Finishing Techniques Research Articles

Effect of initial surface topography during laser polishing process: Statistical analysis

Abstract Surface finish is one of the most important quality characteristics of fabricated components. Laser polishing (LP) is one of the advanced manufacturing surface finishing techniques that has been recently developed and successfully employed for improving surface quality without deteriorating the overall structural form through surface smoothing by melting and redistributing a thin layer of molten material. This paper advances the statistical analysis of the LP process emphasizing aspects of the effect of the initial surface topography. Flat and ground initial surfaces are used for comparative statistical analysis of initial and polished profiles obtained experimentally. Their profile geometries and surface quality characteristics, such as, roughness, were compared and analyzed. In addition, LP process was experimentally investigated as a thermodynamic operator represented by a transfer function and it was examined by means of a coherence function.

Directions of the Finishing of Fibres and Textile Development

The development of textile finishing techniques and technologies outside of reports in world-wide publications is also very visible at subsequent fairs. At international fairs, such as ITMA, ATMA and FESPA, machine, equipment and dye manufacturers present new techniques and technologies. The development of chemical fibre processing nowadays goes mainly towards the “ecological optimisation” of technological processes as well as the economics of processes. In this article, the main development directions of the chemical treatment of textiles in the field of the pre-treatment, bleaching, dyeing, printing and finishing of textile products are discussed.

DEVELOPMENT OF COMMERCIAL FLAME RETARDANT IN UPHOLSTERY LEATHERS BY BORON DERIVATIVES

The production of flame retardant leather is significant for some leather types as aircraft and automotive upholstery leathers, and protective leathers as for motorcyclist jackets. For this reason, in this research it was aimed to modify effect of commercial flame retardant (CFR) on upholstery leathers treated with borax, boric acid and zinc borate. Control (group 1), 200 g/L CFR (group 2), 10 g/L borax + 60 g/L boric acid + 200 g/L CFR (group 3) and 10g/L zinc borate + 60 g/L boric acid + 200 g/L CFR (group 4) chemical solutions were applied to the leathers by padding finishing technique, and after the flame retardant application the leathers were finished with traditional finishing recipe. Flame retardant property of leathers was determined by vertical flammability (ISO 6941:2007) and limit oxygen index (LOI) (ASTM D 2863-77) fire resistance tests. In addition, the treated leathers were characterized by ATR-FTIR and SEM devices. According to LOI results, CFR CFR+borax+boric acid and CFR+zinc borate+boric acid treated groups of leather had 28.5%, 29.2% and 29.9% oxygen concentration respectively, while control sample had 27.0%. Flame retardant property of leathers was significantly enhanced by the effect of boron derivatives.

Local Effects in EHL Contacts with Oil-Impregnated Sintered Materials

Oil-impregnated open-pored sintered materials can be used to provide the intrinsic self-lubrication of tribological contacts. Although its general functionality was recently confirmed for highly-loaded contacts, detailed analyses on the local effects of surface porosity in tribological contacts are required in order to understand and improve its operating behavior. In this context, this study investigates the influence of different surface finishes at a twin-disk test rig, and the local effects of surface porosity in elastohydrodynamically lubricated (EHL) contacts at an optical tribometer, based on thin film colorimetric interferometry. The results show the detrimental influence of high surface porosity on the operating behavior. Local observations of the lubricant film in EHL contacts indicate the presence of “open” pores, resulting in local film breakdown, and “closed” pores, transporting the additional lubricant into the pressurized zone. An appropriate surface finish technique to manufacture a low permeable layer with an adequate mechanical strength is demanded.

THE EFFECT OF ACETONE AS A POST-PRODUCTION FINISHING TECHNIQUE ON ENTRY-LEVEL MATERIAL EXTRUSION PART QUALITY

Entry-level material extrusion artefacts persistently suffer from questionable weakened end-product production quality, according to industrial standards. These limitations can be addressed by the development of improved finishing techniques that may narrow the gap between low-cost and high-end production methods in additive manufacturing. In doing so, the technology may become available to a larger spectrum of prosumers who previously were reluctant to use entry-level technology because of these limitations. This article describes the effect that acetone has as a post-production finishing technique for low-cost artefact production. Through a series of quantitative investigations, the study provides evidence that acetone reduces the tensile strength, increases polymer ductility, and significantly reduces the surface profile roughness of thermoplastics such as acrylonitrile butadiene styrene. The potential cost and waste reduction for entry-level manufactured products can then be identified.

EFFECT OF TWO POLISHING TECHNIQUES ON SURFACE ROUGHNESS OF THREE DIFFERENT DENTURE BASE MATERIALS (AN IN VITRO STUDY)

INTRODUCTION: A direct link was found between surface roughness, the accumulation of plaque and the adherence of microorganisms concerning acrylic resins. However, the surface properties of the new thermoplastic materials remain questionable especially after using the conventional finishing and polishing techniques. Studying surface properties of each material makes the recommendation of the proper techniques easier. OBJECTIVES: This in vitro study intended to compare three types of denture base materials in regarding to the effect of different polishing techniques on their surface roughness. MATERIALS AND METHODS: 36 specimens were incorporated in this study. 12 specimens were in each group. 3 groups were formed: Group A: Heat cured Polymethylmethacrylate (PMMA). Group B: Thermoplastic Polyamides. Group C: Thermoplastic Acetal. Dimensions of specimens were (20×20×3 mm) with projection at the side. Statistical analysis was carried out using two way analysis of variance (ANOVA). Statistical significance was defined at P≤0.05. RESULTS: Technique no. 1 showed a high significant value in compared to technique no.2 for polishing the tested materials. CONCLUSIONS: PMMA was the highest affected group followed by thermoplastic acetal and the last affected group was thermoplastic polyamide. Prepolishing rubberizing with rubber bur improves the polishing procedure. RESULTS: Remarkable improvement in the histology and the ultrastructure of the alveolar bone of rats in Group III was observed. Moreover, hematological values revealed significant decrease in the inflammatory condition of rats with induced RA after fish oil treatment. CONCLUSIONS: Rheumatoid arthritis is an important risk factor for alveolar bone loss. The treatment of the RA induced rats with fish oil not only prevented the alveolar bone resorption and stimulated new bone formation, but also reduced relatively the level of rheumatoid factor in the blood.

Reaction of Au/Pd/Cu and Au/Pd/Au/Cu multilayers with Sn-Ag-Cu alloy

The requirements of low resistivity and small magnetic permeability in the high-frequency signal delivery applications have driven the development of Ni-free surface finishes, such as Au/Pd (EPIG) or Au/Pd/Au (IGEPIG), over the Cu conducting lines. The compatibility of these newly developed surface finish techniques with microelectronic packages and their long-term, high temperature reliability still require investigations in the current state. We conducted a solderability evaluation on the Au/Pd/Cu and Au/Pd/Au/Cu multilayers and found no noticeable differences of the intermetallic compound species (i.e., (Cu,Pd)6Sn5 and Cu3Sn) in the joint interfaces between the two examined cases. However, numerous bump voids might be formed in the vicinity of the solder/Cu interface of the EPIG case, degrading the shear resistance of solder joints. The formation mechanism of the bump voids and the evolution kinetics were proposed in this study.

Multifunctional finishing treatments applied on textiles for protection of emergency personnel

The paper presents the results of the researches carried out for obtaining multifunctional textile materials with multiple effects, by means of superior finishing techniques, using functional chemicals in the form of aqueous dispersions. It has been studied the possibility of combining treatment with dispersions with photocatalytic and antibacterial effects with a hydrophobic/oleophobic treatment that simultaneously provides both sustainable photocatalytic and antibacterial effect as well as hydrophobic/oleophobic effect within satisfactory limits for all these effects. The results of the laboratory evaluations performed on 50% cotton and 50% functionalised HT polyamide textile fabrics showed that hydrophobization treatment with fluoropolymer dispersions can be combined with the treatment with titanium dioxide photocalatytic dispersions or silver chloride and titanium dioxide dispersions to obtain multiple photocatalytic, antibacterial and hydrophobic/ oleophobic effects without diminishing the functionalization effects that would have been achieved by individual treatments

Comparative Evaluation of the Effect of Surface Polishing of a Glaze/composite Sealant and Different Polishing Systems on Surface Roughness of Three Composite Resin Type

The aim of the study was to evaluate the influence of different techniques of finishing and polishing as well as the use of sealants on the surface condition of some composite resins used in the dental office. 80 specimens of composite materials (Nanoceramic, Nanocomposit and Nanohybrid) were made and divided into 3 groups G1-coated composite with sealant lacquer, G2 - finished in 2 stages, and G3 - finished in 3 stages. Roughness (Ra) was determined with the Taylor Hobson Form Talysurf Profiometer. The data was analyzed using one-way ANOVA followed by a multiple comparison t test. Significant differences were found between the groups in terms roughness (p [ 0.001). The results showed that Seal - and - Shine (PULPDENT) was capable of reducing surface roughness and provided polished surfaces for all materials.

Nanofinishing of FDM-fabricated components using ball end magnetorheological finishing process

ABSTRACTFused deposition modeling (FDM) is among the extensively used and the most economical additive manufacturing processes. Currently, the surface finish obtained for FDM additive manufactured parts are not at par with the current industrial application. To overcome the limitation of high surface roughness of 3D printed parts, a novel finishing technique has been proposed which includes primary and secondary finishing processes. While facing and lapping has been used as primary finishing technique, the secondary finishing involves the use of ball end magnetorheological finishing (BEMRF) process. BEMRF process is an unconventional finishing process which utilizes an advanced approach to impart finish on magnetic as well as non-magnetic materials that may be flat or freeform in shape. This article presents the experimental and analytical study to finish a polylactic acid (PLA) workpiece material manufactured by FDM process and finished using the BEMRF technique. The surface roughness of the FDM component has been reduced from initial surface roughness Ra = 20 µm to final value of Ra = 81 nm by combined primary and secondary finishing processes. The effect of magnetorheological polishing (MRP) fluid’s composition and finishing time is discussed and is followed by optimization of MRP fluid for maximum percentage reduction in surface roughness.

Experimental evaluation of diamond burnishing for sustainable manufacturing

Diamond burnishing is one of the most popular surface finishing technique used to achieve an excellent surface finish. The aim of the present study is to investigate the effect of process parameters in diamond burnishing of 17-4 PH stainless steel (PH SS) under cryogenic environment. The requirement of a sustainable environment for various machining processes urged to explore the importance of cryogenic burnishing over other cooling techniques. Surface modification was achieved by the application of liquid nitrogen (LN2) during diamond burnishing. The process parameters considered to reduce the surface roughness (Ra) and increase the surface hardness (H) are burnishing speed, burnishing feed and burnishing force. The diamond burnishing experiments were conducted based on the L9 orthogonal array. The significant parameters and the optimal level of each parameters were determined by using analysis of variance (ANOVA) and main effect plots respectively. Multi-response optimization has been carried out for cryogenic diamond burnishing of 17-4 PH stainless steel by using Taguchi’s grey relation analysis (TGRA). From the TGRA, it was observed that at burnishing speed 73 m min−1, burnishing feed 0.048 mm/rev and burnishing force 150 N, improved diamond burnishing performance characteristics were obtained. An improvement in grey relation grade (GRG) was found to be 38.47%. Cryogenic diamond burnishing has led to modifications in the microstructure and also an improvement in the subsurface hardness of the material.

Cool garment leathers for hot environment

Traditionally garment leathers are used in cold environment to protect the humans from chill weather. This is because leather garments have low heat storage capacity and high thermal insulation properties. Here, we report a method to prepare cool garments that can be wearable in hot environment using a phase change material, N-octadecane, microcapsule. Microcapsules containing N-octadecane were prepared through in situ polymerization and applied on the leather surface through conventional finishing techniques. Synthesized spherical microcapsules had melamine–formaldehyde polymer shell with 226 nm average diameter and 142 J g−1 heat storage capacity as characterized through differential scanning calorimetry, particle size analysis, scanning electron microscopy and Fourier transformed infrared spectroscopy. When the leathers were treated with 20 mass% microcapsules, they exhibited a heat storage capacity of 59.8 J g−1 and thermal resistance of 0.014 K m2 W−1 without any significant change in the physical properties. Hence, the treated leathers are suitable for application in hot environment for cooling the body.

Non-leaching bactericidal cotton fabrics with well-preserved physical properties, no skin irritation and no toxicity

We developed an isocyanate group containing quaternary ammonium salt (IQAS) as a potential antimicrobial finishing agent that can be stored in a high purity form for more than a year in dry environments to permit convenient transportation and storage. Additionally, we report a facile and eco-friendly finishing technique to fabricate durable antimicrobial cotton fabrics using IQAS as an antimicrobial finishing agent by a dipping–padding–drying process. IQAS was bound onto the surface of cotton fabrics by a covalent bond to obtain a cotton fabric with excellent bactericidal activity, tearing strength, breaking elongation, bending rigidity, water vapor permeability, surface roughness and smoothness. The antimicrobial rates of these fabrics reached 92.2% and 98.5% against gram-negative bacterium Escherichia coli and gram-positive bacterium Staphylococcus aureus, respectively, even after 50 laundering cycles. These values are much higher than the reference antimicrobial rates of AAA class antimicrobial fabrics, as well as those of conventionally finished cotton fabrics, indicating that the IQAS finished cotton fabrics maintained excellent antimicrobial activity even after long-term repeated launderings. Moreover, the results indicate that the IQAS-treated cotton fabrics could improve the breaking strength (increased by 13.5% in the warp direction and 20.3% in the weft direction), the bursting strength (increased by 11.9%), the air permeability (increased by 12.6%) and the hydrophilicity compared to untreated cotton fabrics. Additionally, our non-leaching antimicrobial cotton fabrics treated with IQAS were non-toxic and showed no skin stimulation. Therefore, IQAS and the antimicrobial finishing technique reported here have great potential applications in antimicrobial fabrics used in hospitals, hotels and other susceptible situations. An isocyanate group containing quaternary ammonium salt that permits convenient transportation and storage was developed as a potential antimicrobial finishing agent to fabricate excellent antimicrobial cotton fabrics with well-preserved physical properties and security using a dipping–padding–drying process.

Discrimination of Ceramic Surface Finishing by Vertical Scanning Interferometry

Finishing techniques are significant markers of the technological ‘know‐how’ involved in the production of the traditional, clay‐based ceramic ware. In order to provide a reliable tool to discriminate among two main surface processing techniques—that is, smoothing and burnishing—vertical scanning interferometry (VSI), a recently developed non‐destructive technique for analysing the surface roughness and topography, is applied. The smoothed areas have an obvious roughness expressed by linear structures. The latter are made of parallel ridges and trenches with an average depth of 15–20 μm. Burnishing leads to a lower topography and a lower roughness compared to the smoothed surface section. VSI quantifies the spatial distribution of the surface building blocks, which consist of phyllosilicate aggregates of variable size. The statistical treatment of the roughness data obtained by VSI shows that the surface topography provides significant information on the pottery processing and a clear qualitative and quantitative discrimination between different surfaces. VSI supports the reconstitution of the chaîne opératoire for traditional ceramic pottery and the recognition of the surface finishing techniques.

Review of several precision finishing processes for optics manufacturing

The ultrasmooth optical components with atomic-order surface roughness and nanometre-level shape accuracy are in immense demand with the rapid advancement of modern optical technology. In recent years, aspherical and free-form surfaces are gaining more interest for its favorable properties. Moreover, the new optical materials with immensely enhanced mechanical properties are being developed to meet the stringent requirements of modern optics. Fabrication of complex-shaped ultrasmooth optical components becomes a significant challenge as conventional finishing techniques are unable to machine aspherical or free-form surfaces precisely. This situation demands some highly deterministic finishing processes. Mostly, the optical components are fabricated by shaping or pre-finishing methods followed by final finishing processes. In the shaping or pre-finishing methods, the rigid abrasive tools are used to remove the material at an enhanced rate and near net shape of the elements can be attained. Surface finish and shape accuracy can also be improved to some extent. Owing to the presence of residual finishing marks generated by shaping methods, the application of the components is limited to the infrared (IR) optics. Final finishing processes include more deterministic and flexible polishing techniques that can achieve desired surface finish, figure accuracy and surface integrity to make it suitable for shorter wavelength applications. In recent years, single point diamond turning, precision grinding, plasma chemical vaporization machining and magnetorheological fluid-based finishing are widely used for fabricating ultrasmooth optics. In this article, principle, mechanism of material removal and applicability of the aforementioned precision finishing processes to different materials are discussed.

A novel magnetically driven polishing technique for internal surface finishing

This paper presents a novel magnetically driven polishing tool for internal surface finishing. Differing from the existing magnetic abrasive finishing or magnetic field assisted finishing (MAF) methods; this new technique performs material removal inside a tube using a spherical magnet with abrasives driven by external bar magnets. This configuration of magnets not only simplifies the design but also allows more flexibility in the potential application to internal finishing of manifolds. The physical principle was introduced and polishing experiments were conducted to investigate the effect of magnetic abrasive particles and abrasive size based on the two major criteria of surface roughness and material removal. The results unequivocally substantiated the capability of the developed method with a more than 98% improvement in surface roughness for ring polishing and an 86% improvement for section polishing. An analytical model was devised to illustrate the material removal mechanism of the proposed internal polishing technique based on the experimental results. The technique developed in the paper shows signs of future success in finishing internal surface of complex components in a wide range of industrial applications.

Surface topography and bacterial adhesion of CAD/CAM resin based materials after application of different surface finishing techniques

Aim: This study evaluated the surface topography and bacterial adhesion of a hybrid ceramic and a nano ceramic resin composite after different surface finishes. Methods: Hybrid ceramic (Vita Enamic, VITA - EN) and nano ceramic resin composite (Lava Ultimate, 3M/ESPE - LV) blocks of 12 x 14 x 18 mm were cut into 1 mm slices. Each slice was divided into four specimens (6 x 7 mm) that were randomly allocated into 4 groups (n=8) according to the surface finishing: CTL - without surface finish (control); DB - wear with a diamond bur; VT - polishing system for hybrid ceramic (VITA); and DD - polishing system for ceramics (Dedeco). The specimens were analyzed regarding surface roughness parameters (Ra, Rz, Rq), sterilized and subjected to bacterial adhesion. Representative specimens from each group were observed by SEM and Confocal Laser Scanning Microscopy. Data were submitted to two-way ANOVA and Tukey's test (α=0.05). Results: EN had lower surface roughness and bacterial adhesion than LV (p<0.05), regardless of the surface finish. The highest values for all roughness parameters was observed in LVDB group, differing from the other groups, which were not significantly different. Smaller bacterial adhesion values (CFU/mL) were observed for ENDD and ENVT, which differed significantly from the other groups, except ENCTL. For LV groups there was no significant difference between the different surface finishes (p>0.05). The type of material and surface finish system significantly interfered with surface roughness parameters and bacterial adhesion. The hybrid ceramic performed better after polishing than the nano-ceramic resin. Conclusion: An adequate finishing/polishing technique should always be performed after any kind of adjustment to indirect restorations made with these materials tested.

The effect of surface treatments on dental zirconia: An analysis of biaxial flexural strength, surface roughness and phase transformation

ObjectivesThis study investigates the effect of selected surface finishing techniques on the biaxial flexural strength, surface roughness and phase transformation of a zirconia dental restorative material. Materials and methodsFully-sintered zirconia discs (⌀19.5 mm × 0.85 mm) were treated on one side with a single or a combination of the following treatments: diamond and/or tungsten-carbide burs without water coolant in an air-turbine handpiece, air-particle abrasion, rubber-point polishing in a contra-angle handpiece, or no treatment (control). Biaxial flexural strength (BFS) (eleven groups, n = 10) was determined using a universal testing machine and surface roughness (thirteen groups, n = 6) was assessed using a profilometer. Results were analysed using one-way ANOVA and Student-Newman-Keuls Post-hoc test (α = 0.05) with Bonferroni correction. Specimens were observed under scanning electron microscopy (SEM) and x-ray diffraction (XRD) for their microstructure and crystalline phases respectively. ResultsGrinding with diamond burs did not weaken zirconia (p > 0.0045) but produced rougher surfaces than the control group (p < 0.0038). Tungsten-carbide burs smoothened diamond ground specimens (p < 0.0038) for both grits of diamond. Specimens ground by tungsten-carbide burs have significantly reduced mean BFS (p < 0.0045) by up to two-thirds and SEM revealed fine surface cracks. Air-particle abrasion restored the mean BFS of tungsten-carbide ground specimens to control levels (p > 0.0045) and surface cracks were not observed. Phase transformation was not detected by XRD. ConclusionsDental zirconia ground dry with tungsten-carbide burs has a significantly reduced BFS and a smooth but defective surface. These defects may be removed and BFS restored by air-particle abrasion. Clinical significanceThe use of tungsten-carbide burs for grinding dental zirconia should be cautioned. Diamond grinding does not weaken zirconia but requires further polishing.

The effect of different finishing and polishing techniques on surface roughness and gloss of two nanocomposites

ObjectivesThe aim of this in vitro study was to evaluate the effect of four finishing and polishing protocols in Surface Roughness (Ra) and Surface Gloss (Ga) of two different nanocomposites. Materials and MethodsIn total, 50 disc samples of a nanofilled resin and a nanohybrid resin were prepared. The samples were assigned randomly to one of the five groups to which different polishing protocols were applied. Analysis of surface roughness was performed using an Atomic Force Microscope (AFM), with the gloss evaluated using a gloss meter.Statistical evaluation of the results were analyzed using SPSS software, based on one-way ANOVA parametric tests along with the Welch correction and the Dunnett test for multiple comparisons of the tested protocols. ResultsThe results evidence the significant influence of the applied Protocol Types and Resin Types on Surface Roughness (Ra) and Surface Gloss (Ga). The multiple comparisons between polishing systems highlight the contrast between the most complex protocol, evidencing the lowest average Ra and the highest value Ga, and control protocol, evidencing the highest average Ra and the lowest percentage Ga. Filtek™ Supreme XT provided the best results in both Ra and Ga, in Protocol 4, while Brilliant Everglow™ performed better in Protocols 2 and 3. ConclusionsBoth Ra and Ga are dependent on the type of protocol used, as protocol 4 evidence a higher performance, depending also on the type of resins tested in the research, as nanofilled resin provided the best results. Furthermore, the gloss is influenced significantly by the surface roughness of the composite resin. Clinical RelevanceIn order to achieve excellent aesthetic appearance and high durability of the direct restoration, it is important to select initially the appropriate biomaterial for use and then to base preference for a polishing technique on achieving perfect results in the surface texture.

Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars

Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.