Most PCBs have a component legend to show which component goes where.
Today we use ink-jet printers to image the legends direct from the board digital data. Like a conventional paper printer the ink-jet printer sprays minute droplets of ink onto the panel to generate the image. If a legend is needed on the second side the ink is tack-dried on a conveyorised heater and the printing process is repeated. Ink-jet printing needs no set-up. Previously we lost time preparing and cleaning silk-screens for each legend printing. That is why the legend is often called the silk-screen.
Now we finally cure both the epoxy ink soldermask and the legend. Once this took 90 minutes in a batch oven. Now it takes less than 10 minutes using a 5 stage conveyorised oven.