Final Roughness Research Articles

Effect of various treatment and glazing (coating) techniques on the roughness and wettability of ceramic dental restorative surfaces

Surface treatment procedures such as grinding and polishing are needed to provide the ceramic dental restorative materials with proper fitting and occlusion. The treated surfaces are customarily glazed to improve the strength and smoothness. Though smoothness and wetting of the dental surfaces are important to minimize bacterial plaque retention, influence of the surface treatment and glazing procedures on the final surface roughness and its correlation to wettability are overlooked. In this work, effect of various treatment (diamond fraising, stoning, sanding and aluminum oxide and rubber polishing) and glazing (auto and overglazing) techniques on the final roughness and the resulting wettability of dental ceramic surfaces were investigated using scanning electron microscopy (SEM) observations and atomic force microscopy (AFM) scans, 75 scans per sample. The surfaces were characterized and assigned an average roughness measure, R a. The wettability of the same surfaces was evaluated using micro-contact angle measurements (25 micro-bubbles placed on a grid on each surface) to correlate the final surface roughness and wettability. The results show that overglazing prevails over surface irregularities from different treatment procedures and provides homegeneously smooth surfaces with mean R a < 10 nm. It also produces uniformly wetted surfaces with low contact angles around 20°. The autoglazed surfaces are less smooth (mean R a around 50 nm) and displays sporadic topographic irregularities. They display larger and less uniform contact angles ranging between 35° and 50°. The results suggest that overglazing should be preferred after surface treatment to obtain a smooth and well-wetted dental ceramic surface.

Behaviour of Self-Standing CVD Diamond Film with Different DominantCrystalline Surfaces in Thermal-Iron Plate Polishing

Self-standing CVD diamond films with different dominant crystallinesurfaces are polished by the thermal-iron plate polishing method. Theinfluence of the dominant crystalline surfaces on polishing efficiencyis investigated by measuring the removal rate and final roughness. Thesmallest rms roughness of 0.14 μm is measured with smallest removal ratein the films with the initial (220) dominant crystalline surface.Activation energy for the polishing is analysed by the Arrheniusrelation. It is found that the values are 170 kJ/mol, 222 kJ/mol and214 kJ/mol for the film with three different dominant crystallinesurfaces. Based on these values, the polishing cause is regarded as thegraphitization-controlling process. In the experiment, we find thattransformation of the dominant crystalline surfaces from (111) to (220)always appears in the polishing process when we polish the (111)dominant surface.

Study of magnetic abrasive finishing in free-form surface operations using the Taguchi method

This study employed magnetic abrasive finishing (MAF) to conduct free-form surface abrasion of stainless SUS304 material operations. The operations were demonstrated using a permanent magnetic finishing mechanism installed at the CNC machining center. The operations were performed using the Taguchi experimental design, considering the effects of magnetic field, spindle revolution, feed rate, working gap, abrasive, and lubricant. Furthermore, the experimental data was collected using the Taguchi experimental design. The optimal parametric conditions for processing stainless SUS304 material were applied in a two-stage process comprised of rough finishing that involved MAF followed by a precise finishing of the surface. Prior to rough finishing, the Rmax value was 2.670 μm; after rough finishing, the value was 0.158 μm. Precise finishing yields an even lower value of 0.102 μm similar to that of the mirror surface. Therefore, the results revealed that MAF provides a highly efficient way of obtaining surface finish.

The effect of ball burnishing on heat-treated steel and Inconel 718 milled surfaces

In this paper the use of the ball burnishing process to improve the final quality of Inconel 718 surfaces is studied. This process changes the roughness and residual stresses of the previously end milled surfaces, achieving the finishing requirements for engine components. Both the burnishing system and main parameters are taken into account, considering their influence on finishing. Workpiece surface integrity is ensured due to the compression effect of this surfacef enhancement process and its associated cold working. Results of different tested pieces are discussed in relation to the maximum and mean surface roughness achieved microstructure and surface hardness. Results of heat-treated low carbon mould steel P20 (32 HRC) are compared with those for the nickel alloy Inconel 718 (solution treated and age hardening, 40 HRC). The main conclusions are that using a large radial width of cut in the previous end milling operation, together with a small radial width of cut during burnishing can produce acceptable final roughness. And compression cold working is higher and deeper in the Inconel 718 than in the steel case.

Fabrication and characterisation of 200 mm germanium-on-insulator (GeOI) substrates made from bulk germanium

The formation and detailed characterisations of a 200 mm germanium-on-insulator substrate made from germanium bulk material as donor wafer using the Smart CutTM technology is reported. Detailed characterisations of final GeOI structures are presented: final roughness, defectivity evaluation, thickness measurement, and electrical characterisation.

Effects of ultrasound on the preparation of zeolite A coatings

Preparation of zeolite 4A coatings on stainless steel substrates by direct synthesis at 60 °C from a clear aluminosilicate solution was carried out in the presence of ultrasound of 35 kHz at different times and the results were compared to those obtained by performing conventional static synthesis of zeolite 4A coatings under similar conditions. XRD and SEM analyses revealed that more nuclei formed at earlier times in the presence of ultrasound, allowing the preparation of thinner and continuous zeolite coatings in significantly shorter synthesis times. When zeolite 4A coatings were prepared by using conventional static synthesis at 60 °C, a closed layer with a thickness of about 1.5 μm could be obtained on stainless steel after a synthesis time of 10 h. Under the same experimental conditions, when sonication was applied, the layer thickness and the closure time were decreased to about 0.6 μm and 3 h, respectively. The surface roughness, which decreased initially, later started increasing upon continued nucleation and crystal growth, and showed a final decrease towards the closure of the layers. The final roughness value was smaller for the coating prepared in the presence of ultrasound.

Performance-based optimization of multi-pass face milling operations using Tribes

The paper proposes a new optimization technique based on Tribes for determination of the cutting parameters in multi-pass milling operations such as plain milling and face milling by simultaneously considering multi-pass rough machining and finish machining. The optimum milling parameters are determined by minimizing the maximum production rate criterion subject to several practical technological constraints. The cutting model formulated is a nonlinear, constrained programming problem. Experimental results show that the proposed Tribes-based approach is both effective and efficient.

Quality improvement of ball-end milled sculptured surfaces by ball burnishing

In this paper, the use of the ball burnishing process to improve the final quality of form tools (moulds and dies) is studied. This process changes the roughness of the previously ball-end milled surfaces, achieving the finishing requirements for plastic injection moulds and stamping dies. Ball burnishing can be easily applied in the same machining centres as those used for milling. In this way, both lead times and production costs can be dramatically reduced. Both the burnishing system and its main parameters are taken into account, considering their influence on finishing. Workpiece surface integrity is ensured due to the surface smoothing effect of process and the associated cold working. Examples of different materials, machined surfaces, and industrial applications are explained, with respect to the maximum and mean surface roughness achieved. The main conclusion is that using a large radial depth of cut in the previous ball-end milling operation, together with a small radial depth during burnishing can produce acceptable final roughness. Savings of production times are high, as burnishing is applied using the maximum linear feed of the machine, while milling must be made at moderate feeds. Moreover, ball burnishing NC programming is less critical and needs less care in its definition than CAM for milling.

PEN as substrate for new solar cell technologies

Abstract The possible use of polyethylene naphthalate as substrate for low-temperature deposited solar cells has been studied in this paper. The transparency of this polymer makes it a candidate to be used in both substrate and superstrate configurations. ZnO:Al has been deposited at room temperature on top of PEN. The resulting structure PEN/ZnO:Al presented good optical and electrical properties. PEN has been successfully textured (nanometer and micrometer random roughness) using hot-embossing lithography. Reflector structures have been built depositing Ag and ZnO:Al on top of the stamped polymer. The deposition of these layers did not affect the final roughness of the whole. The reflector structure has been morphologically and optically analysed to verify its suitability to be used in solar cells.

Tribological behaviour of hot rolling rolls

The study of wear mechanisms represents a very important task for the development of roll materials, with improved hot tribological properties. In the present paper the wear behaviour of different materials, i.e., high alloy steels (high speed steels (HSS)) and cast irons (high chromium irons (HiCr) and indefinite chill irons (IC)), produced by centrifugal casting, has been comparatively evaluated by means of a rolling sliding hot wear test. A disc specimen of C40 plain carbon steel, induction heated up to 700 °C, is allowed to rotate against a high alloy steel/iron at 200 rpm, corresponding to a slip rate of 28%, for a total period of time comprised between 1 and 3 h. A maximum contact hertzian stress of 300 MPa was imposed. The wear rates have been evaluated by weight measurements of the specimen, before and after each test period. The surface roughness was also determined as representative for the roll profile retention during service. The friction was continuously monitored. The wear mechanism is given by the combination of abrasion and oxidation. High speed steels show remarkable lower wear rates than high chromium and indefinite chill irons, because of their higher hot hardness. The retention of high hardness at elevated temperature is very important to reduce abrasive wear and also to support the protective oxide layer which develops on the surface of the roll material. As a general rule the roughness at the end of test tends to increase with increasing wear rate, as demonstrated by the relatively soft indefinite chill iron. However, the oxidation resistance also influences the final roughness, higher roughness values being observed for poorly oxidized materials. A simplified model explaining this experimental evidence is proposed.

Mirror Grinding of Quartz-Crystal with EPD Pellet(Grinding technology)

Fine silica abrasives wheel by electrophoretic deposition phenomenon, EPD pellet, was fabricated and applied to mirror grinding of 3 inches quartz-crystal wafers for the purpose of evaluating the grinding performance. Then. EPD pellets made a mirror surface and the final roughness was 6.5nmRy. The time required for making the mirror surface was less than 10min. No residual strain was found on the ground surface.

Electron-beam patterning with sub-2nm line edge roughness

Negative tone patterns were created by polymer-contamination writing in a transmission electron microscope. Typical line edge roughness of the polymer lines was found to be below 1nm. The patterns were transferred to bismuth films using an anisotropic ion etch, resulting in final bismuth line edge roughness less than 2nm. This low roughness was achieved by growing the bismuth film such that the same crystallographic planes were exposed to the etching flux of ions.

Micro-grooving of glass using micro-abrasive jet machining

Abrasive jet machining (AJM) is similar to sand blasting, and effectively removes hard and brittle materials. AJM has been applied to rough working such as deburring and rough finishing. With the increase of the needs for machining of ceramics, semiconductors, electronic devices and LCD’s, micro-AJM has become a useful technique for micro-machining. This paper describes the performance of micro-AJM in the micro-grooving of glass. The diameter of the hole-type and the width of the line-type groove are 80 μm. Experimental results showed good performance in micro-grooving of glass; however, the size of machined groove increased about 2–4 μm. With the fine-tuning of the masking process and the compensation for film wear, micro-AJM could be effectively applied to the micro-machining of semiconductors, electronic devices and LCD.

Micro-grooving of glass using micro-abrasive jet machining

Abrasive jet machining (AJM) is similar to sand blasting, and effectively removes hard and brittle materials. AJM has been applied to rough working such as deburring and rough finishing. With the increase of the needs for machining of ceramics, semiconductors, electronic devices and LCD’s, micro-AJM has become a useful technique for micro-machining. This paper describes the performance of micro-AJM in the micro-grooving of glass. The diameter of the hole-type and the width of the line-type groove are 80 μm. Experimental results showed good performance in micro-grooving of glass; however, the size of machined groove increased about 2–4 μm. With the fine-tuning of the masking process and the compensation for film wear, micro-AJM could be effectively applied to the micro-machining of semiconductors, electronic devices and LCD.

Creation of Ultraprecision V-shaped Microgrooves Using Non-Rotational Cutting Tools

The study deals with the creation of ultraprecision microgrooves using non-rotational diamond cutting tools with angle of 90 degrees, which are mounted on an ultraprecision machining center. Machining experiments of micro grooves were conducted to find the optimal value of cutting speed, depth of cut, rake angle, changing the cutting speed from 1mm/min to 200mm/min, the depth of cut from 0.1m to 10m and the rake angle from -5 degrees to 30 degrees. Workpieces were machined with the cutting tool submerged in the cutting fluid to know the influence of cutting fluid supply method. From the experimental results, the adequate cutting condition is obtained such as the rake angle of 10 degrees to 20 degrees, the finish cutting speed of 1mm/min and the depth of cut in rough cut and finish cut of 1m and 0.5m respectively. As the cutting fluid supply method, workpiece submerged in the cutting fluid is effective. Using the cutting condition, fine V-shaped microgrooves are obtained in various materials. In addition, frontlight optical plate and micro Fresnel lens with the designed micro grooves were designed and manufactured by non-rotational diamond cutting method. As a result, it is also found that the non-rotational diamond cutting method enables to accurately and neatly manufacture microgrooves without any burr generation.

Design of a film surface roughness-minimizing molecular beam epitaxy process by reduced-order modeling of epitaxial growth

Molecular beam epitaxy of germanium was used along with kinetic Monte Carlo simulations to study time-varying processing parameters and their effect on surface morphology. Epitaxial Ge films were deposited on highly oriented Ge(001) substrates, with reflection high-energy electron diffraction as a real-time sensor. The Monte Carlo simulations were used to model the growth process, and physical parameters were determined during growth under time-varying flux. A reduced version of the simulations was generated, enabling the application on an optimization algorithm. Temperature profiles were then computed that minimize surface roughness subject to various experimental constraints. The final roughness after two layers of growth was reduced to 0.32, compared to 0.36 at the maximum growth temperature. The study presented here is an initial demonstration of a general approach that could also be used to optimize properties in other materials and deposition processes.

Interference-free tool path generation in five-axis machining of a marine propeller

The manufacture of a marine propeller typically requires long lead-time to generate five-axis tool paths. It usually takes several days to generate satisfactory tool paths with a general purpose CAD/CAM system. This paper proposes a novel methodology that generates effective five-axis tool paths for marine propellers. The machining of a propeller is accomplished in three steps: rough cut, semi-finish cut, and finish cut. For generating accurate finish cut tool paths, the proposed system computes check vectors that determine a maximum range of valid tool motion based upon tool size and passage width for each CL (Cutter Location) point along the tool path. Interference-free tool paths can be acquired by positioning the tool inside the two check vectors. The modelling capability for propellers is also of importance because it determines the eventual success or failure of the whole process. An iterative B-spline surface modelling technique is employed to improve the accuracy of the models and to increase the productivity. The proposed system generates interference-free tool paths with superior surface finish and reduces lead-time to manufacture a propeller. The system validation and sample results are given and discussed.

Experimental characterization of superfinishing

An experimental study has been made of the superfinishing process. A force measurement system, developed for external cylindrical superfinishing, has been used to measure directly the forces acting on the abrasive stone. A systematic parametric study of material removal rate, force ratio, specific energy and surface finish is detailed. The force ratio and specific energy are found to be sensitive indicators of the cutting action of the stone. This indicates that force ratio could be used to monitor the process, on line in industrial applications. The two regimes of rough finishing and fine finishing have been characterized. A sharp transition from fine to rough finishing occurs at a stone oscillation frequency of about 1600 cycles/min. This characteristic frequency is mostly independent of stone-work contact pressure. The experimental data are used to construct a superfinishing process map to depict the various regimes in which different modes of superfinishing dominate.

Cu ( In 1−x Ga x ) Se 2 growth studies by in situ spectroscopic light scattering

The growth of polycrystalline Cu(In1−xGax)Se2 thin films using a three-stage deposition process has been investigated by in situ diffuse spectroscopic light scattering in the wavelength range of 400–800 nm. Differences in the time dynamics of the intensity at different wavelengths can be explained by the development of surface roughness at different length scales. Of specific interest is the development of roughness around the stoichiometric points of film formation. It is shown that on-line monitoring of the spectroscopic light scattering can be used for process control and for adjustment of the final film roughness.

ＭＴ‐ＣＶＤ法を用いて製作したＴｉ（Ｃ，Ｎ）コーテッド工具の長寿命化に関する一考察

A Ti(C, N) coated tool which has a balanced performance of the expected high wear resistance in the coated layer with high toughness of the substrate, has been widely used for machining of ferrous materials. Applying this tool to the machining of the nodular cast iron, however, formation of the adhered layer at the tool tip occurred intensively, tool-tip failure and or separation of the coated layer tends to take place especially in semi-final and/or rough finishing. It is also indicated that there is possibility to yield a finished product with some faults caused by continued cutting operation without noticing serious damage occurred on the tool-tip. In the present investigation, effects of reducing the pre-existing cracks in tool surface layer, thickness of the coated layer and the existence of the η phase in substrate material (WC-Co) on the tool life were extensively investigated in order to increase efficiency and to stabilize the tool life on the cutting process for semi-final finishing of nodular cast iron. As the results, it is clarified that the thinner the coated layer the lower became the tensile residual stress on the surface, resulting in the extension of the tool life without taking place separation of the coated layer. The separation is also able to suppress by controlling the surface roughness of the tool substrate to several μm with certain homogeneity.