Electron Beam Rapid Prototyping And Its Temperature Field Simulation

Electron beam rapid prototyping technology has its special value in prototyping metals with high melting point or easily oxidized property. This paper presents a new rapid prototyping method with three-dimensional scanning electron beam. Electron beam scanning tracks on the X-Y plane are controlled through deflection coil and the focus in the Z direction is controlled by focalizing coil.A new measuring method of dynamic focal point is used to identify focalizing current of every focus in the Z direction. Depending on the fuzzy linear relationship between energy density and powder temperature when electron beam acts on the metal powder a series of data about focalizing current and working distance can be gotten, then the fitting function of focalizing current about working distance can be analyzed by software Origin to support three-dimensional scanning technology.Iron powder is adopted to do rapid prototyping experiment in this paper. The effect of various parameters on the prototyping results is compared: working plane of electron beam need to be near the focal plane; the powder thickness of every layer between 0.5 mm and 1mm will be appropriate; electron beam current can not be too large; scanning time in a certain point can not be too long; powder thickness should be consistent with electron beam current.Software ANSYS is used to simulate electron beam rapid prototyping temperature field. Its material properties and boundary conditions are modified by compared simulation result with measured temperature until the results are satisfied. Temperature distributions of different scanning modes are studied and analyzed. Based on the experiment and simulation results, to produce a certain width cylinder, circle scanning orderly with degressive radius from outer to inner is suitable as small electron beam current can reach temperature above the melting point, and the scanning range is consistent with the melting scope, melted powder in the depth is almost the same for the entire scanning area, so the prototyping result is uniform and surface is flat.Temperature field of multi-layered scanning and 4-petal scanning with same and different heat density are predicted respectively by simulation, and the simulation result is useful to instruct practical prototyping.