Analysis of Cutting Forces From Conventional to High-Speed Milling with Straight and Helical-Flute Tools for Flat-End Milling Incorporating the Effect of Tool Runout

This paper presents a systematic study to analyze the dependence of cutting forces on tool geometry, workpiece material and cutting parameters such as spindle speed, tool engagement and cutting direction in flat-end milling with tool runout. The cutting forces are determined according to a mechanistic force model considering the trochoidal flute path to calculate the undeformed chip thickness, and average cutting force and linear regression model are applied for identifying the coefficients of the force model. A series of milling processes are conducted on AZ31 Magnesium (Mg) alloy and titanium alloy (Ti6Al4V) to analyze the instantaneous cutting force curves, amplitudes of cutting forces and peak forces over a wide range of spindle speeds from conventional to high-speed milling. It is demonstrated that the values of the cutting force coefficients are higher at conventional spindle speed and decrease with an increase in spindle speed, especially when machining Ti6Al4V alloy. For the edge force coefficients, it is observed a slight variation when using cutting tools with different helix angles. Besides, the cutting force amplitudes strongly depend upon the workpiece material. The helix angle has a significant influence on the transverse force amplitude at conventional speed. The forces obtained mechanistically are also substantiated by comparison with measurements.

An Improved Cutting Force Model in Micro-milling Considering the Comprehensive Effect of Tool Runout, Size Effect and Tool Wear

Tool runout, cutting edge radius-size effect and tool wear have significant impacts on the cutting force of micro-milling. In order to predict the micro-milling force and the machining performance related to the cutting force, it is necessary to establish a cutting force model including tool runout, cutting edge radius and tool wear. In this study, an instantaneous uncut thickness (IUCT) model considering tool runout, a nonlinear shear/ploughing coefficient model including cutting-edge radius and a friction force coefficient model embedded with flank wear width, are constructed respectively. By integrating the IUCT, the nonlinear shear/ploughing coefficient and the friction force coefficient, a comprehensive micromilling force model including the tool runout, size effect and tool wear is derived. Experiment results show that the proposed comprehensive model is efficient to predict the micro milling force.

Feasibility Study of On-Machine Inspection of Micro Milling Cutter Runout

During the process of micro machining, the existence of tool runout not only aggravates the wear and breakage of the cutter, but also seriously affects the surface quality of the parts. In order to observe the runout of micro-milling cutter, a detection method based on machine vision was proposed in this paper, which can calculate the tool runout by measuring the maximum value of external fluctuation of the cutter assembly near the tool tip. The proposed method can realize the direct measurement of radial runout of a micro-milling cutter. A dedicated prototype measuring system was established, which includes an on-machine measurement unit, a controller and the software. To obtain the images of maximum profile of the cutter at different angles, the cutter should be perpendicular with the optical axis of camera lens in the on-machine measurement unit. The experiments verified that the proposed method is feasible and the developed measurement system can fulfill the needs of industrial applications.

An In-Process Intervention to Mitigate the Effect of Built-Up Edges in Micromilling

This paper is focused on developing an in-process intervention technique that mitigates the effect of built-up edges (BUEs) during micromilling of aluminum. The technique relies on the intermittent removal of the BUEs formed during the machining process. This is achieved using a three-stage intervention that consists first of the mechanical removal of mesoscale BUEs, followed by an abrasive slurry treatment to remove the microscale BUEs. Finally, the tool is cleaned using a nonwoven fibrous mat to remove the slurry debris. An on-machine implementation of this intervention technique is demonstrated, followed by a study of its influence on key micromachining outcomes such as tool wear, cutting forces, part geometry, and burr formation. In general, all relevant machining measures are found to improve significantly with the intervention. The key attributes of this intervention that makes it viable for micromachining processes include the following: (i) an experimental setup that can be implemented within the working volume of the microscale machine tool; (ii) no removal of the tool from the spindle, which ensures that the intervention does not change critical process parameters such as tool runout and offset values; and (iii) implementation in the form of canned G-code subroutines dispersed within the regular micromachining operation.

Influence of tool rotation errors on flank machined surface

In flank milling, the machined metal surface is formed by the edge of the cutting tool and is thus affected by tool errors. Cutting tool rotation errors affect the movement of the tool teeth and thus change the trajectory of the tool edge. This change will also affect the cutting force, which will result in deformation in the cutting process. Previous studies focus mostly on the cutting tool runout error and ignore the effect of tool deformation. In this article, we built a mathematical model of the machining process that considers not only the tool runout error but also the tool tilt deformation error. Using this model, we analyzed how the tool rotation error will influence workpiece surface quality and surface frequency. Results show that feed rate and rotation errors will affect surface roughness, geometric error, and surface energy distribution.