Operation of the VISION automatic mode
The Virtual Machine (VM) developed by ELMA-Tech GmbH is a control system which has successfully proved itself thousandfold in nearly all of ELMA-Tech’s machines: Arc-Welding, Plasma-Generators, Spot Welding machines.
The Core of this technology is a non-disruptive working microprocessor system which uses a physically oriented high-level language to control the welding process.
It coordinates the parameters provided by the internal database, adjusts all necessary settings and implements the process relevant data in the so called “Execute” level. In the field of resistance spot welding the VM in VISION operating mode controls the welding process fully automatic.
Following is a short description on how this process usually works in practice.
- After pressing the start button the gun closes. The VM is now in the retention segment. During this segment the distance value between the surfaces of the electrode caps is determined.
In welding mode, the measured distance value for each welding spot is accurate to 0,1mm. This is possible through a nil value which has been pre-determined by a calibration-cycle (Check). Different arm geometries are also taken into account by the internal database of the VM.
The measuring system has a life expectancy of >25 million cycles, works temperature independent and thus delivers the most precise measurements for every single spot weld. The measuring process itself takes less than 0,1s and is part of the force build-up process in the retention segment.
- After including the arm geometry, the newly determined distance value now provides the exact distance between the surfaces of the electrode caps and thus also the total thickness of the workpiece in between them. Arm deflections through electrode force and reworked electrode caps are also already taken into account by the VM.
- The total thickness parameter is the input parameter for the synergy chart which is stored in the internal database. The so called “MASTER” compiles and prepares all necessary parameters and segments in a few milliseconds and sends it to the VM for execution.
- The first current which flows into the workpiece is generated by a virtual generator that is based on the surfaces of the electrode caps. Unlike common constant current technologies this is based on a completely different characteristic curve. The crucial thing is that the generator is able to measure without any loss on the surfaces of the electrode caps and the workpiece through the virtual technology.
- Under the synthetically provided generator characteristics the workpieces show their nature in two-tenths of a second. If there is a single high-strength steel workpiece it will characterize the whole process. The VM takes this information from the curve of the process impedance which is measured between the electrode caps.
- In case of a partial isolation due to glue or paint residue the VM will automatically switch to a pre-heating mode to break through the isolation first before starting the actual welding process.
- Once the direct electrical contact of the sheets is achieved in the area of the electrodes, the automatically selected welding parameters for high-strength steel or mild steel are executed in the welding segment. These parameters are derived from the specific impedance curve.
- The energy control of the VM monitors the implemented process-energy between the electrode caps also the total thickness of the workpiece in between them. Arm deflections through electrode force and reworked electrode caps are also already taken into account by the VM.
- If a shunt should occur the misguided energy is automatically taken into account and a new target energy will be calculated to ensure a reproducible high quality for each single spot weld.
- Based on the nature of the workpiece, which was determined by the synthesized characteristic of the virtual generator, the process will now end with the according post-heating phase. (normal or high-strength).
- The QS-System which runs parallel to the VM now checks the target energy taken from the database and also whether the energy was used properly during the process in a set time frame or not. It will signal the user accordingly through the QS-LEDs.
- When the gun opens after the post heating phase the fully automatic welding process is finished. If needed you could now move on to any other welding spot and continue welding without doing any adjustments. Even if the total thickness and material compositions vary.