Investment in smarter production

For the past few months complete modules for bus chassis have been welded using a welding robot at VDL Bus Chassis in Eindhoven. Valk Welding supplied a system that positions modules varying from 2.5 to 5 square metres with 11 axes and welds them with the robot. Apart from the size of the system and the variation of the modules, the most important gains for VDL Bus Chassis were flexibility, the straightness of the modules after the welding and productivity.

After VDL Containersystemen and VDL Bus Modules, VDL Bus Chassis is the third company in the VDL Group to which Valk Welding has supplied a welding robot system. Factory Manager Louis de Jong from VDL Bus Chassis: "The experiences from our other colleagues are what prompted us to ask Valk Welding to make us a detailed proposal. At an earlier stage we had had difficulty with an overly complex proposal from another integrator, but Valk Welding immediately produced a good concept. That made it possible for us to get the green light for this investment quickly."

Automatic handling
Up until now the modules were welded manually. Not including assembly and preattachment, the modules were welded in 6 ¾ hours in welding boxes. Louis: "The modules were clamped in a frame and in a turntable.
After a number of welds the modules were manually positioned to balance the heat input as effectively as possible. That's what took most of the time. Also, after manually welding the modules had to be corrected for straightness. The robot welding system we've bought doesn't weld more quickly, but the time gains are found mainly in the automatic module handling.

High flexibility
"Our main requirement was for the welding robot system to be usable for all of the modules we manufacture here. That means that it must be possible to position both the small module of 2.5 x 2.5 m and the 2.5 x 5
m. The investment was therefore not for just one project, but an investment in producing more efficient at a lower cost price. The welding robot also had to be able to reach both sides of the modules. This is what we asked
Valk Welding for. The idea was for them to deliver the complete system, including offline programming and measurement system. The clamping system and the load/unload system for the modules was designed and supplied by VDL Bus Chassis itself," says Louis de Jong.

Freely moveable over 11 axes
The system that Valk Welding delivered six months later consists of a Panasonic TL-2000WGH3 robot that is positioned with a horizontal and vertical displacement over a track. This makes it possible for the robot
to move freely over nine axes for optimal accessibility. The modules which are clamped into a frame and mounted in a C-frame are positioned by a heavy positioner that moves over two axes. "We produced the construction
for the frames and the pneumatic clamping ourselves", explains Roel Bullens and Jos van Dijk from VDL Bus Chassis.

Short changeover time
Louis de Jong: "With only one way of clamping on the welding robot system it's a logistical challenge to minimise the changeover time for the frames with modules. For this purpose we've developed our own rail system on which the frames are moved on trolleys. The trolleys are currently still manually driven into the cell, but the idea is that we will eventually be able to control them by remote so that the operator no longer has to go into the cell. We also developed the clamping system for which we use the air cylinders from the group's bus construction operations. All in all we've succeeded in being able to change a complete frame in three minutes."

Cooperation with programming
The use of the welding robot system calls for more programming know-how. Experiences are exchanged with other VDL companies for this purpose. "They are now helping us with the programming of the new modules. The
intention is to put all junior programmers in the VDL Group who work with DTPS in contact with each other next year. This is VDL's credo: 'Strength through cooperation". It is important also to involve the construction engineers in this process. In the development of the new modules they have to take account of the robot's capabilities", emphasises Louis de Jong.

Division of VDL Bus & Coach
VDL Bus Chassis assembles the complete bus chassis in Eindhoven, the steel components for which are supplied by other VDL companies in the group. VDL Bus Chassis is the supplier for the VDL Bus & Coach division,
which builds its buses in Heerenveen, Valkenswaard (NL) and Roeselare (BE). Chassis are also exported to customers outside of VDL Bus & Coach.