Your volunteer, like many of us here, may not have experience with many different machines; the best we can usually say is that the particular machine we bought worked for us (or didn't) on the particular projects we attempted. I've never seen a "Fusion3 F400" printer, let alone used one. You might show him some of the parts you want to make, explain the tolerances you expect to hold, and ask him if he thinks it will work. At least it will get you started with printing, so you can get a more realistic idea of what can - and can't - be expected from a consumer-level single-head FDM 3D printer.