.: Genesis Systems Group, LLC :.

The following factors can have an impact on several welding issues including Porosity, No Arc Start, Wire Stick, Burnback, Seam Tracking.

SHIELD GAS

Has the gas mixture changed
Bottle or manifold. Changed?
Check the flow rate 30-40 CFI should be plenty.
Check the Pressure. Is there a big surge of gas as soon as the solenoid is turned on at the start of the weld?
Check the holes in the gas diffuser, making sure that they are not plugged or deformed.
Is the area windy (fans, outside wind, open door, pneumatic tooling)? Move a lighted cigarette along the weld path to check the smoke stream.
Check the condition of the shield gas lines.
When porosity occurs stop the system and place a cup of water under the nozzle to see if any air may be leaking through an air blast solenoid.
Replace the input side of the shield gas to the torch directly to a bottle with a flowmeter/regulator on it. Just let the gas run while experimenting. Do not run it through the weld equipment solenoid.
On butt welds make sure the back side of the weld joint is protected from wind. If possible try to backshield the weld area - even if it is a temporary experimental try. Place a hose with gas flowing near the back of the joint

TORCH

Check the holes in the gas diffuser, making sure that they are not plugged or deformed.
Check the condition of the contact tip.
Check the size of the tip.
Replace the tip. Try another type like pure copper or CZ type.
Check the condition of the torch. Look for worn spots or places where it may have been pinched or repaired.
Check the nozzle insulator. Make sure the shape is proper; some pulse modes cause the nozzle insulator to shrink. Use a High Temp insulator for pulsing.
Check the shield nozzle. Make sure the silts at the top of the nozzle are not open to the welding end of the nozzle. This can cause air to be sucked into the weld area.
Check the torch for any water leaks.
Make sure the torch is not bent.
Check the torch for proper gas flow. You may have to compare it to other torches to see if their are any obstructions
Check the torch for spatter buildup. Even very light spatter can cause porosity sometimes.
Check for anti-spatter gels, sprays, etc... Make sure it is not too covered or thick.

WELD EQUIPMENT

Check to make sure the wire feeder is clean. Look for dust or metal particles in the conduit, drive rolls, or dereeler.
Check the condition of the wire, look for rust, oil, dirt or try another spool.
Check all of the weld power connections for corrosion and poor contact. Make sure all connections are tight.
Check all of the weld power connections for proper isolation. Use an OHM meter.
Check all of the welding sense leads for proper condition and isolation. Add a temporary jumper wire that can be contacted while it is welding. Look for any change in the welding output when the sense lead is contacted. You may have to use a long piece of plate to get a good test.
Replace the cooling water with fresh De-Ionized water. Sometimes some of the welding current (especially pulsing) can be lost through the water lines.
Insulate the water lines from wire feeder, wire conduit, system structure, etc.
Check the power into the weld power supply. Make sure all of the legs are at the proper voltage (480 V). Look for a low leg when having porosity.
Check the connections between the robot/welder/feeder/interface.
Monitor the welding feedback in the robot if possible to look for variations in weld output.
Monitor the meters on the front of the power supply for changes in the weld output.
Check the condition of the roto-ground. Make sure it is clean, lubricated and tight.
Is the part heating up while welding? Convection can cause wind near the weld but it will not be present on a cold part. Place a lighted cigarette near the weld joint on a hot, just welded part, look for air movement.
Is the power supply heating up?
Turn the power supply off for a while then back on and try.
Is the interface heating up? Turn off then back on.
Try another power supply.

MATERIAL

Look for surface condition of material. Clean, dirty, oily, residue from forming operations.
Look at the cut edges. Sharp?
Look at the pre-processing operations to see if any changes have been made.
Look at the material condition or chemical composition.
Look for changes in the grain of the material. (Direction of forming).
Temperature of the material.
Gaps caused by forming process.

TOOLING

Look for positional changes caused by tooling
Look for air leaks in pneumatic tooling that can cause a wind.
Look for good electrical contact for the ground path.
Clamp a ground wire to the part to eliminate tooling from the weld ground.
Look for arc Blow while the robot is welding.
Look for places of spatter buildup.

ROBOT/PROGRAMMING

Look at the path of the robot. Location, vibration.
Check for the proper welding parameters.
Check welding stickout.
Check the torch angle with respect to the weld joint. With the shield gas flowing place a lighted cigarette near the end of the nozzle and look for the smoke to be sucked into the shield gas. Sometimes this can be caused by torch angle or by the flow rate of the shield gas. Reduce the flow rate or change the angle of the torch.

OTHER THINGS TO CHECK

Does the shop temperature seem to have any effect?
Does it happen on one shift more than another?
Does it happen to one part more or less than on another part?
Does it happen to one operator more or less than to another?
Check the system ground.
Check the condition of the wire after a burnback. Sometime if the robot does a high speed air move immediately after a weld the wire will still be molten and cause the ball at the end of the wire to become oxidized. Leave the shield gas flowing at the end of the weld to protect the wire during an air move with a hot wire. Sometimes you will see a pop (mini-explosion) of the tip of the wire during the air move.
Check the burnback. Is the wire burned back to the proper length at the end of the weld? Make sure the wire is not touching the part before it tries to strike an arc. This may cause the power supply to change to a burnoff parameter. This may cause a burnthrough and a chain reaction of porosity.