Marshall Vehicle Engineering goes ‘large’ with first production robot implementation

The specialist vehicle and shelter manufacturer, part of the Marshall Group, has designed and developed cargo beds, or loading platforms, for the new MOD Support Vehicle project. Working with prime contractor MAN Truck and Bus Ltd, the programme will see over 7,000 logistic vehicles supplied up to 2014.

Peter Hardisty, General Manager at MVE, explains, “This is as near to volume production that we have come to at Marshall and robots haven’t been used in production to date. For the manufacture of the load platforms we moved to a new dedicated site in Mildenhall and brought in specialist skills to enable us to design and implement a purpose built production facility.

“The robot systems, together with a new phosphating plant and paint facilities represent a £5million investment in the site. Essential to the success of the facility has been the understanding of everyone involved for the need to embrace the technology available to us.”

An in depth tendering process, involving several of the UK’s leading robot suppliers, illustrated to Marshall that the whole welding process could be undertaken robotically and with confidence. Based on its approach to the requirement and proven capability FANUC Robotics was selected to supply the complete welding system and provided detailed simulations using its RoboGuide simulation package.

Off Line Programming (OLP) at the early stage was carried out using solid models of the fixtures that were imported into FANUC’s overall cell model.

The system comprises two FANUC Robotics ArcMate 120iL robots, each mounted independently and hanging from a 24 Mt travel gantry. In addition each robot is mounted on a supplementary gantry giving two additional axes – one opposed to the 24Mt axis and one vertical axis.

This configuration of having each robot with three additional independent axes allows the robots to operate with complete flexibility. It provides the best possible positioning to ensure maximum operating efficiency, and ease of manual access for loading of parts to the fixtures.

The Support Vehicle loading platforms are in three variants – 6 Tonne, 9 Tonne and 15 Tonne and respectively comprise 120, 140 and 160 parts each that require welding. After loading the accurately laser-cut components into the jig, the robots MIG weld the components together over a 3½hour period.

Simon Hale, Marshall’s welding production manager, explained, “We put a lot of heat into the platform during the operation – over 2,000 welds are laid down in the 3.5 hour cycle. Maintaining tolerance is essential and if parts are not jigged correctly we could lose up to 15 mm through distortion. Therefore the sequence of programming that we developed with FANUC is very important and to date it has produced good results.

“The first platform programmed was the 6 Tonne and FANUC programmed this for us – subsequent platforms, 9 and 15 Tonne we’ve programmed ourselves.
“The platform fixture is positioned on a head and tail stock which allows the platform to rotate 80 degrees in either rotational direction. The use of the auxiliary axis has made difficult welding easy as all critical welds can be presented in the correct orientation,” added Hale.
In addition to the large welding system, FANUC Robotics also provided a FANUC Robotics System 100 – stand alone weld cell. This system is used for smaller sub assembly components.

Andy Caine, Marshall’s Operations Manager for the Mildenhall site, comments, “This operation is a significant achievement for Marshall. This is not a volume production business and yet over a period of 18 months the business has acquired a dedicated site, invested in capital equipment and human resource, and has achieved a very high level of sustainable quality. Even more impressive was the achievement of an initial operational capability in just 7 months”