  This paper presents an accurate machining feedrate prediction technique by
modeling the trajectory generation behaviour of modern CNC machine tools.
Typically, CAM systems simulate machines motion based on the commanded feedrate
and the path geometry. Such approach does not consider the feed planning and
interpolation strategy of the machines numerical control (NC) system. In this
study, trajectory generation behaviour of the NC system is modelled and
accurate cycle time prediction for complex machining toolpaths is realized. NC
systems linear interpolation dynamics and commanded axis kinematic profiles are
predicted by using Finite Impulse Response (FIR) based low-pass filters. The
corner blending behaviour during nonstop interpolation of linear segments is
modeled, and for the first time, the minimum cornering feedrate, that satisfies
both the tolerance and machining constraints, has been calculated analytically
for 3 axis toolpaths of any geometry. The proposed method is applied to 4
different case studies including complex machining tool-paths. Experimental
validations show actual cycle times can be estimated with greater than 90
percent accuracy, greatly outperforming CAM-based predictions. It is expected
that the proposed approach will help improve the accuracy of virtual machining
models and support businesses decision making when costing machining processes.
