A substrate loading station including a frame forming a chamber configured to hold a controlled environment, a transfer robot connected to the frame and one or more substrate cassette holding locations each capable of having a substrate cassette holder disposed within the frame. Each of the one or more substrate cassette holding locations being configured to removably support a respective substrate cassette in a predetermined position for communication with the transfer robot to effect substrate transfer between a respective cassette and the transfer robot where the one or more substrate cassette holding locations are configured to effect the interchangeability of one or more substrate cassette holders with other substrate cassette holders for changing a substrate cassette holding capacity of the substrate loading station.