Valk Welding: 2005

Two determining factors for Zuidberg, a manufacturer of front linkage systems for tractors, in their choice of new robotic welding system were the DTPS off-line programming system and the semi-automated calibration system.

An eight-workcell configuration guarantees the high efficiency needed for automated welding of a wide variety of heavy steel plate products.

Robotic welding was not a new concept for Zuidberg Techniek Holding; hence, a complete reengineering of their production processes was not necessary, as is often the case. This successful manufacturer of front linkage systems for tractors (based in Ens, Flevoland, NL) first introduced welding robots onto the work floor fourteen years ago. Front linkage systems are widely used for agricultural mechanization. They are mounted on the front of farm tractors allowing them to raise and lower tillage machinery. The assembly frames used to mount the linkage systems onto the tractor are supplied to dealers and manufacturers as a single unit rather than in component form (two gusset plates and one separate top plate). This simplifies and speeds up assembly. The complete front linkage system can be mounted onto the tractor in one go. Head of Welding, Martin van Dijk, expresses this as a customer-oriented, logistic advantage, “We supply front linkages online. Before the tractor leaves the factory, the front linkage system arrives and is quickly assembled. We had been following this approach for about five years, but noticed that the old robotic welding system was no longer performing optimally. That system was mainly designed for semi-manufactured components and not for three-dimensional assemblies with longer turnarounds. In addition, production levels had increased two-fold from 150 to 300 units per week within just a few years. Long tool-up times also meant that production periodically came to a standstill and so it came time to replace the whole robotic welding process.”

A view of four workcells on one side of the track, which is hidden from view behind the red partition. The welding workcell is completely cordoned off. At the adjacent workcell, a new unit is being clamped. In the foreground are a number of partially welded assembly frames.
 


The new system, a result of numerous intensive brainstorming sessions between Valk Welding and Zuidberg employees, resulted in an unusual design. Two identical Panasonic TAWERS robots are placed on a fifteen-metre long track with four workcells on either side. Seven of the eight workcells are fitted with manipulators capable of handling 1,000kg loads and two workcells are fitted with stationary supports. The workcells are equipped with Panasonic MIG/MAG power sources (350A). The robots traverse from workcell to workcell. A partially transparent curtain slides over the area where welding is being carried out to protect employees. All hazardous waste gases are extracted from the workcell area during welding operations. With this complete system in place, not only can the partially standardized linkage systems be completely welded in a respectable number of different configurations, but also individual linkage system components can be assembled.

A linkage unit clamped in a manipulator.

A lot more time is available for tooling up the templates than with the previous system and robots theoretically can remain 100% operational. Van Dijk says that, in practice, he is very satisfied if they remain 80% operational.

The new ‘Lift Arc Starting’ and ‘Lift Arc Ending’ systems guarantee a neat, straight weld and greatly reduce the droplets formed at the start and end of the seam.

Offline Programming
“There are other suppliers who could deliver these elements configured into a logical, working system, but the deciding factor to choose Valk Welding was the 3D offline programming system, DTPS G2, which enables you to create, test (for collisions for example) and optimize welding programs in a very user-friendly manner. Programming is not carried out using the robot, but offline, so that the robot can carry on with production.

System demonstrations given at Valk Welding and at several of their customers’ premises convinced us of the system’s merits. Another big advantage is the ability to send programs from one robot to the other and from one manipulator to another without any problems. Not only is the programming time greatly reduced, but one-off programs can also be implemented universally. Previously we would lose half a day. It is now considerably less with DTPS G2.”

The TAWERS robot in action.

Fast Recalibration
Another important factor in choosing Valk Welding was the semi-automatic recalibration system with which the TAWERS robots are fitted. In the event of a collision or other undesired interruption, the servo-software registers any abnormal loads on the welding torch or robotic arm. The system automatically drops into 'soft-servo' mode, which causes the robotic arm to become 'limp' and prevents any damage from occurring. The system can then be re-zeroed and welding operations can be restarted without having to step through the program code line by line. “When the robots were first installed, we often had to make use of this reset function", says Van Dijk. “Now we use it a lot less.” He also cites the integrated control of power sources, robots and external axes as additional system benefits. Compressed air-cooling maintains constant torch temperatures within certain thresholds, which prevents spatter build-up in the welding cup. If the compressor is not running or the protective screens are not closed, then a separate safety device ensures that welding operations cannot continue. The PLC-controlled safety system was jointly developed by Henk Zuidberg and Spit Elektronica in Almelo, NL. The commissioning of this new system has not only improved Zuidberg’s welding productivity through increased operating times, but has also moved the company towards unattended operation. Van Dijk, “The most complex product in terms of welding operations has a production cycle of about 25 minutes. If we load up as many of the workcells as possible with this particular product, then the system can run unattended for some time during work breaks or for the first part of the evening.”
 

Offline programming using the DTPS G2 programming and simulation system.

TAWERS Robots: Automatic Welding Productivity
Zuidberg is one of the first companies in the Netherlands to implement TAWERS robots. The name stands for The Arc Welding Robotic Solution. The robot was jointly developed by Valk Welding and Panasonic, who markets it as its new generation robot.

The most notable characteristics include high-speed, ultra low spatter welding, intelligent collision detection and integrated arc data monitoring. The most striking visual feature of this robot is its curved robotic arm, as well as its sleek construction, hidden connecting cables, integrated robot and power source control and onboard servo wire feeder. The robot was specifically designed to increase the productivity of automatic welding systems. The new SP-MAG welding technology is unique. The software allows the arc characteristics of conventional MAG and pulsed MIG to be combined exploiting the benefits of both types of welding technology. The arc physics are continuously analysed and controlled by means of advanced arc data monitoring, which also records all the welding arc parameters and information to a data log. This allows for better analysis of the welding process and for feedback and adjustment, where necessary. The new servo-software installed in the TAWERS robot prevents excessive loads from being exerted on the torch and robotic arm. Externally applied loads automatically cause the system to drop into ‘soft-servo’ mode, which deactivates the robotic arm preventing any damage to the torch or arm from occurring.

Speciality: Front Linkage Systems
Front linkage systems are mounted on the front of agricultural tractors. Tractor manufacturers generally fit coupling systems for agricultural machinery at the rear. A tractor equipped with a front linkage system can therefore be fitted with two machines simultaneously Front linkage systems are available in various models and lifting capacities. Zuidberg supplies systems complete with all the necessary couplings and hydraulic accessories to tractor manufacturers, dealers and importers worldwide. Around 92% of production is destined for export markets abroad, where Zuidberg has gained a reputation for quality, service and a broad range of products. Systems are available for most well-known makes and models of tractor complete with all accessories. An added improvement to customer service was made several years ago when Zuidberg began supplying dealers and manufacturers the front linkage assembly frame in one piece instead of in component form. This enabled the front linkage system to be installed onto the tractor in one go.