I am gathering opinion regarding a problem I am having with a part I am having produced and need an expert opinion. It is an aluminum plate welded to an outer rail of a long shelving unit. it appears they attached this plate for cosmetic reasons with a series of tack welds. these tacks welds run the entire length and are parallel. i am wondering if that is the best distribution (parallel) of tack welds? also, why is it warping or fluxing and shipping? whats the difference between spot welds and tacks? see fellas, im lost..