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.

FreeCAD allows users to create and manipulate assemblies, which are collections of parts. The parts are simple 3D solids, which can be connected by joints, constraints, contacts, motors, actuators, springs, dampers, forces, torques, or gravity.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.

Version 8 adds spline function of user data for motion and force inputs.