Scheduling the production of medical 3D-printed devices in hospital

3D-printed medical devices and anatomical models may support surgeons in planning interventions, training activities and other relevant tasks. At present, outsourced companies usually supply 3D-printed devices to hospitals, while only in a few cases the printing service has been in-sourced within hospital. However, this configuration is more effective, because it involves physicians more directly in the production process, reducing production times and costs. Therefore, this configuration will be exploited more and more in the next future. Managing in-hospital 3D factories is a difficult task, due to the complex requirements to be taken into account when scheduling the operations. An order for a 3D-printed model involves: two pre-processing activities, i.e., the segmentation of patient- specific medical images and the design of the device; the 3D printing itself; a post-processing activity consisting of cleaning and finishing. Each order requires a specific set of materials on the printer, and changing materials could be wasteful (expensive) and time consuming. Moreover, each order has a due date, usually quite strict, which is set according to the scheduled surgical procedures. We developed a multi-phase scheduler for in-hospital 3D factories, which considers the production of devices with different due dates, priorities, activity durations and material consumptions. We formalized a hierarchical multi-objective integer linear programming model and proposed a matheuristic approach to solve real-size instances. The goals are to maximize production, starting from the devices with highest priority and closest due date, and minimize production costs. In particular, variable production costs are related to material consumption and wastage, which depend on the assignment of orders to printers and their sequencing. The effectiveness of the proposed approach has been demonstrated through the application to realistic and real instances coming from the 3D4Med Clinical 3D Printing Laboratory of the IRCCS Policlinico San Matteo, Pavia, Italy.