Papers by Keyword: Chipping

Abstract: Reducing the pressing temperature of plywood on the FF binder allows you to reduce its cost, but at the same time, the physical and mechanical characteristics of plywood deteriorate. Modification of the phenol-formaldehyde binder with hydrogen peroxide reduces the curing time of the phenolic binder, the pressing temperature of the FSF plywood, and improves the physical and mechanical properties of the FSF plywood. Regression models have been developed for dependence of the plywood strength during cleavage along the adhesive seam, strength during static bending, and thickness swelling after 24 hours in water on the factors varied in the experiment – the proportion of hydrogen peroxide addition and the pressing temperature. The IR spectra of plywood allow us to estimate the effect of H₂O₂ on the bonds involved in the structure formation of material. With the addition of hydrogen peroxide, the number of active methylene groups decreases, which indicates an increase in degree curing of modified binder.

Abstract: The reported paper presents a field pattern of sliding lines in a plastic zone of flow chip formation in the process of cutting metals considered for front and rear angles on the cutting blade other than zero. Equations of sliding lines for these conditions are proposed. Using calculation data, plasticity zone border lines are plotted for positive and negative front angles. The paper suggests methods and calculation data on average stress and plane stress state components in nodal points of the plastic zone of chip formation. The study provides data for plotting distribution diagrams of normal and tangential stresses of contact stresses on work surfaces of a cutting blade.

Abstract: Micro-machining of hard dies and molds for optical parts or precision instruments is required to extend die and mold life. This paper investigates the effect of cutting fluid on diamond tool life under micro V-groove turning of cobalt-free tungsten carbide. Zinc dialkyldithiophosphate fluid (ZnDTP) displayed excellent diamond tool wear resistance in previous experiments. The performance of this cutting fluid is compared to newly developed vegetable oil based cutting fluid with dispersed MoS₂ nanotubes. This paper investigates nanopolycrystalline diamond (NPD) tool life with a rake angle of 0° and-30° under continuous micro V-groove turning (i.e. face turning), of cobalt-free tungsten carbide using the developed cutting fluids. Superior diamond tool edge wear resistance is observed when using the dispersed MoS₂ nanotubes in vegetable oil and using a NPD tool with a-30° rake angle.

Abstract: The various feed rate and cutting speed have an important influence on cutting force, tool wear and chip morphology in machining titanium alloy. Cutting experiments are carried out analyzing the titanium alloy Ti6Al4V under different cutting speed and feed rate, the cutting force values are obtained. The analysis results show that the dominant wear pattern is adhesion wear and chipping. And the tool wear also has an influence on chip morphology.

Abstract: Purpose: To establish the incidence of chipping of zirconia-based restorations, either implant or tooth supported in a retrospective study. Material and methods: Sixty patients received 222 cemented units of zirconia-based restorations. One hundred thirteen units were cemented on teeth, 97 on implants and 12 units were pontics. After the delivery of the restorations, during the recalls, the patients were examined in regard to the presence of chipping of the veneering ceramic. Location of the restoration, the type of support and the design of the restoration were assessed as possible factors influencing chipping rate. Results: During an observation period of up to 5,5 years, 27 (12,16%) zirconia-based units showed chipping of the veneering ceramic. A total of 14 units had to be remade, resulting in a survival rate of 93,69% of the zirconia-based restorations. The chipping rate seemed to be higher in restorations on implants than those supported by teeth. In the molar region chipping occured twice as often as in the premolar and front regions (15,83% vs 7,84%). An increased chipping rate was observed in multi-unit restorations (13,95%) as compared to single-unit restorations (9,67%). Conclusion: Chipping of the porcelain veneering is the most frequent complication of zirconia-based restorations. They should be recommended with care in the molar region, especially as multi-unit restorations.

Abstract: The purpose of this study was to achieve grooving on glass substrates with high levels of efficiency and precision with the use of a diamond grindstone with a small diameter in the range of 1.0-1.8 mm. Mechanical material removal by grinding has high efficiency and enables process control for creating complicated forms, but has a drawback of generating chippings on the processed surface of the brittle glass material. The study gave ultrasonic vibration of 10 μm at 20 kHz in the thrust direction to the rotating small-diameter diamond grindstone in the grinding process, in order to attain high levels of efficiency and precision in micro-grooving of glass. The grooving approach with ultrasonic vibration did create some minor chippings, but succeeded in meeting the target of reducing the average size of chippings around the groove to 0.1 mm or less.

Abstract: We have developed a new scaife polishing machine for the purpose of polishing the high precision diamond cutting tools. As a high precision cutting tool, the high sharpness and flawless cutting edge are required. By using this polishing machine, the sharpness of a diamond tool at the cutting edge can be controlled within the range of 20nm. This machine is equipped with a submicron-scale mirror finished hardened-steel polishing Scaife, a supporting table can reduce the face deflection to less than 1μm, and a plastic diamond tool holder for protecting the edge of the diamond tool from the unexpected shock, which is supported by three points consisting of the edge of diamond tip and two control screws, this structure can help to adjust the work surface to any angles by only adjusting the two control screws. To facilitate the advanced angle operations, the algorithm was created to calculate the overhang length variations of the two control screws for controlling the changes of roll- and pitch-angle of the diamond tools.

Abstract: Cutting tool material technology in recent years has made great strides with substantial improvements in their strength, toughness, and wears resistance, which are designed to increase productivity, improve tool selection and aid to decrease costs and promote machining quality. This investigation presents the effect of various cutting speeds in turning of Al6061 with respect to different coatings. Experiments carried out under orthogonal dry cutting, and two different cutting speeds applied which were 250, 500 m/min. Feed rate and depth of cut kept constant respectively at 0.05 mm/rev and 0.5 mm in experiments. Three different carbide cutting tools have been used namely CVD tri-phase multilayer TiC/TiCN/TiN coated, PVD TiN coated and CVD TiC/Al2O3 coated. Tool performance was determined with respect to tool wear and surface finish in tests. Results obtained that tri-phase coated illustrated longest tool life, however best surface finish achieved by TiN coated tool. In addition adhered material which mainly formed in CVD tri-phase TiC/TiCN/TiN and TiC/Al2O3 coated tools, at higher cutting speed deteriorated surface finish in comparison to lower cutting speed.

Abstract: Glass disks are used as substrates for the recording media in magnetic disk devices. To mass produce glass disks, a technology is required for machining glass (a material that is difficult to machine) with both high precision and high efficiency. Consequently, this study adopted a method that processes the inner- and outer-diameters simultaneously using a double core tool. In addition, the thrust force in coring process was also reduced using an ultrasonic spindle to apply ultrasonic vibration to the feed direction of the rotating tool. This resulted in high quality machining with less chipping. Furthermore, this study conducted experiments to compare the three methods of stabilizing the stack of glass substrates. As a result, it was found that the method using ultraviolet curable resin was able to limit the chipping to a smaller size.

Abstract: Rubbing tests between a diamond stick and a tungsten carbide plate and planing experiments of cobalt-free tungsten carbide using a mono-crystalline diamond tool are conducted, and the effect of lubricants on tool wear is investigated. Five kinds of lubricants such as: sulfur-base extreme-pressure additive; dimethyl-silicone; oleic acid; zinc dialkyldithiophosphate (ZnDDP); and chemical solution type coolant (FGC950) are chosen for the lubricants. Through the rubbing experiments, diamond stick wear is the greatest when using dimethyl-silicone, followed by FGC950 and it is the least using ZnDDP. On the other hand, tool edge chipping is the greatest when using FGC950, followed by sulfur-base extreme-pressure additive and it is the least using ZnDDP. Through the planing experiments, tool chipping is dominant in diamond-tool wastage in comparison with abrasive wear. Tool life is the longest when using ZnDDP and obtained surface roughness is 0.022 mm Ra after 177 m planing.