At least one substrate location sensor is provided on a piece of equipment containing two adjoined chambers between which substrates may be transferred one at a time. Deviation of substrate position from a predetermined optimal position is measured as a substrate is transferred between the two adjoined chambers. Measured data on the deviation of substrate position is entered into a statistical control program hosted in a computing means. The measured data indicates the level of performance of the robot and/or the condition of alignment of components in one of the two chambers. As the statistical control generates flags based on the measured data, maintenance activities may be performed. Thus, maintenance activities may be performed on a “as-needed” basis, determined by the measurement data on performance of the equipment.