Complex sentence: Bimetallic liners, usually zinc-lined copper, can be used; during jet formation the zinc layer vaporizes and a slug is not formed; the disadvantage is an increased cost and dependency of jet formation on the quality of bonding the two layers.
Split into simpler sentences: Bimetallic liners, usually zinc-lined copper, can be used; during jet formation the zinc layer vaporizes and slug is not formed. The disadvantage is an increased cost and dependency of jet formation on the quality of bonding the two layers.