The way Ryan designed this build it works even with slight imperfections in the emt, but the machine will compensate for such tiny imperfections by slowly grinding away surface material until it normalizes all axis. this wouldn’t work very well with pvc… for starters there is no guarantee that it’s straight, especially at such small diameters. the second larger problem is how well pvc would hold up against the constant friction of the bearings grinding across it. couple that with pvcs low melt point and you would end up rails that are almost triangular in no time. when routing your machine might not have a problem other than the weight of the tool, but when printing this thing and reach some pretty fast speeds, speed + friction = intense heat. i know I’ve probably scraped up enough zinc and steel from my print bed to make at least 50 cents worth of nickels… I can only imagine how that would relate to a piece of pvc, which is toxic once it reaches a certain temperature. now as far as using emt to build a delta… that would be a nifty little project, but you’d have to be incredibly selective when choosing the straightest pieces of conduit you could find. tolerance would be the biggest setback as you’d have to keep it pretty tight on a vertical rail but it still needs to be loose enough to accommodate the fact that no 2 pieces of conduit are guaranteed to be the same exact demensions. if you are interested in delta printers in the cheap, makers muse is putting together a design based on the 101 hero. a mostly plastic and 2020 delta style printer that’s shooting for a sub $99 printer once they finish their crowdfunding.