Valk Welding: 2000

For one of the most important parts of the combine harvesters in its production plant at Zedelgem, New Holland employed two very modern spot welding robots. Production capacity and machine speed could be considerably increased. New Holland took care of engineering and mounting, Valk Welding supplied robots and support for the integration. The complete spot welding cell consists of two Nachi robots on a track, working fully continuously along four clamping stations.

Machine speed
At New Holland Belgium, the well-known yellow agricultural machines are being built for the European market. An important part of combine harvesters are straw shakers that eject the rest material at the backside of the combine harvester after the chaff has been separated from the corn. Because every combine harvester is equipped with five to six straw shakers, the production quantity is five to six times larger than with other production parts. The straw shakers are being composed from laser cut thin plates and spot welded.

Until recently an ARQ1 spot welding installation was used for this. After almost 18 years, the installation now forms a risk factor in the complete production route because of its decreasing reliability. Because of the low machine speed,  the installation had to be used in peak seasons in three shifts, meaning extra overtime for loading and unloading.

The increasing maintenance works also meant unwanted expenses. Furthermore, there was no alternative production method in case the ARQ1 spot welding robot should fall out.

Nachi SA200F
Valk Welding supplied two Nachi SA200F-robots on a track, whereby the robots were provided with double spot welding tongs. Spot welding with two robots in stead of only one, results in almost 40% more capacity. This can then be used for spot welding preparations, that were manually welded before. This also solved the problem of downtime.

Both robots have been programmed as a backup for each other. Compared with the previous installation, there is a strong improvement of connection quality due to the fact that the spot welding process is better monitored.

Two steps
The renovation of the installation has been done in two steps, in order to also carry out the required adjustments for a new generation of combine harvesters and to adjust the safety of the installation to the current machine guidelines.

In the first step, in December '98 the robot track was increased from 12 to 18 meters, and the number of workstations could be increased from two to four. Due to this expansion, an automatic welding mould for a new type could be taken into use as well as a workstation for spot welding of small products for the lining of straw shakers.

The second step, the installation of new robots, was carried out during the holiday period. The Nachi robots have a load capacity of 200 kg, with which two spot welding tongs with a total weight of 167 kg and a maximum speed can be manipulated with a guaranteed accuracy of ± 0.5 mm.

Higher capacity
Due to the higher capacity, sufficient products can be made in the busiest months with 2 shifts, even with the additional charge of spot welding the linings that form a partial product of the straw shakers. Previously these preparations were done manually, but the new installation has brought the work of six men to less than four men.

In the new situation, the operators mainly take care of loading the plates and unloading the finished product. The programme provides a simultaneous start for both robots when making the preparations, after which both work simultaneously at the automatic welding mould to complete the product.

Spot welding quality
The two new double ARO spot welding tongs deliver a constant and improved spot welding quality. The electrodes are provided with disposable caps so that the operator does no longer have to polish the electrode points. The spot welding quality can be maintained constant during the tool life of the electrodes by automatically adjusting the welding current.

(With collaboration of Bart Dedeurwaerder, Luc Lefebvre and Piet Buyse of New Holland Belgium NV, welding department MBU3 and Remco Valk and Michel Devos of Valk Welding).

(Source: Metallerie 15 / September 2000)