5-Axis Mechanistic Models
Mechanistic modelling involves predicting the forces produced by a machining operation. Knowledge of these forces can allow for efficient tool path planning (by adjusting material removal depending on the cutter load), efficient selection of cutting conditions (i.e., appropriate cutter feeds and speeds) and quality control (by predicting cutter deflection and identifying conditions prone to tool chatter). Of particular interest here at Waterloo are milling forces.
Force measurement during 5-axis machining of a surface.
During a milling operation, a tool will remove material from the stock in the form of chips. The forces encountered while milling may be decomposed into two quantities: a tangential component on the tooth (a cutting force) and a radial component (a thrust force). The critical quantity in determining each component is the instantaneous chip area, which is related to the instantaneous metal removal rate. A secondary quantity, still of great importance, is the instantaneous edge contact length.
Here at Waterloo, a mechanistic model based on an adaptive and local depth buffer technique has been developed. By adaptive, it is meant that the depth buffer is kept continuously aligned to the tool - an important quantity in 5-axis machining. By local, it is meant the depth buffer is sized to the tool, or tool teeth, rather than the stock material, greatly improving the simulation resolution and memory requirements. Essentially, the technique calculates the instantaneous metal removal rate from differences in the depth buffer at discrete time intervals. The instantaneous edge contact length is calculated by projecting depth buffer elements onto the tool shape.
Further work on mechanistic modelling of 5-axis machining is ongoing as part of the Ph.D. program of D. Roth.