Hard Milling Research Articles

Energy consumption and process sustainability of hard milling with tool wear progression

Tool wear progression is inevitable in precision cutting. However, the effect of tool wear on energy consumption at machine, spindle, and process levels is yet to understand. In this study, specific energy in dry milling of AISI H13 was studied at the machine, spindle, and process levels. The effect of process parameters and tool wear progression on energy consumption at each level was investigated. The emissions and environmental impact induced by the machine tool’s energy consumption and the cutting tool embodied energy were investigated. The results indicated that tool wear progression only has a predominant influence on energy consumption at the process level but not the machine and spindle levels. However, the cutting tool embodied energy had a significant effect on total specific energy, process emissions, and environmental impact in hard milling. The predictive models have been developed to quantify the relationships between material removal rate and specific energy, emissions, and environmental impact.

Non-Destructive Analysis of Surfaces after Hard Milling Based on Barkhausen Noise Technique

This paper deals with the non-destructive evaluation of surface made of hardened roll bearing steel after hard milling via Barkhausen noise technique. The paper discusses magnetic anisotropy linked with the structure transformations with regard to variable flank wear of cutting tool. Effective value of Barkhausen noise (BN) and Peak Position derived from the raw BN signal as well as BN envelopes are compared with metallographic observations and theoretical background about magnetic domains reconfiguration when the near surface undergoes severe plastic deformation at elevated temperatures.

Wear of a high cBN content PCBN cutting tool during hard milling of powder metallurgy cold work tool steels

The wear characteristics of a high cBN content PCBN cutting tool during hard milling of two different hardened cold work tool steels have been evaluated. Post-cutting examination of the worn cutting inserts was performed using high resolution field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy, Auger electron spectroscopy and optical surface profilometry. Also, the machined work material surfaces and collected chips were characterized in order to evaluate the prevailing wear mechanisms.The results show that both flank and crater wear are controlled by continuous wear due to tribochemical reactions, adhesive wear and mild abrasive wear. Besides, the cutting inserts show a tendency to micro-chipping along the cutting edge especially at higher cutting speed. The latter mechanism was also found to be dependent on type of work material. High lateral resolution Auger electron spectroscopy of the crater region shows that the worn surface is covered by a thin SixOy rich tribofilm with a thickness of 50–500nm, the tribofilm being thicker on the binder phase regions. Also, the Co-rich regions of the binder phase seem to be more tribochemically affected by the prevailing contact conditions as compared with the W-rich regions of the binder phase and the cBN phase.

Computer Aided Design and Manufacturing Evaluation of Milling Cutter when High Speed Machining of Hardened Steels

This paper presents the influence of CAD modelling and CAM simulation advanced techniques for hard milling technology. The main aim of simulations is the ability and importance to improve and optimize hard milling process even before the real production of its own products, because their manufacturing process is rather expensive. The reached results present us roughing and finishing process of hard milling and milling strategy or generation of tool-paths in CATIA V5. All simulations of milling experiments show that the proposed clear-up tool path works well in the real cutting process and can improve the machining efficiency of the machining process. At the same time, the manufacturing must have the advanced process equipment and method due to the requirements of the design performance and machining efficiency. Finally, hard milling simulations in CAD/CAM system CATIA V5 were performed in order to determine and evaluation of suitability of the proposed shapes of the hard milling product.

Energy Consumption Characteristics in Finish Hard Milling of Tool Steels

Energy consumption is a serious concern for manufacturing industry because it not only consumes substantial amounts of energy but also produces huge amount of greenhouse CO2 emissions. Previous research has focused on the relationship between energy consumption and process conditions at the machine tool and spindle levels. However, little has been done to investigate the energy consumption in actual material removal at the process level. In this study, power profile and energy consumption at the machine tool, spindle, and process levels were characterized in hard milling. A new concept at the process level, net cutting specific energy, was defined to investigate the energy consumed by actual material removal. The relationship between cutting conditions and energy consumption at each level was studied. The results indicate that net cutting specific energy may not be predicted by the traditional model.

Monitoring of Hard Milled Surfaces via Barkhausen Noise Technique

This paper deals with the non-destructive evaluation of surface made of hardened roll bearing steel after hard milling via Barkhausen noise technique. The paper discusses magnetic anisotropy linked with the structure transformations with regard to variable flank wear of cutting tool. Effective value of Barkhausen noise (BN) and Peak Position derived from the raw BN signal as well as BN envelopes are compared with metallographic observations and theoretical background about magnetic domains reconfiguration when the near surface undergoes severe plastic deformation at elevated temperatures.

Development of cutting edge geometries for hard milling operations

Milling of hardened steels is a challenging task for mould and die manufacturing due to the high material strength. One major drawback is the tool wear, which is a result of the high thermo-mechanical stress on the tool. The wear rate can generally be influenced by the tool geometry, coatings and substrates. A further approach is to modify the flank face of the tool, which leads to geometrical limitation of the flank wear. The challenge of this approach is to design flank face modifications, which offer process reliability and increased performance. Against this backdrop a finite element simulation has been constructed to analyze tool stresses. Therefore, different material and friction models were investigated. Based on this simulation a regression model has been developed. Due to the regression model the flank face modifications have been designed and manufactured by laser machining. In cutting tests the potential of the flank face modifications compared to conventional hard milling tools was investigated. The flank face modifications enable the increase of tool life time and the production of workpieces with reduced tensile residual stresses.

The Effect of Machining Parameters on Surface Integrity when Milling Hardened Steel

This study discussed about the influence of the cutting speed and radial depth of cut on surface integrity (microhardness and work-hardening) when performing hard milling of AISI D2 workpiece. By using PVD-TiAlN, nine experimental trials were performed at various cutting speeds of 80, 100 and 120 m/min and various radial depth of cut of 3, 4 and 5 mm as feed and depth of cut remain constant at 0.05 mm/tooth and 0.05 mm. From the result, due to high cutting temperature generated, the cutting speed adversely affects the microhardness value of the subsurface layer. At higher cutting speed of 120 m/min higher hardness values were obtained when compared with lower cutting speed of 80 m/min. As for the effect of the radial depth of cut it is clear that it influences the microhardness beneath the surface. Higher microhardness recorded from the radial depth of cut increment associated with high cutting temperature generated during machining.

Machinability Aspects Investigations in Hard Milling of AISI W1 Hardened Tool Steel

The performance of a high speed milling process of hardened tool steel depends on various machining conditions which affect the surface quality achieved on the component, the cutting force involved, the mechanism of chip formation, etc. The paper propose is to experimental investigate the cutting forces involved in the machining of a difficult-to-cut material, AISI W1 steel of different hardness states.

Electrochemical characteristics of white layer generated by hard milling AISI H13 steel

In the field of hard cutting, researches on white layer have become more extensive and in-depth in recent years, because white layer has an important influence on the performances and life of components. Nevertheless, properties of white layer, especially its corrosion properties, have not been well understood or clearly defined. In this study, specimens with different subsurface microstructures (no obvious change, dark layer, and white layer) were produced in the process of tool wear to analyze their electrochemical properties using electrochemical methods. It was found that electrochemical properties were distinct between specimens with and without white layer. A specimen with white layer had obviously lower electrochemical impedance and more anodic steady-state open-circuit potential than that without white layer in 3.5 wt.% NaCl solution. That is to say, specimens with white layer were prone to corrosion in this solution. The results also manifest that electrochemical method can be a reliable, convenient, and nearly nondestructive method to detect white layer.

Laboratory Experiment of New Cutting Materials in Milling Processes

The development of manufacturing technology is mostly given by economics, environmental trends and the development of cutting materials and machine tools. Manufacturing is a significant part of the worldwide economy. Machining (material removal processes) represents major part of production costs. This paper yield inquiries into the hard and precise milling with a focus on force effects in experimental machining, tool wear and final surface qualities (roughness, micro hardness). The precision machining of hardened steel differs from conventional machining in terms of the hardness of the workpiece materials and the cutting tool materials that are required. Hard materials are characterized by high hardness (> 45 HRC) and abrasiveness. Machining processes require cutting tools of much higher hardness and also higher resistance of the abrasive wear. Recently developed cubic boron nitride (CBN) and coated sintered carbides cutting tools are considered to have the ability of cutting such as steel. CBN cutting tools show good performance during machining of the hardened steel because of their hot hardness and good fracture toughness.

Modeling and Virtual Simulation of Hard Surface Milling and Forming Process Using Advanced CAE Systems

This paper presents the influence of modeling and simulation techniques for hard milling and forming. The aim of these simulations is the ability to optimize the manufacturing technologies even before the real production of its own tools, because their manufacturing process is very difficult in terms of production time, materials and other costs. The simulated results visualize roughing and finishing process of milling and generate tool-paths in CATIA V5. Simulation results of forming realized in PAM-Stamp 2G using a 3D model of the punch and the blank confirm the suitability of the proposed design of the forming tool. Finally, hard milling and forming simulations in CAE systems CATIA V5 and PAM-Stamp 2G were performed in order to determine and evaluation of suitability of the proposed shapes of the forming tool.

Eco-friendly face milling of titanium alloy

Recently, a use of difficult to cut materials including titanium alloy has been substantially increasing in aerospace and automotive industries. Eco-friendly machining technology, which eliminates or minimizes cutting fluids in machining fields, has been emerged in compliance with green manufacturing trend. In this regard, machining technologies, such as hard milling, laser assisted machining (LAM), and enhanced lubrication/cooling method, have been adapted by the industries. Among the technologies, cryogenic machining has been considered for a viable solution for the materials without any environmental problems. LAM and minimum quantity lubrication (MQL) can be useful method to cut these materials with an appropriate use. In this study, machining performance of ecofriendly machining techniques was compared experimentally for the titanium alloy (Ti-6Al-4V). The machining performance was evaluated in terms of tool wear and cutting force. From experimental results, coated cutting tool with flood cooling condition was not recommended in titanium machining. The cryogenic, MQL, LAM showed outstanding machining performance than dry and flood cooling. Especially MQL machining was superior with relatively simple system setup. In addition, lubrication and cooling mechanism by combination of MQL and cryogenic reduced cutting force and tool wear. For energy consumption, MQL and cryogenic methods can be a sustainable solution.

Modeling and Multi-response Optimization of Hard Milling Process using Desirability Function Approach

The characteristic features of hard milling are variable chip thickness and intermittent cutting. Such tendency rapidly increases the tool wear and reduces the metal removal rate against the cutting temperature results poor surface finish. Therefore, the objective of this present study was to present the mathematical models for modeling and analysis on the effects of process parameters, including the feed per tooth, radial depth of cut, axial depth of cut and cutting speed on cutting temperature, tool wear and metal removal rate in hard milling of 100MnCrW4 (Type O1) tool steel using (TiN+TiAlN) coated carbide inserts. A central composite rotatable design with four factors and five levels was chosen to minimize the number of experimental conditions. Further, the reduced developed models were used for multiple-response optimization by desirability function approach in order to determine the optimum cutting parameters. These optimized machining parameters are validated experimentally and the experimental and predicted values were in a good agreement with small consistent error.

Fuzzy and Regression Modelling of Hard Milling Process

The present study highlights the application of box-behnken design coupled with fuzzy and regression modeling approach for making expert system in hard milling process to improve the process performance with systematic reduction of production cost. The important input fields of work piece hardness, nose radius, feed per tooth, radial depth of cut and axial depth cut were considered. The cutting forces, work surface temperature and sound pressure level were identified as key index of machining outputs. The results indicate that the fuzzy logic and regression modeling technique can be effectively used for the prediction of desired responses with less average error variation. Predicted results were verified by experiments and shown the good potential characteristics of the developed system for automated machining environment.

The Effect of Hard Milling on Surface Finish of Medium Carbon Steel

This research was to study the effect of hard milling on the surface finish of medium carbon steel. The sample specimen was selected to AISI 1050. The vertical milling process was chosen to experiment, which used insert PVD carbide tool. The experiment was applied on factors: cutting speed, depth of cut and feed rate and they were consisted of three levels. The factorial design on 33 experiments was applied. The surface roughness average (Ra) was indicated for surface finish. The experiment results were analyzed by ANOVA. The main factors and factors interaction that affected to surface finish were investigated. Effect of cutting speed, feed rate and depth of cut on surface finish of harden medium carbon steel was discussed.

Structure and Magnetic Properties of NdFeB Powder Prepared by Hydrogen Decrepitation and High-Energy Ball Milling

An ingot of NdFeB alloy was disintegrated by hydrogen decrepitation (HD). High-energy ball milling technique with hard metal milling elements and balls was employed to refine HD powders down to particle size optimum for magnet processing. The experiments were performed according to experimental plan to optimize the milling parameters regarding particle size, contamination and magnetic properties of the powder. The effect of milling time, speed of rotation, ball-powder weight ratio (BPR) and amount of wet agent was investigated. The highest influence was shown to be from attritor speed of rotation, ball-to powder ratio and combined effect of milling wet agent and rotating speed. Unified parameter of estimated number of total ball impacts was calculated, which allows predicting the final particle size of the powder at different milling speeds. Magnetic moments of powders were measured.

Barkhausen Noise Emission of Surfaces Produced by Hard Milling Process

This paper deals with influence of tool wear on surface integrity after hard turning expressed mainly through the Barkhausen noise responses. Grinding operations can be sometimes replaced by hard machining (hard turning and milling). Chip separation in hard turning differs from mechanism of chip separation during grinding. For this reason surface integrity expressed in variable terms differs. Surface integrity can be expressed in such term as surface roughness, shape deviations as well as characteristics such as residual stresses, structure transformations, and microhardness alteration. Being so, it can be beneficial to apply the suitable nondestructive surface testing techniques to obtain information about surface integrity expressed in complexity of this term. Nowadays, Barkhausen noise technique is widely used in a variety of industrial applications. This technique is sensitive to stress state as well as microstructure features. For this reason, Barkhausen noise emission is used in this study to reveal magnetic and stress anisotropy developed in a certain stage of tool wear. The paper also discusses very high BN responses associated with the specific aspects of produced surfaces.

Growth Environment Influences Grain Protein Composition and Dough Functional Properties in Three Australian Wheat Cultivars

ABSTRACTThe objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial Australian Hard milling wheat cultivars was analyzed from four growth locations in 2008 and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin‐to‐gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations, and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax, and extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein fractions was mostly owing to genotype.

Multi-response optimisation of hard milling process parameters based on integrated Box-Behnken design with desirability function approach

The mathematical modelling and multi-response optimisation of cutting forces, work piece surface temperature and sound pressure level during hard milling of 100MnCrW4 tool steel using coated (TiN+TiAlN) carbide inserts were presented in this paper based on integrated Box-Behnken design with desirability function. The parameters that influence hard milling such as work material hardness, nose radius, feed per tooth, radial and axial depth of cut were discussed. Various test results and reliability of developed quadratic models were verified using analysis of variance (ANOVA) and they were found to be highly close to experiment and significant. The optimised results were validated experimentally and less than 2% error variation was found. Work material hardness, feed per tooth and nose radius have a significant influence on all response variables. Abrasion marks, coating peel off on the tool surface and saw tooth chips were characterised through SEM analysis.