Edge Force Coefficients Research Articles

A mechanistic approach to investigate drilling of UD-CFRP laminates with PCD drills

Carbon fiber reinforced plastics (CFRPs) possess desirable material properties that satisfy the aerospace industry's high strength to weight ratio objective. Therefore, CFRPs are commonly used in structural parts, either alone or together with aluminum and titanium alloys. Drilling of CFRPs has been studied extensively in the literature in recent years, with special emphasis on process parameters and delamination. This study identifies mechanical properties of uni-directional CFRPs through drilling tests. Drilling of uni-directional CFRP plates with and without pilot holes has been performed, and cutting and edge force coefficients are identified. A polycrystalline diamond (PCD) drill was used in tests since this type of drill is commonly used in practice. Finally, validation tests on multi directional CFRP laminates have been performed and good results have been obtained.

An improved dynamic milling force coefficients identification method considering edge force

The identification of the dynamic coefficients is the key to realize accurate simulation of dynamic milling process. To enlarge the scope of dynamic simulation without ignoring edge force, an improved method is presented to calculate milling force coefficients. In this method, linear approximation of average milling force is integrated with multiple linear regressions by supposing that milling force coefficients are time invariant for small variation of feed rate. Therefore, both the shear coefficients and the edge coefficients can be calculated simultaneously. A comparison of simulated milling force with and without the edge force is illustrated and the result shows that the accuracy is higher if the edge force coefficients are considered. This method casts new light on fast and accurate simulation of the dynamic milling force in real industrial environment.

Orthogonal cutting mechanics of maple: modeling a solid wood-cutting process

The experimental results of orthogonal cutting of maple and the modeling of the cutting mechanics are presented. The tool cutting forces were measured for different feed rates. A set of equations relating the tangential and feed forces to the tool edge width and feed rate (chip thickness) to calculate the chip and edge cutting force coefficients was developed. Then the chip force and edge force coefficients were calculated from experimentally obtained cutting forces and were plotted in a polar-coordinate system with respect to the fiber orientation of the maple disk. The polar-coordinate presentation of the cutting force results and the calculated cutting force coefficients provides an excellent visual appreciation of the relation between the cutting forces and the wood fiber orientation. Chips were also collected from various sectors of the wood disk. This analysis further identified the effects of fiber orientation and cutting forces on the types of chip formed and hence the cutting mechanics involved. By applying the calculated cutting coefficients for each tool orientation (in respect to the grain) it is possible to predict the feed and tangential forces for any feed rates. There is good agreement between the predicted and measured cutting forces.

Mechanistic identification of specific force coefficients for a general end mill

The paper presents expressions for semi-empirical mechanistic identification of specific cutting and edge force coefficients for a general helical end mill from milling tests at an arbitrary radial immersion. The expressions are derived for a mechanistic force model in which the total cutting force is described as a sum of the cutting and edge forces. Outer geometry of the end mill is described by a generalized mathematical model valid for a variety of end mill shapes, such as cylindrical, taper, ball, bull nose, etc. The derivations follow a procedure originally proposed for a cylindrical end mill. The procedure itself is improved by including the helix angle in evaluation of the average edge forces. The resulting expressions for the specific force coefficients are verified by simulations and experiments.

THE UNIFIED-GENERALIZED MECHANICS OF CUTTING APPROACH—A STEP TOWARDS A HOUSE OF PREDICTIVE PERFORMANCE MODELS FOR MACHINING OPERATIONS

This paper presents the series of on-going investigations, which led to the development of the ‘Unified-Generalized Mechanics of Cutting Approach’ to predictive modelling of various technological performance measures for the wide spectrum of machining operations used in practice. It is shown that this approach involved the development of generalized mechanics of cutting analyses of the cutting processes for machining with single edge and multi-edge (form) tools and the establishment of a generic database of basic cutting quantities and edge force coefficients. This was followed by the development of a methodology for modelling each machining operation used in practice, based on the generalized cutting analyses and database. The models developed for turning, drilling and milling operations as well as machining with form tools and the novel rotary tool turning operations are briefly described together with recent research on predictive modelling of ball end-milling and machine tapping operations. It is shown that the models for the different machining operations could be ‘unified’ into a modular computer application structure, drawing on the generic cutting analyses and database. This ‘unified’ approach could represent a step towards the development of a ‘House of Predictive Models’ sought by the CIRP Working Group on modelling of machining operations. The considerable scope for further research is discussed in this paper.

Predictive Models for Machining with Multi-Edge Form Tools Based on a Generalised Cutting Approach

In this paper predictive models for the force components, chip flow and power in single and multi pass turning of helical vee grooves as well as single pass turning at high and low feed to depth of cut ratios with triangular profiled form tools have been developed. The predictive models are based on generalised mechanics of cutting analyses for machining with single and multi-edge form tools together with a ‘generic’ database of basic cutting quantities and edge force coefficients found from ‘classical’ orthogonal cutting tests. The mathematical models allow for all the tool and cut geometrical variables as well as the cutting speed while the database allows for the tool-workpiece material effects and tool coatings. The models have been experimentally verified over a wide range of operation variables and their predictive capabilities estimated in terms of the percentage deviations between the measured and predicted forces. The developed models are capable of predicting the tangential, feed and radial forces within a deviation of 10 % ‘on average’. This investigation has enabled the ‘Unified Mechanics of Cutting Approach’ to performance prediction to be extended to include machining with form tools.