Blind rivets tend to grab all the riveting headlines, but there’s much more to the rivet sector. Torque visits GESIPA’s Olpe production house to discover an underestimated fastener technology with plenty of potential…
Olpe is close to the Ebbe Mountains in Germany and one of three manufacturing sites for GESIPA in the country (the others are in Mörfelden‐Walldorf and Thal). It is here that GESIPA produces solid rivets, semi‐tubular rivets, bolts and extruded parts ‐ under the watchful and enthusiastic gaze of Plant Manager Christoph Dumpe, who is also our guide for an efficient and intense two‐hour tour of the recently refurbished facility.
Torque Magazine battled through snowy conditions in the winter of 2017 to see the updated production halls first‐hand and takes notes from the knowledgeable Plant Manager.
While riveting technologies such as blind riveting and clinching are well documented and researched, awareness of this other aspect of riveting is woefully lacking, argues Dumpe.
“Knowledge around solid riveting technology is underdeveloped and is hardly taught at universities. This means the possibilities and potential applications for rivets have been massively underestimated,” he warns. “Compared to other fastening technologies, there is virtually no literature around.”
All of which makes the knowledge of Dumpe and his colleagues all the more invaluable. That specialist experience and knowledge is supplemented still further – thanks to GESIPA’s connections with Swiss parent group SFS Group AG, engineers can access techniques and expertise from SFS.
Decades of specialist riveting know-how
The Olpe business has roots that stretch back to 1874, approximately 80 years before GESIPA Blindniettechnik GmbH was officially founded in 1955. Weber & Ochsenfeld was picked up by GESIPA in 1994 and re‐founded with a new name that focused on its riveting technology ‐ W + O Niettechnik GmbH.
Now, GESIPA’s Olpe facility focuses on the production of solid riveting technology, including semi‐tubular rivets, extruded parts and bolts (from 4mm to 24mm diameter). It features one to six‐step presses up to 24mm wire diameter. There’s a high degree of automation, including fully automated packaging systems and all parts are sorted by camera. The facility also has a thermal diffusion system for coating fasteners with optional topcoats (but more on that later).
The automotive sector is one of the main markets for product manufactured at the Olpe plant, including seats, door modules and safety technology. The commercial vehicles market is also important, where the rivet tech is used in frame construction and wheel suspension. Less than 10% goes to industry, where it is used in special connectors, overhead line construction and scaffolding, to name a few examples.
GESIPA develops products and solutions alongside clients, which is when Dumpe and his team get the chance to share their specialist riveting knowledge. He explains: “When using riveted joints, you have to think about the setting process at the beginning of the construction of an assembly. Then you will be rewarded with enormous cost savings.
“Riveting technology brings special advantages through its features in terms of applications and advantages over other fixings. There are cost savings and weight savings, compared to a screw and nut connection.
“There is no relative movement of the connected components after riveting. They have a high load capacity and they have a very large scaling range (in terms of clamping length, strength, shear strength, pull‐out force) all while maintaining the weight and cost advantages.”
With the automotive industry under continued cost pressures, it seems fair to predict that rivets have a secure future in the sector.
Proprietary tech and rigorous testing
Thanks to having tooling developed in‐house, GESIPA’s Olpe factory uses unique machines. Production has its challenges, including the setting process which can lead to mechanical damage of the corrosion protection ‐ high deformations or geometry changes can lead to a limitation of the coating thickness. With that in mind, GESIPA has a solution in its proprietary coating SheraBlack®, an in‐house corrosion resistance process. SheraBlack is a modified thermal diffusion process and top coat system, suitable for all types of cast iron and steel. GESIPA’s other coating solutions are – like SheraBlack – Chromium VIBlind free. Crucially, the coatings are available at competitive prices over zinc‐nickel and zinc‐plate, GESIPA says.
Rivets are put under the full rigours of Olpe’s considerable testing facilities, including a hydraulic press. Sample production and riveting are internally tested, with sample riveting tested up to 600kN, while corrosion test, pull‐out tests and shear tests are carried out with the results analysed and agreed with the customer.
The test facilities give GESIPA a significant advantage over less well equipped production houses, Dumpe argues: “Without the opportunity to test riveting joints in‐house, you are curtailed by fear and you will never exhaust the full potential of the connection and technology in different applications.”
Test results are funnelled into the development of customised rivet connections. Designs are optimised for shear and extraction forces/long hole riveting and suitable corrosion protection in riveted conditions.
As Torque’s tour draws to a close, Plant Manager Christoph Dumpe took the time to emphasise his message: “The mechanical properties of riveted joints are massively underestimated.
“A screw‐nut connection has elaborately produced points (hexagon, thread, etc) where you apply force. They are only required once for the tightening process.
“A riveted joint, however, is pure value analysis: you only rivet the place where it is needed.”