Machining Process Analysis and Simulation

Machining Process Analysis Using Simulation and Finite Element Models

Three types of analyses process are performed.  One is force, power, and cycle time analyses using kinematic simulations (or mechanistic models). Structural analysis is done for for clamping and fixturing using finite element methods. Detailed chip formation analyses are also done using finite element models.  

Kinematic simulations of machining processes are used to calculate cycle times and time histories of cutting forces and power. The inputs required include the part and tool geometries, tool paths, and cutting pressures for the tool–workpiece material of interest, which may be measured in tests or estimated from finite element calculations. The tool geometries and tool paths are preferably read directly from CAD and CAM systems. Based on this information, the kinematic motions of the tool with respect to the workpiece as a function of time can be simulated, and the instantaneous area of material being cut (the interference between the tool and workpiece) at any time can be computed from the tool path and part geometry.

Commercial programs for kinematic simulation include Third Wave Systems’ Production Module programs  and MillSim from Manufacturing Laboratories, Inc..

Structural finite element analysis is used to estimate workpiece distortions due to clamping and machining. The objective of the analysis is to minimize such distortions for critical features, which may be accomplished by stiffening the part or fixture in directions of heavy loading, modifying the tool path or cutter geometry to direct forces in stiff or noncritical directions, choosing clamping and locating schemes, which minimize clamping distortion and support compliant portions of the part, and minimizing clamping forces. Finite element analysis permits a wider variety of options to be investigated more quickly and cheaply than through prototype part and fixture tests.

TURNING

Turning  is easy to simulate because the geometry and kinematic motions of the tool and workpiece are easily described. When turning large volumes of parts on CNC lathes, simulation helps to reduce cycles times and thus the number of machines and capital investment required.

Cutting forces are calculated by multiplying measured cutting pressures by the calculated uncut chip area. Various formulas are available to calculate many variables required or simulation.