A turn-key welding robot system for Kubota tractor cabins

In 2015, Kubota Farm Machinery Europe (KFME) invested 57 million euros in a new factory in Bierne (59), located near the port of Dunkirk. This investment has made it easier to import parts from Japan and export fully assembled machines. The Kubota M7 is produced at this new 120,000 m² site (including 40,000 m² of workshops) in models ranging from 130 to 170 hp. “Originally, our finished tractor cabins were imported from Japan and we only had to assemble and paint them”, recalls Benoît Frezel, Assistant Manager. “But because of the high logistical costs and the storage required for months of work in progress, we decided in 2018 to integrate the welding of these at KFME.”

800 welds per cabin

This type of welding is very demanding because it requires a ROPS (Roll Over Protection System) certification, a safety standard for structures designed to protect drivers if a machine tips over”, continues Benoît Frezel.

From accessory supports to posts, each cabin requires approximately 90 steel parts with thicknesses ranging from 1.2 to 9 mm. Thus, each cabin requires 23 metres of welding, divided into 800 welds, of which about thirty are critical. At the heart of a 1,100 m² workshop is a Valk Welding welding cell with two TM-2000WG robots working almost symmetrically on a track to perform 60% of the total welding work.

Eight individual welding stations

The automation is highly optimised: during a work cycle, the robots spend between 60% and 70% of their time welding, with the remaining time spent on air movements. Upstream, the robot cell is supplied by eight individual welding stations required for subassemblies. To eliminate manual handling while minimising risks, all assembled cabins are placed on jigs moved by ‘MasterMover’ electric trolleys.

From robot to jig

In addition to designing the robotic system and developing the programs, Valk Welding also handled the design and development of the welding jigs, which are essential for positioning the parts before they are robotically welded. “Valk Welding has not only proven to be competitive in installing the turn-key robot cell, but also in supporting and optimising the entire production line, from the individual stations to the special mobile jigs, whose precision has been checked in 3D”, explains Benoît Frezel.

Training and quality assurance

Kubota then qualified all its welders through an approved body. This ensures the continuity of production while maintaining a high level of quality in the event of a problem with the robots. The welds are inspected through two quality portals. During the grinding process, the cabin is checked for any leftover weld spatter. After sealing, each cabin is degreased before being phosphated and painted. “Since the installation of robotic welding in 2020, we have assembled more than 4,000 cabins without any major failures. We only had one technical problem with a robot, which was fixed within 24 hours. Even back then, we appreciated Valk Welding’s excellent response time”, says Benoît Frezel. Ten years ago, the factory employed 100 people, but today 250 employees produce between five and fifteen tractors a day, depending on the season.

Well-being as a priority

Like the rest of the factory, the welding line stands out for its ergonomics and cleanliness. Kubota places great emphasis on well-being in the workplace, and as part of this commitment, the Japanese company has introduced four-day workweeks per month, followed by a fourth five-day workweek. KFME is also considering the automation of subassembly stations in the future, and another project is the development of a second cabin model. To be continued!

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