Small Feed Rate Research Articles

Fabrication and characteristics of cube-post microreactors for methanol steam reforming

The lamination-plate structure patterned with microchannels and triangle manifolds regarded as one of the preferred constructions for micro fuel reformers. Learned from the microchannel plate structure, a similar plate structure with cube-post array and triangle manifolds is proposed in this work. A micro-milling process is applied to fabricate the cube posts on the plate surface, and the influences of cutting parameters on the burr formation are analyzed. Experimental results indicate that larger cutting speed, smaller feed rate and cutting depth are in favor of obtaining relatively small burrs. Two plates with different cube-post dimensions and manifold structures are experimentally investigated the performances of methanol steam reforming over the Cu/Zn/Al/Zr catalyst. It indicates that the reactor with small-scale cube posts and acute triangle manifold presents better reforming performances at 260 °C than that of the one with large-scale cube posts and right triangle manifolds. However, their performances are closed to each other at relatively high reaction temperature since the catalyst activity is situated in dominated position at the time.

Predicting the Effects of Cutting Parameters and Tool Geometry on Hard Turning Process Using Finite Element Method

To explore the effects of cutting speed, feed rate and rake angle on chip morphology transition, a thermomechanical coupled orthogonal (2-D) finite element (FE) model is developed, and to determine the effects of tool nose radius and lead angle on hard turning process, an oblique (3-D) FE model is further proposed. Three one-factor simulations are conducted to determine the evolution of chip morphology with feed rate, rake angle, and cutting speed, respectively. The chip morphology evolution from continuous to saw-tooth chip is described by means of the variations of chip dimensional values, saw-tooth chip segmental degree and frequency. The results suggest that chip morphology transits from continuous to saw-tooth chip with increasing feed rate and cutting speed, and changing a tool’s positive rake angle to negative rake angle. There exists a critical cutting speed at which the chip morphology transfers from continuous to saw-tooth chip. The saw-tooth chip segmental frequency decreases as the feed rate and the tool negative rake angle value increases; however, it increases almost linearly with the cutting speed. The larger negative rake angle, the larger feed rate and higher cutting speed dominate saw-tooth chip morphology while positive rake angle, small feed rate and low cutting speed combine to determine continuous chip morphology. The 3-D FE model considers tool nose radii of 0.4 mm and 0.8 mm, respectively, with tool lead angels of 0 deg and 7 deg. The model successfully simulates 3-D saw-tooth chip morphology generated by periodic adiabatic shear and demonstrates the continuous and saw-tooth chip morphology, chip characteristic line and the material flow direction between chip-tool interfaces. The predicted chip morphology, cutting temperature, plastic strain distribution, and cutting forces agree well with the experimental data. The oblique cutting process simulation reveals that a bigger lead angle results in a severer chip deformation, the maximum temperature on the chip-tool interface reaches 1289 deg, close to the measured average temperature of 1100 deg; the predicted average tangential force is 150N, with 7% difference from the experimental data. When the cutting tool nose radius increases to 0.8 mm, the chip’s temperature and strain becomes relatively higher, and average tangential force increases 10N. This paper also discusses reasons for discrepancies between the experimental measured cutting force and that predicted by finite element simulation.

Optimal-Feedrate Interpolation for Machining Parametric Curves

Abstract In high-speed precision machining systems, trajectory requires very small feedrate fluctuation and contour error, which can be achieved with pazametric interpolation. This paper proposes aspeed-controlled interpolation method based on optimal-feedrate algorithm. The real-time interpolation method was taken full its advantages, the chord error and the difference between the orientation of tangent vector of the curve at current point and previous point were repeatedly checked through the whole interpolation process. If either chord error exceeded the prescribed tolerance or sharp corner was detected, the feedrate in the proposed interpolation method was automatically adjusted in order to confine the chord error within the prescribed tolerance. A parametric curve, determined by the non-uniform rational B-spline (NiJRBS), was employed to test the feasibility and precision of the proposed interpolation method.

Feasibility investigations on multi-cutter milling process: A novel fabrication method for microreactors with multiple microchannels

Abstract A novel multi-cutter milling process for multiple parallel microchannels with manifolds is proposed to address the challenge of mass manufacture as required for cost-effective commercial applications. Several slotting cutters are stacked together to form a composite tool for machining microchannels simultaneously. The feasibility of this new fabrication process is experimentally investigated under different machining conditions and reaction characteristics of methanol steam reforming for hydrogen production. The influences of cutting parameters and the composite tool on the microchannel qualities and burr formation are analyzed. Experimental results indicate that larger cutting speed, smaller feed rate and cutting depth are in favor of obtaining relatively good microchannel qualities and small burrs. Of all the cutting parameters considered in these experiments, 94.2 m min −1 cutting speed, 23.5 mm min −1 feed rate and 0.5 mm cutting depth are found to be the optimum value. According to the comparisons of experimental results of multi-cutter milling process and estimated one of other alternative methods, it is found that multi-cutter milling process shows much shorter machining time and higher work removal rate than that of other alternative methods. Reaction characteristics of methanol steam reforming in microchannels also indicate that multi-cutter milling process is probably suitable for a commercial application.

Surface integrity analysis in the super duplex stainless steel ASTM-A890 after machining

The purpose of this paper was to study the main effects of the turning in the superficial integrity of the duplex stainless steel ASTM A890-6A. The tests were conducted on a turning centre with carbide tools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed and cutting fluid utilisation. The answers were analysed: microstructural analysis by optical microscopy and x-ray diffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress by x-ray diffraction technique and the microhardness measurements. The results do not show any changes in the microstructural of the material, even when the greater cutting parameters were used. The smaller feed rate (0.1 mm/v), smaller cutting speed (110 m/min) and the greater cutting depth (0.5 mm) provided the smaller values for the tensile residual stress, the smaller surface roughness and the greater microhardness. [Received on 3 April 2006; Accepted on 21 February 2007]

NURBS curve interpolation algorithm adaptive to the machine's kinetic characteristics

NURBS curve interpolation algorithm for high speed NC machining, which can fit diverse machine tool's kinetic characteristics and has the function of look-ahead control, is proposed. By integrating curve geometry features and machine tool dynamic characteristics, the look-ahead control information can be obtained. The interpolating process can be divided into two phases: getting the look-ahead control information including the particular points in the curve and their suitable max feed rate, modifying the real-time interpolation feed rate all the time according to the look-ahead control information. This algorithm has advantages over others on three aspects: wide adaptation to machine tool, high profile precision, and small feed rate vibration.

THE EFFECT OF THE CUTTING FLUID ON SURFACE ROUGHNESS IN BORING OF LOW CARBON STEEL–TECHNICAL COMMUNICATION

In spite of their environmental and human health problems, the cutting fluids still have been used widely in industry due to cutting fluid application can increase cutting performance in metal cutting. In this article, the effect of the cutting fluid on surface roughness in boring of AISI 1030 low carbon steel was investigated depending on BUE and chip formations and other cutting parameters, such as cutting speed, feed rate and tool nose radius. In most of boring experiments, the wet cutting did not show more preferable results than dry cutting. However, cutting fluid application with big nose radius and small feed rate improved the surface roughness up to 80%. This progress was attributed to a favorable chip formation as much as effective cooling.

Effect of Different Coating Materials on Cutting Performance in High-Speed Machining of Mold Steels

Different materials coated on milling tools (tungsten carbide) such as TiCN, TiAlN, TiN and DLC are integrated in this study for the analysis of cutting performance such as tool wear, surface roughness and noise induced in high-speed machining of mold steels such as NAK80 and SKD61 under different combinations of cutting conditions. The study attempts to find out the advantages and adaptabilities in various coating materials being suitable for which cutting circumferences with specific performance request. High-speed milling experiments of NAK80 and SKD61 mold steels with four materials coating tools were carried out in the laboratory. The tool wear was measured through the toolmaker’s microscope and the roughness of the machined surface was measured by the roughness measuring instruments after each surface layer was removed from the workpiece in the experiment. Besides, the noise-mediator was used to detect cutting noise during each surface layer workpiece removing of high-speed milling process, and the curl chips removed from the workpiece were also collected for the result verifications. Good surface quality and small amount of tool wear can be achieved under the cutting conditions of high-speed revolutions, small feed rate and small depth of cut for four materials coating tools. From the observations of the annealing temperature from the removed chips and the analysis of the cutting noise levels, TiAlN material coating tool has the better tool life and it is suitable for rougher high-speed machining, while DLC material coating tool only has a good surface roughness in shallow cut and hence it is not suitable for high-speed machining of mold steel with excellent cutting performance request.

123 ボールエンドミルによる多軸制御切削加工における被削物除去状態の幾何的解析(OS-1 切削加工)

This study deals with geometric analysis of workpiece removal in multi axis control machining with ball end mill. In order to predict both surface roughness and accuracy of workpiece shape in finish machining process, it is required to apply a new estimation method which can cope with quite small feed rate in cutting conditions. So, in this study, we introduce the developed removal model of workpiece, which is designed to consider influences of cutting edge roundness. And, we analyze both removal depth on each cutter mark and cutting error on workpiece shape, for a case of ball end mill with a throwaway chip. From results, we can find that distribution of removal depth on cutter mark is strongly influenced by tool posture and shape error caused by tool deflection is often bigger than height of cusps.

Finite Element Analysis of Effects of Ball Burnishing Parameters on Residual Stresses

A three-dimensional coupled thermal-mechanical model of ball burnishing process is developed using commercial explicit finite element code MSC. Marc. The workpiece is modeled as being elastic-plastic, while its flowstress is taken as a function of strain, strain-rate, and temperature. Temperature-dependent material properties are also considered in this analysis. The burnishing ball is considered as rigid and only heat transfer analysis is carried out for it. In the zone of the workpiece and tool contact, the Coulomb friction is taken into account. Effects of ball burnishing parameters (burnishing force, feed rate, speed, ball diameter and number of tool passes) on residual stresses are analyzed. The results show that burnishing force, ball diameter, number of passes and burnishing feed have the most significant effect on the residual stresses. However, burnishing speed seems to just produce little effect on those. Larger burnishing force, larger number of passes, smaller ball diameter and small feed rate seem to be more effective in increasing in the maximum compressive residual stress and the depth of the layer at the compressive stress state.

425 Cutting Force Prediction on the Basis of Actual Depth of Cut in End milling

This paper deals with an accurate cutting force prediction method of end milling. Cutting condition with small feed rate is often adopted in finish machining. In such conditions, the depth of cut in the radial direction of end mill cannot be estimated accurately by conventional cutting force prediction methods. When the depth of cut is quite small, the error on workpiece surface and the displacement of cutting edge are regarded as dominant factors to determine cutting force. Then, two estimation models about tool deflection and elastic recovery named "Actual depth of cut" are introduced in order to predict the depth of cut. In order to evaluate the effectiveness of introduced models, a prototype simulation system is developed and an experimental cutting is conducted. The measured cutting force in the experiment shows a good qualitative agreement with the predicted force.

Effect of process parameters on formability in incremental forming of sheet metal

The formability of sheet metal appears better in incremental forming than in conventional forming. In this study, the effect of process parameters—tool type, tool size, feed rate, friction at the interface between tool and sheet, plane-anisotropy of sheet—on the formability was investigated by experiments and FEM analyses. It was found that the formability is improved when a ball tool of a particular size is used with a small feed rate and a little friction. Due to the plane-anisotropy, the formability differs according to the direction of the tool movement.

The machinability and tribological characteristics of aluminum alloys with improved elevated temperature properties using rapidly solidified powder

In this investigation the tribological characteristics of rapidly solidified Al–8Fe–4Ce with improved elevated temperature properties were studied. Such characteristics were compared with cast aluminum–silicon alloy and cast zinc–aluminum alloy. These materials included Al–13Si, Zn–35Al, Zn–35Al–Si, Zn–35Al–3.75Si and Zn–35Al–5.8Si. The wear rates of all materials were tested on a crossed-cylinders wear machine against 440C stainless steel counterface lapped by random abrasion using diamond paste to the desired average surface roughness. The effects of sliding distance on both the worn volume and the coefficient of friction were examined. The aluminum–iron–cerium alloy (Al–8Fe–4Ce) showed the lowest wear rate. The experiments were then extended on this material to examine the effect of varying the applied load and sliding speed on its wear rate. It was found that increasing the applied load increased the wear rate while it was slightly sensitive to the change in sliding speed. As the wear results showed that the Al–8Fe–4Ce alloy has the lowest wear rates, its machinability during turning operation was studied. Statistically-based experimental design (response surface methodology) using central composite second-order rotatable design technique was used to improve the experimentation design without loss of accuracy of the results. The interaction of cutting parameters (cutting speed, feed rate and depth of cut) was examined and their effect on the average surface roughness was reported. It was found that employing a combination of high cutting speed and small depth of cut with small feed rate causes a significant reduction in Ra. The data were represented in three-dimensional and contour graphs for selecting the appropriate machining conditions required to achieve desired values of surface roughness.

白金合金Ｐｔ８５０の切削における工具摩耗特性

In turning of platinum alloy Pt850, the wear behavior of tools and the cutting characteristics of Pt850 are investigated experimentally. K10 carbide, cermet, ceramics and PCD are used as tool materials. K10 carbide and cermet are not suitable for the cutting of this material because severe wear on the tool flank was observed after a few second of cutting, that is, the width of the flank wear land was about 1 mm after 10 seconds cutting. The width of wear land of Al2O3 and Si3N4 ceramic tools was small compared with K10 carbide tool, but the cutting forces increased rapidly as the cutting proceed. PCD tool can be used for cutting of Pt850 because the width of flank wear land is much small compared with other tool materials used in this experiment and the increasing rate of cutting force is not so great. The influence of cutting speed on the flank wear of PCD tool is small. The surface roughness of work material Pt850 becomes lower when the smaller feed rate is chosen as a cutting condition and the cutting tool of larger radius corner is used.

The no-flow problem for granular material in rotating kilns and dish granulators

Granular material, contained in a long, inclined cylinder, slowly rotating about its axis, forms a flat surface whose intersection with the cylinder is an ellipse. We postulate that the granular material falls in a thin layer along the line of steepest descent in the surface, which line is inclined at the angle of repose to the horizontal; the granular material then rotates with the cylinder in `solid body’ motion. With no axial flow, each particle remains in the same plane normal to the axis of the cylinder. The predicted length of the ellipse, measured in the direction of the axis of the cylinder, is in excellent agreement with experiments using sand or TiO 2. The same theory is applied to granular material in a dish granulator operated at low speed, so the bed surface is flat. The theory for no-flow gives results for the position of the bed surface which are in fair agreement with published data at small feed rate. For the case when centrifugal accelerations are small, but not negligible, theory is given which predicts their effect.

Cutting Force Acting on Blunt Cutting Edge. 1st Report. A Basic Consideration on Cutting Force Occurrence.

Undeformed chip thickness may be smaller than radius of cutting edge at small feed rate when workpieces are cut by a finishing tool with large round corner. Therefore, in finish cut, sharpness of cutting edge has to be taken into consideration in cutting process. The purpose of this study is to find mechanism of cutting force occurrence at smaller undeformed chip thickness than radius of cutting edge. In this study, the effects of cutting edge radius both on cutting force and on burnishing force were investigated in orthogonal cutting. Furthermore, contact length between tool flank face and woprkpiece during cutting was measured in order to consider the relation between the burnishing force and the contact length. As a result, the conclusions were reached as follows. First, the following parameters very inversely as the nth power of undeformed chip thickness normalized by radius of cutting edge: (i) cutting forces per unit area of chip section, (ii) specific burnishing force defined as burnishing force divided by undeformed chip thickness and by width of cut, and (iii) specific burnishing length defined as burnishing length divided by undeformed chip thickness. Second, cutting force occurring on flank face of ploughing force is greater than excessive cutting force caused by reduction of rake angle on round face of cutting edge.

Elemental sulfur production during the regeneration of iron oxide high-temperature desulfurization sorbent

The production of elemental sulfur instead of SO 2 during the regeneration of high temperature desulfurization sorbents will improve the efficiency of advanced power generation processes such as the integrated gasification combined cycle (IGCC). While much research is directed at developing zinc-based sorbents because of the favorable thermodynamics of the ZnO–H 2S reaction, SO 2 is the inevitable product from ZnS regeneration. Iron-based sorbents, although less efficient for H 2S removal, permit significant amounts of elemental sulfur to be formed during regeneration. A laboratory-scale fixed-bed reactor has been used to study the regeneration of FeS in steam-oxygen mixtures. The experimental results are interpreted on the basis of four simultaneous reactions. Oxygen reacts rapidly with FeS to produce SO 2 and Fe 2O 3. Steam reacts to give Fe 3O 4 and H 2S. Elemental sulfur is formed by the reaction between H 2S and SO 2, and additional O 2 is consumed in converting Fe 3O 4 to Fe 2O 3. The maximum yield of elemental sulfur, approximately 75% of theoretical, was achieved using a large H 2O-to-O 2 ratio (200-to-1) at the lowest feasible regeneration temperature (600°C), and using a small regeneration gas feed rate.

パイロッティングドリルによる加工穴精度の向上

This paper deals with the improvement of hole accuracy by piloting drills. The piloting drills have two short cutting edges and a piloting part on the projection of twist drill point. Experiments showed the following results. These drills improve the roundness at the hole entrance, because the wandering motion of drills can be suppressed by a short chisel edge and has already damped under the effect of a piloting part when the corners of primary cutting edges enter workpiece. In the rotating drill-stationary workpiece system piloting drills produce smaller hole oversize, hole deviation of axis and its scatter at the hole entrance than conically ground drills. Further improvement of them can be obtained by two-step feed, which consists of a very small feed rate and an ordinary feed rate before and after the primary cutting edges enter workpiece, respectively. The improvement of hole accuracy results from small oversize of pilot hole at a small feed rate. Longer piloting part is desirable from the viewpoint of the reduction in hole oversize.

スプレイフォーミング法で製造したハイスエンドミルの切削性能

A spray forming technique, which can produce semi-finished products with high density and rapid solidification structure in a single operation, has been developed recently. This method is called the Osprey process. This process can control size and distribution of carbides and takes lower production cost than powder metallurgy (P/M) process owing to a single operation. In this paper the cutting performance of high-speed steel (HSS) end mill produced by Osprey process was investigated by comparison with conventional ingot metallurgy (I/M) and P/M ones. This Osprey HSS end mill exhibited superior wear resistance to I/M and P/M ones in milling tool steel (SKD 11), but some chippings and fracture appeared at the end cutting edge in milling stainless steel (SUS 304) in small feed rate.

合金鋼粉末の被削性について

An investigation was made of the influence of pressing and sintering conditions, and S addition up to 0.4% on the machinability of SUS304L and other sintered alloy steels manufactured by the water atomization.The results were as follows:(1) The sintered density gave remarkable influence on cutting resistance. The resistance got smaller first, and then larger with increasing density having the minimum value around 7g/cm3 of density.(2) The surface roughness of SUS304L sintered steel was improved with smaller feed rate and higher cutting speed in turning.(3) The cutting resistance of SUS304L and 316L sintered steels got smaller with increasing S-content in powders. As the result of it, the tool life was remarkably improved for SUS304L sintered steel bearing 0.2% S.