Robust Feedrate Selection for 3-Axis NC Machining Using Discrete Models

Abstract

This research effort is focused on improving the efficiency of CNC machining by automatic computer selection of feedrate for 3-axis sculptured surface machining. A feedrate process planner for complex sculptured end milling cuts is developed from mechanistic and geometric end milling models. The selection program uses tool deflection, surface finish, tool failure and machine power to set constraints on the cutting force and the feed-per-tooth for rough, semi-finish, and finish passes. A NC part program is processed one tool move at a time by the planner. For each tool move a geometric model calculates the cut geometry, and an inverse mechanistic model uses this information along with the constraint force to calculate a desired feedrate. The feedrate is written into the part program resulting in a file that contains a feedrate for each tool move. Experimental results for a sculptured surface show the accuracy of the algorithms in maintaining a desired force.

Integration of Pre-Simulation and Sensorless Monitoring for Smart Mould Machining

“…The instantaneous cutting force F c is computed by adding the element cutting forces of tooth N along the axial depth of the cut d a , as shown in Eq. (3) [21][22][23][24][25].…”

“…The element cutting forces on a tooth are computed from the chip area and specific cutting energy, which also changes with the uncut chip thickness. The relationship between a specific cutting energy and uncut chip thickness, as proposed by Sabberwal, is used to consider the size effect [21][22][23][24][25][26]. The specific cutting energy is a function of the uncut chip thickness and empirical constants K c and p, which are dependent on the tool and material.…”

“…The uncut chip thickness t c , i.e., the thickness of the material removed by a flute, at any location on the cutter, can be determined using Eq. (1), where f t is the feed per tooth vector and n s is the unit normal vector of cutter surface at the angular position θ and axial height z [21,22]. The element cutting forces on a tooth are computed from the chip area and specific cutting energy, which also changes with the uncut chip thickness.…”

“…Instantaneous cutting forces and average powers are computed from the specific cutting energy and intersection of tool and workpiece [17][18][19][20][21][22][23][24]. The active feed rate is inserted in NC data to reduce machining time while the instantaneous maximum cutting force is below the limit.…”

Mechanistic modelling of the milling process using an adaptive depth buffer

“…The authors achieved good success reducing the time of machining even with a model error of up to 50%. Later, Fussell et al [14] conceptually extended their work to 5-axis tool paths, although no experimental verification was provided. Kim et al [15] discussed the application of a Z-map to the prediction of 3-axis ball-end milling forces, relying heavily on the simple geometry of the sphere and linear movements.…”