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Riveting plant for universal shaft clevices 

Wobble riveting plant connects joint head, joint disk, and connecting shaft in automatic operation and documents the attained quality.

 

Universal shafts are used as a connecting element whenever two shafts with radial or angular alignment errors, or with axial offsets, need to be connected with each other. The reliable function of such rotationally rigid compensation couplings is materially impacted by an accurate connection of the clevice joint with the joint disk and the connecting shaft. This is particularly true on high performance components for vehicle assembly.

 

In order to meet these requirements, a well-known manufacturer of vehicle accessories was looking for a solution to automate its universal shaft fabrication, so that it could meet the demanding quality requirements of its customer segment. According to the specification document and depending on the universal shaft type and size, the solution needed to take into account two different riveting clearances, and an additional centred riveting operation of the rivet bolt for certain sizes.

 

In Dunkes (Kircheim/Teck), the company found a manufacturer who was clearly able to demonstrate its expertise for the planning and delivery of such complex projects due to its many years of experience with riveting technology, and a large number of custom plants used worldwide.

 

For space reasons and because of the favourable accessibility, the Swabian machinery builder decided in favour of the round table concept. All receiver tools with clamps and counter supports are mounted to a ring-shaped indexing table, and cycle in a clockwise motion past the externally arranged riveting machines, the measurement and inspection stations and the labelling unit. The indexing table with a circular component diameter of 650 mm supports 12 receiver and clamping tools. Six tools spaced by 60° are arranged to rivet the minor clevice joint clearances; six tools additionally arranged between these are intended for the major rivet clearance. Due to the length differences of the clevices joints, a hold-down is required to secure and hold these parts in the fixture. So that only one configuration is required for both riveting clearances, all six hold-downs are secured to a separate, centrically arranged plate that is permanently connected with the gearbox. A quick connect coupling allows the ring shaped indexing table to be adjusted to the interior rivet clearances as quickly as possible - an advantage with significant impact when changing over to other components sizes.
 

The parts to be riveted are manually inserted and aligned in station 1. The operating cycle is initiated by breaking the light curtain or by actuating a two-hand safety control. Station 2 inspects the position and length of the inserted rivet. This is accomplished with a fork shaped load arm that travels over the clevice joint and checks whether the rivet protrusion is sufficient to fully form the rivet head. If the length is correct, Station  3 is given the "green light", where the interior rivet head that faces the centre of the indexing table is formed. This is accomplished with a pneumatically actuated wobble riveting machine with 40 kN of riveting force. Since the riveting location is slightly concealed by the component, this does not permit a linear stroke motion. The machine uses elbow-shaped anvils so that the riveting location can nevertheless be reached reliably.

 

The outward facing side of the clevice joint is riveted in station 4. This process also uses a riveting machine with an elbow shaped anvil. In contrast to the previous station, this machine travels radially to the outside on a carriage. This avoids a collision between the clevice joint and the anvil on the next cycle. Station 5 subsequently connects the centering bolt of the connecting shaft with the clevice joint. The standard riveting machine used for this purpose is conveniently and quickly adjusted to other parts sizes by manually adjusting the carriage.

 

Stations 3, 4, and 5 are of material significance for the quality of the rivet, and consequently for the function of the universal shaft clevices. For this reason, a force-distance measurement at each of these stations checks whether all rivets were set and formed within a tolerance range. The distance is measured by a separate distance sensor, the pressure is measured with a load cell. The actual values are reported to the control, which only gives the "green light" for the next cycle after the inspection was completed successfully. A printer logs the measured values for a 100% quality inspection record.

 

As a final operation, a mechanical labelling unit in station 6 marks the universal shaft clevices before the fully assembled component is secured by a pneumatically actuated dual action gripper and placed into a storage container in the correct orientation.

 

The riveting plant is working in a two shift operation. During operations, the plant achieves a riveting cycle of 2 seconds per component. These throughput times meet the requirements of the specification document, and even exceed these for certain dimensions. Of much greater importance for the customer is the reliability of the plant and the reproducibility of the riveting results, which position the customer to supply its products with a 100% quality guarantee.

Wobble riveting planned for universal shaft clevices of various dimensions and configurations. The " indexing roundtable" works fully automatically in a two shift operation.
The tools are located along the outside perimeter of the ring-shaped indexing table