Modelling and characterisation of a 3D printed peristaltic pump

Abstract

Peristaltic pumps are positive displacement pumps that mechanically imitate the peristaltic process. The unique design and operation of the pumps allows it to have a wide range of applications, from blood pumps in heart-lung ma-chines to industrial cement pumps. Another possible application might be as an electro-hydrostatic actuator (EHA), provided that the pump completely occludes the process tube. In order for the pump to be utilised as an EHA, the pump must have known flow characteristics for accurate actuation capabilities. This study aims to create a model-assisted design approach to calculate the required pump geometry needed to adhere to required design specifications as an EHA. A first principles modelling approach is followed with the flow character-istics derived from the geometric relations pertaining to roller-type peristaltic pumps. Novel methods of approximating the volume displacement caused by a roller engaging the tube are presented within this model. A generalised lumped parameter model is created in an attempt to model the pressure response of the hydraulic circuit that the pump is integrated with. A three-roller peristaltic pump is designed using the model-assisted ap-proach in Solidworks. Manufacturing commences using polyethylene tereph-thalate (PETG) material on a Prusa MK2.5 and Prusa MK3 printer. A test bench is constructed for model validation purposes regarding the roller volume displace-ment, pump flow rate, and pressure pulsations of the pump over varying motor speeds. A two-roller configuration of the same pump is also tested to validate some of the premises of selecting a three-roller pump as an EHA and further model validation. The simulation of the three-roller pump shows an average correlation coeffi-cient of 0.83 for the inlet pressure and 0.74 for the outlet pressure when com-pared to experimental results. The modelled flow of the three-roller pump had an average error of 2.37 % and a maximum deviation of 9.02 %, where the two- roller pump had an average error of 1.97 % and a maximum deviation of 4.03 %over all tested motor speeds. The flow rate of the pump was found to have a non-linear relationship to the motor speed, where the model represents an idealistic linear relationship. The non-linear flow was found to correlate strongly to the peak inlet pressures of the pump. The pump managed to achieve vacuums under 5 kPa (absolute) and gen-erate pressures above 140 kPa (gauge) for both the two-roller and three-roller configurations. The three-roller configuration had a more stable hydrostatic capability for high-pressure, tests as expected. Due to the friction of the rollers the two-roller configuration had a maximum operational speed of 400 r/min compared to 150 r/min for the three-roller configuration. This is associated with a maximum flow rate of 9.35 L/min for the two-roller configuration and 3.28 L/min for the three-roller configuration.