Being a casual welder I only use my mig about once a month. Usually by the time half the tank is gone my welds go to crap. I work for a medical device manufacturer an we have gas mixtures that have to be put on a tank roller before we can use them for equipment calibration to ensure the gas is mixed. I thought I could make a home version. A 4 4" skate wheels, some angle stock and a drive motor from a discarded kids ride on toy and presto! I'm at 700psi and still welding great!