Dear All
This is sunil from ador pune.
We have made one SPM (plc based)for automotive component by MIG welding.
After completion of welding cycle globule forms at end of wire.
Globule diameter=1.0-2.8 mm
the welding parameter are
Power source= chopper based design , chopper freq. = 40 KHz i.e.
welding power source o/p is at 40 Khz
current=120-160 A
voltage=16-22 V
the current & voltage can't be increased because of job limitation
wire diameter used is 0.8 mm
gas used Argon:co2=92:8
thickness of sheet to be welded=1.6-3 mm

please suggest methods to eliminate the globule.
especially what plc logic should be implemented.
How to monitor actual current & voltage. We had
used shunt feedback which is first isolated , sampled & hold
& then given to PLC analog i/p as 0 to 10 V. For welding voltage
, it is attenuated to 10 V for max. value of welding voltage
then isolated,sampled & hold & then given to PLC analog i/p
But we still get current voltage variation as PLC takes
sample at its scan rate ( typical 2 to 10 ms ) & at that
perticular moment there can be surge as welding current
range is in short ckt. type.