Scheduling 3D Printing Machines to Minimize Makespan

Abstract

AbstractManufacturing industry has been evolving during the last few centuries. Industry 1.0 started with mechanization and the use of steam power. Mass production using production lines and assembly lines dominated Industry 2.0 era. Industry 3.0 era brought automation, flexibility and product diversity and Flexible Manufacturing Systems (FMS) and cellular systems were extensively used. Recently, there is a shift towards the fourth industrial revolution (Industry 4.0). Industry 4.0 includes the combination of technologies working together to fulfill a manufacturing task. Industry 4.0 utilizes internet of things (IIoT), big data, cloud computing, cybersecurity, autonomous robotics, augmented reality, and additive manufacturing (AM). The purpose of Industry 4.0 is to integrate the entire network to function as one system. In this study, we are focusing on scheduling 3D printing machines, namely Markforged Mark Two printers. Process parameters that can be considered in these printers are layer height, infill density, print speed, build orientation, infill patterns, and print temperature. These machines are Fused Filament Fabrication (FFF) 3D printers. The parameters considered in this study are infill density and layer height. Infill density dictates the amount of material that is filled on the inside of an object while it prints. Infill density has a role in a part’s strength and weight. Generally speaking, the greater the infill density, the stronger and heavier an object will be. Lower infill densities on a part suggest that the object’s intentions are purely visual with higher infill densities meant for functional parts. Markforged Mark Two allows infill density for rectangular infill to be from 0–92%. On the other hand, layer height determines the amount of material that is extruded through the nozzle during each pass. Markforged Mark Two allows for three different layer heights to be examined, 100, 125 and 200 mm. Layer height plays a large role in print time as the amount of material extruded effects the completion rate of the object. Layer height’s impact can also be seen by a part’s fineness or detail. This is represented visually on the object by being able to see each pass of the plastic material. For example, an object with a larger layer height will look rougher and not as smooth as an object with a lower layer height. However, it is well known that a lower layer height increases print time whereas a larger layer height implies a faster print time. Several parts with different geometries and also sizes are included in the study. The scheduling performance measure considered is makespan. The objective of the study is to find the optimal parameter settings for multiple jobs such that makespan is minimized subject to minimum restrictions on print parameters for various jobs. A mathematical model is presented to minimize makespan first. Once the optimal makespan is found, the model is re-run such that better quality parameter settings are determined while keeping the optimal makespan unchanged. Later, the results of the experimentation with various parts are discussed and future work is recommended.Keywords3D PrintingSchedulingMakespan