Coating vacuum systems are normally staged: a mechanical pump takes the chamber down from atmosphere to rough vacuum, and a high-vacuum pump continues from there. Oil-free rotary vane pumps are used in the backing and roughing stage, and also at fixture holding and chamber cleaning stations.
Three points matter in this duty. First, process residue in the gas (fine dust, moisture, solvent vapour) will reach the pump chamber, so fit filtration and condensation upstream. Second, roughing time sets the cycle, so calculate it from chamber volume, target roughing pressure and the effective pumping speed. Third, heat has to go somewhere: leave ventilation clearance when the pump sits inside the machine.
Losses across piping bore, valves and bends lengthen roughing noticeably, so include system resistance in the sizing rather than reading the nameplate capacity on its own.