System and method for adjusting a working distance to correspond with the work surface

Abstract

The inventive mechanism adjusts a working distance between a tool and a work surface. The provision for automatically setting and adjusting the working distance between two parts of an apparatus, possibly a coating apparatus, permits the mechanism to adjust in real time for unknown and possibly random variations in the dimensions of the work surface, the apparatus supporting the work surface, and imperfect leveling of the tool or the work surface. In a preferred embodiment, the inventive mechanism is used to accurately set and maintain the working distance of a dispenser above a substrate so as to provide that a consistent coating thickness is applied across the substrate. The mechanism preferably employs direct precision distance sensing means independent of the motor of drive means to continuously measure the working distance in real time with a high degree of resolution and accuracy. When the sensor reports that the working distance has deviated from the ideal setting, a control system employs a standard P.I.D. control scheme to precisely restore the ideal working distance. The mechanism may perform the working distance control function using the main or host software, or, more preferably delegate this function to a dedicated processor for the duration of the process during which working distance is being precisely adjusted. The host preferably resumes control of the drive means in the direction of the working distance once the precision adjustment scheme is concluded, and may then perform larger scale motion of the tool using feedback from the position reporting means integral to the motor or drive means.