New flow hole forming screw to extend application limits 04 July 2024

With the original Flowform®, Arnold Umformtechnik developed and established a joining solution on the market that met the increasing demands of sheet metal joining. Now the company is responding to growing customer requirements with the new Flowform® Plus.

Compared to the conventional Flowform®, the developers at Arnold have changed the dimensions of the Flowform® Plus from a diameter of 5mm to a diameter of 4mm. In addition, the geometry of the flow form tip has been optimised and the heat treatment process adapted so that the performance remains virtually the same.

Depending on the head and length, the new Flowform® Plus 4.0 weighs around 3g, meaning a weight saving of 25%. When extrapolated to the total number of screws used in a vehicle’s body, this adds up to quite a bit of weight. For example, the weight of 500 elements of the conventional Flowform® 5.0 per vehicle is 2kg, with 500 elements of the Flowform® Plus 4.0 per vehicle it is 1.5kg. This alone means a saving of 500g.

This is important when the automotive industry is focusing on weight reduction against the backdrop of ever decreasing CO2 emissions. 

Classic applications of the Flowform® Plus

In principle, the Flowform® Plus is designed for higher strength steel sheets and thicker sheet combinations. By using aluminium components, thicker joint combinations with several layers can also be created. In the past, this meant that the top and middle layers of three layer joints were pre-punched. The use of Flowform® Plus now allows thicker material combinations of up to 7.5mm to be joined without pre-punching, depending on the joining materials.

This is due to the lower material displacement caused by the diameter reduction, which results in a smaller gap between the sheets and less friction surface – due to the smaller dimensions. 

With regard to the fastener, higher strength is achieved by selecting a suitable material in combination with a suitable heat treatment process. Due to the smaller diameter of the Flowform® Plus, and therefore also the smaller head diameter, the screw is also suitable for applications where only a small flange width is available.

“We joined a three layer sheet metal joint with 2.5mm thick aluminium sheets with both the conventional and the new Flowform® element. The result clearly showed less gap formation with the Flowform® Plus. It was also possible to join without a pilot hole. In applications with adhesive, which is usually the case, the adhesive is also trapped if a pilot hole is avoided and therefore cannot escape to the pilot hole,” says Heiko Miller, application sales engineer Flowform® at Arnold Umformtechnik GmbH & Co KG.

“Joining without a pilot hole is much more cost-effective in terms of the cost efficiency of the process, as the user does not need expensive camera technology to check whether the screw hits the centre of the pilot hole during the joining process.” 

The new flow form is suitable for use in car body shell construction, aluminium steel mixed construction, for profile intensive construction methods, for one sided accessibility, for hybrid connections, as well as for battery packs.  

Claire Aldridge Deputy Editor t: +44 (0) 1727 743 889

Having spent a decade in the fastener industry experiencing every facet – from steel mills, fastener manufacturers, wholesalers, distributors, as well as machinery builders and plating + coating companies, Claire has developed an in-depth knowledge of all things fasteners.

Alongside visiting numerous companies, exhibitions and conferences around the world, Claire has also interviewed high profile figures – focusing on key topics impacting the sector and making sure readers stay up to date with the latest developments within the industry.