Methods and systems for generating support structures for additively manufactured objects are described herein. In some embodiments, a method includes receiving a digital representation of a dental appliance configured to implement a treatment stage of a treatment plan for a patient's teeth. The method can include generating a support structure arrangement configured to support the dental appliance during an additive manufacturing process. The support structure arrangement can be generated using a machine learning model. The machine learning model can be trained on a training data set including appliance data representing geometries of a plurality of dental appliances, support structure data representing geometries of a plurality of support structure arrangements, and outcome data representing outcomes of the additive manufacturing process for the plurality of dental appliances with the respective support structure arrangements.