Chip Width Research Articles

Investigation of Chip Dimensional Characteristics Created by the Specific Cutting Tool at the Machining of 12 050 Steel

The article deals with the investigation of chip dimensional characteristics that are created by the tool with linear cutting edge nonparallel to the workpiece axis. It is the tool with special geometry that was designed by authors in order to improve product quality and shorten the time of its production. Aim of the research has been focused on the obtaining of dependencies of the chip dimensions on both feed per revolution and setting of tool corner height in relation to the workpiece axis during machining of 12 050 steel. Measured data were processed statistically and they were evaluated by means of regression analysis in matrix expression. Measured data have indicated that with the increasing of feed per revolution, the chip width and chip thickness are increasing, too. As for the depth of cut, if it is increasing, the width of chip is also increasing, but chip thickness is not changing. The experiments have shown that the shape of chips at the machining by tool with linear cutting edge is not suitable for usage in production without direct control by operator. Therefore, when considering usage of this tool, it will be necessary to design the tool with chip breaker.

Effect of non-proportional damping on the dynamics and stability of multi-cutter turning systems

Parallel turning operations offer considerable potential in increasing productivity, since they ensure high material removal rates and high feasible accuracy simultaneously. According to preliminary calculations, the stable parameter region for a 2-cutter turning system can significantly be extended by its dynamical detuning via modifying the natural frequency of one of the tools. Mechanical models are presented for a 2-cutter turning tool fixture to predict the dynamics and stability properties of the system. First, a 2-degree-of-freedom (DoF) model with dynamically uncoupled cutters is analysed. A test fixture incorporating 2 cutters was built, in order to verify theoretical predictions on cutting stability. Measurement results resulted in the extension of the mechanical model with another DoF, which captures the physical coupling between the tools. Experiments indicate that for close natural frequencies, the corresponding modal dampings are essentially different, consequently, the damping properties of the 3-DoF model can properly be modelled by non-proportional damping only. It is also shown that the presence of this non-proportional damping results in a significant increase in the robust chip width limit of stable cutting, which enhances the effect of detuning the tool frequencies in the 2-cutter turning system even further.

Chatter avoidance in cutting highly flexible workpieces

Robust stability analysis of turning is presented for flexible workpiece. The varying dynamic properties due to the material removal process is modelled by means of finite element method. The Frequency Response Function is traced along tool position. The results show significant change in the natural frequency and modal stiffness, which have strong influence on regenerative chatter vibration. Different sections of the multiple-parameter stability lobe diagram are presented and validated with experimental results. The robust stable parameters of initial diameter and chip width are identified for which no chatter occurs along the whole tool position for any spindle speed.

An Investigation of Side Flow during Chip Formation in Orthogonal Cutting

Orthogonal cutting is a simplified two-dimensional model that neglects many geometric complexities, which describes complicated three-dimensional cutting process quite well in most cases. The orthogonal cutting should satisfy the plane strain assumption to prevent the extensive deformation perpendicularly to the cutting direction due to the pressure between the cutting tool and the workpiece, which is named as the side flow. To satisfy this assumption, the depth of cut (the uncut chip width) needs to be much greater than the feed (the uncut chip thickness) with a certain ratio. However, this criterion is not valid all the time. This paper presents an experimental study of the side flow with different cutting conditions by comparing the profiles of the cross section of the machined chip in machining of aluminum alloy. It is shown that the higher ratio between the uncut chip width and the uncut chip thickness (chip width-to-thickness ratio) and the lower cutting speed can prevent the side flow during chip formation. A new criterion for plane strain assumption has been proposed in this study as well.

Optimal Detuning of a Parallel Turning System—Theory and Experiments

Parallel turning is an excellent candidate for keeping up with current trends set by manufacturing industry, namely, to increase accuracy and productivity simultaneously. In the field of manufacturing of cylindrical parts, these cutting processes offer huge potential in increasing productivity, since they ensure high material removal rates and appropriate accuracy at the same time. The above benefits can yet only be harvested if the process is free of chatter vibration, which affects the workpiece surface quality. In this study, it is shown that by means of tuning the dynamical properties of cutting tools, it is possible to expand the stable machining parameter regions in order to eliminate adverse chatter. A parallel turning system is investigated, where tuning of the system is realized by varying the overhang of one of the tools, that is, by modulating the frequency ratio of the cutters. Measurements have been carried out for the validation of the theoretical predictions of robustly stable chip width limits, below which the turning operation is stable for all spindle speed values.

A coupled dynamics, multiple degree of freedom process damping model, Part 1: Turning

Self-excited vibration, or chatter, is an important consideration in machining operations due to its direct influence on part quality, tool life, and machining cost. At low machining speeds, a phenomenon referred to as process damping enables stable cutting at higher depths of cut than predicted with traditional analytical models. This paper describes an analytical stability model which includes a process damping force that is dependent on the surface normal velocity, chip width, cutting speed, and an empirical process damping coefficient. Model validation is completed using time domain simulation and turning experiments. The results indicate that the multiple degree of freedom model is able to predict the stability boundary using a single process damping coefficient.

Investigation of serrated chip morphology change regular in the burning of titanium alloys

Titanium alloys are regarded as difficult-machining materials due to their high strength at elevated temperature, relatively low thermal conductivity, small elastic modulus, and high chemical reactivity. It is prone to produce cutting burn defect in end milling. In order to investigate the variation regular of serrated chip morphologies and the relationship between chip macro morphologies and tool flank wear in the burning of milling titanium alloys TC4, a series of cutting experiments were conducted in this study. The chip morphology and cutting vibration characteristic in different tool wear stages were examined using an optical microscope, SEM, and vibration test system. In addition, the variation characteristics of serrated chips in the burning of milling titanium alloy TC4 were analyzed. The results revealed that the occurrence of tool flank wear can make an influence on serrated chips morphologies and surface color in the cutting burning process. Besides, the chip segment degree, shear angle, and width of adiabatic shear band increased rapidly as the cutting burning occurring. The present research could be potentially used to evaluate tool wear and surface quality in the burning of end milling titanium alloy process.

Effect of tool wear on chip formation during dry machining of Ti-6Al-4V alloy, part 2: Effect of tool failure modes

Variation in the geometric and surface features of segmented chips with an increase in the volume of material removed and tool wear has been investigated at cutting speeds of 150 and 220 m/min at which the cutting tools fail due to gradual flank wear and plastic deformation of the cutting edge, respectively. Among the investigated geometric variables of the segmented chips, slipping angle, undeformed surface length, segment spacing, degree of segmentation and chip width showed the different variation trends with an increase in the volume of material removed or flank wear width, and achieved different values when tool failed at different cutting speeds. However, the chip geometric ratio showed a similar variation trend with an increase in the volume of material removed and flank wear width, and achieved the similar value at the end of tool lives at cutting speeds of both 150 and 220 m/min regardless of the different tool failure modes. Plastic deformation of the tool cutting edge results in severe damage on the machined surface of the chip and significant compression deformation on the undeformed surface of the chip.

Error Analysis for Finite Element Simulation of Orthogonal Cutting and its Validation Via Quick Stop Experiments

This work focuses on the chip formation during gun drilling of a 50CrMo4 (DIN 1.7228, AISI 4150) steel grade with a fixed set of cutting parameters and a fresh coated tool. Chip roots were investigated by means of quick stop experiments providing a measured chip width d at the chip root. Furthermore, the tool-chip contact length, L, was measured with high accuracy. Rastegaev compression tests were performed at different temperatures and strain rates for material characterization. The measured data was fit with the Johnson–Cook material model. A 2D finite element (FE) model of the orthogonal cutting process was set up starting with modelling data from literature. A parameter study was performed to determine the sensitivity of the prediction of d and L to the input parameters, i.e., the discretization, the modelling of friction and the material model. The presented error analysis of both the experimental and the numerical investigations shall serve as error estimation for similar FE simulations of the cutting process aiming at the prediction of the tool loading and/or the chip formation and breaking. Authors who have to rely on literature data may use the results presented in this work to estimate the resulting error.

The energy conservation optimization design of the cutting edges of the twist drill based on Dijkstra’s algorithm

The energy conservation optimization design about geometrical shape and dimensions of the cutting edges (lips) of the twist drill is meant to determine the main cutting edge curve in the rake face that minimizes the drilling power. Dijkstra’s algorithm is introduced and applied to serve the above purpose. The rake surface of the twist drill is discretized into a set of nodes and arcs between the adjacent nodes, which together compose a digraph. Cutting angles of elementary cutting tools on the lips of a twist drill are determined by the method of displaying planar image; those angles, together with undeformed chip thickness and width, are substituted into the empirical model of cutting force for elementary cutting tool to obtain the weights of arcs in the digraph, that is, the drilling power. Then, a main cutting edge curve in the rake face that minimizes the drilling power is generated using Dijkstra’s algorithm. Meanwhile, an improvement in Dijkstra’s algorithm procedures is put forward to reduce time and space complexities of the process and improve smoothness and machinability of the cutting edge curve. A computer program is developed with Matlab 2011b to determine the main cutting edge curve. The calculation results with 0.50 % carbon steel show that the new curved cutting edge reduces the drilling power by 7~8 %, compared to a conventional straight cutting edge.

Effects of the cutting pattern and log provenance on size distribution of black spruce chips produced by a chipper-canter

Chips of black spruce (Picea mariana (Mill.) B.S.P.) logs coming from two provenances, Montmorency (at 47°N) and Chibougamau (at 50°N) sites, were produced by a chipper-canter using three cutting widths (12.7, 19.1, and 25.4 mm). Chip dimensions were assessed by thickness, width, and length (Domtar and Williams classifications). Earlywood density, latewood density, ring density, ring width, rings per mm (R/mm), shear, splitting, modulus of elasticity (MOE), modulus of rupture (MOR) in bending, and basic density (BD) were evaluated on samples obtained within each cutting width area. The results showed that these wood attributes were significantly different between sites or/and cutting widths (12.7 and 25.4 mm). The weighted mean chip thickness (WCT) and chip class distributions (Domtar and Williams) were significantly affected by site and cutting width (CW). WCT increased as cutting width increased and its value was higher at Montmorency than at Chibougamau. The differences in WCT could be associated with the variation of growth ring characteristics, mechanical properties, and BD between sites. Moreover, chip thickness (Domtar) was significantly affected by MOR and BD while chip width and length (Williams) were significantly influenced by R/mm, BD, MOR, and shear. The analyses showed the importance of growth ring characteristics, mechanical properties, and basic density on the chip size variation. Multiple linear regressions showed that CW, MOR, BD, and R/mm were the variables that better described the variation in WCT. Chip dimensions can hence be adjusted as a function of CW but they could vary depending on the provenance of the wood and their specific attributes.

Analysis of chip morphology in dry hard turning of AISI 52100 alloy steel using RSM

This paper presents chip morphology analysis in hard turning of AISI 52100 alloy steel with multilayer hard surface coating (TiN/TiCN/Al2O3/TiN) insert under different cutting parameters (cutting speed, feed rate, and depth of cut). Response surface methodology (RSM) and Analysis of variance (ANOVA) is employed to determine effect of the cutting parameters on four response variables (tooth pitch, saw height, chip width and chip thickness). Optimisation of each response variable is performed. The results indicate significant effect of all three cutting parameters on both the chip width and the chip thickness, significant effect of the feed rate and the depth of cut on both the tooth pitch and saw height, significant increase in the tooth pitch and saw height with increase in both the feed rate and the depth of cut, and significant increase in the chip width as well as chip thickness with increase in all three cutting parameters.

Tool Condition Monitoring in Microturning of Aluminium Alloy Using Multiple Sensors

In the present work, an attempt has been made to monitor the tool condition status during microturning of aluminium alloy (AA 6061) using multiple sensors such as cutting force dynamometer, acoustic emission (AE) and accelerometer. The tool wear (nose wear) is correlated with surface roughness (Ra), chip width, thrust force (Fx), tangential force (Fy), feed force (Fz), AERMS and vibration signals. It is observed that Ra, chip width and cutting forces are increased with increase in the tool wear. Among the cutting forces, the tangential force (Fy) is found to be more sensitive to the tool wear status compared to that of the thrust force (Fx) and feed force (Fz). From the signal analysis, it is observed that during machining with good tool condition, the dominant frequency of the AERMS and vibration signals are found to be 81 kHz-110 kHz and 2.07 kHz-3.84 kHz respectively, whereas with the worn out tool the dominant frequencies are shifted to higher levels. Chip morphological studies indicated that favourable type of chips are formed upto 40th minute and unfavourable chips are observed from 41st minute to 60th minute.

Chip Formation in High-Speed Milling of Titanium Alloy with PCD Tools

This paper presents a detailed analysis of chip morphology through an experimental study of high-speed milling of Ti-6Al-4V alloy with PCD tools. Milling tests were conducted for cutting speed range from 125 m/min to 2000 m/min with water-soluble cutting fluid. The collected chips were firstly examined with a digital cameras and the free surface of the chips was analyzed by a scanning electron microscope (SEM). Geographical parameters of chip morphologies were described in saw-tooth/lamella frequency on the free surface and chip width. Experimental results show that the variation of chips in high-speed end milling of Ti-6Al-4V alloy is as follows, long and straight-shaped → spiral-shaped → curly-shaped → irregular-shaped. The free surface of chips exhibits saw-tooth lamella structures. The lamella becomes clearer and more obvious at higher cutting speeds. Within the same measurement distance, there is a sharp decrease in the lamella number within same measuring range. This should be attributed to the enhancement of the thermal mechanical coupled field applied to the chip formation processes.

Extension of Tlusty׳s law for the identification of chatter stability lobes in multi-dimensional cutting processes

Chatter vibrations in cutting processes are studied in the present paper. A unified approach for the calculation of the stability lobes for turning, boring, drilling and milling processes in the frequency domain is presented. The method can be used for a fast and reliable identification of the stability lobes and can take into account nonlinear shearing forces, as well as process damping forces. The applicability of Tlusty׳s law, which is a simple scalar relationship between the real part of the oriented transfer function of the structure and the limiting chip width, is extended to milling and any other multi-dimensional chatter problem without neglecting the coupled dynamics. The given analysis is suitable for getting a deep understanding of the chatter stability dependent on the parameters of the cutting process and the structure. Basic examples based on experimental data of real machine tools include the dependence of the stability behavior on the rotational direction in turning, the effect of axial–torsional structural coupling in drilling, and the dynamics of slot milling.

Dynamics and Cutting Stability of Dynamically Loaded Worktable Subjected to Elastic Supports

This paper investigated the dynamic characteristics and the cutting stability of a dynamically loaded worktable on elastic supports in a surface grinder. The operation of worktables is usually dynamically loaded in various positions, which results in a complex system of governing equations. In this study, the assumptions of elastic and rigid body modes of a free-free beam were specified in analyzing the worktable. By combining the Lagrange energy method with the technique of assumed mode expansion, the system of equations was developed. The absolute value of the maximum negative real part of the overall dynamic compliance (MNRPODC) and the limiting chip width were used as the performance indicators to evaluate the structural characteristics of the worktable during simulated machining. The 3D stability lobe diagram was then computed. The cutting stability was verified by comparing the results obtained in time-domain analysis with the lobe diagram. The procedure presented in this study to improve the dynamics performance of a surface grinder can also be implemented in a similar fashion for many other machine tool applications.

Analiza wpływu zmian konstrukcyjnych lasera azotkowego na możliwość zwiększenia jego wyjściowej mocy optycznej

This paper presents calculation results of performance of III-N-based laser diode and its arrays (bars) with various package modifications. We adjusted our 2D thermal-electrical model to room-temperature continuous-wave operating characteristics of nitride-based edge-emitting laser fabricated in the Laboratory of Institute of High Pressure Physics. The impact of chip width, substrate thickness, thickness of p-type gold electrode, number of emitters and emitter-to-emitter distance on output power limits of nitride laser diode is investigated. Computational analysis of output power limits of III-N-based laser diode with various package modifications

Analytical Prediction of the Critical Depth of Cut and Worst Spindle Speeds for Chatter in End Milling

The frequency response function (FRF) method has been well used to determine the worst spindle speeds and their critical limiting chip width for turning operation by finding the maximum negative real part of the FRF. In this study, a modified FRF concept is adapted for a 2 DOF milling system of planar isotropic dynamics to determine the worst spindle speeds and the critical limiting axial depth of cut in explicit, analytic formulas. Analogous to the formulation of worst spindle speeds, similar expression for the best spindle speeds is also obtained. The modified FRF is obtained by multiplying the original FRF of the structure with a complex scaling factor, corresponding to a scaling and a rotation of its original Nyquist plot. The scaling factor is determined analytically from the system characteristic equation with the radial cutting constant and radial immersion angle as the major system parameters. Through the presented method, it is also shown that the worst spindle speeds for a milling operation can be found without the prior knowledge of modal dynamics and stability lobe diagram. The proposed analytical expressions are confirmed by the existing stability models and experimentally verified.

Determination of the Chip Width and the Undeformed Chip Thickness in Rotational Turning

The accurate knowledge of the defining parameters of chip removal in rotational turning is necessary for the description of the complex kinematic relations. In this paper two characteristic parameters of the chip cross-sectional area undeformed equivalent chip thickness, chip width is defined. Lastly the application of the gained relation is shown for a specific example.

Experimental study on cutting temperature and cutting force in dry turning of titanium alloy using a non-coated micro-grooved tool

Various non-coated micro-grooves with 7–149μm in depth and 0.14–0.50 in aspect ratio are proposed on tool rake surfaces along cutting chip flowing. The objective is to understand how the micro-groove shape and size influence cutting temperature and cutting force in dry turning of titanium alloy. First, the micro-grinding with a diamond wheel V-tip was employed to fabricate accurate and smooth micro-grooves; then dry turning experiments were performed with regard to material removal rate; finally, cutting temperature, cutting force and tool wear were investigated. It is shown that these micro-grooves patterned on tool rake surface contribute to decreasing cutting chip frictions and excluding cutting heat. The micro-grooved tool decreases cutting temperature by 103°C and more against traditional plane tool. The predicted cutting tip temperature reaches about 1322°C for traditional plane tool, but it does only about 500°C for micro-grooved tool. Moreover, the cutting temperature decreases and the shear angle increases with decreasing micro-groove depth except for the case of 7μm in micro-groove depth. The 25-μm-depth micro-grooved tool decreases cutting temperature and cutting force more greatly in larger material removal rate turning. In the dry turning with a micro-grooved tool, it is required that the micro-groove width is less than cutting chip width and its aspect ratio is enough large to maintain the air spaces between chip back surface and tool rake surface.