You use your pile of lathes and mills to make replacement little parts. Probably skip making integrated circuits on-planet at first, but anything metal or plas

You use your pile of lathes and mills to make replacement little parts. Probably skip making integrated circuits on-planet at first, but anything metal or plastic can be done by the huge group of machinists. And for every fifty people on mars you can have a thousand people back on earth figuring out the best way to make every component. The hard part is building chemical stocks of all these different things. And while that's a huge task, it's so much less hard than a make-anything machine. Once you have graphite, clay, rubber, and wood, making it into a pencil is simple. Cut, mix, extrude, clamp. Wood (and rubber if that's the easiest way) can be grown on-site, wood can be turned into graphite, and clay shouldn't be amazingly hard to get from martian soil. Oh and glue, we can figure out a glue.