High-speed Face Milling Research Articles

Surface roughness and chip formation in high-speed face milling AISI H13 steel

Many previous researches on high-speed machining have been conducted to pursue high machining efficiency and accuracy. In the present study, the characteristics of cutting forces, surface roughness, and chip formation obtained in high and ultra high-speed face milling of AISI H13 steel (46–47 HRC) are experimentally investigated. It is found that the ultra high cutting speed of 1,400 m/min can be considered as a critical value, at which relatively low mechanical load, good surface finish, and high machining efficiency are expected to arise at the same time. When the cutting speed adopted is below 1,400 m/min, the contribution order of the cutting parameters for surface roughness Ra is axial depth of cut, cutting speed, and feed rate. As the cutting speed surpasses 1,400 m/min, the order is cutting speed, feed rate, and axial depth of cut. The developing trend of the surface roughness obtained at different cutting speeds can be estimated by means of observing the variation of the chip shape and chip color. It is concluded that when low feed rate, low axial depth of cut, and cutting speed below 1,400 m/min are adopted, surface roughness Ra of the whole machined surface remains below 0.3 μm, while cutting speed above 1,400 m/min should be avoided even if the feed rate and axial depth of cut are low.

Surface integrity of biodegradable orthopedic magnesium–calcium alloy by high-speed dry face milling

Biodegradable magnesium–calcium (MgCa) implants have the ability to gradually dissolve and be absorbed in human body after implantation. Since the implant surface is in direct interaction with body fluids, surface integrity of MgCa implants are key factors influencing degradation rate of the biodegradable implants. Machining is often very necessary to make geometric features of implants. The effects of process parameters in dry high-speed face milling of MgCa0.8 (wt%) alloy on surface integrity characteristics, i.e. surface topography, surface roughness, microstructure, microhardness, and residual stresses, are investigated in this study. Polycrystalline diamond inserts are used to avoid material adhesion in milling MgCa alloy. High cutting speeds of up to 2,800 m/min and a broad range of feed and depth-of-cut values are selected to cover the regimes of finish and rough cutting. Average roughness value of 0.4 μm and shallow strain hardened depths are achieved. Little change of grain size can be observed in the near surface even for very slow feed value of 0.05 mm/rev. The surface residual stresses are measured to be highly compressive.

Spectra Analysis of Face Milling Cutter Aeroacoustic Noise

The noise produced by high speed face milling is detrimental to the machine operators.The major source of aeroacoustic noise is primarily dipole in nature.A noise prediction model based on Ffowcs Williams-Hawkings equation is used to predict aeroacoustic noise in face milling cutters.Numerical simulation of air flow in the milling cutter system is performed by using CFD method.The predicted sound pressure level based on mathematical model is 4.0 dB lower than measurement results at 9 000 rpm.And the error is about 7%.The chip flute region and insert rake face are found to be important factors in determining aeroacoustic noise in rotating face milling cutter.The directivity of aeroacoustic noise is verified in the axial direction.The broadband noise spreads over a broad range of frequencies and contributes significantly to overall noise,but the discrete noise at the rotational frequency is significantly higher.It can provide theory for low noise design and prediction of high speed face milling cutter.

Effect of Cutting Parameters on Ignition of AM50A Mg Alloy during Face Milling

The ignition of magnesium alloy chips is an important problem during dry machining. In this paper, the influence of cutting speed, feed rate, and depth of cut on ignition of AM50A magnesium alloy during high-speed face milling was investigated. It was found that ignition could easily be caused under some cutting speed and feed rate when the depth of cut was fixed and ignition was rarely observed when the depth of cut was 80 µm. Moreover, the relationship between morphology of chip and frequency of ignition was explored. We found that intertwined chips easily produced ring of fire.

Simulation and analysis of aerodynamics for high speed face milling cutters

In high speed face milling, noise can be broadly categorized as idling noise and cutting noise. Idling noise mainly consists of aerodynamic noise. A mathematical model is developed based on the Ffowcs Williams-Hawkings Equation. The noise predicted with the mathematical model compares well with the experimental observations. The characteristics of aerodynamic noise with the different model parameters (number of teeth, tooth spacing) and locations of observation points are investigated. The directivity of noise is found and the peak value of sound power can be moved from the rotating frequency to higher frequency. This investigation can provide theoretical foundation for the design of face milling cutters with low noise.

The Improvement of Machinability of Gray Cast Iron Using Nonmetallic Inclusions in High Speed Cutting (2nd Report)

This paper deals with machinability in high-speed face milling of gray cast iron to which small quantities of Al and Mg were added. The machinability of Al-Mg-added gray cast iron was evaluated in face milling with cermet inserts at cutting speed from 100 to 1000 m/min in comparison with conventional gray cast iron and Al-added gray cast iron. In the face milling of conventional gray cast iron and Al-added gray cast iron, the wear increased significantly as the cutting speed increased. The wear pattern of tools in the milling of these irons were almost the same, and the thermal cracks similarly occurred in both cases. On the other hand, the addition of both Al and Mg has drastically decreased the wear rate and the wear hardly progressed even in prolonged cutting length after initial wear. The amount of the adhesion on tool faces increased as the cutting speed increased. The adhered layer mainly consisted of the elements added to the work material. As this result, the increase cutting speed resulted in the thick adhered layer and the reduction of tool wear. Furthermore, the small addition of Al and Mg prevented the thermal cracks in the face milling of the gray cast iron.

Research on Dynamic Cutting Performance of High Speed Face Milling Cutter

According to the characteristics of high speed face milling process, the models of dynamic cutting forces and frequency spectrum were established. By means of frequency spectrum analysis for dynamic cutting forces of high speed face milling cutter, the law of influence of cutter’s structure and parameters on dynamic cutting performance of cutter was acquired, high speed face milling cutter for machining aluminum alloy was developed, and evaluation for dynamic cutting performance of cutter was processed based on experiment. The results indicate that more teeth of cutter and greater cutting contact angle can make the energy more dispersible, higher cutting speed and greater rake of cutter can depress dynamic cutting forces, and improve effectively dynamic cutting performance of cutter. High speed face milling cutter with five teeth takes on better dynamic high speed cutting performance for machining aluminum alloy, as cutting contact angle exceeds ninety degrees but it is less than one hundred eighty degrees, and cutting speed exceeds 2260m/min.

High-speed Milling of Polybenzimidazole Using the Fine Crystalline Diamond Coated Tool

This paper deals with an experimental investigation of high-speed face milling of polybenzimidazole (P.B.I.) using a fine crystalline diamond coated tool which has reshaped sharp edge. Especially, the effects of a sharpened cutting edge and an increasing cutting speed on machined surface are investigated. It has been confirmed that the edge of a diamond coated tool could be reshaped in a sharpened form by a heat chemical polishing. The diamond coated tool which has a reshaped edge is superior to a normal coated diamond tool in machined surface with little damage by cracks. Moreover, this tool when it has a rake angle of 10 degree is effective in controlling cracks. Furthermore, as a result of the investigating the effects of different speeds on damages to a machined surface, it is clear that the best machined surface with very little damage is obtained at a cutting speed of 40.0 m/s. At less than 40.0m/s, the damage was determined by mainly micro-crack and, on the other hand, tear damage to the machined surface was observed at speeds beyond 40.0m/s. The viscoelastic behavior of P.B.I. material accompanying change of cutting temperature had influenced these kinds of damages, and it showed clearly for the temperature of 650K which begins to produce the viscosity to be equivalent to cutting speed 40 m/s. Also, a drop in the bending strength after cutting can be limited to 2%.

Research on High Speed Face Milling Cutter Based on the Model of Stress Field

According to the characteristics of high speed face milling process, the models of the stress field for high speed face milling cutter with two sorts of structure are proposed and established. By means of the finite element analysis of the stress field for high speed face milling cutters, the law of influence of the cutter’s structure, the cutter’s subassemblies and the fixing rake of inserts on the stress field of cutter is acquired under the action of high rotate speed. In this foundation, the model reconstruction and the stress field analysis of the cutter are completed, and the model of evaluation for dynamic cutting performance of high speed face milling cutter is established. The results of high speed face milling experiment and frequency spectrum analysis of dynamic cutting force of the cutter indicate that high speed face milling cutter with the fixing rake of zero degree and less subassemblies takes on better dynamic high speed cutting performance.

Performance of single Si 3N 4 and mixed Si 3N 4+PCBN wiper cutting tools applied to high speed face milling of cast iron

In this work two face milling cutter systems were used in high speed cutting of gray cast iron under cutting condition encountered in the shop floor. The first system, called ‘A’, has 24 Si 3N 4 ceramic inserts all with square wiper edges. The second system, called ‘B’, is a mixed tool material system, having 24 wiper inserts, 20 of them are Si 3N 4 intercalated by four PCBN inserts. Cutting speed ( v c), depth of cut (doc) and feed rate per tooth ( f z) were kept constant. Surface roughness ( R a and R t) and waviness ( W t), tool life (based on flank wear, VB Bmax) and burr formation (length of the burr, h) were the parameters considered to compare the two systems. System ‘B’ presented better performance according to all parameters, although only end of life criterion based on R t parameter has been reached.

The Impact of Tool Materials and Cutting Parameters on Surface Roughness in High-Speed Face-Milling

The Impact of Tool Materials and Cutting Parameters on Surface Roughness in High-Speed Face-Milling

High Speed Face Milling of a Aluminium Silicon Alloy Casting

High speed machining of aluminium silicon alloy castings has gained significant interest from automotive industry involved in the development of the new generation of lightweight vehicles. This paper investigates the influence of workpiece microstructure, namely the secondary dendritic arm spacing (SDAS), tool material and geometry on tool wear mechanisms, cutting forces and surface integrity when face milling at cutting speeds of 5,000 m min −1. It was found that the SDAS is the parameter with the main influence on tool wear rate; higher SDAS values require polycrystalline diamond (PCD) tooling due to the lower wear rates when compared with carbide tools. Finite Element Analysis (FEA) was employed to study the influence of tool wear on temperature and shear stress distribution in the workpiece material.

複合工作機械によるミルターニング加工に関する研究―切削油剤なしでの高能率丸物加工―

High speed dry turning is one of the most important themes in ecological manufacturing. But in conventional turning style, it is difficult to reduce cutting temperature because the cutting edge is contacted to the work-piece continuously. Then in mill-turning, high speed face milling is applied for machining of cylindrical parts, and it is possible to reduce cutting temperature by using high speed-interrupted-small depth cutting method so as high speed endmilling. In this study, we have made clear the ability of mill-turning, and optimum cutting conditions for tool life. So we developed the prototype cutters for mill-turning, and tested their performance

Wear patterns and mechanisms of cutting tools in high-speed face milling

High-speed machining has received important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due to the high temperature at the tool–workpiece interface. Tool wear impairs the surface finish and hence the tool life is reduced. That is why an important objective of metal cutting research has been the assessment of tool wear patterns and mechanisms. In this paper, the wear performances of PCBN tool, ceramic tool, coated carbide tool and fine-grained carbide tool in high-speed face milling are presented when cutting cast iron, 45# tempered carbon steel and 45# hardened carbon steel. The tool wear patterns were examined through a toolmaker’s microscope. The research results show that the tool wear types differed in various matching of materials between the cutting tool and the workpiece. The dominant wear patterns observed were rake face wear, flank wear, chipping, fracture and breakage. The main wear mechanisms were mechanical friction, adhesion, diffusion and chemical wear promoted by cutting forces and high cutting temperature. Hence, the important considerations of high-speed cutting tool materials are high heat-resistance and wear-resistance, and chemical stability as well as resistance to the failure of coatings. The research results will be of great benefit in the design and the selection of tool materials and in the control of tool wear in high-speed machining processes.

Analysis on high-speed face-milling of 7075-T6 aluminum using carbide and diamond cutters

This research is concerned with the analytical and experimental study on the high-speed face milling of 7075-T6 aluminum alloys with a single insert fly-cutter. The results are analyzed in terms of cutting forces, chip morphology, and surface integrity of the workpiece machined with carbide and diamond inserts. It is shown that a high cutting speed leads to a high chip flow angle, very low thrust forces and a high shear angle, while producing a thinner chip. Chip morphology studies indicate that shear localization can occur at higher feeds even for 7075-T6, which is known to produce continuous chips. The resultant compressive residual stresses are shown for the variation of cutting parameters and cutting tool material. The analysis of the high-speed cutting process mechanics is presented, based on the calculation results using extended oblique machining theory and finite element simulation.

Suppression of tool wear by using an inert gas in face milling

In order to reduce crater wear and thermal cracks of cutting tool in high speed face milling of plain carbon steels, an inert gas, which flowed through a spindle of a milling machine, was used. Nitrogen gas was supplied through spindle to the cutting edge so that the cutting edge would not be oxidized. The effects of the nitrogen gas on the tool failure were influenced by shape of the nozzle and velocity of the gas from the nozzle. Under the good conditions, crater wear of the carbide tool P10 was reduced by 50% compared to cutting in the air.

Ａｌ２Ｏ３‐ＺｒＯ２系セラミック工具による炭素鋼の高速正面フライス切削

High speed face milling for plain carbon steel S 45 C was carried out with ceramic tools. TiC added alumina, and zirconia toughened alumina ceramic tools were mainly used. Among the tested ceramic tools, the zirconia toughened alumina ceramic tool showed the largest crater wear resistance in high speed face milling. However, in turning the same steel, the crater wear resistance of the ceramic tool was almost the same degree as compared to the other ceramic tools. The superior wear resistance of the zirconia toughened alumina ceramic tool is based on its stability for the reaction with Fe0 at high temperature.

Cutting Performance and Wear Characteristics of an Alumina-Zirconia Ceramic Tool in High-speed Face Milling

Summary High speed face milling for plain carbon steel S45C was carried out with ceramic tools. Pure alumina. T/C added alumina, and Zirconia toughened alumina ceramic tools were mainly used. Among the tested ceramic tools, the zirconia toughened alumina ceramic tool! showed the largest crater wear resistance in high speed face billing. However, in turning the same steel, the crater wear resistance of the ceramic tool was almost the same degree as compared to the other ceramic tools. The superior wear resistance of the zirconia toughered alumina ceramic tool is based on its stability for the reaction to Fe0 at high temperature.

Dynamics of High-Speed Milling

This paper is based on previous work of the author and his associates which was published in a series of papers, mainly on those given here as references [2–6], dealing with time domain simulation of chatter in milling, with cutting process damping and with stability lobes. These matters are reevaluated here from the particular point of view of high-speed milling. First, the derivation of limit of stability of chatter in the frequency domain is recapitulated, and lobes of stability explained. These lobes should lead to substantial increases of stability at high speeds of milling. Further, corrections to the results of the simple theory using time domain are presented as they are obtained by time domain simulation which takes into account, in a very realistic way, all the main aspects of milling. It is shown that still, in many instances, high gains of stability are achievable by determining and using a particular spindle speed such that the cutter tooth frequency approaches the frequency of the decisive mode of vibrations as measured on the cutter. The usual modes of vibration of a spindle with a long end mill are discussed, and it is shown how a long end mill stabilizes cutting at medium speeds but becomes a flexible element strongly involved in chatter at higher speeds. In the following section, cutting process damping is discussed which has a very strong stabilizing effect at low speeds but is also partly effective at speeds presently in use. This damping is lost in high-speed milling. Typical cases of high-speed face milling of steel and long end milling of aluminum are discussed and a need of about seven times more stiffness for spindle modes and 14 times more stiffness for the end mill mode derived. The former should be achieved by spindles with larger diameter roller bearings while simultaneously the technology for the design of these spindles running at high speeds must be developed. Present research work shows good promise for this development. For the latter, methods of maximum use of the lobing effect should be developed as well as methods of increasing the damping of the end mill mode.

正面フライス切削時の工具損傷に及ぼす雰囲気の影響(第2報)

From the results of the previous paper, it has been confirmed that the atmosphere is important as well as mechanical or thermal shock in intermittent cutting. In order to clarify the effects of oxygen content in the atmosphere on thermal cracks, high speed face milling tests were carried out in the sealed chamber reported before. The main results obtained were as follows: (1) The thermal cracks on the rake face were suppressed with the decrease of oxygen content in the atmosphere. (2) A logarithmic relation was found between the number of cutting cycles which the thermal crack was observed and the concentration of oxygen in the atmosphere. (3) The effects of the atmosphere on thermal cracks decreased with the increase of cutting speed.