Interacting with personal fabrication devices Personal fabrication tools such as 3D printers are on the way of enabling a future in which non technical users will be able to create custom objects. However while the hardware is there the current interaction model behind existing design tools is not suitable for non technical users. Today 3D printers are operated by fabricating the object in one go which tends to take overnight due to the slow 3D printing technology. Consequently the current interaction model requires users to think carefully before printing as every mistake may imply another overnight print. Planning every step ahead however is not feasible for non technical users as they lack the experience to reason about the consequences of their design decisions. In this dissertation we propose changing the interaction model around personal fabrication tools to better serve this user group. We draw inspiration from personal computing and argue that the evolution of personal fabrication may resemble the evolution of personal computing: Computing started with machines that executed a program in one go before returning the result to the user. By decreasing the interaction unit to single requests turn taking systems such as the command line evolved which provided users with feedback after every input. Finally with the introduction of direct manipulation interfaces users continuously interacted with a program receiving feedback about every action in real time. In this dissertation we explore whether these interaction concepts can be applied to personal fabrication as well. ...