The UMS factory in Sochaux- Montbéliard, in the French province of Franche-Comté, produces suspension systems for Peugeot and Citroën cars. Introduction of ESAB Marathon Pac bulk wire systems has improved productivity and reduced fabrication costs.

Sochaux-Montbéliard is the cradle of Peugeot, the leading brand of PSA Peugeot Citroën – the automotive company with 14% market share in Europe and over 5% worldwide. Here, in 1810, the Peugeot brothers, descendents of a family of millers, converted a corn mill into a steel foundry to supply springs to the local clock industry. Soon the portfolio was extended with bandsaws, tools, coffee mills, frames for hoop skirts and, eventually, in 1886, the production of bicycles in the city of Montbéliard.

The private car venture started in 1889, when the company exhibited a steam driven three-wheeler at the Paris world exhibition. A chassis factory was built in 1912, in Mandeure, and in the same year Peugeot bought the land on which the UMS factory stands, today. Some 12,500 people are employed on the 265 hectare site. Activities are two-fold: deep-drawing, assembly and painting of chassis in one section; mechanical construction, development and testing in another section. In addition to suspension systems, the UMS factory produces some 45,000 shock absorbers a day - mainly for Peugeot Citroën cars, but also for other brands (altogether 180 models).

Shock absorber cross-section.

Automated production
Car suspension system shock absorbers - regarded as safety components - have high weld quality demands. The housings of the absorbers are MAG welded with 1.0mm diameter EN 440: G3Si welding wire in 82%Argon/18% CO2 shielding gas protection.

Weld metal consumption per housing averages 6g which, at a daily production of 45,000 absorbers, equates to 270 kg. The MAG process is fully automatic, the equipment consisting of two 4-head, one 3-head, four 2-head and two 1-head installations, and a robot. In total, 22 welding heads are to be fed with welding wire.

Before the introduction of Marathon Pac, the company used wooden spools with 100kg or 200kg welding wire with a mechanical pay-off system. It involved a rather complicated method of wire feeding, consumed a lot of space and hindered operations. What's more, the dimensions of the spool remained the same - full or empty – and they needed to be transported and stored before being returned to the supplier.

The main reason for considering Marathon Pac, however, is that the welding wire from the previously used wooden spools maintains the mechanical deformation (cast & helix) it receives when it is spooled onto the spools. The result is the so called dog-tailing of the wire extension when the wire leaves the contact tip. This is a big problem in automated production with precisely pre-programmed weld paths, resulting in wrongly positioned welds and increased contact tip wear.

Towards the end of 2005, the idea emerged for a production test using one Marathon Pac drum on the SERDA 2 production line - motivated by ESAB's claim that this system overcomes the dog-tailing problem.

The Marathon Pac system
ESAB France supplied a Marathon Pac drum with 250kg of 1.0mm diameter OK Autrod 12.51 and installed it on the SERDA 2 line, to run a test until the drum was empty. Success was so overwhelming that production management immediately ran a wider test and, soon after, introduced Marathon Pac at all welding stations.

Wire in Marathon Pac is pre-twisted before being spooled into the drum, to compensate for the limited mechanical deformation it receives in the spooling process. As a result, the wire extension is virtually straight when the wire leaves the contact tip for exact positioning of the weld. This results in better weld quality and lower defect rate. It also reduces contact tip wear and the associated maintenance of the welding gun, resulting in less downtime.

No accessories are needed for the supply of the wire. The system works with the wire feed unit, which is less subject to wear because of low feeding forces.

PSA UMS Sochaux also purchased a number of Marathon Pac accessories - lifting yokes, trolleys and re-inforced liners with quick connectors - for easier internal transport, installation and reduced maintenance.

The image to the right shows how the Marathon Pacs are positioned for a four-head welding installation (not visible). The liners are arched over the pathway and are – in this way – easily accessible for maintenance. Available in lengths from 0.6m to 12m, they are adaptable to any workshop situation. The spare drum (in the foreground) is ready to be installed when one of the four connected drums is empty.

OK Autrod 12.51 is a high quality copper-coated welding wire with a more stringent chemical analysis than required by the European norm G3Si. This assures consistent mechanical properties from delivery to delivery.

Increased production
PSA UMS Sochaux calculates a 3% increase in shock absorber housing production resulting from the use of Marathon Pac, compared with the wooden spools. This is due to significantly lower downtime for spool exchange and, annually, 60 hours less downtime for maintenance – a significant figure in automated mass production.

By Joel Perrin
Key Account manager, ESAB France