金刚石工具磨削石材摩擦磨损特性实验研究

使用电镀金刚石工具磨削石材,通过改变不同的实验参数,对金刚石工具的摩擦磨损特性进行研究。在MMW-1型立式万能摩擦磨损试验机上测试了工具在室温条件下干摩擦磨损性能,采用FA2004电子天平测量金刚石工具的磨损量,用VDM600体式电子显微镜对工具磨损表面进行微观形貌观察,用HV-1000显微硬度计测量石材的显微硬度。实验结果表明:金刚石工具的磨损量和摩擦系数都随着载荷的增加而增加,同时也随主轴转速增加而增加;另外,工具的磨损量和摩擦系数随着石材硬度的增加而增加。     

Bio-mimetic surface structuring of coating for tribological applications

A novel multilayered coating was developed for applications associated with friction reduction and wear resistance improvement. The nano-engineered coating integrates a soft lubricating layer, consisting of MoS₂-PTFE, onto hard load-supporting layers, with controlled surface morphology (roughness and patterning) of cBN-TiN. The coating was synthesized by sequential procedures including electrostatic spray deposition of cBN particles with different average particle sizes, chemical vapor deposition of TiN, deposition of nano- and micro-sized MoS₂ dispersed in PTFE, and curing. The effect of cBN particle size (with different combinations of particle size) and deposition parameters (specifically electrical voltage) on the cBN-TiN surface morphology were studied experimentally and optimized. SEM characterization of the as-synthesized cBN-TiN coating shows surface features similar to that of colocasia esculenta, with alternating nano- and micro-sized domes and “pockets”; the MoS₂-PTFE top layer has MoS₂ particles retained in the pockets by a basket structure formed during PTFE curing. Tribological and scratch tests were carried out for the as-prepared cBN-TiN and cBN-TiN/MoS₂-PTFE multilayered coatings. Sliding test results demonstrate significantly lower friction coefficient for the multilayered coating, showing that the unique integration of soft lubricating layer and biomimetically structured hard layer can effectively improve tribological performance. It is suggested that lubrication at the frictional contacts was realized by continuous release of the lubricants, MoS₂ and PTFE, from the pockets.     

Injection molded spherical grinding tools: manufacture and application of a novel tool concept for micro grinding

Micro grinding offers the possibility of machining micro structures in hard and brittle materials producing small-scaled parts. Novel micro grinding systems and machines require miniaturized tools and spindles to meet the demands of small or desktop machines providing a small working space. This paper introduces a novel grinding module called ’GrindBall’, with highly integrated tool drive and bearing functions as well as a shaft-free, spherical grinding tool for micro machining applications in small-scaled machine tools. One of the challenges within the development of the GrindBall module is the manufacture of spherical grinding tools, which are not commercially available. A promising method to produce such grinding tools, the injection molding of micro particle filled polymers, is demonstrated in this paper. Injection molding and grinding experiments show that such spherical grinding tools meet the main requirements of this novel grinding technique and show significant material removal rates.     

Multicomponent nanostructured films for various tribological applications

Many engineering materials working under severe cutting, stamping, or bearing conditions including humid and corrosive environments, as well as temperature fluctuation require a combination of chemical, mechanical, and tribological properties. For load-bearing metallic implants, the combination of excellent mechanical and tribological properties with biocompatibility and bioactivity is also of great importance. Desired properties can be achieved in hard films based on carbides, borides and nitrides of transition metals by alloying with metallic (Al, Cr, Zr) or nonmetallic (O, P, Si, Ca) elements. The present work demonstrates the potential of self-propagating high-temperature synthesis (SHS), magnetron sputtering (MS), and ion implantation assisted MS of SHS-composite targets to produce multicomponent nanostructured films with enhanced combination of properties. Three groups of recently developed films for mechanical engineering and medicine are considered: hard tribological Ti–(Al, Cr)–(Si, B, C, N) films with enhanced thermal stability, corrosion and oxidation resistance; nanocomposite and multilayered TiCrBN/WSe_x films with improved lubrication; and multifunctional bioactive nanostructured (Ti, Ta)–(Ca, Zr)–(C, N, O, Si, P) films (MuBiNaFs).     

ELID grinding and tribological characteristics of TiAlN film

This paper presents the results of electrolytic in-process dressing (ELID) grinding experiments performed on TiAlN film and characterization of the tribological characteristics of the produced films. In advanced films coated by physical vapor deposition, such as CrN and TiAlN, the low surface roughness required for attaining superior tribological characteristics is difficult to attain by use of only a coating process. ELID of grinding wheels improves wheel performance, enabling the attainment of specular finishes on brittle materials, with surface roughness on the nanometer scale (4 to 6 nm). In the present study, high-quality TiAlN film surfaces were fabricated by the ELID technique, typically achieving a surface roughness of around Ra 0.0024 μm by employment of a SD#30,000 wheel. Scanning electron microscopy reveals that ELID improved the finish, as indicated by the shape of grinding marks. Chemical element analysis by an energy-dispersed x-ray diffraction system suggests that ELID grinding formed an oxide layer in the machined surface of TiAlN film. Therefore, in addition to the highly smooth surface, an oxide layer formed by ELID grinding imparts superior tribological properties to ELID-ground TiAlN film.     

Structure-property relations in ZrCN coatings for tribological applications

ZrCN coatings were deposited by dc reactive magnetron sputtering with N₂ flows ranging from 2 to 10 sccm in order to investigate the influence of the nitrogen incorporation on structure and properties. Information about the chemical composition was obtained by glow discharge optical emission spectroscopy and Rutherford backscattering spectroscopy. The evolution of the crystal structure studied by X-ray diffraction revealed the formation of a face-centred cubic ZrCN phase for N₂ flows greater than 4 sccm. Additionally, the presence of an amorphous phase in the coatings deposited with the highest N₂ flows could be evidenced by Raman spectroscopy and X-ray photoelectron spectroscopy. This phase can act as a lubricant resulting in a low coefficient of friction as shown in the conducted ball-on-disc tests. Nanoindentation measurements showed that coatings deposited with a 6 sccm N₂ flow had the maximum hardness which also revealed the best performance in the conducted dry cutting tests.     

Influence of controlled tool orientation on pattern formation and waviness in surface grinding

The surface of ground components can exhibit quality impairments which are attributed to grinding wheel irregularities. A remaining grinding wheel imbalance or a non-uniform grinding wheel topography results in a radial run-out which strongly affects the generated surface. By measuring and adjusting the phase-shift of the grinding wheel orientation during consecutive grinding passes, the resulting workpiece surfaces can significantly be improved. Experimental investigations show a strong effect of the phase-shift on the waviness profile and the pattern formation, as the pattern wave length coincides with the tangential feed. Setting the phase-shift directly affects the engagement conditions like the contact stiffness, remarkably influencing the dynamic process behaviour. The amplitudes of the normal force at rotational frequency have a strong effect on the workpiece surface, which can be influenced by a variation of the phase-shift. Constancy of table oscillating period will further increase due to faster machine control hardware, making longer periods of constant phase-shifts more likely to occur. As this parameter is mostly uncontrolled, it can cause intermittent grinding errors.     

Toward a new tribological approach to predict cutting tool wear

This work aims at improving the numerical modelling of cutting tool wear in turning. The key improvement consists in identifying a fundamental wear model by means of a dedicated tribometer, able to simulate relevant tribological conditions encountered along the tool–workmaterial interface. Thanks to a design of experiments, the evolution of wear versus time can be assessed for various couples of contact pressure and sliding velocities (σ_n, V_s) leading to the identification of a new wear model. The latter is implemented in a numerical cutting model to locally simulate tool wear along the contact with regard to each local tribological loading.     

Hard CrCN/CrN multilayer coatings for tribological applications

Hard coatings were deposited using a cathodic arc evaporation method. The results of investigations of multilayer CrCN/CrN coatings are presented in this article. The microstructure and crystallinity of films have been investigated using X-ray diffraction (XRD). The composition was determined with energy dispersive spectroscopy (EDS). The adhesion of films was estimated on the basis of an analysis of scratch-test results. The hardness and tribological properties of films deposited on hardened and tempered HSS substrates were also investigated. The tribological tests were carried out in a pin-on-disc geometry. The influence of a normal load, sliding speed and a counterpart material on the friction coefficient and the specific wear rate of the coatings were studied. The counterparts were made of HSS and four types of wood: oak, beech, spruce and pine. The hardness and adhesion of multilayer CrCN/CrN coatings are respectively 25 GPa and 120 N.     

Nanolayer coatings for hard disk and demanding tribological applications

Coating properties and performance can be tailor-designed by proper control of nano structure andprocess conditions. This paper presents two examples: first, the synthesis and optimization of 1 nm thick nitrogenated carbon (CN_x) nano-layers as protective overcoats in extremely highdensity harddisksystems, and, second, the development of multilayer coatings for wear protection at elevated temperatures. Synthesis of these coatings was done by magnetron sputtering. These studies demonstrate that one canproduce atomically smooth 1 nmthickCN_xovercoatswith acceptable corrosionperformance. In addition, this paper shows that, with the proper choice of nanolayer thickness and process conditions, superhard coatings based on TiN/SiN_x and TiB₂/TiC multilayers with high thermal stability, low internal stress, and high wear resistance can be synthesized.     

钢轨打磨用新型复合砂轮及其磨削试验

利用钎焊技术和传统热压技术研发出一款钢轨打磨用新型复合砂轮,复合砂轮除含传统树脂砂轮的成分外还含金属结合剂金刚石插片,用其在钢轨打磨试验机上与传统树脂砂轮进行工件打磨对比试验,分析工件打磨后的打磨温度和表面粗糙度变化,并对钢轨打磨后的磨屑进行电镜、能谱分析。试验结果表明:与纯树脂砂轮相比,采用新型复合砂轮打磨工件,其打磨温度峰值下降10%左右,砂轮中插片数越多下降比例越大;工件表面粗糙度下降比例在9%以上,且随着砂轮中插片数量的增加而增大;同时,磨屑中球状磨屑比例更低,球状磨屑中O元素质量分数更小。      

Mirror surface grinding of ceramics using a three-axis precision cnc grinding machine

In this paper, the mirror surface grinding of ceramics, such as Si₃N₄ and Al₂O₃---TiC, was realized with average roughness less than 10 nanometers. For the grinding operation, a three-axis CNC grinding machine tool was designed and manufactured. The grinding machine is composed of an air spindle, a high damping resin concrete bed and a three-axis CNC controller with high resolution AC servo motors. The dynamic properties of the grinding machine, such as the natural frequencies and damping of the spindle, were experimentally measured to improve the ground surface quality. Also, the truing method to improve the straightness of the grinding wheel with 1 μm accuracy, was developed.     

Flexible forming tool concept for producing crankshafts

Forging, casting and machining compete on quality and price for the production of crankshafts. Forging and casting are commonly utilized for mass production because the capital investment in equipment and tooling are very high. Machining is employed only in case of small production batches of high quality crankshafts made from materials that are normally difficult to forge or cast because it is time and energy intensive, generates a lot of waste and is generally more costly than forging and casting.As a result of this, conventional manufacturing routes for crankshafts are not suitable for flexible small to medium-batch production and, therefore, are not appropriate for the growing agile manufacturing trends requiring very short life-cycles and very short development and production lead times.This paper is concerned with these issues and is focused on the development of an innovative forming tool concept for producing small to medium-batches of cost competitive crankshafts. The proposed tool concept combines knowledge on buckling of solid rods under compression with flexible construction solutions based on modular dies to allow crankshaft production to change output rapidly. Single cylinder to multi cylinder crankshafts including multiple main bearing journals, crankpins and crank webs can be easily produced by fastening or removing appropriate die modules in the overall tool set.The presentation is illustrated with test cases obtained from finite element modelling and experimentation with a laboratory prototype tool conceived to operate exclusively with lightweight materials exhibiting high ductility in cold forming.     

Development of a micro diamond grinding tool by compound process

This study presents a novel micro-diamond tool which is 100 μm in diameter and that allows precise and micro-grinding during miniature die machining. A novel integrated process technology is proposed that combines “micro-EDM” with “precision composite electroforming” for fabricating micro-diamond tools. First, the metal substrate is cut down to 50 μm in diameter using WEDG, then, the micro-diamonds with 0–2 μm grain is “plated” on the surface of the substrate by composite electroforming, thereby becoming a multilayer micro-grinding tool. The thickness of the electroformed layer is controlled to within 25 μm. The nickel and diamond form the bonder and cutter, respectively. To generate good convection for the electroforming solution, a partition designed with an array of drilled holes is recommended and verified. Besides effectively decreasing the impact energy of the circulatory electroforming solution, the dispersion of the diamond grains and displacement of the nickel ions are noticeably improved. Experimental results indicate that good circularity of the diamond tool can be obtained by arranging the nickel spherules array on the anode. To allow the diamond grains to converge toward the cathode, so as to increase the opportunity of reposing on the substrate, a miniature funnel mold is designed. Then the distribution of the diamond grains on the substrate surface is improved. A micro-ZrO₂ ceramic ferrule is grinded to verify the proposed approach. The surface roughness of R_a = 0.085 μm is obtained. It is demonstrated that the micro-diamond grinding tool with various outer diameters is successfully developed in this study. The suggested approach, which depends on machining applications, can be applied during the final machining. Applications include dental drilling tools, precision optic dies, molds and tools, and biomedical instruments.     

Trenker公司推出生产大规格金刚石/CBN电镀砂轮的新概念设备

德国Trenker磨料磨具设备技术公司开发出了新系列电镀设备，实现了制造大规格，大型号的金刚石和立方氮化硼（CBN）外圆磨及仿形磨电镀砂轮，砂轮直径最大可达700mm，重量达300kg.     

Interactions of grinding tool and supplied fluid

This paper reviews the physical and chemical interactions between the rotating tool and the supplied fluid in grinding. The mechanisms of this tool-fluid interaction are the key for high performance grinding processes due to an efficient fluid supply resulting in a minimal thermomechanical impact on workpiece and tool. Reduced wear, increased surface finish, suitable subsurface properties of the machined material, increased material removal rates, and also energy efficiency can be achieved. In this context, the fluid supply towards the contact zone between tool and workpiece, the tool cleaning with high pressure cleaning nozzles as well as (tribo)-chemical phenomena between the abrasive layer and the supplied fluid are analysed and discussed. Finally, knowledge gaps are revealed which are indicating future research needs.     

Dynamic modeling of a novel workpiece table for active surface grinding control

In order to implement active control during surface grinding, a workpiece micro-positioning table utilizing a piezoelectric translator has been developed. The workpiece table has a working area of 100×100 mm and a nominal working range of 45 μm. The resolution of the workpiece table is less than 20 nm and the natural frequency is 579.2 Hz. The rigidity of the workpiece table under the open loop condition is approximately 17 N/μm. Under the closed loop condition, the rigidity is better than 400 N/μm. The design of the workpiece table is presented together with considerations to achieve the high dynamic characteristics, where the maximum acceleration is up to 33g (g is the acceleration of gravity). The dynamic models of the piezoelectric translator and the workpiece table have been established. Experimental testing has been carried out, verifying the performance of the workpiece table and the established dynamic models for the workpiece micro-positioning table.     

Micro grinding tool for manufacture of complex structures in brittle materials

This paper presents a novel micro shaft grinding tool with cylindrical tool tip diameter between 13 μm and 100 μm. The manufacturing of the tool itself is carried out on a prototype desktop machine. The shaping of the tool is accomplished by grinding the tool tip directly onto the cylindrical carbide tool shank. During tool grinding, the tool shank rotates in a micro spindle with air-lubricated bearings, leading to high concentricity and low run-out. The tool tip is electrically nickel plated with diamond grains. During first experimental tests of the tool, very low surface roughness values and sharp edges without burrs were achieved.     

SiC陶瓷非球面磨削工艺实验研究

为了研究磨削工艺参数对SiC材料磨削质量的影响规律,利用DMG铣磨加工中心做了SiC陶瓷平面磨削工艺实验,分析研究了包括主轴转速、磨削深度、进给速度在内的磨削工艺参数对工件表面粗糙度的影响。结果表明:工件表面粗糙度随着主轴转速的增加而减小,随着磨削深度和进给速度的增加而增加。在粗糙度工艺试验的基础上,以表面粗糙度最小为目标优选一组磨削工艺参数,进行了小口径SiC陶瓷非球面磨削实验,获得了较低的表面粗糙度值(0.5150μm)和较小的面形精度误差(4.668μm)。     

Rotary dressing model for grinding wheel active surface prediction

A kinematic model of rotary dressing of corundum grinding wheels is presented. Based on wheel and dresser specifications and process kinematics, effects of rotary dressing parametres on wheel topography are predicted. For model validation, wheel surface is characterized by areal roughness parametres, obtaining a deviation less than 15%. Besides, influence of wheel topography on ground part surface quality is investigated. Results highlight the significance of modelling the dressing process and show the model translates into a useful tool for selection of most suitable dressing parametres for achieving specific surface qualities. Moreover, it eases the way to predicting dressing originated defects.