IQR – Integrated Quality Control
The integrated IQR quality control regulates the current during welding as a function of the resistance curve or power curve. The aim is to control disturbance variables in the welding process. The welding time adjustment is controlled depending on the time of the resistance maximum. The most prominent time in the resistance curve is the end of the warm-up phase and the beginning of melting. From this point on, the resistance curve starts to fall again, as the contact resistance between the material is eliminated and the electrode starts to sink in. We call this point “resistance maximum”. This timing varies. It depends on the disturbance variables that have an influence on heating. Influencing disturbance variables are e.g.:
- the electrode diameter
- the conditions of subordination
- the mains voltage variations
- the force losses due to poor fit
From the moment of the resistance maximum, the up to now rising setpoint of the current from previous process information is kept at its current level with a delay. This results in a new welding power for the further course of the weld that is dependent on the interference size in each case. By programming the initial current and the steepness of the rise, called “aggressiveness”, the heating can be changed up to the resistance maximum. If, as in rare cases, this is not sufficient, the welding time can also be adjusted depending on the resistance maximum. Here, the intervention in the cycle time must be taken into account. Experience shows that variations in magnitudes of no more than ±5 ms result in robotic applications.