Valk Welding: 2009

Downtime welding robots is minimal.

Case New Holland (CNH) is using more than 30 years arc welding robots to produce agricultural machines. At this moment CNH has automated a large part of their welding activities in the production site at Zedelgem. In this production site MBU3, 14 arc welding robots are being used 24 hours a day (depending on production). The largest challenge from this production department is to reach the highest duty cycle possible with the welding robots. With the Panasonic TAWERS robot, the newest generation welding robots which have been purchased by CNH, an uptime of 98% is reached.

COMPANY PROFILE
Case New Holland is for a long period the leading manufacturer of agricultural machines with European production sites in Zedelgem (B), Plock (P), Croix and Tracy (FR). Due to its yearlong experience with arc welding robots, this company has build up a leading position in robotised welding, based on their knowhow and experience. The real breakthrough however came 10 years ago when CNH started using offline programming creating the possibility to weld a large variety of products. Especially after the introduction of new models and positive market situations, CNH has seen a fast increase of sales of their combines. The employees were asked to increase their production and this combined with full continuous production (24 hours a day), the manufacturer has doubled their production in the last 5 years. strong>WELDING DEPARTMENT In the last 10 years, the welding department has increased the use of welding robots drastically. Bart Dedeurwaerder, manufacturing engineer at the production facility MBU3: "Every welding robots creates an advantage of at least 50% compared to manual welding, in other words, the robot only takes 50% of the manual welders time. In doing so you can increase output drastically but above all continuously.

NEED FOR NEW ARC WELDING ROBOT SYSTEMS
Market survey: problem definition.Together with Bart Dedeurwaerder and Piet Buyse (super visor maintenance department), Luc Lefebvre head of manufacturing engineering MBU3 started 10 years ago a market investigation on available arc welding robots. "At that time we were working with arc welding robots from several brands with a big difference in programming and restriction of exchange of programs between robots. The largest problem we encountered however was to readjust existing programs due to the fact that the TCP of the robot was effected after a crash in the product. At that time it cost easily three days to solve the problem. THE CHANGE
During the search to a new system, items such as programming, calibration, peripherals and especially service support from the supplier were the leading factors. In doing this market research CNH ended up at Valk Welding, supplying Panasonic robots which can be easily and especially fast calibrated. Above all, it was possible to create programs using the DTPS offline programming and simulation system, which was developed specifically for arc welding robots. Ten years ago, CNH started working with Valk Welding when they were looking for uniformity of their arc welding robot and the reduction of downtime due to crashes or deviations caused by other reasons. 

  

NEWEST GENERATIN ARC WELDING ROBOTS
In the last 10 years the developments in the field of robot technology have lead to faster arc welding robots and (hidden) features through which the welding process can be controlled much more and better. The last 2 arc welding robots which were installed at CNH are from the latest generation were the arc welding power source is integrated in the robotcontroller. Buyse: "These arc welding robots are even more efficient and faster than the previous generation. In addition to this the automatic calibration system has been optimised. If we would exchange the older robot by the newest generation we can, thanks to the software, reuse the old programs without any corrections. We already converted 8 year old programs into the new robot which could be used immediately without any correction.

All robots are equipped with an ATC (Automatic Tool Check). Using this feature every morning the TCP is checked in order to be sure that programmed position and actual position are identical.

THE ANALYSIS
Half years gain Bart Dedeurwaerder from CNH was the first one who was involved in the offline programming system. "Products and clamping jigs could be completely programmed in the same time when the robot was producing other components. It is not necessary to stop the robot whilst programming using the DTPS offline programming software. Another advantage of this system is that if the product from CNH is modified using the DTPS offline programming, the robot programs can be modified simultaneously, even before the new product is taken into production. In case of our new combine, this specific approach gave us an advantage of more than half a year.

CALIBRATION
Downtime due to program corrections was the most important issue for CNH when investigating the market 10 years ago. With the Panasonic robots, 10 years ago we could solve this issue within a couple of hours. We can do that with our own people from the service and maintenance department and were not forced to wait for any support from our supplier. Due to the narrow cooperation with our supplier, the system has been simplified in such a way that it takes us maximum half an hour to recalibrate the robot after a severe crash. Three years ago a new shock sensor was developed for the arc welding robot, using pneumatics instead of the all-known spring loaded shock sensor.

Using this new pneumatic shock sensor the servo drives are immediately switched of and using intelligent sensor, the damage to robot and/or torch is minimised. In the meantime we have adapted all existing robot systems to this new pneumatic shock sensor again reducing downtime to a minimum.

SIMPLIFIED ROBOT SYSTEMS
The engineers from CNH want to have an output as high as possible from all robotic systems they use. In doing so they prefer simple system concepts such as systems with indexing tables or H-frames. Lefebfre: "Applications and systems in which tracks, changers, vision systems etc. are being used, make a system only more complex with a higher chance on downtime. Our approach is mainly based on simple and straight forward robotic systems. We had rather go for 2 separate cells than one complex one. As long as the product allows us to do so, of course".


HIGH PERFORMANCE
Because of their vision on simplicity, combined with the use of offline programming as well as the choice of the correct robot, CNH has created an approach in which the automatic calibration system from the Panasonic robots is used resulting in an extremely high uptime of all robotic systems. With the constant drive to increase performance of the robotic systems using developments which are supported by CNH such as pneumatic shock sensor, automatic tool check (ATC) etc. the engineers from CNH know how to reduce the downtime to a minimum. Just for preventive maintenance the robot is making a "pitstop". An average duty cycle / performance from the arc welding robots at CNH of 98% is therefore no exception.