Is it practical to build a separate hotend temperature controller to assemble hotends without taking up printer time?
You can get a suitable board for $20 or so, print a case for a few cents, and either repurpose an old PC power supply or buy a new one just powerful enough for the hotend (not bed) heater very cheap, so I think it's a lot less costly than a cheap printer, and cobsumes less space. But I'm not clear what you need it for.