Grinding Disc Research Articles

Experimental investigation and theoretical prediction of tensile properties of Delonix regia seed particle reinforced polymeric composites

Possibility of using Delonix regia (Dr) seed particles as reinforcement for production of new polymeric composites has been studied. Dried Dr seeds were processed using a disc grinder and then classified. Dr particles of 105μm average size were incorporated into recycled low density polyethylene (RLDPE) up to 10wt% and RLDPE/Dr particle composites were produced through compounding and compressive moulding technique. Effects of Dr particle addition on morphology and the tensile properties of the produced composites were investigated. The composite tensile properties were confirmed and validated using mono-variate regression model involving full factorial design of one factor-five levels. Results obtained indicated presence of void within the composite grain which impair the tensile strength and strain of the RLDPE composite at 10wt% of Dr seed particle addition. About 300% and 41% maximum increments in tensile strength and strain were noticed at 4wt%. The developed models show that wt% of Dr particles has significantly statistical influences on both tensile strength (P=0.00827) and strain (P=0.01756). About 93% and 89% response prediction by the models shows that the models exhibit fit goodness and they are appropriate for confirmation of experimental tensile properties. Therefore, this study has given birth to a new polymeric composite for engineering applications.

Proposed methodology for the study of the level of emerging risk from exposure to hand-arm vibrations in manufacturing environments

Occupational exposure to vibrations, regulated by Directive 2002/44/EC, is currently on the rise. This situation makes it necessary to increase knowledge of the exposure, considering amongst other factors, its nature as an emerging risk.To do so, a methodology has been developed for application in manufacturing environments. This has been designed by combining the principles of the DMRA Technique with a theoretical framework of new and emerging risks established from recent research.This methodology grades the Emerging Risk Level (ERL) on 9 levels, from ‘not at all significant’ (ERL=1) to “fully significant” (ERL=9). This methodology has been applied to hand-arm vibrations generated by using an electric disc grinder. Thirty-two entries from the National Institute of Safety and Health at Work (INSHT) ‘Vibra’ database have been considered for this.The main findings indicate that 55% and 36% of cases give rise to ‘moderately significant’ (ERL=7) and ‘very significant’ (ERL=8) emerging risk, respectively.

Effect of Post Weld Toe Treatments on Fatigue Life of Welded Structures using FEA

Welding joints is the weak region for the components of all earth-moving machines as they are exposed to the repeated fluctuating stresses which cause fatigue cracks at the toe and throat of welded joints due to the metallurgical imperfections. This is why welded joints must be fully understood to improve the fatigue and service life of the earth-moving machines. Here failure at throat can be minimized by achieving optimum strength but problem of weld toe cracking only be eliminated by reducing stress concentration at weld toe. To do this, R & D work has been initiated by preparing set of five T-joint weld samples having 6mm (sample A to E) throat thickness with one as-welded sample i.e. E (without post weld toe treatment) using GMAW welding process. As per IIW guidelines, samples A to D has post weld toe treated with cylindrical & hemispherical burr tool, cutter (A24PBF) and flap disc grinder respectivelyto reduce the stress concentration at weld toe by making smooth transition at weld toe with undercut of 0.5mm. Fatigue analysis shows that, sample “B” with 8mm weld size post weld toe treated with hemispherical burr tool has given maximum optimization in fatigue life of 76.22% as compared to as-welded samples i.e. E.Validation carried out by hardness testing at Heat affected zone (HAZ) of etched samples.

The Process of Composite Materials Machining Cutting Tools Profiling

Сutting composite materials might be associated with difficulties, namely the severe wear of cutting tool due to materials characteristics. The active part of a cutting tool should have high tensile strength, a certain hardness index and a small tool angle. To meet the requirements, the cutting part of a tool must be made of hard alloy, however, shaping the edge of such geometry results in the unsatisfactory quality of the product. The article suggests that the cutting edge of the tool should be grinded by using a diamond wheel along with an electrochemical process, making cutting easier. This requires defining the rational modes of combined diamond grinding for hard alloys with specific cutting edge geometry. Lab tests have revealed the dependence of surface roughness and a specific removal rate of wheels from the current density of diamond wheel dressing and the current density of the detail etching. The research has established that with the increase of electric grinding parameters the surface roughness decreases but the specific wear of the grinding disk increases. The research found that the combined method of electric diamond grinding has the advantage vs the rest ones; the machined surface has a quite satisfactory quality and the amount of tool chipping does not exceed 10 micrometers. Based on the presented research, the practices for application of grinding mode for cutting tool are worked out to be used for composite material.

Influencing Factors on the Melting Characteristics of NdFeB-Based Production Wastes for the Recovery of Rare Earth Compounds

During the processing of neodymium-iron-boron (NdFeB) magnets, the blank is ground into its final form. During this step, there are slurries arising which contain major amounts of magnetic materials as well as lubricative and abrasive particles from the grinding disk. Since there is no tailor-made recycling process for this kind of wastes, a thermal treatment in combination with a melting step is proposed in this paper as a possible way for separating rare earth compounds from iron and other accompanying elements. During this process, a metallic Fe-based phase is separated from a rare-earth-containing oxide phase. Pretreatment has to be performed in order to separate the remainder of the cooling lubricant from the grinding process. Besides, the contents of accompanying elements such as oxygen have to be adjusted, since these elements can influence the melting process and phase separation. This paper deals with the factors which enable melting and phase separation by considering different input materials and the needed pretreatment. An oxygen content of more than 7 wt% needs to be maintained after the oxidation to enable phase separation during the melting. In addition, the presence of carbon is essential to avoid the formation of iron oxides. By this way, rare earth oxides from various NdFeB materials can be extracted with a high output and purity. This investigation shows that it is also possible to achieve an oxygen content of more than 7 wt% in different scraps produced by means of a thermal treatment. This provides an opportunity for making the recycling concept suitable for various kinds of scrap.

A power model for fine grinding HIGmills with castellated rotors

A grinding power model has been developed to predict the power draw of Outotec’s vertical fine grinding mill (HIGmill). The model is based on a combination of laboratory, pilot and full-scale measurements taken over a range of process conditions. The power draw of the mill is influenced by a variety of factors, ranging from simple geometric factors like the grinding disc diameter, spacing and speed to various process factors like the viscosity, density, grinding bead size, fill level and fluidisation velocity. The focus of the model is on scale up to full-scale from laboratory and pilot-scale data, and how to configure the mill for different process scenarios.

Investigation of the interrelations between defibration conditions, fiber size and medium-density fiberboard (MDF) properties

Defibration conditions and raw material properties affect wood fiber characteristics, and thereby the properties of fiber-based panels such as high-density fiberboard (HDF), medium-density fiberboard (MDF) and wood fiber insulation board. This study investigates the influence of steaming conditions (time and temperature), grinding disc distance, wood species (pine, beech, birch and poplar), method of refiner discharging (radial and tangential stock outlet) and wood chip size on fiber length and fiber length distribution, and further the influence of fiber size on MDF properties. Fiber lengths were determined applying the recently developed image analysis-based fiber size measuring system FibreCube. This system enables an automated and nearly complete mechanical separation of woolly-felted fiber samples prior to image acquisition, software-supported post-separation of overlapped-lying fibers at the beginning of image analysis, and flow line tracing-based length measurement. It was found that grinding disc distance and wood species are the most influential parameters on fiber length characteristics. Especially the content of undefibrated fiber bundles (shives) was found to strongly correlate with the grinding disc distance. Wood anatomical differences between hardwood and softwood were reflected clearly by the fiber length characteristics. Fiber size was found to be one of the parameters influencing panel properties. However, other fiber characteristics—in particular the chemical nature of the fiber, which is responsible for its wettability with water (thickness swelling) and glue (mechanical properties)—have to be considered as important influencing parameters on panel properties.

Mechanical properties of diamond grinding discs brazed in a continuous-belt tunnel furnace or vacuum furnace

A new method for brazing diamond grains is presented. The brazing was conducted in a continuous-belt tunnel furnace under a dissociated ammonia atmosphere, which allows for a continuous large-scale production and greatly enhances productivity. To compare the brazing quality, identical samples were also brazed in a traditional vacuum oven. The surface morphology and interfacial microstructure were characterized, and the residual stresses, the static compressive strength, and the impact toughness were determined for both types of brazed diamond samples. Furthermore, grinding tests were conducted using the brazed diamond grinding discs. The results revealed that graphitization did not occur on the surface of the diamond grits. Cr3C2 and Cr7C3 were found at the interface between the diamonds and the Ni-Cr filler alloy brazed in the tunnel furnace. The residual stresses in the tunnel-brazed diamond grits were smaller than the stresses in the vacuum-brazed diamond grits in case of an identical measuring height, and the static compressive strength and the impact toughness of the etched tunnel-brazed diamond grits were 2316.7 MPa and 66.5 %, respectively, which was higher than the values obtained for the vacuum-brazed diamond grits (1865.6 MPa and 59.3 %). After grinding a granite test sample using the brazed diamond grinding discs, the fraction of abrasive grains pulled out from the surface of the tunnel-brazed grinding disc was slightly higher than the fraction of grains pulled out from the surface of the vacuum-brazed disc, whereas the overall abrasive grain fracture rate was lower at the same grinding length.

Effect of species and grinding disc distance on the surface roughness parameters of medium density fiberboard

Surface quality of medium density fiberboard (MDF), as a very important criterion for further finishing and utilization, was evaluated using a wide range of measuring parameters (instruments, filters, filtering cut-off length, measuring length, measuring resolution, roughness parameters). However, these various approaches make any data comparison rather difficult. Furthermore, filtering the measured data with a simple Gaussian filter has proved unreliable for wood surfaces. A new, more robust approach by using a Robust Gaussian Regression filter together with a previously tested set of measuring and evaluating parameters was used in this paper in order to quantify the surface roughness of MDF manufactured from different species (beech, poplar, birch, Scots pine, mixture 50 % Scots pine and 50 % beech) and using three different grinding disc distances (0.06, 0.15 and 0.6 mm). If manufacturing parameters are kept constant, the processing roughness of MDF is similar, but variable species anatomy and fuzziness effects will give differentiation in total roughness. The results indicated that fibers made of a mixture of wood chips from Scots pine and beech led to the smoothest MDF surface, followed closely by poplar, birch, and Scots pine. The roughest surface was measured for the panels made of beech fibers. Investigating the influence of the grinding disc distance, the roughest MDF surface was obtained when a grinding gap of 0.6 mm was used. However, surface roughness was found to be quite similar applying a grinding disc distance of 0.06 mm slightly lower for 0.15 mm. This finding indicates that a too fine grinding gap does not improve the MDF surface roughness.

Surface microstructural changes of spark plasma sintered zirconia after grinding and annealing

Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140nm 372nm and 753nm grain sizes by sintering at 1250°C, 1450°C and 1600°C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60µm, under a pressure of 0.9MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after a ruff grinding of specimens at 1100°C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575°C for one hour, the nano-grain layer was not observed. The resulted grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.

Effects of mechanical fibrillation time by disk grinding on the properties of cellulose nanofibrils

Cellulose nanofibrils (CNF) were successfully produced from a bleach kraft eucalyptus pulp by a supermasscolloider. Effects of grinding time on structure and properties of CNF and the corresponding CNF films were investigated. Grinding time was important to increase the optical transparency of CNF suspensions. The degree of polymerization (DP) and crystallinity index (CrI) of CNF decreased linearly with the increase in CNF suspension transparency. This suggests optical transparency of a CNF suspension can be used to characterize the degree of fibrillation. Specific tensile strength and Young’s modulus of the CNF films made of CNF suspension with only 0.5 h grinding were increased approximately 30% and 200%, respectively, compared with conventional handsheets prepared by valley beating to 300 Canadian Standard Freeness (CSF). Energy input was only 1.38 kWh/kg for 0.5 h grinding. Grinding beyond 0.5 h produced negligible improvement in specific tensile and specific modulus. Opacity of CNF films decreased rapidly during the first 1.5 h of fibrillation and then plateaued.

Повышение качества и производительности при профильном глубинном шлифовании турбинных лопаток

A new concept of working quality assessment and cutting mode setting at profile creep feed grinding of some complex conjugate surfaces simultaneously on a multiaxes NC machine is presented. The analysis of dynamic and thermo-physical phenomena at machining each of the conjugate surfaces grinded simultaneously by one profile abrasive disk is carried out. The simulators for the definition of contact patch parameters of a grinding disk and a billet at a creep feed grinding of different conjugate profile surfaces of turbine and nozzle blades of GTEs allowing the prediction of material removal intensity, grinding disk wear, and roughness of every surface on the basis of changes in cutting modes, disk characteristics, dynamics of elastic, thermal and operation processes in a technological system are shown. This procedure allows controlling the process of profile creep feed grinding to achieve preset parameters of surface quality, dimension accuracy in blade profiles of gas turbine engines, productivity increase and decrease of machining prime cost.

Technological Aspects of Forming the Surface Microrelief of Low-Wear Coatings after Electro-Diamond Grinding

The results of electro-diamond grinding of coatings based on the WC25 powder material are presented in the paper. It is shown that after electro-diamond grinding of the WC25 coating, an obtained magnitude (Ra=2.02µm) of surface roughness doesn’t meet the qualifying standards to parts surface working in wear-out conditions. The forming of the obtained microrelief is probably connected to the features of electrochemical dissolution of the WC25 coating material in the electrolyte being used. Based on the polarization studies, it is revealed that the electrochemical dissolution character of the indicated coating in the water solution of 10%NaNO3 is determined by the dissolution character of cobalt (Co) component. The intensive cobalt (Co) dissolution during the electro-diamond grinding of the WC25 coating leads to the tungsten carbide chipping by the grinding disk particles that increases the roughness. One of the way to improve the surface quality of low-wear coatings after electro-diamond grinding is an introduction of an additional step in a technological process, carrying out with the switched off source of technological current. For realization of the process according to this scheme a technological dimension chain is made which takes into consideration the dissolution value of the most active coating composition element while the calculating of the operating dimensions of a detail.

Manufacturing Process for a Face Gear Drive With Local Bearing Contact and Controllable Unloaded Meshing Performance Based on Ease-Off Surface Modification

A manufacturing process for fabricating ease-off surfaces of a face gear drive that is provided with controllable unloaded meshing performance and local bearing contact is proposed. In order to control the unloaded meshing performance, a predesigned transmission error, a predesigned contact path, and the length of contact ellipse are applied in the redesign of the ease-off surfaces of the pinion and face gear. A method of point contact between the grinding disk and the manufactured pinion is proposed to generate the pinion's ease-off surface, the grinding disk is driven by a series of parabolic motions. Numerical examples are used to illustrate the application of the proposed method, the proposed method is proven to be feasible, and the redesigned face gear is proven to be able reproduce the predesigned unloaded meshing performance simulated by tooth contact analysis (TCA). The influence of misalignment on unloaded meshing performance is also analyzed.

Study of tensile properties, fractography and morphology of aluminium (1xxx)/coconut shell micro particle composites

Aluminium (1xxx)/coconut shell micro particle (Al/CMP) composites have been developed using a compo cast technique. Coconut shells (CSs) were processed with the aid of mortar/pestle and disc grinder and then classified with a set of sieves vibrated with a sine shaker. The CMP additions increased from 2% to 10% at 2% interval. Microstructural/chemical composition analyses were carried out with the aid of scanning electron microscopes (ASPEX 3020) with attached energy dispersive X-ray spectroscopy. Phases were identified using an X-ray diffractometer (XRD). The tensile properties and mode of fracture were studied using Instron extensometer and Avery Denison Impact Testing Machine respectively. Results revealed 99.3% purity of aluminium matrix. The presence of new phases in the aluminium matrix is attributable to chemical interaction between Al and CMPs. The fine grained structure of Al/CMPs composites was confirmed by SEM and optical micrographs. The enhancement in the tensile properties is attributable to the presence of hard phases in the Al matrix and good interfacing bonding between Al matrix and CMP reinforcements. The cone and cup surface appearance with fibrous, dull, dimple and goose grain microstructure of the fracture surfaces of the composites is an indication of ductile fracture. Hence low cost metal matrix aluminium based composites have been developed.

Development of an In-House Test for Nut Integrity in F-Type Wheels

Nut embedded disc grinding wheels, also known as disc grinding or F-Type wheels, are required for many production jobs. Nut pull-out is a common problem encountered in disc grinding wheels. The present work proposes a simple fixture, using which the integrity of the nut in the grinding wheel can be assessed. This method can be adopted by any grinding wheel manufacturer for a realistic estimate of nut pull out strength in double disc grinding wheels.

Совершенствование конструкции дисковой установки для шлифования семян сахарной свёклы

The article is devoted to the development of device design for grinding seeds of sugar beet of disk type. Analyzing the number of scientists’ researches, we offer an improved version of the disc sander installation, devoid of the drawbacks of existing disk grinding plants. An analytical study of the trajectory and speed of the seeds was conducted, which are on the surface of the disc and justification of optimal, constructive and kinematic parameters of the installation.

A CNC grinding method and envelope residual model for face gear

This paper proposes a grinding method for face gears with CNC machines. Interpolation formulas of CNC linkage are deduced based on a five-coordinate machine tool. An analytical model for predicting envelope residual when grinding face gears based on grinding disc wheel is developed. The generating laws of envelope residual for the envelope manner are investigated. The influence of tool feed magnitude on surface envelope residuals is analyzed in circumferential angle direction. The maximum envelope residual increases nonlinearly with incremental angle. A grinding experiment is performed on a CNC grinding machine. The tooth surface deviation indicates that the CNC grinding method is efficient. The variation trends of different feed magnitudes along circumferential angle direction coincide with the simulation results. Finally, the values of envelope residuals are verified by an envelope simulation with software AutoCAD. The study provides an effective approach for parameter selection of highly precise and efficient grinding of face gear.

Optimizing cellulose fibrillation for the production of cellulose nanofibrils by a disk grinder

AbstractThe fibrillation of a bleached kraft eucalyptus pulp was investigated by means of a laboratory-scale disk grinder for the production of cellulose nanofibrils (CNF), while the parameters disk rotating speed, solid loading, and fibrillation duration were varied. The cumulative energy consumption was monitored during fibrillation. The degree of polymerization (DP) and water retention value (WRV) of the resultant cellulose fibrils were determined as measures of the degree of fibrillation, which was also visualized by scanning electron microscopy, field emission-scanning electron microscopy, and transmission electron microscopy imaging. A higher rotating speed than 1500 rpm did not improve the fibrillation judged by DP and WRV measurements. Solid loading has an insignificant effect on fibrillation in a wide range. The energy consumption (E) was determined as a function of the DP and WRV. The optimal grinding conditions were between 1200 and 1500 rpm at 2.0%–2.2% solid loading.

ERGONOMIC BASED MODIFICATION OF HAND GRINDER TO IMPROVE PHYSIOLOGICAL RESPONSES, AND TO INCREASE PRODUCTIVITY AND USER SATISFACTION

Hand grinder is one of the tools used in manufacturing jobs, particularly for metal processing. Grinding is usually performed in the finishing process of a product, such as removing the ridges of welded joint. This tool has two main parts, namely the grinding disc and the electrical power motor for driving its spindle. Based on the work sampling in the several manufacturing shops, workers spent 20% of eight hours working time for grinding process. Observations and interview with several operators found some problems in the using of hand grinders such as fatigue and musculoskeletal complaints due to not ergonomic shape, size, vibration, and noise. This study aimed to improve a hand grinder design through ergonomic assessment. Twenty two parameters of assessment were identified by a questionnaire to 16 samples of hand grinder users. By considering those parameters and using the Microsoft Visual Basic 6.0, the ergonomic assessment software was created. The recommendations from the ergonomic assessment suggest that the hand grinders be modified by equipping them with two dumping covered handles. To determine the effects of the modification to the hand grinders, furthermore, the improved hand grinders were applied in the experimental research used treatment by subject design. Variables in the research were user physiological responses regard to musculoskeletal complaints, fatigue, energy expenditure, productivity and satisfaction. The research was conducted in March until August 2012 with 16 participated samples. The samples in the research were randomly selected from the students of Industrial Engineering Department of Atma Jaya Yogyakarta University. The data were analyzed statistically for descriptive analysis, normality test by Shapiro-Wilk, and the compare means analysis by t-paired test and Wilcoxon with significance level of 5%. The results of data analysis showed that the use of the modified hand grinder being yielded better results: 19.6% decrease in musculoskeletal complaints (p = 0.001), 17.7% decrease in fatigue (p = 0.004), 20.9% decrease in energy expenditure (p= 0.017), 15.97% increase in productivity (p=0.041) and 29.9% increase in satisfaction (p = 0.001). Empirically, it can be concluded that ergonomic based modification of hand grinders able to improve physiological responses in terms of musculoskeletal complaints, fatigue, energy expenditure, and increase productivity and user satisfaction.