Spot the capable welder

Details
Product: Wielander+Schill Inverta Spot welder
Distributed by: Sydney Automotive Paints & Equipment
tel: (02) 9568 2233
Key features: Water-cooled, handles new steels

Allan Higginbotham checks out the Inverta Spot welding system from Wielander+Schill and finds that ordinary welders just don't cut it when handling new vehicular steels.
Today we are relying on spot welding much more than we were in the past. The machines now available produce welds which are as good as the factory welds. If you are still welding on panels using the plug MIG method you should consider spot welding as it will save you time and the weld will match the original finish of the vehicle. Also, if you have an old spot welder it may be time to update, as the new range of spot welders are far superior than those manufactured even five years ago. In fact, if you have not got a good spot welder you will not be able to weld the types of steel used in new cars today.
Would you know how to weld new steels such as zinc, bona-zinc, grano-coated or BOR steel? High strength steels are changing in car manufacturing. Their properties allow thinner gauges to be applied throughout an auto body, rendering a stronger, lighter vehicle without significant changes in cost structure. These new high strength steels have unique characteristics that require particular attention.
Existing spot welders are capable of welding the older steels but this will not hold true when it comes to welding ZSTE steel. When Boron is introduced, the existing welders will find it impossible to weld the new steel correctly. The new Holden Vectra and the Ford Focus as well as the Porsche Cayenne are all made with the new steels. Every European manufacturer is using ZSTE 340-380 in the manufacture of their cars.
The criteria for welding the new steels successfully is:
1. High welding power -- at least 8000A (rms) at the tips, with a very short burn time of about 0.5 seconds.
2. Very high electrode force of at least 300 decaNewtons (daN approx. 300kg).
3. Very flat profile electrode tips (not domed) with at least 14mm diameter.
If the welder cannot meet these requirements it is not able to successfully weld the new steels. As you are aware, if the steel is not welded correctly, warranty problems may occur and the vehicle may not react correctly in an accident.
Inverter welders have been proven to be the only welders capable of welding the new steels correctly, provided the power clamping force and tip size are correct.
The Wielander+Schill Inverta Spot ATM and ATL spot welders will fulfill these requirements. With a two-year warranty, the welders are fully water-cooled to keep the diode, gun, cable and tips cool. The correct size nugget for the new high strength steels is now calculated at 4X????ADD SQUARE ROOT SIGN?????t (where t = the thickness of the thinnest sheet in millimetres).
When using the Inverta Spot, it is apparent that the unit is of a high quality as well as robust design. There are 45 welding programs and special settings for mild steel, galvanised sheet and high strength steel. Even after 30 spot welds, which were done on a sill panel the tips remained cool. For ease of use, the unit has a counter-weight which you can adjust to correctly balance the welding gun, important when using the unit regularly.
The Inverta Spot system is recommended by Audi, BMW, Ford, DaimlerChrysler, Opel, Porsche and Volkswagen. The distributor of the machine, Sydney Automotive Paints & Equipment, has some good fact sheets which will inform you as to why this welding technology is essential when welding new vehicles. Remember; this is a high quality welder and is more than capable of performing all your welding needs.

Allan Higginbotham is head teacher of panel beating at Mt. Druitt TAFE, Sydney. If you have a product you would like Allan to report on, please contact Max Yaffa in Sydney on (02) 9213 8246 or Neville Moulden in Melbourne on (03) 9690 8199.