printer for mass-production of pcb masks
At my university, the local geeks have a dedicated printer for PCBs. It's a completely normal SOHO desktop printer, it's always under a dust cover and you're not allowed to print anything else with it. It's used a couple of times per week, been there for many years, and always seem to give good, solid prints. We only use transparencies.

This is probably the way to go if you don't want to overdo it, and you probably don't, considering the quote from Chris Stratton in the comments: Mass production of DIY boards makes no sense whatsoever.