Perfect surface finishes for large and small gear components

Innovative drag finishing system for aerospace applications

When designing a new helicopter model, Airbus had to find a solution for finishing large gear components. For this challenging task Rösler developed an innovative drag finishing system with automatic work piece clamping and a clever work piece handling system.    

Airbus has been using a Rösler drag finishing system for treating helicopter gear components for quite a few years. So it was only natural that this renowned aerospace company turned to Rösler to supply another drag finishing machine for finishing larger gear components used in a new helicopter model. In addition, with the new equipment the manufacturing capacity for current helicopter models needed to be expanded. Around 35 different work pieces made from special high performance steel alloys with diameters from 40 to 800 mm and weights of up to 75 kg must be processed in the new drag finisher.

Newly designed, flexible drag finishing system
Based on numerous processing trials in Rösler’s test center the company developed an entirely new drag finishing concept that meets all customer requirements. With work bowl dimensions of 1,700 (H) x 2,600 (Ø) mm this new machine is one of the largest ever built! To allow the operator easy, ergonomical access to the work stations the machine was placed in a foundation pit. Three 3.6 kW vibratory motors mounted to the sidewall of the work bowl ensure that the processing media in the work bowl, weighing about 6.7 metric tons, is thoroughly mixed in between process cycles. A crane placed behind the machine allows easy and quick filling of media into the work bowl. Worn media that has become too small is discharged through screens in the work bowl bottom. A level indicator shows the operator when to add new media, which is done manually. A Z 1000 centrifuge with fully automatic sludge discharge cleans the process water, with a timer controlling the automatic compound replenishment.
The rotating carousel (spinner) is equipped with 6 workstations with independent rotary drive units. In addition, the workstations can be shifted to form a smaller or larger circle, and their angle can be adjusted. The system allows the simultaneous processing of two large and four small gear components.

Handling system and automatic clamping facilitate work piece handling
Since some of the work pieces are quite heavy, they are loaded/unloaded with a mechanical handling system: The operator guides the handling system holding one single work piece in a precisely defined position to the workstation. After the work piece has been mounted to the station, it is automatically clamped. Smaller gear components are mounted manually.  Once the mounting operation is completed, the operator selects one out of 100 different, work piece specific treatment programs stored in the PLC to start the finishing cycle. The shape and size of the specially developed ceramic RCP processing media ensures that all surface areas in the gear components are reached for creating an absolutely even surface finish and reducing the surface roughness readings from Ra 0.25 - 0.4 µm down to Ra 0.2 µm. Based on the cycle times in the existing drag finishing system the process parameters like circular orbit, rotary speed and covered distance were translated to the larger, new machine in a manner so that no changes had to be made to the existing finishing process.
For unloading of the finished work pieces the carousel moves into a position that allows the operator to spray-rinse them with water and then remove them from the workstation.

Continuous monitoring ensures absolute process safety
In order to meet the high safety standards required in the aerospace industry, all equipment functions are continuously monitored and controlled. This includes the movement of the work piece handling system as well as the correct positioning of the work pieces in the workstation clamping system. Any deviations will cause the automatic stop of the machine. To make certain that the process water is safely evacuated from the work bowl, the draining screens in the work bowl bottom are not only flushed with water but also regularly cleaned with compressed air. Maintenance is made easy with a central lubrication system that automatically supplies the guides and work stations with grease according to preset time intervals.