High Speed Cutting Research Articles

Development of cutting force components in high-speed cutting on turning centre

The article deals with the investigation of high-speed cutting. The influence of cutting speed on the development of individual cutting force components in turning was determined. Cutting tests were carried out on turning centre during the machining of C45 medium carbon steel material. The cutting tool material was cubic boron nitride. Cutting speed was selected with respect to the high-speed cutting (HSC) based on previous studies. In the experiment, cutting force components were recorded. From the results, a decreasing trend in the cutting force values was observed from the cutting speed higher than 1100 m.min-1. It can be caused by changing of metallurgical and mechanical properties in the cutting zone because the overall cutting resistance during HSC was reduced. Chips changed colour to orange during the machining due to temperature changes. No great benefit was observed when high-speed cutting for turning medium carbon steel material. The inefficiency, in this case, is caused by the high price and low tool life of the CBN cutting inserts as well as the cutting force that decreases slowly after the initial increase with a rapidly increasing cutting speed.

Finite element modeling of high-speed orthogonal cutting: A contribution to understanding the influence of mesh parameters on saw-toothed chip formation

Modeling of metal cutting using finite element (FE) method has been investigated in many studies. They make it possible to better understand the chip formation. However, the mesh dependence of the numerical solution is still unsolved. The purpose of this paper is the modeling and simulation of saw-toothed chip formation during high-speed orthogonal cutting. Further, the influences of mesh parameters on saw-toothed chip formation are investigated as an innovative highlight of this study. The investigation of high-speed cutting (HSC) is based on FE analysis, where the Johnson-Cook (JC) constitutive model is combined with an energy-based fracture criterion. The mesh parameters considered include element dimension, element orientation, and hourglass treatment. The results show that the peak and valley values of saw-toothed chip obtained through the model mesh10 × 10 are close to the measurements, but the pitch value is predicted with a larger error than those of peak and valley values. Square elements of dimension 10 μm can be also used to avoid the influence of element orientation on cutting forces with an error about 10%. When using square elements, the hourglass treatment causes slightly differences in chip morphology and cutting force. On the other hand, the enhanced is the more efficient method to prevent the hourglass effect for rectangular elements. The model mesh8 × 10 gives an error less than 15% for cutting force. Moreover, the effect of element dimension on cutting force can be reduced by applying the fracture energy criterion controlled through a characteristic length to different mesh dimensions.

Impact of cooled compressed air and high-speed cutting on the drilling of hybrid composite-metal stacks

Hybrid composite-metal stacks (HCMS) combine metal alloys and composite materials and are used in the manufacturing and maintenance of aircrafts. Drilling is an important manufacturing process necessary for installing rivets in fuselages. This work sought to identify the influence of cooled compressed air and high-speed cutting (HSC) on drilling multi-material joints with different configurations. Among the factors observed are the composite type (carbon- or glass-fiber-reinforced polymer), joint type with 2024 aluminum alloy (simple or composed), presence or absence of cooled air, cutting speed (40 and 220 m/min), and feed rate (0.02 and 0.08 mm/rev) in HCMS drilling. Adjusted delamination factor, hole-wall roughness, hole roundness, and thrust force were evaluated. The combined effect between cutting speed and cooled air did not significantly impact the defects generated, making it possible to use HSC without harming the joint. Cooled air showed a tendency to decrease defects in HCMS drilling.

Effect of the Geometry of Thin-Walled Aluminium Alloy Elements on Their Deformations after Milling.

The aim of this paper is to analyse the effect of the selected geometric properties of thin-walled structures on post-machining deformations. In the study, EN AW-7075 T651 and EN AW-6082 T651 aluminium alloys were used to prepare specially designed thin-walled sample elements, i.e., elements with walls arranged in a semi-open and closed structure and with a dimension of 165 × 262 × 50.8 mm consisting of bottom and vertical stiffening walls and so-called ribs with a thickness of 1 mm. The measurements of the absolute deformations of the thin-walled bottom were performed with the use of a Vista coordinate-measuring machine by Zeiss with a PH10 head by Renishaw. Based on the obtained results, it was found that absolute deformation values were higher for walls arranged in a semi-open structure. It is related to a lower rigidity of the tested structure resulting from the lack of a stiffening wall, which is the so-called "rib". Notwithstanding the geometry of the elements, greater absolute deformation values were recorded following conventional cutting methods. The use of high-speed cutting (HSC) provided positive outcomes in terms of minimising the deformation of thin-walled elements. Additionally, it was found that higher absolute deformations were obtained for EN AW-7075 T651 alloy.

Analiza stabilności skrawania z dużą prędkością stopów aluminium

Progress in the production of cutting tools, CNC machine tools, and CAM software has contributed to improvement in subtractive machining processes, including milling, the so-called high speed cutting (HSC) and high performance cutting (HPC) machining. The cutting parameters that define the boundaries between the aforementioned technologies and conventional machining are not clearly defined. This is due to the close correlation between the process conditions and the types of processed material. High speed cutting and high performance cutting can be used for processing such as: machining of materials in the hardened state, machining without cutting fluid and with minimal lubrication, and thin-wall integral aerospace structures. The study examined complex analyses of HSC machining due to the process stability. The test results prove the dominant influence of cutting speed changes on a method’s effectiveness for spindle speeds up to 80,000 rpm.

Cascaded sliding mode position control (SMC-PI) for an improved dynamic behavior of elastic feed drives

The precision of machine tools is essentially determined by the feed drive control. To improve the dynamic behavior of elastic feed drives, this paper presents a novel position control concept, substituting the conventional P position controller of the industrial cascade control with a continuous sliding mode controller (SMC) together with a Kalman Filter for state estimation. The novelty of this approach lies in the focus on practical applicability: The underlying PI-cascade structure leads to low commissioning effort and the SMC controller’s parameterization is simplified to a single tuning parameter. A general compliant feed drive model is used as plant, whose parameters usually are already known from commissioning of the velocity controller. The SMC position controller is derived analytically and its stability and damping properties are investigated for the dominating mechanical mode for uncertainties of the model parameters and a wide range of controller gains. The effectiveness of the SMC-PI controller is validated for an industrial ball screw feed drive. Extensive experimental results show a considerable decrease of tracking errors in command tracking, disturbance rejection and for a high speed cutting (HSC) milling experiment compared to P-PI cascade control, while stability margins remain almost independent of the controller gains. The parameterization is discussed on the basis of a theoretical analysis and measuring results. Furthermore, excellent robustness properties regarding model errors are demonstrated.

Low and High Speed Orthogonal Cutting of AA6061-T6 under Dry and Flood-Coolant Modes: Tool Wear and Residual Stress Measurements and Predictions.

The present research work aimed to study the effects of cutting environments and conditions on tool wear and residual stresses induced by orthogonal cutting of AA6061-T6. Cutting environments included dry- and flood-coolant modes and cutting conditions consisted of cutting speed and feed rate. A 2D finite element (FE) model was developed to predict tool wear and residual stresses and was validated by experimental measurements including machining forces, tool wear, and residual stresses. This was obtained by exploring various magnitudes of the shear friction factor and heat transfer coefficient and choosing proper coefficients using the calibration of the predicted results with the measured ones. The experimental results showed that the effect of cutting environment including dry and flood-coolant modes was negligible on machining forces. The experimental investigation also demonstrated that increasing feed rate raised machining forces, tool wear and residual stresses in both cutting environments. Low Speed Cutting (LSC) led to the highest value of tool wear and High Speed Cutting (HSC) provided the lowest values of resultant machining forces and residual stresses in both modes. Flood-coolant mode reduced tool wear and slightly decreased tensile residual stresses in comparison with dry mode. As a result, low feed rate and high-speed cutting under flood-coolant mode were proposed in order to improve tool wear and residual stress in orthogonal cutting of AA6061-T6.

Modeling of Heat Phenomenon in Rolling Kinematic Pairs Using the Finite Element Method

In the spindles of HSC (High Speed Cutting) machines with rolling bearings, higher temperatures in the bearings can be expected, which may affect the resistance to movement of the bearing itself. Therefore, to estimate these resistances, it is necessary to know the temperatures of the bearing components. The article presents the results of FEM simulation tests of temperature distribution in a rolling bearing. These studies were focused on assessing the influence of such features as the distribution of heat sources, the geometric form and size of the contact areas of the balls with the raceways, the conditions of heat convection to the environment and heat conduction inside the bearing. It has been recognized that FEM simulations for the default conditions offered by most commercial FEM systems can lead to out-of-the-box results. As part of the experimental research, conclusions from the simulation studies were verified.

Dynamic stress propagation induced transition of stress state and microstructure characteristics during high-speed cutting of OFHC copper

High-speed cutting (HSC) is a popular technique applied in manufacturing as it can significantly improve machining efficiency and surface quality. However, when the cutting speed is increased to extremely high, the deformation process of the material will be changed due to the alteration of microstructures and loading conditions; as a result, some deeper understandings of the mechanisms are still required. In this study, a dislocation density-based constitutive model is implemented to describe the material behavior of OFHC (oxygen-free high conductivity) copper during high-speed cutting process, which is then used to obtain the characteristics of dynamic stress propagation through physical parameters of the material, so that the relationship between dynamic stress propagation and microstructure evolution can be directly described. The results show that the propagation of plastic deformation will be significantly changed when cutting speed is increased to extremely high, and the transformation of stress states between loading and unloading will lead to the change of gradient distribution of strains and microstructures. This research can be used to understand the stress state variation during dynamic deformation in the cutting process through microstructure characterization in future investigations.

Validating Continuum Model for Onset of Adiabatic Shear Banding during High Speed Cutting by Finite Element Method

High-speed cutting (HSC) is frequently adopted to manufacture parts in many industries, including aerospace and automotive. To manufacture high-quality parts, adiabatic shear banding (ASB), often observed on serrated chips of various metallic materials during the HSC process, should be suppressed and studied. ASB is formed due to work hardening of metallic materials and work softening induced by adiabatic heating. The onset of ASB during the orthogonal cutting of Ti6Al4V is modeled based on the continuum mechanics, taking both work hardening and work softening into considerations. The model is validated by finite element method (FEM) and experiments. Moreover, the ASB onset process is simulated in FEM to reveal the ASB formation mechanism. The effect of the mechanical properties of Ti6Al4V on the onset of ASB is investigated based on the Johnson-Cook model. The investigation reveals the main factors that affect the onset of ASB during the HSC process. Future work includes characterizing the mechanical behavior of Ti6Al4V after the onset of ASB during a cutting process by coupling the continuum mechanics and micromechanics.

New milling methodology for sealing planes in AlSi9Cu3(Fe) alloy machined with PCD tool

The use of self-moulding resins in industry makes it necessary to specify minimum values for the surface roughness parameters in order to avoid fluid leaks between the sealing planes. To meet this requirement, new tool classes, machining parameters, and methodologies are being used. Thus, this work applies a new methodology for plane milling, with the objective of increasing the tightness of the union with adhesive. The investigation was based on experimental planning techniques for the behaviour of the surface roughness in machining of AlSi9Cu3 alloy by frontal milling with refrigeration, carried out in a transmission union support, in high-speed cutting (HSC) machining centres. The evaluated parameters were the cutting speed (Vc) between 1250 m/min and 2250 m/min, and the feed per tooth (fz) between 0.050 mm/tooth and 0.100 mm/tooth. Two cutters with ten polycrystalline diamond (PCD) inserts were used to mill the sealing surface, with one of the cutters having eight cutting inserts and two scratching inserts. The cutoff considered was 2.5 mm and the statistical technique of design of experiment (DOE) was used to evaluate the experimental results. The optimum roughness values, achieved with the cutter with scratching inserts, were a Vc of 1250 m/min and fz of 0.05 mm/tooth.

Mechanism of ultra-high-speed cutting of Ti-6Al-4V alloy considering time-dependent microstructure and mechanical behaviors

High-speed cutting (HSC) and ultra-high-speed cutting (u-HSC) (6.07–32.7 m/s) tests of Ti-6Al-4V alloy were developed based on an improved Split Hopkinson Pressure Bars (SHPB) system. Specific cutting energy was calculated and scaling effect was observed in HSC with different uncut chip thicknesses (20–200 μm). Considering time-dependent (in situ and ex situ) microstructure and mechanical parameters, chip morphology, adiabatic shear band (ASB), chip-free surface, material separation characteristic at chip-workpiece interface, and surface integrity were investigated. The micro-hardness within ASB was 25% higher than that outside of the ASB. Ultra-fine grains (77% grain sizes less than 330 nm) and micro-texture were observed by electron backscattering diffraction (EBSD) test. Grain refinement in ASB was explained by rotation dynamic recrystallization. The maximum shear strain and the range of shear strain rate in ASB at the condition of v = 10 m/s and t1 = 100 μm were approximately 17 and 6.44 × 106 s−1–8.5 × 106 s−1, respectively. Severe plastic deformation was observed by the dimples at ductile fracture surface along ASB. Mechanism of parabolic and ellipsoid dimples caused by shear and tensile stresses was explained for HSC of Ti-6Al-4V alloy. Additionally, the micro-hardness of machined subsurface and the ASB (ex situ parameter) exhibits a relationship with specific energy (in situ parameter), which can provide an effective way to control the formation of ASB and surface integrity by the control of in situ parameters in HSC and u-HSC conditions.

Fragmented chip formation mechanism in high-speed cutting from the perspective of stress wave effect

In this study, fragmented chip formation mechanism in high speed cutting (HSC) process is explored by using continuum-based discrete element method (DEM) based on the stress wave theory. The continuum-based DEM model established with Godunov frame is suitable for capturing multiple cracks propagation under high-speed impact. The chip forming mechanism based on stress wave theory is quantitatively analysed by DEM simulations against experimental data, which shows that the unloading wave reflected by the free surface of chips under high-speed conditions has a fundamental influence on chip formation.

Preload Control of Spindle Bearings by Means of Shape Memory Alloys

Commercial, motor-driven spindles for applications in machine tools are generally developed for specific machining operations. Spindles can be distinguished between spindles for HPC (High Performance Cutting) and spindles for HSC (High Speed Cutting). HPC and HSC require opposing specifications concerning motor configuration and the preload of the spindle bearings. To realize a universal machine tool spindle, changeable motor configuration and preload of the spindle bearings are necessary. In this paper, a new approach for an adaptive preload element is presented to control the preload of a spindle bearing arrangement. The adaptive preload element consists of actuators based on shape memory alloys in combination with Peltier elements. By controlling the current through the Peltier elements the temperature of shape memory alloys bending springs is controlled. Thus, the preload force of the bending springs can be variated. Experimental tests reveal the properties of the preload element and its suitability for preload modification. Within these tests, the adaptive preload element enables a preload modification of about 850 N.

Pre-Machining of Rolled Plates as an Element of Minimising the Post-Machining Deformations.

The paper presents the influence of the milling strategy, the relation between the cutting tool feed direction and the rolling direction, as well as the pre-machining consisting of the removal of the textured surface layer of rolled plates in the rolling process on the thin-walled elements deformations made of the EN AW-2024 T351 wrought aluminium alloy, after milling. The research used strategies such as: high-performance cutting (HPC), high-speed cutting (HSC) and conventional milling (CM), as well as their combinations. Another tested variable was the relation between the tool feed direction and the rolling direction. In addition, the tests were carried out in the following versions: leaving the textured surface layer created after plastic working and with its removal with technological parameters corresponding to HSC and CM. Based on the obtained results, it was found that the post-machining deformation of thin-walled elements can be minimised owing to the use of a selected milling strategy and its combination with pre-machining (or lack thereof). It was also observed that larger deformations were obtained for samples after milling in the direction perpendicular to the rolling direction.

WR-3 Band Waveguide Filter Tolerance Analysis and Surface Metallization Comparison

In this paper, a fifth-order WR-3 band waveguide filter with two transmission zeros (TZs) is presented. The design process is described and manufacturing issues are addressed. The filter is designed to fulfill a center frequency of 237.9 GHz and a fractional bandwidth of 2.64%. Three identical filters are manufactured with the classical computerized numerical control (CNC) milling technique in order to obtain information about the manufacturing repeatability for filter structures in the WR-3 band. The comparison shows that even in very high frequency regions a good repeatability can be achieved, if modern high-speed cutting (HSC) CNC milling machines are used. A comprehensive tolerance analysis is accomplished to classify the obtained results. The filters were manufactured from brass to ensure a meaningful comparability and due to the good machining qualities in CNC machines. In order to reduce the losses, the filters are afterwards sputtered with different materials (gold, silver, copper) to evaluate the effect on the insertion loss at very high frequencies. In comparison with the literature, it is shown that even narrow-band filters, which show a high sensitivity to machining tolerances, can be manufactured with high reliability and manufacturing repeatability in modern CNC milling machines. One of the measured filters shows a return loss higher than 20 dB over the whole passband.

Characters of Deformation and Surface Quality and Cutter Wearing at High-Speed Cutting

In this paper, the impact of cutting speed and feed amount on cutting deformation and surface quality and cutter wear have been studied by the test of high manganese steel cutting with metal ceramic tool at high speed. The results show that it is feasible by cutting high manganese steel with cermet tool at high-speed cutting (HSC). Chip changes into succession segment from band in macrostate. Sawteeth can be seen on the top surface of chip while high temperature feature in burning color and cold welding form appear on the bottom of the chip. The model of surface roughness built can be used to predict surface quality at HSC, and provided cutting optimized parameters scheme. Further research indicates that high-speed cutting has its special deformation mechanism and plastic chips exhibit hot brittleness which provides a favorable condition for solving the chip breaking problem in the cutting of high manganese steel.

Synergistic approaches to ultra-precision high performance cutting

Diamond milling allows for the flexible production of optical and high precision parts, but suffers from poor setup and production speeds. This paper presents recent advances that aim towards achieving high performance (HPC) and high speed cutting (HSC) in ultra-precision machining. After a short introduction, the benefits of high speed cutting for both metals and brittle-hard materials are shown. Thereafter, novel mechatronic devices are presented that enable an automated balancing of the applied air bearing spindles and the application of multiple diamond tools on one tool holder and by thus, contribute to HPC. These developments are supplemented by a novel linear guiding system based on electromagnatic levitation that, along with a dedicated model-based control system, enables fast and precise movements of the machine tool. After presenting the recent developments in detail, their synergistic performance is assessed and an outlook to future developments is given.

On the precipitation behaviour of 7055 aluminium alloy during high-speed cutting

ABSTRACTThe following paper examined changes in the microstructure of 7055 aluminium alloy before and after high-speed cutting (HSC) were examined, for various (T6, T7, and T84) heat treatment conditions. In the T6 state, the results demonstrated that the number of η″ particles gradually reduced and there was pinning in the η″ particles. After both the T7 and T84 heat treatments, a dislocation was observed in the microstructure by transmission electron microscopy. Grain boundaries in the T6 state were continuous with no obvious non-precipitate zone before HSC. The grain boundary width in the T7 state before HSC was double the T6 value. The grain boundary width for the T84 state alloy was similar to that in the T7 state, but less clearly defined.This is part of a thematic issue on Small Scale Mechanics - EUROMAT.

Influence of pre-machining on post-machining deformation of thin-walled elements made of aluminium alloy EN AW-2024

The paper presents analysis of influence of pre-machining, consisting of removing the textured surface layer of the semi-finished product formed after plastic working, on deformation of thin-walled elements made of EN AW-2024 alloy after milling. The textured layer was removed from surface opposite to the machined surface. During tests, the influence on thin-walled elements deformation of the following machining strategies was analysed: High Speed Cutting (HSC), High Performance Cutting (HPC), and hybrid strategies HPC + HSC, HPC + CM, and HPC + CM (CM – Conventional Machining). On the basis of received results it was determined that residual stresses stored in subsurface, rolled, and unmachined surface layer have significant influence on value and character of deformations of thin-walled elements. Removing the textured surface layer formed after rolling changes character and value of the deformations of thin-walled elements. The largest difference between samples with initially removed textured layer and samples without such machining was determined for HPC + CM milling strategy. For this strategy, deformations without pre-machining were much larger than in the case of samples with removed textured surface layer.