Modelling Of Machined Surface Topology And NC Machining Simulation Of Vehicle Bumper Mold

Vehicle bumper concave mold is always in large size and drop, with a lot of curved surfaces, convex plate and grooves. Since high dimensional accuracy and surface accuracy are needed, milling, electron discharge machining and manual grinding and polishing are always combined in vehicle bumper mold manufacturing. With the development of manufacturing, milling technology becomes more and more important. Nowadays, study for numerical control machining process planning and machining simulation becomes an important issue in mold industry. AISI P20 steel is used in plastic injection molds due to the good cutting performance. However, surface defects emerge frequently. So it is a good help for mold finishing process cutting parameters choosing to study the surface topology and surface defects.Surface topology simulation prediction model based on five-axis ball-end milling motion equations is established in this research. Effects of process parameters on surface topology are analyzed based on P20 milling experiment. This is significant for finishing process parameters decision. After that, CAM (computer aided manufacture) software NX 9.0 is used for NC (numerical control) programming and post processing. What’s more, software VERICUT is used for NC simulation.First, a surface topology simulation model for ball end milling was made based on cutting edge line equation and geometric transformation. An orthogonal experiment was presented to investigate the effects of process parameters (including feed per tooth, cutting path interval, cutting depth, spindle speed, lead angle and tilt angle) on surface topology. After that, the accuracy of the simulation and prediction model is verified by experiments. What’s more, the formation mechanism of the surface defects in five-axis ball-end milling of P20 steel is revealed based on observed results by white light interferometer, SEM (scanning electron microscope) and EDS (energy spectrum analysis). The relationship between the chip and surface defects is also discussed.Secondly, a process strategy for mold machining is made. Cutting tool holders, cutting tools and process parameters are decided for mold machining in detail. Machine tool is five-axis bridge gantry machining center. Source files for cutting tool paths are obtained by NX9.0.At last, the post processor special for five-axis bridge gantry machining center is built, the source files of cutting tool paths is converted into NC programs through the special post processor. What’s more, the NC machining simulation work is carried out by VERICUT. A special simulation machine tool for five-axis bridge gantry machining center and a tool library that mold NC machining needed is established. Potential interference, super stroke and collision error are eliminated by NC machining simulation.Amounts of work have been done in vehicle bumper concave mold machining research. Process parameters in finishing process have been optimized. Reasonable machining strategy is made. NC programs have been obtained by the special post processor. The correctness of NC programs has been ensured by VERICUT machining simulation. All these work provides scientific basis and technical support for the vehicle bumper mold real machining.