Effect of various parameters on the surface roughness of an aluminium alloy burnished with a spherical surfaced polycrystalline diamond tool

The effect of various parameters on the surface roughness of an aluminium alloy burnished with a spherical surfaced polycrystalline diamond tool are studied experimentally with a theoretical analysis. Problems in selecting the optimum burnishing parameters and some burnishing mechanisms are discussed. With suitable parameters employed, the new no-chip finishing process developed can eliminate or reduce the cutting marks left on the workpiece surface by diamond cutting tools, with its surface roughness reduced to Ra=0.026 μm from the original 0.5 μm.     

An investigation into roller burnishing

Burnishing, a plastic deformation process, is becoming more popular as a finishing process: thus, how to select the burnishing parameters to reduce the surface roughness and to increase the surface microhardness is especially crucial. This paper reports the results of an experimental program to study the influence of different burnishing conditions on both surface microhardness and roughness: namely, burnishing speed, force, feed, and number of passes. Also, it reports the relationship between residual stress and both burnishing speed and force. The residual stress distribution in the surface region that is orthogonally burnished is determined using a deflection etching technique. Mathematical models are presented for predicting the surface microhardness and roughness of St-37 caused by roller burnishing under lubricated conditions. Variance analysis is conducted to determine the prominent parameters and the adequacy of the models. From an initial roughness of about R_a 4.5 μm, the specimen could be finished to a roughness of 0.5 μm. It is shown that the spindle speed, burnishing force, burnishing feed and number of passes have the most significant effect on both surface microhardness and surface roughness and there are many interactions between these parameters. The maximum residual stress changes from tensile to compressive with an increase in burnishing force from 5 to 25 kgf. With a further increase in burnishing force from 25 to 45 kgf, the maximum residual stress increases in compression.     

A Taguchi and experimental investigation into the optimal processing conditions for the abrasive jet polishing of SKD61 mold steel

This study introduces an abrasive jet polishing (AJP) technique in which the pneumatic air stream carries not only abrasive particles, but also an additive of either pure water or pure water with a specified quantity of machining oil. Taguchi design experiments are performed to identify the optimal AJP parameters when applied to the polishing of electrical discharge machined SKD61 mold steel specimens. A series of experimental trials are then conducted using the optimal AJP parameters to investigate the respective effects of the additive type and the abrasive particle material and diameter in achieving a mirror-like finish of the polished surface. The Taguchi trials indicate that when polishing is performed using pure water as an additive, the optimal processing parameters are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm², a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Applying these processing parameters, it is found that the optimal polishing effect is attained using #8000SiC abrasive particles and a 1:1 mixture of water-solvent machining oil and pure water. The experimental results show that under these conditions, the average roughness of the electrical discharge machined SKD61 surface is reduced from an original value of R_a=1.03 μm (R_max: 7.74 μm) to a final value of R_a=0.13 μm (R_max: 0.90 μm), corresponding to a surface roughness improvement of approximately 87%.     

Investigations on the surface roughness produced by ball burnishing

Burnishing, a plastic deformation process, can be used to finish surfaces. Experimental work was conducted on a vertical machining centre to establish the effects of various ball burnishing parameters: depth of penetration, feed, ball material, burnishing speed and lubricant, on the surface roughness of AISI 1045 specimens. The ball materials used were WC and SUJ2. It was found that all the parameters studied affect the surface finish to varying degrees. The surface roughness parameter R_tm first decreases and then increases with increasing depth of penetration. The effects of feed and burnishing forces on the surface finish also showed similar trends. The effect of speed depends on the type of lubricant used. Grease is a better lubricant than cutting oil for the speed range of 450 mm min⁻¹ to 1200 mm min⁻¹. With appropriate selection of the process parameters, a pre-machined surface roughness of about 4 μm can be finished to approximately 0.7 μm.     

Effect of Ball Burnishing Process on the Surface Quality and Microstructure Properties of AISI 1010 Steel Plates

A newly developed ball burnishing tool was designed and tested for surface finishing of large flat surfaces in a shortest possible time. Optimization and analysis of the burnishing process were carried on AISI 1010 steel hot-rolled plates using the Taguchi technique and response surface methodology (RSM) to identify the effect of burnishing parameters (i.e., burnishing speed, burnishing force, and feed rate) on surface roughness, surface hardness, and microstructure of burnished surfaces. The optimal burnishing parameters were found after conducting the Taguchi’s L₂₅ matrix experiments and obtaining the response models for the surface roughness and the hardness. It was found that the burnishing force has the most influential effect on the surface roughness and hardness, followed by the burnishing speed, and least influence by the feed rate. In addition, microstructural examinations of the burnished surface indicate that burnishing force more than 400 N causes flaking of the burnished surfaces. The optimal burnishing parameters for the steel plates were a combination of a burnishing speed of 235 rpm, a burnishing force of 400 N, and a feed rate of 0.18 mm/rev. Using these parameters, the mean surface roughness has been improved from Ra = 2.48 to 1.75 μm, while the hardness increases from 59 to 65.5 HRB.     

Freeform surface finish of plastic injection mold by using ball-burnishing process

The objective of this study is to introduce the possible ball-burnishing surface finish process of a freeform surface plastic injection mold on a machining center. The design and manufacture of a burnishing tool was first accomplished in this study. The optimal plane ball-burnishing parameters were determined by utilizing the Taguchi’s orthogonal array method for plastic injection molding steel PDS5 on a machining center. Four burnishing parameters, namely the ball material, burnishing speed, burnishing force, and feed, were selected as the experimental factors of Taguchi’s design of experiment to determine the optimal burnishing parameters, which have the dominant influence on surface roughness. The optimal burnishing parameters were found out after conducting the experiments of the Taguchi’s L18 orthogonal table, analysis of variation (ANOVA), and the full factorial experiment. The optimal plane burnishing parameters for the plastic injection mold steel PDS5 were the combination of the tungsten carbide ball, the burnishing speed of 200 mm/min, the burnishing force of 300 N, and the feed of 40 μm. The surface roughness R_a of the specimen could be improved from about 1 to 0.07 μm by using the optimal burnishing parameters for plane burnishing. Applying the optimal burnishing parameters for plane burnishing to freeform surface plastic injection mold, the surface roughness R_a of freeform surface region on the tested plastic injection part could be improved from about 0.842 to 0.187 μm, through a comparison between using the fine milled and using the ball-burnished mold cavity.     

Synthesis process of Mg–Ti BCC alloys by means of ball milling

The synthesis process of Mg–Ti alloys with a BCC (body centered cubic) structure by means of ball milling was studied by X-ray diffraction and various microscopic techniques. The morphology and crystal structure of Mg–Ti alloys changed with increase of milling time. During ball milling of Mg and Ti powders in molar ratio of 1:1, firstly, plate-like particles stuck on the surface of the milling pot and balls. After these plate-like particles fell off from the surface of the milling pot and balls, spherical particles with the mean diameter of 1 mm, in which concentric layers of Mg and Ti were disposed, were formed. These spherical particles were crushed into spherical particles with the diameter of around 10 μm by introduction of cracks along the boundaries between Mg and Ti layers. Finally, the Mg₅₀Ti₅₀ BCC phase with the lattice parameter of a = 0.342(1) nm and the grain size of 3 nm was formed. During milling of Mg and Ti to synthesize the BCC alloy, Mg and Ti were deformed mainly by the basal plane slip and the twinning deformation, respectively. Ti acted as abrasives for Mg which had stuck on the surface of the milling pot and balls. The BCC phase was found after Mg dissolved in Ti.     

A novel method of composite electroplating on lap in lapping process

A lapping machine with the composite electroplating to dress the lap in-process has been developed. Mirror surface lapping operations on silicon wafers were conducted by plating tin with 0.3 μm Al₂O₃ particles on the lap surface in-process. During the lapping process, the cathode current density ranged from 0.28 to 1.68 A/dm². Results showed that the removal rate of the silicon wafer for this process ranges from 0.12 to 0.18 μm/min, which is about 2.5–3.5 times higher than those without dressing in-process. This indicates that this novel method can produce sharp new edges on the lap surface continuously. It is found that the growth rate for the coating thickness of the lap is almost equal to its wear rate at the cathode current density of 0.28 A/dm². Hence, it is not necessary to replace and dress during the lapping by using this method. The silicon wafer can be lapped to a surface roughness, R_a=2 nm in this novel method.     

Polishing of fiber optic connectors

The polishing characteristics of end faces of fiber optic connectors consisting of the combined structure of silica inlaid zirconia were investigated using a connector polisher and polishing papers with different abrasive types and grit sizes. The geometrical quality was measured using optical interferometry and fiber optical microscopy. The quality parameters included fiber and ferrule surface roughness, end face morphology, fiber height, radius of curvature, and apex offset. The optical performance was eval uated in terms of return and insertion losses using a loss tester. The surface roughness smaller than 20 nm R_a in the fiber area, the fiber heights smaller than 75 nm, the end face curvature radii of about 20–50 mm, and the apex offsets smaller than 100 μm were obtained in a polishing cycle of 1 min. The corresponding average return and insertion losses of −48 and 0.15 dB, respectively, were also achieved. The polishing efficiency was raised by at least 30% compared to the commercially applied processes. Finally, the polishing mechanisms of the fiber optic connectors were investigated regarding material response to abrasive machining.     

Modeling and experimental validation of the force–surface roughness relation for smoothing burnishing with a spherical tool

The effect of a smoothing-burnishing process strongly depends on the initial roughness of a workpiece. This factor has not been considered by existing classical models of the processes. In this paper, assuming a model of burnishing with a spherical tool, in the form of wedges of surface roughness deformed with a force normal to the base line, expressions describing the relation between burnishing force and displacement of the tops of surface asperities is derived. The expression includes the effect of mechanical properties of the workpiece material, geometry of contact of the tool with the workpiece and the roughness of the burnished surface. Using the derived expressions it is possible to determine an optimum burnishing force. This has been verified experimentally. The experiment made it possible to demonstrate that the optimum burnishing force of the ground 42CrMo4 steel samples was 11–15 daN and that the burnishing effect depends a lot not only on the mechanical properties of the machined workpiece and the geometry of the contact area between the tool and the workpiece but also on the initial surface roughness. The applied optimum burnishing force, calculated on the basis of the theoretical, assumed model-derived dependences, is 12–13 daN. The above proves the validity of the adopted assumptions and the formulas worked out.     

A new approach to cutting state monitoring in end-mill machining

A new cutting state monitoring approach is proposed for the real-time predicting of the machining trouble and the surface quality of the machined products. In this approach, the relationships among the mechanical model of cutting process and its corresponding time series model, the surface roughness of the machined workpiece are evaluated through theoretical analysis and experimental investigation. It is therefore revealed that there is the linear relationships among the AR parameter a₁, the stiffness k₃ of cutting model and surface roughness P_z, and consequently the cutting process state can be estimated by only monitoring time series parameter a₁ of vibration signal measured during machining operation. In particular, it was found that the variation in the surface roughness of P_z=3–5 μm can be fully monitored.     

Shear-thickening polishing method

A shear-thickening polishing (STP) method utilizing the shear thickening mechanism of non-Newtonian power-law fluid based slurry is proposed for curved surface polishing. The STP principle and micro-material removal action are analyzed. The high-performance STP slurry with the shear-thickening rheological behaviors has been prepared. To achieve the material removal mechanism of STP process, based on the Preston formula, fluid dynamics and shear thickening mechanism, the material removal rate (MRR) model is established and the difference of MRR between theoretical and experimental results is 6.12%. The experimental and theoretical tests of STP process are conducted to investigate the influences of polishing velocity, abrasive concentration and grain size on MRR and surface roughness. Compared with Newtonian fluid slurry, STP slurry can achieve much higher MRR and better surface quality due to shear-thickening effect. MRR of Cr12Mo1V1 (die steel) is up to 13.69 μm/h, and surface roughness is reduced from R_a 105.95 nm to R_a 5.1 nm within 0.5 h of processing. This indicates that STP is a promising processing method for precision finishing or polishing.     

Servo scanning 3D micro-EDM based on macro/micro-dual-feed spindle

Using the end discharge of micro-rod-shaped electrode to scan layer by layer, micro-electrical discharge machining (EDM) can fabricate complex 3D micro-structures. During the machining process, the discharge state is broken frequently due to the wear of the tool electrode and the relative scanning motion. To keep a favorable discharge gap, the feed spindle of the tool electrode needs the characteristics of high-frequency response and high resolution. In this study, an experimental system with a macro/micro-dual-feed spindle was designed to improve the machining performance of servo scanning 3D micro-EDM (3D SSMEDM), which integrates an ultrasonic linear motor as the macro-drive and a piezoelectric (PZT) actuator as micro-feeding mechanism. Based on LabVIEW and Visual C++ software platform, a real-time control system was developed to control coordinately the dual-feed spindle to drive the tool electrode. The micro-feed motor controls the tool electrode to keep the favorable discharge gap, and the macro-drive motor realizes long working range by a macro/micro-feed conversion. The emphasis is paid on the process control of the 3D SSMEDM based on macro/micro-dual-feed spindle for higher machining accuracy and efficiency. A number of experiments were carried out to study the machining performance. According to the numerical control (NC) code, several typical 3D micro-structures have been machined on the P-doped silicon chips. Our study results show that the machining process is stable and the regular discharge ratio is higher. Based on our fundamental machining experiments, some better-machined effects have been gained as follows. By machining a micro-rectangle cavity (960 μm×660 μm), the machined depth error can be controlled within 2%, the XY dimensional error is within 1%, the surface roughness R_a reaches 0.37 μm, and the material removal rate is about 1.58×10⁴ μm³/s by using a tool electrode of Φ=100 μm in diameter. By machining multi-micro-triangle cavities (side length 700 μm), it is known that the machining repeatability error is <0.7%.     

A study on stainless steel mirror surface polishing by using the electrophoretic deposition method

Polishing wheels with homogeneously organized micro abrasive grains, uniformly dispersed by electrophoretic deposition (EPD), can be applied in mirror-like polishing process. This work studies the characteristics of EPD and mechanical polishing when SUS316LVV is polished. Abrasive grains with blunt edges are easily ablated from the polishing wheel by friction during polishing. The polishing wheel can be continuously refreshed by adding new abrasives. A superior surface polishing quality can thus be obtained. The control parameters of the EPD polishing process include the working voltage, the rate of rotation of the polishing wheel, the polishing feed rate, the polishing time, the axial loading and the pH value of the electrolyte, etc. Experimental results indicate not only that SiC particles of size 0.9–1.5 μm were used in EPD polishing, but also that the initial roughness of a machined surface could be improved from 0.5 μm Ra to 0.02 μm in 8 min, yielding a mirror-like surface.     

Crystal structure of the R3Ag1−δSiS7 (R = La, Ce, Pr, Nd, Sm, δ = 0.10–0.23) compounds

The crystal structure of the R₃Ag_1−δSiS₇ (R = La, Ce, Pr, Nd, Sm, δ = 0.10–0.23, space group P6₃, Pearson symbol hP23.80 − 23.54) compounds were determined by means of X-ray single crystal diffraction (a = 1.04168(8) nm, c = 0.57825(4) nm, R1 = 0.0116 for La₃Ag_0.90SiS₇; a = 1.0312(1) nm, c = 0.57395(7) nm, R1 = 0.0152 for Ce₃Ag_0.82SiS₇; a = 1.0248(1) nm, c = 0.57223(5) nm, R1 = 0.0105 for Pr₃Ag_0.85SiS₇; a = 1.0192(1) nm, c = 0.57020(6) nm, R1 = 0.0292 for Nd₃Ag_0.81SiS₇, a = 1.0100(1) nm, c = 0.56643(6) nm, R1 = 0.0208 for Sm₃Ag_0.77SiS₇. Gradual decrease of the silver amount in the series of chalcogenides was found.     

Characteristics of Rb40 steel superficial layer under ball and roller burnishing

Both ball and roller burnishing processes are largely considered in industrial cases in order to ameliorate surface characteristics. Usually, roughness and hardness are sought to measure surface integrity. The aim of this study is to develop a device for mechanical plastic deformation of structural Rb40 steel using ball and roller burnishing and to investigate the evolution of associated roughness, hardness and wear resistance. It was found that roller burnishing provides optimal roughness results, particularly when initial surface quality is close to 3 μm whereas in terms of hardness, ball burnishing becomes interesting. Optimum roughness and hardness are obtained for a specific operating regime in which decisive parameters are the applied force as well as the number of passes. When considering roughness criterion, it is recommended to limit the number of passes to two while three passes are advised for a hardness basis. Rb40 steel superficial layers treated by either roller or ball burnishing behave as a grinded surface with an appreciable wear resistance.     

A study on the effect of tool nose radius in ultrasonic elliptical vibration cutting of tungsten carbide

Nowadays, ultrasonic elliptical vibration cutting (UEVC) technique is being successfully applied for ultraprecision machining of difficult-to-cut materials. Previous study reported that the tool geometry especially tool nose radius notably influences the performance of 1D ultrasonic vibration cutting (UVC). However, the effect of tool nose radius in the UEVC technique is yet to be studied. This study aims to investigate the effects of tool nose radius on the UEVC performance in terms of cutting force, tool wear and surface finish when machining a hard-to-cut material, sintered tungsten carbide (WC), using PCD tools. The experimental results show that the UEVC technique performs remarkably better in all aspects at a 0.6 mm nose radius compared to a lower (e.g. 0.2 or 0.4 mm) and a higher nose radius (e.g. 0.8 mm). When machining about 412 mm² surface area, an average surface roughness, R_a of 0.010 μm is achieved with a 0.6 mm nose radius. Analyses are conducted to justify the findings in this study.     

Non-abrasive polishing of glass

Supersmooth surfaces are often needed in high- and new-technology products. The traditional polishing method to obtain supersmooth surfaces is abrasive polishing. In this paper, a new kind of polishing method, non-abrasive polishing (NAP), is presented. The polishing wheel of NAP is made of ice that is frozen deionized water, so there is no abrasive in the polishing wheel. Compared with traditional polishing methods, NAP can obtain Ångström-order surface roughness values free from microscratches and subsurface cracks. Based on adhesion theory, the material removal mechanism of NAP is presented in the paper. The paper also analyzes the polishing equipment and processing technique of NAP. The best surface roughness, R_a=0.48 nm, of K9 glass is obtained using NAP. According to the relationship between surface roughness and adhesion, the surface roughness fluctuation phenomenon is explained in the paper. The surface roughness fluctuation phenomenon is expected to be avoided by measuring the fractal dimension of the polished surface.     

Surface integrity of finished turned Ti–6Al–4V alloy with PCD tools using conventional and high pressure coolant supplies

 Surfaces generated when machining Ti–6Al–4V alloy with PCD tools using conventional and high pressure coolant supplies was investigated. Longer tool life was recorded when machining Ti–6Al–4V with high-pressure coolant supplies and the recorded surface roughness R_a values were well below the tool rejection criterion (1.6 μm) for all cutting conditions investigated. The micro-structure of the machined surfaces were examined on a scanning electron microscope. Micrographs of the machined surfaces show that micro-pits and re-deposited work material were the main damages to the surfaces. Micro-hardness analysis showed hardening of the top machined surfaces when machining with conventional coolant while softening of the subsurface layer was observed when machining under high-pressure coolant supplies. The later is probably due to lower heat generated, with the consequent tempering action when machining with PCD tools with high-pressure coolant supplies. The microstructure below the machined surfaces had minimal or no plastic deformation when machining with conventional and high-pressure coolant supplies.     

Mixed cerium valence and unusual Ce–Ru bonding in Ce23Ru7Cd4

The rare earth-rich compounds Ce₂₃Ru₇Cd₄ and Pr₂₃Ru₇Cd₄ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. Both structures were refined on the basis of diffractometer data: P6₃mc, Z = 2, a = 988.7(3), c = 2241.6(5) pm, wR2 = 0.0439, 1976 F² values for Ce₂₃Ru₇Cd₄ and a = 992.7(2), c = 2236.4(7) pm, wR2 = 0.0466, 2528 F² values for Pr₂₃Ru₇Cd₄ with 74 variables per refinement. Striking structural motifs are ruthenium centered trigonal prisms RuCe₆ and RuPr₆ which are condensed via common edges and corners, building rigid three-dimensional networks. Larger voids within these networks are filled by slightly elongated Cd₄ tetrahedra. Five of the nine crystallographically independent cerium sites in Ce₂₃Ru₇Cd₄ show Ce–Ru distances which are shorter than the Pr–Ru distances in Pr₂₃Ru₇Cd₄. This strong hint for mixed cerium valence is supported by the magnetic behavior. Pr₂₃Ru₇Cd₄ shows Curie–Weiss behavior above 50 K with an experimental magnetic moment of 3.62 μ_B/Pr atom, indicating stable trivalent praseodymium. Complex magnetic ordering sets in at 13 K. Ce₂₃Ru₇Cd₄ shows a reduced magnetic moment of 2.05 μ_B/Ce atom. The trivalent cerium atoms show ferro- or ferrimagnetic ordering below T_C = 3.6 K.