Large Grinding Research Articles

Analisis dan Upaya Preventif Risiko Tingkat Kebisingan Pekerjaan MEP (Mechanical, Electrical, Plumbing) Konstruksi Rumah Susun di Ibu Kota Negara

Construction work is one of the jobs that has various high risks for workers and people who are around it. These risks come from various sources, one of which is noise from various equipment and ongoing activities. One of the jobs that cause high noise in construction work is MEP (Mechanical Electrical Plumbing) work. Based on Permenaker Number 13 Year 2011, the Threshold Value (NAB) for noise that can be accepted by workers is 85 dBA for 8 hours a day. Based on the measurement of the construction of the flats, the MEP work in the form of Beam Separator Elevator Installation, Pipe Fabrication, Electrical Wiring Lighting Installation, as well as Welding and Grinding of Iron Pipe causes noise above the NAB. The highest noise comes from pipe fabrication in the form of iron pipe cutting activities using large grinding tools and bevel machines that produce noise of 107 dBA. From the Daily Noise Dose (DND) calculation, the noise generated from MEP work has a dangerous risk level for workers' hearing. Risk control efforts that can be done are preventive actions based on the K3 hierarchy in the form of administrative controls such as changing working hours or shifts and conducting safety talks before work is carried out. In addition, another preventive measure is the use of PPE such as ear plugs. Based on the calculation of the noise reduction level, the use of ear plugs has not reduced the noise level to reach the NAB, so it is recommended that workers in pipe fabrication work use ear muffs to reduce noise exposure.

Study on nickel-based single crystal superalloy DD6 subsurface damage of belt grinding with a large cutting depth of one pass

Single crystal superalloy has been widely utilized as a crucial manufacturing material for aeroengine turbine blades due to its excellent properties. However, machining this alloy is easy to cause subsurface damage, resulting in the engineering failure of blades. To explore a large cutting depth and low damage processing method, this paper established a grinding depth analytical model for the abrasive belt. The model provides insights into the material removal behavior mechanism during belt grinding and predicts the impact of process parameters on the grinding depth. Subsequently, the grinding experiments of this alloy with different abrasive belts were conducted. The experimental results showed that grinding depth increased as normal force amplified and exhibited a nonlinear growth pattern with the reduction of feed velocity. This preliminary verified the prediction model of grinding depth. The material removal properties of the pyramid, diamond, and hollow-sphere belts were analyzed, and the ratio of material removal capacity for the three was found to be 12:8:5. Based on the analysis of the topography and roughness of the grinding surface, the study examined the influence mechanism of grinding force, feed velocity and abrasive grain morphology on grinding depth and surface quality. The subsurface damage behavior mechanism and recrystallization depth change law of belt grinding were revealed. The grinding depth of the pyramid and diamond belts could exceed 160 μm and the recrystallization depth was less than 5 μm. To achieve efficient and low-damage machining, it is recommended to reduce the feed velocity rather than increase the grinding normal force. It is important to note that the feed velocity should not exceed 10 mm/s. This study is to furnish a theoretical groundwork and offer engineering technical recommendations for achieving large grinding depth and low damage machining of single crystal superalloy.

Ultrasonic-Assisted Grinding of Microholes Using Ultrasmall-Diameter Cemented WC Tools

Although grinding is a widely employed method for hard and brittle materials, drilling microholes requires the use of an ultrasmall-diameter grinding wheel that is difficult to fabricate and breaks easily when grinding force is applied, resulting in a high tool cost. To solve this problem, cemented WC micropins were fabricated by electrical discharge machining, and microholes were drilled using them as micro-grinding tools with the assistance of ultrasonic oscillation. The micropin tools can be employed in grinding because the convex parts of the electrical discharge craters formed on their surfaces serve as cutting edges of abrasive grains in grinding wheels. To clarify the drilling conditions necessary for ultrasmall-diameter tools to drill holes with a diameter less than 5 µm, the relationships between drilling conditions and drilling characteristics were investigated. The drilling conditions included the tool rotation speed, tool feed speed, ultrasonic oscillation amplitude, and use of grinding fluid. The drilling characteristics included the hole diameter and grinding force evolution. The investigation showed that a high tool rotation speed prevented the increase in the grinding force because of the faster grinding speed. A low tool feed speed was favorable to lower grinding force. At a high tool feed speed, most likely, the tool was fed before the workpiece material was sufficiently removed, thereby exhibiting a large grinding force. The ultrasonic oscillation amplitude had no noticeable effect on the grinding force. The hole diameter was not affected by the tool rotation speed, tool feed speed, or ultrasonic oscillation amplitude. Although the use of grinding fluid reduced the grinding force, the hole diameter increased, probably because enhanced lubrication caused the tool to slip on the workpiece surface at the beginning of drilling, resulting in an increased rotational runout. Under the favorable conditions obtained, a hole of 3.2 µm in diameter was successfully drilled in crown glass.

Terminal sliding mode control based on recursive stochastic configuration network for ball mill lining replacement process

The precise control of multi-joint manipulators presents significant challenges in the context of replacing internal liners of large grinding machines. These challenges arise due to the uncertainty of system parameters and external disturbance. A terminal sliding mode control based on a recursive stochastic configuration network is proposed to ensure that the system is stable, and it reduces system oscillations in this article. In addition, a disturbance observer based on recursive stochastic configuration network is designed to estimate and compensate for the uncertainties in the system, thereby improving the robustness of the system. To enhance the realism of the simulations, the simulation modeling process incorporated uncertainty parameters and external disturbance information. The simulation results demonstrated the effectiveness of the proposed terminal sliding mode control approach in meeting the practical control requirements. This accomplishment presents a valuable new method for controlling mechanical arms. The method is applicable under conditions of system uncertainty and external disturbance.

Microstructure Evolution and Formation of Gradient Structures in Single Crystal Nickel-Based Superalloy by Surface Mechanical Creep-Feed Grinding Treatment.

Gradient structures have been created in single crystal nickel-based superalloys (SX alloys) via surface mechanical creep-feed grinding treatment (SMCGT). It has been found that these gradient structures are mainly composed of nano-sized grains, sub-micron-sized grains, dislocation structures, and the matrix material of single crystals along the depth from the treated surface. In addition, the evolution of such structures is found to be dominated by the dislocation movements which run through both γ channels and γ' precipitates, subdividing the two types of microstructures into various dislocation structures, and eventually introducing the refined grains into the surface layer. Furthermore, the evolution process of gradient structures primarily originates from the mechanical effect between abrasive grits and workpiece material, owing to the large grinding force (up to 529 N) and low grinding temperature (less than 150 °C) during the unique creep-feed grinding treatment in the present investigation. Due to the typical grain refinement, the hardness of the nanostructures exhibits the largest value of around 10 GPa in the surface layer, approximately 26% higher than that of the matrix material. This study further enhances the understanding of the microstructure-property relationship of SX alloys subjected to creep-feed grinding treatment and contributes to achievement of high-performance components.

Simulation and Compensation of Axial Geometric Errors for Cycloidal Gears Based on Form Grinding

To increase quality, reduce cycloidal gear noise, and avoid unnecessary vibration and shock, a compensation of axial geometric errors method is proposed based on the cycloidal gear form grinding. In the process of machining cycloidal gears, the relative position relationship between the grinding wheel and workpiece is affected by geometric errors of the motion axes, which has serious effects on the surface accuracy of the cycloidal gears. Combined with cycloidal gear form grinding kinematic principles, a geometric error model for each axis of a four-axis computer numerical control form grinding machine is established. By changing the compensation value of the geometrical errors on six degrees of freedom, the error of the cycloid gear tooth surface machined is obtained. Based on a sensitivity analysis of geometrical errors of each axis, the corrections are determined through an optimization process that targets the minimization of the tooth flank errors. The geometric errors of each axis of the cycloid gear grinding machine are compensated, and then, the cycloid gears produced by the machine are processed. Through the processing experiment, the error data of the actual processing before and after the compensation are compared, which indicates that the machining accuracy of the cycloid gear grinding machine is obviously improved. It has an important guiding significance in improving the precision and performance of large CNC form gear grinding machines.

Gating systems in the casting grinding balls technology

The article presents a number of experimental and research works on the development of parameters of the casting technology of grinding balls by casting in a lined coquille (chill mould) with a vertical connector. The influence of a multi-level gating system on the efficiency of filling the mold cavity of lined coquilles with melt, on the quality of crystallization of large grinding balls, as well as on increasing the output of suitable casting was revealed. The influence of the thickness of the facing layer on the crystallization of large grinding balls is studied. The effect of modifiers containing barium, magnesium and cerium on the physical and mechanical characteristics of grinding balls and separately cast samples is investigated. Technology has been developed to eliminate contraction cavity in cast grinding balls by enhancing direct crystallization by partially replacing the facing layer with a heat-resistant water coating. The equipment for large-lot production of high-quality large grinding balls developed by OJSC “BELNIILIT” and competitive to world analogs is proposed.

Research of the Process of Production of Steel Square Continuous Billets for Rolling Balls of Large Diameter

The paper investigates the technology of production of steel billets continuously cast billets for rolling balls of large diameter. In Kazakhstan, in connection with the development of new copper deposits such as Aktogay and Bozshakol, the need for large diameter steel grinding balls for primary ore processing has increased. The main problem in the operation of large diameter grinding balls is the tendency of the grinding media to break during operation. The authors of the work investigated the process of production of steel billets continuously cast billets with a cross section of 150 × 150 mm for rolling balls of large diameter (d 125 mm) in the PB LLP "KSP Steel", which showed that the breaking of grinding balls is initiated mainly by the presence of internal discontinuities (gas axial looseness) in continuously cast billets. Studies have shown that the technological scheme for the production of grinding balls with a diameter of 125 mm from continuously cast billets with a section of 150 × 150 mm, including steel smelting in an arc furnace with steel finishing on a ladle-furnace unit, deoxidation with aluminum and degassing in a ladle vacuum apparatus, casting steel in a closed jet on a continuous casting and further production of rolled stock on a rough rolling mill ensures the absence of internal discontinuities (gas bubbles, axial looseness) in the workpieces and ensures the production of high quality balls.

A Study on Bistability Analysis and Chatter Suppression for Roll Grinding Process

ABSTRACT As chatter vibration in roll grinding process is the largest limitation in surface quality of machined roll. In this paper, the bistability analysis and chatter suppression are performed for further discussion of patterns of the grinding chatter to reduce the cost of enterprises. A new three degrees of freedom dynamic model with both the regenerative effect and nonlinear stiffness of grindstone indicated by Duffing oscillator is presented, and its availability is validated by the experiment. By means of the DDE-BIFTOOL, a numerical calculation package, the effect of process parameters on grinding stability is studied extensively, proving that a large grinding width worsens the stability in roll grinding and the parameters locating in unsafe areas should be avoided for a stable grinding operation in practice. In addition, the control techniques involving both the nonlinear velocity feedback and the chaos perturbation are proposed for the suppression of chatter vibration in grinding operation to decrease the amplitude of its vibration. The results show that these techniques give a significant performance for reducing the amplitude of chatter vibration, namely, the stability of grinding process is augmented, which give a new idea for firms in chatter suppression.

Study on evaluation of tip shape of abrasive grains on acting surface of large grinding wheel in surface grinding

Study on evaluation of tip shape of abrasive grains on acting surface of large grinding wheel in surface grinding

Microstructure and mechanical behaviors of grinding balls produced by dual matrix structure two-step austempering process

The austempered ductile iron (ADI) grinding balls were austenitized at 900 °C for 2 h and then incomplete quenched in a sodium silicate solution for 100 s, after that austempered in an isothermal furnace at 230 °C for 1 h. Different from the two-step austempering process, this process can prepare a two-phase structure through the incomplete quenching stage and austempering stage, so we called it a dual-matrix structure (DMS) two-step austempering. This work aims to investigate the effect of different concentrations of sodium silicate (30 wt.%, 40 wt.%, 50 wt.% and 60 wt.%) as the incomplete quenching medium on the microstructure and properties of ADI. The microstructure, mechanical properties and wear resistance of ADI were analyzed using SEM with EDS, hardness testing (rockwell) apparatus and impact-toughness tester, as well as friction wear testing and impact wear testing. The result shows that the martensite and lower ausferrite phase in the DMS grinding balls gradually transform to lower ausferrite and upper ausferrite with increasing concentration of quenching liquid. As the sodium silicate concentration increased from 30 wt.% to 60 wt.%, the lower ausferrite volume fraction has initially increased and then decreased. DMS two-step austempering with a 40 wt.% sodium silicate produced the grinding balls with lower ausferrite and a small amount of tempered martensite that has the best overall mechanical properties and wear properties, which were suitable for application of large grinding machines. Besides, this work developed a new method to replace the salt bath austempering process, which was environmentally friendly.

Mechanical grinding method of multi-axis linkage for elliptic contour based on algebraic geometry

Aiming at the shortcomings of traditional elliptic contour grinding methods, such as large grinding roughness and poor contour accuracy, a multi-axis mechanical grinding method based on algebraic geometry is proposed. This method studies the first attempt of elliptic contour. The process includes selecting suitable multi-axis grinding tools and selecting appropriate grinding methods according to grinding process. Using specific workpieces, grinding path planning, motion attitude determination and error compensation based on algebraic geometry for multi-axis mechanical grinding are carried out. The results show that compared with the traditional grinding method, the device has the smallest surface roughness, the contour radian is closer to the expected results, and has higher performance, which solves the grinding defects.

Analysis of load sharing capability of a series-connected twin synchronous motor drive coupled to a common load shaft by gearing

Torque limitations on gear teeth led to the use of two motors on opposite sides of the gear to drive large grinding mills. For such systems, motor overheating and rapid gear-teeth wear have been observed, especially when using synchronous motors due to load imbalance between the two motors. This paper studied a drive system consisting of two separate three-phase synchronous motors whose phase windings are split into two sections in a manner that makes them appear as six-winding machines, and then each of the resulting six windings of one motor are connected in series with those of the other motor, with no phase transposition, such that only three terminals of each motor are available to be connected to supply. The field windings are connected in parallel to the same source. Again, the motors, running on separate shafts, are connected to a common load shaft through a speed reduction gear driven through pinions. A detailed mathematical model is developed in the q-d axis, and the system is implemented on the MATLAB/ SIMULINK environment. A circumferential error in the girth gear was modeled to introduce load imbalance. It is observed that despite the load imbalance, the stator currents and the load torque seen by the two motors are the same. However, a variation is observed in their rotor angles. This suggests that while the motor units inherently share the mill load equally thereby removing the possibility of motor overheating, the varying rotor angle may represent a problem for the motor shafts. Keywords: Six-winding Machine, Synchronous Motors, Series-Connected, Common Load Shaft, Speed Reduction Gear, q-d Axis

Large circulation grinding system

Large circulation grinding system

Experimental study on the characteristics of high speed cylindrical plunge grinding for annealed bearing steel 100Cr6

The bearing steel such as 100Cr6 offers many desirable characteristics for industrial use in terms of its excellent qualities of high hardness, high wear resistance and high contact fatigue strength. For the usage in the bearing, cylindrical grinding should be adopted to machine 100Cr6. In order to ensure processing quality and processing efficiency, it is necessary to carry out high speed grinding. Therefore, the orthogonal experiments of high speed cylindrical plunge grinding (HSCPG) were carried out on the annealed 100Cr6 with a ceramic bonded cubic boron nitride (cBN) grinding wheel, to study the effects of grinding wheel speed, workpiece speed and grinding depth on the grinding force, grinding temperature, surface roughness, surface morphology, surface hardening and deteriorative layer. The study demonstrates that a larger material removal rate and a better surface integrity can be achieved simultaneously by a large grinding wheel speed, a moderate workpiece speed and grinding depth.

A fundamental study of leaching kinetics and mechanisms of molybdenite assisted by mechanical activation

The mechanical activation was applied as a pre-treatment method to improve molybdenite (MoS2) leaching. The effects of grinding ball size, ball to powder mass ratio, milling speed and time, molar ratio of mineral to oxidants, as well as the influence of solution pH, temperature and leaching time were investigated in detail. The results showed an extremely low Mo extraction (less than 2% at acidic and neutral conditions) for MoS2 activated alone. However, Mo extraction was increased significantly after co-grinding of MoS2 with NaClO2 and Na2CO3, e.g., more than 58% in any leaching solution applied. Prolonging the grinding time improved Mo extraction but the efficiency was declined gradually, giving rise to an optimum grinding efficiency at 4 h with a molar ratio of 1:3:5 for MoS2:NaClO2:Na2CO3. Distilled water was selected as the leaching solution since this gave similar Mo recovery to other lixiviants. Higher temperature and longer leaching time were beneficial to Mo extraction. However, it was also found that too large grinding balls and high ball to powder mass ratio adversely affected MoS2 extraction. The kinetics analysis indicated that the leaching of activated MoS2 followed a chemical reaction controlled mechanism. The XRD and SEM analyses indicated that mechanical activation not only reduced the particle size of MoS2 but also triggered solid state reaction to produce soluble Na2MoO4, thereby improving Mo extraction significantly.

Early pastoral economies along the Ancient Silk Road: Biomolecular evidence from the Alay Valley, Kyrgyzstan.

The Silk Road was an important trade route that channeled trade goods, people, plants, animals, and ideas across the continental interior of Eurasia, fueling biotic exchange and key social developments across the Old World. Nestled between the Pamir and Alay ranges at a baseline elevation of nearly 3000m, Kyrgyzstan’s high Alay Valley forms a wide geographic corridor that comprised one of the primary channels of the ancient Silk Road. Recent archaeological survey reveals a millennia-long history of pastoral occupation of Alay from the early Bronze Age through the Medieval period, and a stratified Holocene sequence at the site of Chegirtke Cave. Faunal remains were recovered from test excavations as well as surface collection of material from recent marmot activity. Although recovered specimens were highly fragmented and mostly unidentifiable using traditional zooarchaeological methods, species identification via collagen mass fingerprinting (ZooMS) coupled with sex and first-generation hybrid identification through ancient DNA enabled preliminary characterization of the animal economy of Alay herders. Our new results indicate primary reliance on sheep at Chegirtke Cave (ca. 2200 BCE), with cattle and goat also present. The discovery of a large grinding stone at a spatially associated Bronze or Iron Age habitation structure suggests a mixed agropastoral economic strategy, rather than a unique reliance on domestic animals. Radiocarbon-dated faunal assemblages from habitation structures at nearby localities in the Alay Valley demonstrate the presence of domestic horse, as well as Bactrian camel during later periods. The current study reveals that agropastoral occupation of the high-mountain Alay corridor started millennia before the formal establishment of the Silk Road, and posits that ZooMS, when paired with radiocarbon dates and ancient DNA, is a powerful and cost-effective tool for investigating shifts in the use of animal domesticates in early pastoral economies.

The Study on Grinding Ratio in Form Grinding with White Fused Alumina (WA) Grinding Wheels

The study is carried out based on an experiment of form grinding spur rack with white fused alumina (WA) grinding wheels. In the experiment, SOV-3020A type tri-axial image mapper is utilized to measure the profile of the tooth space in the rack, and the curve equations between the sectional area of the tooth space and the tooth sequence under different grinding depths are established by nonlinear curve regress using software of origin8.0. Then, it deduces the prediction equations for current grinding ratio and cumulative grinding ratio under different grinding depths. The result shows that the grinding ratio is exponential decline relationship with the increase of the number of the tooth to be ground under the same grinding depth, and the decline speed is fast in the initial stage. With the increase of grinding depth, the grinding ratio increases gradually. The cumulative grinding ratio is about twice as high as the current grinding ratio. Thus, large grinding depth is generally used in rough grinding to improve grinding efficiency.

Grinding of Chromium Carbide Coatings Using Electroplated Diamond Wheels

This paper reports an experimental study on grinding of chromium carbide coatings using electroplated diamond wheels. The work was motivated by machining carbide coatings in gas turbine engine applications. The objective is to explore the process conditions and parameters satisfying the ground surface quality requirements. Surface grinding experiments were conducted with water-based grinding fluid on chromium carbide coated on flat surfaces of aluminum blocks for rough grinding at a fixed wheel speed vs = 30 m/s, and finish grinding at vs = 30, 60 m/s. The effects of depth of cut and workspeed on grinding power, forces, and surface roughness were investigated for each of the wheel speeds. Material removal rate Q = 20 mm3/s for rough grinding at a grinding width b = 101.6 mm was achieved. It was found that the maximum material removal rate achievable in rough grinding was restricted by chatters, which was mainly due to the large grinding width. The specific energy ranged from 27 to 59 J/mm3 under the tested conditions. Surface roughness Ra = 3.5–3.8 μm were obtained for rough grinding, while Ra = 0.6–1.5 μm were achieved for finish grinding. Surface roughness was not sensitive to grinding parameters under the tested conditions, but was strongly dependent on the diamond grain sizes. Imposing axial wheel oscillations to the grinding motions reduced surface roughness by about 60% under the tested condition. It was proved that it is feasible to grind the chromium carbide coating with electroplated diamond wheels.

Ground stone tool assemblages at the end of the Chalcolithic period: A preliminary analysis of the Late Chalcolithic sites in the Fazael Valley

The very Late Chalcolithic sites of the Fazael Valley exhibit changes in settlement patterns and material culture. This paper presents the analysis of the ground stone tool assemblages of these sites, and includes the combination of attribute analysis, functional typology, and spatial and contextual analyses, allowing comparisons both between the different sites and between different phases within the sites. The assemblages of the late sites of Fazael 2 and Fazael 7 show similar use of raw materials and tool design, which is clearly different from the assemblage of the earlier typical Ghassulian Chalcolithic site of Fazael 1. In Fazael 2, two phases revealed a shift from the use of large grinding tools to mortars and small grinding tools. In both the earlier and the later phases, the separation of activity areas within the site is clear. Grinding activity in both phases is restricted to the western side of the site, while mortars and spindle whorls were found only in the south-eastern part. Finally, a comparison with Fazael 1, as well as with other Late Chalcolithic sites, such as Gilat, 'Ein Hilu and 'En Esur, show that the large number of mortars found in Fazael 2 and Fazael 7 is unique, and may hint at a shift to different subsistence strategies appearing in this region in the latest phases of the Chalcolithic period.