A system for manufacturing a three-dimensional article includes a resin vessel, a vertical movement mechanism, and a light engine. The resin vessel includes a lower opening closed by a transparent sheet. The vertical movement mechanism is for positioning a support tray which supports the three-dimensional article. The light engine is disposed below the transparent sheet and is configured to selectively harden layers of resin over a build plane above the transparent sheet. The light engine includes a light bar coupled to a lateral movement mechanism. The light bar includes an array of light emitting devices and a device for impinging upon the transparent sheet. The impingement maintains a proper operating distance H between the transparent sheet and the build plane.