freeCAD

freeCAD is a basic 3D CAD with advanced Motion Simulation capabilities. It is suitable for anyone interested in learning 3D CAD and Motion Simulation for free before using more sophisticated packages. Educators, students and new engineers will find it ideal for the teaching and learning of geometry, kinematics, dynamics, vibrations, mechanisms, linkages, cams, machine design and physics. The program runs on Windows, Linux PC, Macintosh PPC and other Unix's. Assembly data are unchanged across platforms. It is a freeware and can be distributed freely.
freeCAD allows users to create and manipulate assemblies of parts. The parts are simple 3D solids, which can be connected by joints, constraints, contacts, motors, actuators, springs, dampers, forces, torques or gravity. The parts and connections define the structure, mechanism or machine of interest. Both open and closed 3D loops are permitted. freeCAD performs full Multibody Dynamics Analysis on the assembly to predict the motion according to Newton's Laws. Animation using the simulated data produces realistic dynamic behavior of the system.
Users can study the mechanical dynamics in the form of plots and tabular output. XY plots can be zoomed and set to equal scales. Data series available include linear and angular displacements, velocities, accelerations, forces, torques, momenta and kinetic energies. Acceleration data include transverse, centripetal and Coriollis accelerations. Users can view forces and torques from joints, constraints, actuators, springs, dampers, applied forces and inertia. Data can be exported to spreadsheets or POVRay, a ray-tracing program.