Designing with computer and sketches 1Supported by the German Research Society (DFG, Project HA 2249/12-1).

We investigated whether and, if so, for what reason, problem solving in design may be supported by “external approaches”, especially sketching. An experimental study with 74 undergraduates analyses whether sketching before and/or during Computer Aided Design (CAD) improves the quality of solutions, reduces time taken as well as the number of processing steps in CAD, by offering the opportunity to test the functions designed. In spite of additional sketching time, the total time taken is significantly reduced for the more complex task analysed. This can be explained by the reduction of the number of processing steps needed. These experimental results verify the perceived utility of sketching before and during Computer Aided Design, confirmed in a questionnaire study with more than 100 experienced engineering designers.