TWI Industrial Member Report Summary 158/1981
By R M Rivett
Work was carried out to assess the performance of the Digimetric NDT 602 and Slee WM60 quality monitors and the Trodyne feedback correction unit when resistance spot welding 1.0mm mild steel and 1.0mm 2117 and 5182 aluminium alloys. The systems were assessed under conditions of varying weld current, weld time. electrode force and weld spacing.
It was established that when spot welding mild steel the Digimetric unit could predict weld size when weld current, electrode force. weld spacing and time were varied but the excessive sensitivity to the latter variable precludes the setting of realistic weld quality limits when time is likely to vary together with any of the other parameters. However, the Slee unit was only sensitive to weld current. When used to monitor the welding of aluminium the Digimetric unit showed no corrrelation between any of these welding parameters and monitor reading. The Slee unit was sensitive to variation in weld current and electrode force.
When used on mild steel the Trodyne unit only functioned consistently when violent splash occurred. Under these circumstances the unit accommodated variations in weld current, electrode force and weld spacing. When used on aluminium violent splash was still necessary, and even then the tolerance to welding parameter variation was not extended by the use of the unit.