The form error prediction in side wall machining considering tool deflection

In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy.     

Estimation and experimental validation of cutting forces in ball-end milling of sculptured surfaces

Chip thickness calculation has a key important effect on the prediction accuracy of accompanied cutting forces in milling process. This paper presents a mechanistic method for estimating cutting force in ball-end milling of sculptured surfaces for any cases of toolpaths and varying feedrate by incorporation into a new chip thickness model. Based on the given cutter location path and feedrate scheduling strategy, the trace modeling of the cutting edge used to determine the undeformed chip area is resulted from the relative part-tool motion in milling. Issues, such as the selection of the tooth tip and the computation of the preceding cutting path for the tooth tip, are also discussed in detail to ensure the accuracy of chip thickness calculation. Under different chip thicknesses cutting coefficients are regressed with good agreements to calibrated values. Validation tests are carried out on a sculptured surface with curved toolpaths under practical cutting conditions. Comparisons of simulated and experimental results show the effectiveness of the proposed method.     

Influence of tool inclination on brittle fracture in glass cutting with ball end mills

Glass milling is discussed with influences of tool inclination on brittle fracture. Cutting tests are performed to observe surfaces in the up-cut and the down-cut processes with a ball end mill inclined in the feed direction of the cutter. Brittle fracture occurs in the down-cut process at high feed rates. Then the machined surfaces in cutting with the ball end mills tilted in the vertical plane with respect to the feed direction are associated with those of the up-cut and the down-cut processes. The cutting forces are also measured to discuss brittle fracture with the change of the undeformed chip thickness. The scratches on the surface finished with the tilted ball end mill are shown in an analytical model with a notched edge shape. The maximum feed rates at which brittle fracture does not occur are shown with the tool inclination in the cutting tests.     

Cutting process of glass with inclined ball end mill

Cutting processes with ball end mills are discussed for machining microgrooves on glasses. A surface is finished in undeformed chip thickness less than 1 μm at the beginning and at the end of the cut during the cutter rotation. The milling process is applied to glass machining. A crack-free surface can be finished in a large axial depth of cut more than 10 μm. Because glass undergoes almost no elastic deformation, roughness on a cutting edge in glass machining has a larger influence on surface finish than that of metal machining. The rotational axis of the tool is inclined to improve the surface finish. The cutting processes are modeled to show the effect of the tool inclination on the machined surface with considering the edge roughness. The tool inclination compensates for deterioration of the surface finish induced by the edge roughness in the presented model. The improvement of the surface finish is verified in the cutting experiments with the tool inclination. The orthogonal grooves 15–20 μm deep and 150–175 μm wide, then, are machined with the crack-free surfaces to prove efficiency and surface quality in the milling process.     

浅析立式加工中心切削液的使用

主要讲述了切削液在北方红旗立式加工中心加工过程中的应用及对比试验,以提高刀具耐用度。     

Modeling of cutting forces in near dry machining under tool wear effect

A predictive model for the cutting forces in near dry machining, in which only a small amount of cutting fluid is used, is developed based on considerations of both the lubricating effect and the cooling effect. For the lubricating effect, with the material properties, lubricating parameters, and cutting conditions, the friction coefficient in near dry machining is calculated based on the boundary lubrication model for use in a modified Oxley's approach to determine the cutting forces. For the cooling effect in near dry machining, a moving heat source method is pursued to quantify the primary-zone shear deformation heating, the secondary-zone friction heating, and flank face air–oil mixture cooling. These two effects are considered collectively to estimate cutting forces under the condition of sharp tools. The predicted variables of flow stress, contact length, and shear angle obtained from the model are used to predict the cutting forces due to the tool flank wear effect based on Waldorf's model. Comparisons are made between predicted and experimental cutting forces for sharp tools and worn tools in the cutting of AISI 1045 with uncoated carbide tools. The results show that the proposed model provides average prediction errors of 14% in the tangential cutting force direction, 21% in the axial directions, and 30% in the radial directions within the experimental test condition range (cutting speeds of 45.75–137.25 m/min, feeds 0.0508–0.1016 mm/rev, and depth of cuts 0.508–1.016 mm). It is also found that the cutting forces in near dry machining are generally lower than those under dry machining condition. Under cutting speeds of 91.5 and 137.25 m/min, the deviations of the predicted forces between near dry machining and dry machining range from 5% to 39% for axial cutting forces, 3% to 36% for radial cutting forces, and 1% to 32% for tangential cutting forces. It suggests that the lubricating mechanism has a stronger effect on cutting forces than the cooling mechanism when cutting AISI 1045 with uncoated carbide tools.     

Modeling of minimum uncut chip thickness in micro machining of aluminum

Micro mechanical machining operations can fabricate miniaturized components from a wide range of engineering materials; however, there are several challenges during the operations that can cause dimensional inaccuracies and low productivity. In order to select optimal machining parameters, the material removal behavior during micro machining operations needs to be understood and implemented in models. The presence of the tool edge radius in micro machining, which is comparable in size to the uncut chip thickness, introduces a minimum uncut chip thickness (MUCT) under which the material is not removed but ploughed, resulting in increased machining forces that affect the surface integrity of the workpiece. This paper investigates the MUCT of rounded-edge tools. Analytical models based on identifying the stagnant point of the workpiece material during the machining have been proposed. Based on the models, the MUCT is found to be functions of the edge radius and friction coefficient, which is dependent on the tool geometry and properties of the workpiece material. The necessary parameters for the model are obtained experimentally from orthogonal cutting tests using a rounded-edge tool. The minimum uncut chip thickness (MUCT) is then verified with experimental tests using an aluminum workpiece.     

Sensor signals for tool-wear monitoring in metal cutting operations—a review of methods

The state of a cutting tool is an important factor in any metal cutting process as additional costs in terms of scrapped components, machine tool breakage and unscheduled downtime result from worn tool usage. Several methods to develop monitoring devices for observing the wear levels on the cutting tool on-line while engaged in cutting have been attempted. This paper presents a review of some of the methods that have been employed in tool condition monitoring. Particular attention is paid to the manner in which sensor signals from the cutting process have been harnessed and used in the development of tool condition monitoring systems (TCMSs).     

Estimation of cutter deflection and form error in ball-end milling processes

This paper presents a method to analyze the 3-dimensional form error of a ball-end milled surface due to the elastic compliance of the cutting tool. In order to estimate the form error in various cutting modes, the cutting force and the cutter deflection models including the effect of the surface inclination were established. The cutting forces were calculated by using the cutter contact area determined from the Z-map of the surface geometry and the current cutter location. The tool deflection responding to the cutting force was then calculated by considering the cutter and the holder stiffness. The cutter was modeled as a cantilever beam consisting of the shank and the flute. The stiffness of the holder was measured experimentally. Various experimental works have been performed to verify the validity of the proposed model. It is shown that the proposed method is capable of accurate prediction of cutting forces and the surface form error.