A new mechanistic model is presented for the prediction of a cutting force system in ball-end milling of sculpture surfaces. The model has the ability to calculate the workpiece/cutter intersection domain automatically for a given cutter location (CL) file, cutter and workpiece geometries. Furthermore, an analytical approach is used to determine the instantaneous chip load (with and without runout) and cutting forces. In addition to predicting the cutting forces, the model also employs a Boolean approach for a given cutter, workpiece geometries, and CL file to determine the surface topography and scallop height variations along the workpiece surface which can be visualized in 3-D. The results of model validation experiments on machining Ti-6A1-4V are also reported. Comparisons of the predicted and measured forces as well as surface topography show good agreement.

Abstract

A new mechanistic model is presented for the prediction of a cutting force system in ball-end milling of sculpture surfaces. The
model has the ability to calculate the workpiece/cutter intersection domain automatically for a given cutter location (CL) file, cutter
and workpiece geometries. Furthermore, an analytical approach is used to determine the instantaneous chip load (with and without
runout) and cutting forces. In addition to predicting the cutting forces, the model also employs a Boolean approach for a given
cutter, workpiece geometries, and CL file to determine the surface topography and scallop height variations along the workpiece
surface which can be visualized in 3-D. The results of model validation experiments on machining Ti-6A1-4V are also reported.
Comparisons of the predicted and measured forces as well as surface topography show good agreement.

1. Introduction

Ball-end milling is a very common machining process especially in the automobile, aerospace, die and mold industries. Due to various reasons, such as structural, optimization or esthetic points of view, nowadays, most of the industrial part geometries are becoming more and
more complicated. The recent advances in CAD/CAM systems and CNC machining centers allows us to supply this demand of machining very complex sculpture sur-faces by ball-end milling.
The importance of predicting the cutting forces in ball-end milling is evident. Some of them can be men- tioned as follows; in the process planning stage, knowl- edge on the cutting forces helps the process engineers to select ‘appropriate values’ for the process parameters.
For example, in the process planning stage, knowing that the process can tolerate a higher value of the cutting forces may help to select optimum cutting parameters (feedrates, depth of cut, etc.) for more productive mach-ining. Besides affecting tool life and productivity.

2. Cutting edge geometry

Cutting edge geometry plays a very important role on the cutting force characteristics in the ball-end milling process, whereas the straight end mill, ball-end mill cut- ting edge geometry varies locally in the ball part. For example, as well as varying the local helix angle, varying
radius r(Fig. 1) directly affects the cutting forces through its effect on the cutting velocity. Therefore, in the process planning and cutter selection stage, besides considering the constraints of ball-end mill diameter due to avoidance of gouging/undercut and limiting the scal- lop height, selection of a proper cutter/cutting edge geometry, as well as other process factors, is very important over the amplitude and wave form of gener- ated cutting forces during the machining.

Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed

keyboard_arrow_up