Helical Flutes Research Articles

An optimized calculation method of the grinding wheel profile for the helical flute forming grinding

An optimized calculation method of the grinding wheel profile for the helical flute forming grinding

Design and Development of Variable Rate Metering System for Fertilizer Application

A variable rate fertilizer metering mechanism was designed by changing the speed of the feed shaft for use in variable rate fertilizer applicator. A micro-controller unit programmed with a Pulse Width Modulation (PWM) motor driver was used to run the feed shaft for varying speeds. Two types of fluted rollers (straight and helical flute) were used with varying number of flutes having same volume for each fluted roller. No significant difference in discharge rate between helical and straight fluted roller was observed with varying number of flutes (6, 8, 10, and 12). However the discharge rate of SSP fertilizer was significantly higher than that for DAP. Also, significant difference was observed in applied torque and power requirement for straight and helical flute.

Nitinol advancements in endodontics: Heat treatment and surface functionalization of NiTi instruments

Nitinol, a nickel-titanium alloy known for its exceptional properties of shape memory, superelasticity, and biocompatibility, has revolutionized the field of endodontics. This article explores the evolutionary journey of Nitinol in endodontics, highlighting its historical inception and subsequent integration into dental instruments. The article delves into pivotal advancements such as heat treatment and surface functionalization, showcasing their transformative effects on the mechanical properties and biocompatibility of Nitinol instruments. The discussion encompasses terms related to NiTi file design, including helical flute angles, pitch, cutting edges, rake angles, radial lands, cross-sectional shapes, and taper. Moreover, the article elucidates the modes of movement employed by NiTi files, including continuous rotary motion, reciprocating motion, and axial motion, emphasizing their significance in enhancing precision and minimizing risks. Through an exploration of Nitinol's evolution and its impact on endodontic procedures, this article underscores the symbiotic relationship between innovative materials and the evolving landscape of dentistry.

Effects of the tool geometry, cutting and ultrasonic vibration parameters on the cutting forces, tool wear, machined surface integrity and subsurface damages in routing of glass-fibre-reinforced honeycomb cores

Honeycomb structured materials have been increasingly used for high-load applications; however, machining of the highly elastic honeycomb cores is still facing challenges from tool wear issues and degraded machined surface integrity. In this work, experimental evaluations were carried out in routing glass-fibre-reinforced honeycomb cores under the parametric control of tool geometries (straight and helical flutes), vibration amplitude (0–12 μm) and cutting speeds (30–120 m/min) in a full factorial design. The recorded cutting forces, cutting temperatures, tool wear and the machined surface integrity indicators were statistically tested and discussed, with their main effects and interactions. Executive findings indicated that the helical-flute routers in the oblique cutting produced lower cutting forces; in contrast, the straight-flute routers in the orthogonal cutting produced lower cutting temperatures. Moreover, the flank wear of the straight-flute routers decreased with the amplitude; whereas the flank wear of the helical-flute routers increased with the amplitude. The use of ultrasonic vibration-assisted energy would reduce propagations of cracks and pull-out fibres, compared to using conventional machining. Additionally, the internal damages such as out-of-plane cracks and fractures were characterised by their width and area via computed tomography scans. When routing at a high cutting speed (~90 m/min), the superimposed assisting energy coupled with the straight-flute routers could adversely convert the minor delamination into severe out-of-plane cracks. Causes and the underlying mechanisms are all discussed and detailed.

Modeling the wetting behavior of grinding wheels

Helical flute grinding is an important process step in the manufacturing of cylindrical cemented carbide tools where the use of cooling lubricants is a defining factor determining process performance. Finding optimal parameters and cooling conditions for the efficient use of lubricant is essential in reducing energy consumption and in controlling properties of the boundary zone like residual stresses. Any mathematical model describing the interactions between grinding wheel, lubricant and workpiece during the process has to account for the complex microstructure of the wheel; however, this renders the identification of parameters like slip or heat exchange coefficients numerically prohibitively expensive. In this paper, results from grinding oil droplet experiments are compared with simulation results for the wetting behavior of grinding wheels. More specifically, finite element simulations of the thin-film equation are used to identify slip parameters for different grinding wheel specifications (grain size, bonding structure, wetting status). Our results show that both the bonding and the grain size have an influence on the wetting behavior. The slip parameters that we identified account for the fluid-microstructure interactions and will be used to effectively model those interactions in more complex 3D fluid-dynamic simulations via the Beavers-Joseph condition.

Grinding damage in the fabrication of polycrystalline cubic boron nitride micro-drill

Micro superhard cutting tool such as polycrystalline cubic boron nitride (PCBN) tool are increasingly demanded in high-end manufacturing field. The grinding is a widely used technology in the manufacture of superhard micro-tools, but its grinding damage is often difficult to control. In order to improve the grinding quality of superhard micro-tools, it is necessary to further understand the damage behavior during tool grinding process. This study aims to reveal the damage form and damage formation mechanism in the grinding process of PCBN micro-drills. The PCBN micro-drill grinding experiment is conducted under different process parameters, and the morphology characteristics of the micro-drill surface and cutting edge are observed and analyzed. The influence of grinding process parameters on the grinding quality of PCBN micro-drill is quantitatively investigated. The results indicate that, the grinding damage of PCBN micro-drill is mainly manifested as micro chipping and micro fracture of the cutting edge, material adhesion on the chisel edge, and micro cracks, micro pits and micro scratches on the grinding surface. For the ground surface of flank and helical flute of PCBN micro-drill, the material removal mechanisms of plastic removal and brittle removal work together. The material in the area with more binder inclusions is removed by plastic removal mode, and the material brittleness removal mode mainly includes cleavage brittleness removal and intergranular brittleness removal. The edge impact fracture brings grinding damage to the main cutting edge of PCBN micro-drill. The CBN grains at the fracture surface mainly undergo cleavage fracture, while the fracture of the binder occurs in the form of micro pit aggregation. The reduction of grinding depth and feed rate will lead to the decrease in the surface roughness of flank and helical flute, the cutting edge radius, and the edge chipping width, thus improve the grinding quality of PCBN micro-drill. These findings contribute to expand the understanding of process characteristics for grinding PCBN micro-tools, and thus to restrain the grinding damage and improve the grinding quality of micro-tools.

Milling force modelling with high-pressure cooling strategy: An integrated analytical approach

Intricately formed parts in a wide range of materials can be produced with slot milling (a crucial machining operation) at a faster rate. Predicting cutting forces is essential in such machining process since they contribute significantly to better surface integrity as well as longer tool life. To assess cutting forces during milling Ti-6Al-4 V alloy, an integrated analytical model based on Armarego-Oxley's predictive machining theory and Johnson- Cook's material law is proposed. The thermal effect of the high-pressure cooling strategy is also considered in the proposed model. The effect of feed rate, depth of cut, cutter's helix angle, and its geometry are taken into account while developing an analytical force model, which consists of three force components: tangential, radial, and axial. Each cutting force coefficient is further subdivided into two parts: cutting and rubbing force coefficients. For the sake of calculation simplicity, no run out or chatter were taken into account. To reduce processing time, each helical flute is discretized into small 2D differential sections and an orthogonal to oblique data transformation approach is followed. The proposed model's viability is confirmed by the real experiment data in milling Ti-6Al-4 V alloy. Experimental studies have demonstrated strong agreement.

A Hybrid Cooling Model Based on the Use of Newly Designed Fluted Conformal Cooling Channels and Fastcool Inserts for Green Molds.

The paper presents a hybrid cooling model based on the use of newly designed fluted conformal cooling channels in combination with inserts manufactured with Fastcool material. The hybrid cooling design was applied to an industrial part with complex geometry, high rates of thickness, and deep internal concavities. The geometry of the industrial part, besides the ejection system requirements of the mold, makes it impossible to cool it adequately using traditional or conformal standard methods. The addition of helical flutes in the circular conformal cooling channel surfaces generates a high number of vortexes and turbulences in the coolant flow, fostering the thermal exchange between the flow and the plastic part. The use of a Fastcool insert allows an optimal transfer of the heat flow in the slender core of the plastic part. An additional conformal cooling channel layout was required, not for the cooling of the plastic part, but for cooling the Fastcool insert, improving the thermal exchange between the Fastcool insert and the coolant flow. In this way, it is possible to maintain a constant heat exchange throughout the manufacturing cycle of the plastic part. A transient numerical analysis validated the improvements of the hybrid design presented, obtaining reductions in cycle time for the analyzed part by 27.442% in comparison with traditional cooling systems. The design of the 1 mm helical fluted conformal cooling channels and the use of the Fastcool insert cooled by a conformal cooling channel improves by 4334.9% the thermal exchange between the cooling elements and the plastic part. Additionally, it improves by 51.666% the uniformity and the gradient of the temperature map in comparison with the traditional cooling solution. The results obtained in this paper are in line with the sustainability criteria of green molds, centered on reducing the cycle time and improving the quality of the complex molded parts.

Optimal design of helical flute of irregular tooth end milling cutter based on particle swarm optimization algorithm

Due to the variable pitch angle and helix angle of the irregular tooth end milling cutter, the mass of the integral end milling cutter is eccentric, and the high stability and precision design of the irregular tooth end milling cutter is still a challenge. Aiming at the influence of dynamic balance of irregular tooth end milling cutter which can not be ignored in high-speed milling, the parameterized design of radial section of irregular tooth end milling cutter was carried out. Based on the space transformation law of the centroid of helical flute, a new method for calculating the centroid coordinate of end milling cutter was put forward, and a general mathematical model of eccentricity of integral end milling cutter was given. It was proved that this model could accurately calculate the centroid position and eccentricity of the end milling cutter. The influence of pitch difference angle and helix difference angle on eccentricity of end milling cutter was studied and analyzed. The particle swarm optimization (PSO) algorithm was creatively applied to optimize the helical flute shape of the end milling cutter, the curvature radius of helical flute curve is optimized, so that the centroid coordinate is infinitely close to the origin of coordinate. The number of iterations was set to 200. In the 32nd iteration, the result approached to infinitesimal, the final function converged, and obtained the groove curvature radius of the milling cuter with the smallest eccentricity. The optimized eccentricity of the end milling cutter is infinitesimal, which can make the vibration damping performance of the end milling cutter be fully developed. On the basis of ensuring the same cutting performance, the cutting tool unbalance was effectively reduced and the dynamic performance of milling cutter was further improved.

A new solution for sharpening helical flute hobs

• A complete model of a hob sharpener to sharpen helical flute hobs is established. • The model of circular arc wheel profile to sharpen helical flute hobs is established. • The model of machine settings for form grinding machine to sharpen helical flute hobs is established. • Using a circular arc profile CBN wheel and a form grinding machine, the result exceeds DIN AA. Sharpening helical hobs with a hob sharpener is relatively easy and efficient, but the hob sharpener has poor versatility due to its tilted spindle for sharpening helical flutes. In this paper, we propose a new solution for sharpening helical flute hobs. Geometrically, we simplified the wheel profile to a circular arc, which made it easy to obtain the wheel profile through the circular arc NC (numerical control) function G02 or G03. With the simplified wheel profile, it is much easier to obtain the profile of the wheel made with CBN (cubic boron nitride), even with the use of an ordinary CNC (computer-aided numerical control) contour dressing machine. We also calculated the machine settings for a 5-axis form grinding machine, in which the machine settings of a hob sharpener were transformed into through coordinate transformation. With such new machine settings, the helical flute hob can be sharpened by the form grinding machine. Finally, our numerical examples evaluate the variations between the proposed simplified circular arc wheel profile and the theoretical one. Moreover, the results of our experiment using the form grinding machine with the simplified circular arc profile wheel are illustrated in the plots of the measuring machine.

WEAR MECHANISMS OF DIAMOND-LIKE CARBON COATED TOOLS IN TAPPING OF AA6351 T6 ALUMINIUM ALLOY

The AA6351 T6 is an Al-Si-Mg alloy, widely used and easily accessible on the market, with low silicon content, sufficient to form magnesium silicates. The present work aims at analyzing the wear mechanisms acting over High-Speed Steels – HSS-E, Diamond-Like Carbon – DLC coated tools during the tapping operation of AA6351 T6 aluminum alloy. It was used a thread cutting tap with four helical flutes, diameter ϕ = 12 mm, and 1.5 mm thread pitch (M 12 x 1.5). Dry ambient was adopted to focus on the DLC performance. Ninety-six threads were machined using one single tool, and wear analysis was performed between the first and last threads. The main results showed aluminum adhesiveness, plastic deformations with more accentuated flank wear in the entry threads of the cutting tap, in addition to the detachment of the DLC coating. On the threads produced, several material detachments marks (adhered to the tool) were observed, as well as groove marks. These findings may help users in selecting appropriate cutting conditions as well as cutting atmospheres that can mitigate the tool wear.

A study of delamination characteristics (drilling) on carbon fiber reinforced IPN composites during drilling using design experiments

The aim of this entire research approach is to produce the damage free drilling operation on the IPN composites by selecting the suitable cutting parameters. The standard combinations of polyurethane and vinyl ester resins were used as the matrix material to fabricate the IPN composite laminate with carbon reinforcement. To expedite this, the analysis of variance (ANOVA) and taguchi combination method was used. Based on the technique proposed in taguchi, the plan of experiments had been carried out, by opting the variant process parameters of the drilling; similarly, ANOVA was used to determine the drilling characteristics of the IPN laminate (carbon fiber) of various drill bits like Helical flute, Four-flute, Helical flute – K12 drill bits. The main objective upon doing this experiment was that, to establish the finest correlation between the feed rate and cutting velocity as the output of delamination in IPN laminate, by precisely choosing the multi linear regression analysis. At last, the evaluation tests were carried out to compare the obtained result with correlated analysis, as well it had shown significant agreement with each other.

Optimization of tool design parameters for thread tapping process of Ti-6Al-4V

Thread tapping is one of the most important machining processes. Although thread tapping is a usual process and has been used for decades, the process still needs improvement for promising materials such as titanium alloys to increase the performance of the process. Titanium alloys are known as difficult-to-cut materials due to their low heat conductivity and elastic modulus. The aim of the work presented in this paper is to optimize the tapping tool primary design parameters for Ti-6Al-4V. The most influential tool design parameters on the process were selected as the rake angle, helical flute angle, chamfer angle, and tool coating. Optimization of the tool design parameters was made by considering the results of the experimental work. Two levels of each parameter were chosen. Taguchi L8 orthogonal array was used as the design of experiment. Tapping tool temperature and tapping torque were determined as the process outputs. According to the results, the optimized tool design parameters were found as 6° rake angle, 12° helical flute angle, 14° chamfer angle, and TiCN coating.

Effect of Drilling Parameters Torque, Thrust Force and Delamination Factor on GFRP and CFRP Composites using Different Size of Drills

The trend of the materials that are being used for various industrial applications has shown a drastic variation over the decades. Pure metals are replaced by alloys and these alloys in turn are being replaced by composites in most of the present day applications. Fiber reinforced polymer composites (FRPs) extensively used materials and a lot of research is going on for further improvement of properties of these materials. Drilling process is important in assembly of components in manufacturing. In case of FRPs drilling process is a great challenge when compared to that of conventional material because of de-bonding, metric cracking, and fiber pullout. The present work is a study on the effect of torque and thrust force on delamination of Carbon Fiber Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) and by drilling process. Experiments are conducted at different feeds, drill diameters and speeds. Image processing approach is used to quantify the drill-induced delamination where helical flute HSS drills of diameters 4mm, 6mm and 8mm are used. Statistical analysis is made to optimize the drill parameters by ANOVA and Taguchi technique. It is observed that at 4mm drill diameter, torque and thrust force are minimum for both CFRP and GFRP. However, the delamination factor is minimum at drill diameter of 6mm in case of GFRP and at 8mm for CFRP.

Simulation-based compensation of deflection errors in helical flute grinding

Static deflections of cylindrical blanks in tool grinding processes lead to core diameter deviations that vary with the axial workpiece position. This paper presents an approach to compensate these errors automatically in process planning. Hybrid modelling is used to predict the current local load, the stiffness based on the moment of inertia and the resulting elastic deflection at each time step. Subsequently, the process is optimized by adapting the process parameters and the tool path in the NC-code. In an experimental study, the core diameter deviation after flute grinding has been reduced in a range from 68% up to 87% using the developed approach.

Cryogenic auxiliary drilling of printed circuit boards

PurposeLarge capacity current carrier printed circuit board (PCB) imposes strict control requirements on the hole wall roughness. The key factors are chip removal, drilling temperature and tool wear. This paper aims to find out a cryogenic drilling process to control the chip removal, chip morphology, tool wear and finally reduce the hole wall roughness.Design/methodology/approachThe chip removal process, chip morphology, tool wear and hole wall roughness of glass fiber epoxy resin copper clad laminate (FR-4) drilling were observed and analyzed. The influence of cold air on the chip removal process, chip morphology, tool wear and hole wall roughness was also investigated. An optimization process of cold air auxiliary drilling was proposed to control the hole wall roughness of FR-4.FindingsThe results showed that the discharge time of copper foil chips with obvious characteristics can be used as the evaluation criterion for the smoothness of chip removal. The cold air can promote chip removal and reduce tool wear. In addition, the chip removal and cooling performance will be the best when using −4.7 °C cold air with the injection angle consisted with the angle of helical flute of the drill. The hole wall roughness of FR-4 could be controlled by drilling with −4.7°C cold air.Originality/valueThis paper was the first study of the effect of three kinds of cold air on PCB drilling. This provided a reference for the possibility that the cryogenic drilling methods apply to PCB drilling. A new cold air auxiliary drilling process was developed for large capacity current carrier FR-4 manufacturing.

Drill bit with a helical groove edge for clean drilling of carbon fiber-reinforced plastic

This paper presents a new drill bit with a helical groove edge for drilling carbon fiber reinforced plastic (CFRP). The drill has double point angles, a helical flute, and a helical groove edge away from the drill point angle. The helical groove edge has the same rotational direction as the flute angle direction of the drill bit. With the help of the additional cutting action of the helical groove edge, the drilled holes showed eliminated burrs, reduced delamination, and decreased tearing. An analysis was conducted for the burr removal mechanism and thrust force model acting on the chip area. The experimental verification assures that the drill can produce good quality of the hole’s surface, entrance, and exit, even after long service life.

ANALYSIS OF CONTACT LOADS CONCENTRATION IN PRESSURE COUPLINGS OF THIN-WALL COMPONENTS

A number of aviation assemblies are made as pressure couplings of thin-wall components, e.g., shafts and hubs, durability of which is related to fitting contact load concentrations under cyclic and dynamic loadings. This article discusses a numeric solution to the contact problem. The solution is introducing into the calculations a conventional boundary layer, any shift of which is equivalent to a roughness deformation of fitting surfaces. The mathematical model of a pressure coupling is founded on a division of deformations into general (axisymmetric bending of components) and local deformations (microroughness compression) that are determined independently. To simplify the solution, the dependence of the contact convergence of the surfaces on the pressure is subjected to linearization in the form of a model of a rigid plastic body with linear strengthening. Convergence values in section are only determined by the pressure and do not depend on the stress-and-strain behaviors of areas adjacent to the rough interfacial space. The Green’s functions method is used to find radial shifts of components, while the solution is expressed by the Fredholm integral equation. That is reduced to a finite system of linear algebraic equations when the contact is made discrete. This approach provides solution stability through strengthening of the main diagonal of the resolving system, while the evaluation accuracy of the concentration coefficient depends on the subinterval value. It has been found that any disclosure of a coupling beneath the faces of an enveloping body is practically impossible for that model. The comprehensive approach provides a generalized solution for orthotropic and stepwise shells, as well as for components with specific design features and various strengths of areas adjacent to fitting sites. Deviations of the shape of the contact surfaces from the straightness are taken into account by its respective pressure coupling function. The analysis of the findings suggests that the concentration coefficient value slumps as the contact compliance coefficient of the borderline layer increases. Any shape deviations of the fitting surfaces, including their coning and concavity, increase the contact load concentration, while their convexity causes a reverse effect. We recommend using strengthening treatment methods, e.g., application of regular micropattern in the shape of helical flute at a certain pitch while applying a constant or a variable force on the diamond indenter, or vibration smoothing in order to control the shaft surface finishing to improve the stressand-strain behavior of the seam and to impart an artificial barrel shape of a preset value to the shaft. These technologies compensate contact load concentrations, and, together with the strengthening factor, enhance the fatigue limit of such assemblies.

Self-optimizing process planning for helical flute grinding

Grinding of helical flutes is an important step in the process chain of cylindrical tool manufacturing. The grinding process defines the dynamic performance of the manufactured tool. Moreover, the surface quality and flute shape are primarily determined. For this reason, finding optimum process parameters is essential, especially in process planning of individual tools. In the industry, manual experiments are carried out for the machine set up. This leads to high costs due to machine hours, labor and material costs. This paper presents a self-optimizing and adaptable process planning method to reduce costs for process planning and improve the process result. The developed method allows to identify optimum cutting speed and feed with respect to economic efficiency and quality for new tools without additional machining experiments. Geometric-kinematical cutting simulations in combination with empirical models are used to predict the process outcome. The empirical models are derived from machine learning and improved automatically with an increase of process data. Applying the presented method in a case study, the machining time could be reduced by up to 38.1% and the core diameter deviation by up to 73.7%. Moreover, it is shown that the presented methods allow a continuous improvement of the process models.

Development of a longitudinal–torsional ultrasonic vibration-aided drilling system for drilling carbon fiber-reinforced polymer materials

This study aimed to explore the motion properties of longitudinal–torsional ultrasonic vibration-aided drilling, the feature of drilling dynamics, and an efficient path of implementing longitudinal–torsional component conversion. It also aimed to propose a spiral chute horn with high performance and low cost based on the propagation characteristics of ultrasonic waves. The finite element software ANSYS was used for modal analysis and the geometric parameters of helical flutes were achieved. The dynamics analysis of the longitudinal–torsional ultrasonic drilling system revealed that the ultrasonic vibration could improve the rigidity of the drill and that the components existed in longitudinal and torsional directions. Drilling the T300-12K/AG80 unidirectional carbon fiber-reinforced polymer using the longitudinal–torsional ultrasonic drilling system revealed that the results of theoretical analysis and numerical simulation were comparable. This drilling system could change the longitudinal–torsional ratio according to the geometrical parameters of the modal converter, improve the surface quality of the carbon fiber-reinforced polymer hole, and reduce the exit delamination.