Technical Article 1.1: Medium Frequency in Car Body Repair.
Medium frequency in car body repair.
As modern car manufacture introduces new materials such as high strength light alloy (HSLA) and boron coated steels, the repairers have a hard time keeping pace with the technology required to weld these materials. It’s no problem for the car manufacturers – they can just increase forces and weld currents on their much larger and more expensive welding equipment.
A repair shop has limitations. Not least among these is the availability of mains power. Most shops are limited to 32 Amps, so large welders can’t be used.
So the technical requirements are:-
- High currents – up to 13,000 Amps
- High forces – up to 500kg required for boron and HSLA
- High level of repeatability and consistency
- Ease of use.
As manufacturers we have to try and get all this out of a welder which will run off only 32A.
To deliver the current, the new InvertaSpot GT uses the latest medium frequency technology. This is similar in many ways to the new generation Mig and Tig inverter welders. We take the 400V 50 cycle (Hz) mains and turn it into 10,000 Hz. This does two things : a) Reduces the size and therefore weight of transformer required to deliver a given current and b) due to the high frequency, permits very precise monitoring and in-process, automatic adjustments to the weld.
To make sure that the force available is high, the InvertaSpot uses mainly a C-type weld gun, where the force is provided directly by the air cylinder. (Using an X-Type gun, the force reduces as arm length increases.) Even with the biggest standard arm, which give a 450mm throat, the force stays at 500kg and the gun still weighs in at less than 15kg, still easy to handle.
As I mentioned above, the higher frequency permits additional functions. One of the most useful is identification of the material you want to weld. It’s hard to see from just looking whether the material is HSLA or not, Boron or zinc coated etc. The InvertaSpot is loaded with a database of 000’s of different resistance profiles for all the different types of sheet, and simply doing a weld in the material test mode will allow the on board computer to match your sheet to the nearest profile. From then on, the welding’s a lot easier.
Technology moves forward at a pace. Many of the higher level functions formerly available only to the car manufacturers is now available in the repair shop. Many repair shops are upgrading both for the new technology and to meet the new PAS-15 standard which is now making big quality waves in the industry.
Contact PW Resistance Welding Products today to find out how we can help you.
