An Empirical Tool Force Model for Precision Machining

Abstract

The accuracy of precision machining operations could be improved through tool force feedback. Tool force is ideally suited for use in a control algorithm because it contains information on the instantaneous depth of cut, feed rate and condition of the tool. A tool force model that could form the basis of this new control technique has been developed. By measuring the shear angle from micrographs of chip cross sections, equations for the forces due to chip formation and the friction between the chip and the tool have been written. Furthermore, the effects of elastic deformation of the workpiece (spring back) on chip formation and the measured forces, which can be significant in precision machining, have been included in the model. Machining experiments were conducted with a 0 deg rake diamond tool and four metals that are commonly diamond turned. For machining with newly lapped as well as worn tools, the calculated forces were in excellent agreement with the measured values for the array of workpiece materials.

Experimental evaluation of cutting force parameters applying mechanistic model in orthogonal milling

“…Both force components have an elastic-plastic part, as suggested by Arcona et al (1998) and similar to the ploughing part, which are responsible for that portion of metal not being sheared, but "extruded" throughout the cutting edge radius. These components (FEC and FER) are the elastic-plastic deformation of the metal and depend on the tool radius, the mechanical properties of the workpiece material and so on, also described by Zimerman et al (1970).…”

“…These models give three different equations with several parameters, which depend on the material properties and on the yield stress. Some other slightly different models have been proposed for explaining chip formation in precision machining, such as that described in Arcona et al (1998). In all models, analyzed at the present work, the tangential force component (or thrust force), perpendicular to the cutting speed direction, was a function of the cutting force.…”

“…Recently, mathematically more detailed and specific models have been proposed including effects of the cutting edge radius (Waldorf, et al 1998, Waldorf et al 1999) and material behavior with temperature effects (Oxley 1998, Özel andAltan 2000). Models have also been proposed to explain chip formation even in precision machining (Arcona et al 1998) where depths of cut are around 0.5 µm. Some models aimed at the prediction of machining performance, besides forces and speeds (Amarego 1998).…”

The effects of machining process variables and tooling characterisation on the surface generation

“…In the cutting zone, the cutting forces will act on the tool rake face, cutting edge and flank face. The forces acted on cutting edge can be deducted based on the empirical formula of the initial stress and elastic recovery [8]. Accumulating the forces acted on the three zones, there will be the dynamic cutting forces in the three directions expressed as: where h is the undeformed chip thickness, which is equal to the feed rate of the cutting tool.…”

A method to include plastic anisotropy to orthogonal micromachining of fcc single crystals

“…The normal stress at the shear plane is assumed be one third of the hardness, H [38]. The cutting force, Fc, is then calculated knowing the shear angle, the shear stress, and the normal stress at the shear plane.…”