Abstract: An infusion pump has an outer housing within which is disposed a support mandrel with a bladder secured thereon. The mandrel has a substantially uniform circular cross-section with a central channel extending from an input end to an outlet end that has an enlarged mandrel flange or collar. An infusion tube is inserted through the inlet end, through the central channel and out through the outlet end of the mandrel. A seating tube bonded at a distal end of the infusion tube becomes seated in a tapered seating portion in the central channel. Thereafter the elastomeric bladder is secured on the mandrel. After both the infusion tube and the bladder have been secured to the mandrel, the inlet end of the mandrel is inserted through a bottom opening in the housing until the collar of the mandrel becomes seated in a circular collar projecting from a lower wall of the housing.