This model is built for modularity. It is expected to complete an electronic toothbrush design with this model from the initial customer requirement definition down to the component design. All the components are defined as High Level Primitives (HLPs). Once enough inputs are given, a geometry shape is displayed. The data and source code are saved seperately. Just like a normal CAD system, user can specify the shape of each component and save it with different name (folder name). Besides geometry modelling, many constraints are also defined in sevel class, such as ergonomics, mechanical interference and the requirments from weight, cost and working time. User can check those constraints in the "message" object. The message object is designed to assist the user not only as warning but also possible solutions are given. This model can also start two test cases with MATLAB. A MATLAB package is required in this case (http://ungil.com/lisp/matlab.html). Through the MATLAB server, An analytic hierarchy process (AHP) is programed in MATLAB and connected with the model. User can specify the weights between cost, weight and working time and then get a proper choise among many motors. Based on the motor selected, a dynamic simulation can be performed. We can output all the input values needs by the dynamic model in MATLAB and perform a simulation. Finally, the simulation results are feedback to the toothbrush model to chek whether one or several constraints are violated. Due to limited time, this model is still developing. It is expedted to complete before 7th October,2013.