TAST (Through-Arc Seam Tracking) follows the seam based on the arc characteristics — without a separate sensor. It is an integrated function in the Kemppi AX MIG series, but not every application benefits from switching it on.
Where it works well
TAST requires a weaving motion and calculates the correction from the variation of the arc current signal. It excels on thicker plate (above 4 mm), fillet welds and long seams — here the compensation of pre-fabrication tolerances and thermal distortion brings a real reduction in scrap.
Where it does not
On thin sheet (below 2 mm) weaving is not an option and the arc signal is noisy — here laser seam finding (KEYENCE) or more precise fixturing is the better answer.
The numbers
In a typical thick-plate application, TAST brings a 1.5–3% scrap reduction and shorter setup times. The cost of the function is a fraction of the total cell investment — payback is typically within a year.