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Programmable riveting

Radial riveting machine with coordinate table permits up to 15 rivets on one workpiece

Joining technology is increasingly integrating riveting processes into automatic  process sequences. Starting with a standard machine, the object is to design the customer specific configuration such that the parameters and influence factors relevant for the respective joint are taken into account, as well as the requirements on process reliability and profitability.

In addition to hydraulic presses, rivet joining technology in various configurations and automation levels are a strength of S. Dunkes GmbH. When manufacturing safety relevant, function specific, fixed, mobile, or visually appealing joints, the know-how and the machinery product line make the machinery builders from Kircheim/Teck to a highly sought after supplier for users world-wide. A radial riveting machine based on a coordinate table yet again demonstrates the company's innovation capabilities for riveting various hardware and joints. The configuration and functional concept of the machine is designed for workpiece feeding  with the customers workpiece pallet. these convey the various components to the machine, where up to 15 rivets per part are set in an automatic sequence.

 

Adapted to the customer's manufacturing process
With a depth of throat of up to 450 mm, the machine of type DN2-CNC can set rivets of grade St 37 up to diameters of 12 mm with a force of 20 kN. With reference to the centre lines, the coordinate table permits travel of 300 mm in Y and 450 mm in X direction to both sides. At travel speeds of approximately 200 mm/s the riveting unit is located with an accuracy of + / - 0.1 mm. In combination with a ram stroke of 50 mm, this provides sufficiently large travel distances to process the current part spectrum. The motions of the actuated axis and the pneumatically controlled riveting axis are programmed with the control. Depending on the workpiece spectrum, up to 50 parts specific programmes with different riveting cycle times can be stored.

 

Designed for the customers workpiece feed mechanisms
All riveted workpieces are positioned in customer supplied workpiece pallets and automatically conveyed it to the riveting machine. The workpiece support of the riveting machine is configured to a working height of approximately 795 mm above the ground and incorporates a hydraulically actuated cylinder with a stroke of 50 mm that compensates component-specific elevation differences between the machine and the workpiece carrier, therefore aligning each part with the "home" position. The customer supplied tools are retrieved with a command issued by two proximity switch. Each tool pallet has an associated proximity switch, which indicates the tools that need to be manually swapped on the operator panel. In order to quickly overcome the workpiece-specific elevation differences between the different riveting locations, the plant uses a a wedge pusher that can quickly compensate the stroke difference at an actuation speed of approximately 27 mm/s, therefore reducing the cycle time compared to the otherwise typical, elaborate adjustments.

 

Controlling and monitoring
The control has a particularly user-friendly design. The operator enters important process parameters, such as the riveting force, stroke and the X/Y travels using the touch panel. The well-designed screen layout also visualizes the respective status. Fault messages are also accompanied by suggested remedies. Riveting forces can also be monitored with a min. / max. envelope in the force-travel diagramme stored in the control. If the detected riveting force is within the specified tolerance, the next riveting process is released. The cycle sequence is interrupted when a defect occurs. Rivet force detection also allows target and actual riveting values to be forwarded for documentation analysis to an external computer or to a printer using a serial RS-232 interface. 32 selectable target value sets with 8 force-travel envelopes each are available for this purpose. Since this matured solution provides significantly more representational formats than a commercially available PC, an analysis of the travel, time, or force dependent measurement results can be analysed at any time, and independent of the respective riveting profile.

 

 

DN2-CNC coordinate riveting machine during the final assembly stage. The work area shows the cylinder actuated from below to adjust to the various workpiece elevations