Hi everyone. I am currently welding in some new panels. Mainly plug welding and seam welding.
I am getting alot of under cut at the edge of the welds on the seam welds . Of course once grinding back the metal is getting very thin in these areas and often separating.
Does anyone have any advise to help stop this? Settings on welder? Or is it a technique problem?
Tried all the usual sources for help and also played a vit with the settings on the welder but not really getting far.
Any help appreciated.

It's a combination of technique and welder settings. Try using the lowest setting possible but still achieving a good weld. Also, try not to concentrate your welding in one spot for too long otherwise you will burn and warp the metal. Patience is the key here.

Panel welding is very tricky due to the thickness of the material, I would suggest getting some scrap of a similar thickness and playing around on that first.

What type of welder are you using? I was able to replace the floor in my van using a gasless MIG using the plug/seam welding method (see pic). Took a bit of time but managed a good job.

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67 Van, 1275cc

Thanks for the reply. I agree that i may be welding to hot and to fast. Patience has never been my strong point!
I have been setting up on scrap metal but it would seem that onve i start the panel is probably getting to hot all over. I am using a gas mig welder. It is fairly new so still trying to figure out the settings properly.
I will donas younsuggest and turn it down a bit more and slow myself down too!
Cheers for the input.

Watch some videos on you tube is my best advice and then practice what you see on scrap the same thickness as what you want to weld on the mini maybe go to the wreckers yard and get some old panels to practice on or buy some sheet steel that you can cut up and practice on and the use whats left for patches on the car
Mike
PS turn off the gas when you finish put a note on the welder or you will lose all your gas

Please correct me if you disagree, as I'm a very amateur welder, but can I suggest that maybe you are trying to make too long a weld run. From watching good welders, they almost do tack welds as far apart as is reasonable and keep jumping around the weld line to let the last weld cool. A good welder can go back to a previous weld and add to it so it ends up looking like a continuous weld. I am content with a rougher looking weld so long as there is good penetration to hold.

trigger on then off 4mm intervals high current, the weld will have a slight build up and you wont blow holes. The panel must be tacked first in the right position. Each weld starts where the last finished you keep welding using this continuous method.
Allen, ex teacher resto 30years

What Allen said ^^
Some MIG welders like my Kemppi have a stitch weld function, you set a timer for on time, then hold the trigger on.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thankyou. I will.try.this method. Self taught welder of many years but having trouble with the thinner gauge metal

Thanks all for your input.

don't use the stich weld function on the welder ,you just trigger on then off .The off is enough time for the weld to cool ,then on again.
VERY easy to do Looks like you are doing a fine job Make sure you check panel gaps after tacking ALWAYS trial fit and measure.
Allen Mini skin panels are 1 mm new cars .8 and .6 mm