This thesis report covers the graduation project that is done in cooperation with Ultimaker. The goal of this project was to research the potential of 3D-printing as an addition to traditional manufacturing, aimed at the production of customized and/or small series of products. There are 7 different manufacturers approached and interviewed on this topic. It was found how and through what workflow manufacturers currently applying 3D-printing, and how they would expect to use 3D-printing in the future. Chapter 3 describes how these results were translated to the design challenge of this project; How to help manufacturers with the integration of 3D-printing within their traditional production workflow? External and internal brainstorm let to the development of a provisional concept (Chapter 4); Design optimization and production planning for 3D-printing. The concept was prototyped and tested by applying it on 3 use cases that were provided by two manufacturers; AXA & Attema. Through an agile process the provisonal concept was optimized and validated, and let to the development of the Ulti-Expert. The Ulti-Expert is a software tool that consists of a design optimization plug-in within CAD-software and a production planning web-environment. Through the plug-in manufacturers will be able to get real-time feedback on their design in order to optimize it for production with 3D-printing. They are able to use the production planning environment to estimate what capacity will be needed to produce a specific amount of these parts, calculate its costs and to determine how fast it can be produced.