of the finishing process significantly. Even parts with complex interior passages can be processed with excellent all-around finishing results. Typically, the outer diameter of castings processed in such DL vibrators can be up to 2,000 mm (80 inches). However, parts with considerably larger diameters can also be processed. The loading of the grinding media into the work bowl is as per other vibratory machines but it can also be fully automated.
Consistent finishing results down from Ra 25 µm to Ra 6 µm
For example, such a DL rotary vibrator is used by an aluminum foundry that utilizes sand casting as well as gravity and low pressure die casting technologies. These castings are made predominantly for aerospace, medical and energy applications, as well as for the manufacture of engines and railway components. Among other parts, the company also produces fan wheels for air conditioning systems with diameters of up to 1,100 mm (44 inches) which to date were finished by hand. In order to reduce its personnel costs and, at the same time, improve the quality and consistency of the surface finishing process, the company purchased a R 420 DL rotary vibrator.
Depending on the design and size of the fan wheels, batches of several parts can be processed simultaneously in this machine. The finishing process usually takes around 2 hours to reduce the surface roughness from the original Ra 25 µm down to Ra 6 µm.
Processing times reduced by more than 50%
The SEKO edm a.s. in Louny in the Czech Republic specializes in the manufacture of turbine components used for the generation of electricity. These include rings for gas turbines made from a high alloy stainless steel with a diameter of 1,500 mm (60 inches) and a value of up to € 100,000.00. With such high-value components it is understandable that the customer is particularly interested in a precisely controlled surface finishing process. This is why the company switched from manual to mechanical surface finishing in a Rösler R 1500 DL rotary vibrator without inner dome.
After they have been produced, the turbine components show a surface roughness reading of Ra 4.0 µm. Compared to over 40 hours required for manually finishing these components, the finishing process in the R 1500 DL takes only about 15 hours to reach the target surface reading of Ra 0.8 µm. This means that with the Rösler equipment SEKO edm not only achieves more consistent and absolutely repeatable finishing results but, in addition, has gained considerably more capacity