Record-breaking drag finisher achieves fantastic grinding results
For the development of a new helicopter model, Airbus had to machine large gear components. To this end, Rösler Oberflächentechnik designed a drag-finishing machine with automatic workpiece clamping and a manipulator for part handling.
Airbus has been using a system from Rösler Oberflächentechnik, a manufacturer of surface technology, for years for the drag finishing of helicopter transmission parts, the system manufacturer reports. When it came to machining large gear parts for a newly developed helicopter, the aircraft manufacturer turned to the company again. The new machine was also intended to expand the production capacity for existing models. The range of workpieces comprises around 35 different parts made of special steels with diameters of between 40 to 800mm and a weight of up to 75kg.
Newly designed, flexible drag finisher
According to Rösler, they met these requirements by conducting tests in their test centre, which is equipped with a completely redesigned drag finishing system. The system is one of the largest of its kind to date. For ergonomic accessibility by the operator, the 1,700mm-high working space with a diameter of 2,600mm is embedded in the hall floor. In order to ensure uniform movement, the container is driven by three 3.6kW-motors mounted on the side. Its maximum capacity is 6.7t of grinding bodies. A crane is placed behind the system for loading purposes. Grinding bodies that have become too small are automatically discharged from the container by floor drain screens. The grinding bodies are replenished manually by means of a filling level indicator. Compounds are automatically re-dosed in a timely-controlled manner. Processed water treatment with a Z1000 centrifuge with automatic sludge discharge is also included in the delivery.
The rotary carousel of the system, which is designed for three-shift operations, is equipped with six separately driven spindles, each adjustable in angle and diameter. Two of these spindles can be used for machining large workpieces and four for smaller gear components.
Manipulator and automatic clamping facilitate part handling
Because of the high weight of some of the workpieces, loading and unloading of the system is carried out with the aid of a manipulator. For loading, the operator guides the handling device loaded with a workpiece to a defined position of the spindle. After inserting the part, it is automatically clamped for large workpieces. For smaller gear parts, the clamping is carried out manually by the operator, who then selects the appropriate part in the system control and starts the process. The system stores up to 100 part-specific machining programs. The specially developed ceramic grinding media RCP ensure that the gear parts are uniformly machined down to the smallest detail and that the required roughness value of Ra=0.2µm is achieved. The raw parts have a roughness value of R=0.25 to 0.4µm. Based on the machining times of the existing system, the process parameters such as circular path, speed and distance travelled by the parts during machining are converted to the large drag finishing system. Thus, no process changes are required.
When unloading, the carousel first moves into a comfortable position for the operator to clean the parts above the container before removing them from the unloading position.
Constant monitoring maximises process reliability
In order to guarantee the safety standards common in aviation, all system functions are constantly monitored. This includes workpiece transport by the manipulator as well as the position of the parts in the clamp during machining. If it changes, this leads to an immediate stop of the system. In order to ensure that the process water is continuously discharged, the screen boxes are not only rinsed with water, but also automatically cleaned with compressed air at regular intervals. The central lubrication system, which automatically supplies the guides and spindles with lubricant at defined intervals, ensures ease of maintenance.