Clearance Angle Research Articles

A comprehensive guide to milling techniques for smoothing the surfaces of 3D-printed thermoplastic parts

PurposeThis study aims to thoroughly examine the milling process applied to fused filament fabrication (FFF) parts. The primary objective is to identify the key variables in creating smooth surfaces on FFF specimens and establish trends about specific parameters.Design/methodology/approachIn this study, PLA and ABS samples fabricated by FFF are subjected to side milling in several experiments. Achievable surface quality is studied in relation to material properties, milling parameters, tooling and macrostructure. The surface finish is quantified using profile measurements of the processed surfaces. The study classifies the created chips into categories that can be used as criteria for the anticipated quality. Spectral analysis is used to examine the various surface formation modes. Thermal monitoring is used to track chip formation and surface temperature changes during the milling process.FindingsThis study reveals that effective heat dissipation through proper chip formation is vital for maintaining high surface quality. Recommended methodology demands using a tool with a substantial flute volume, using high positive rake and clearance angles and optimizing the feed-per-tooth and cutting speed. Disregarding these guidelines may cause the surface temperature to surpass the material’s glass transition, resulting in inferior quality characterized by viscous folding. For FFF thermoplastics, optimal milling can bring the average surface roughness down to the micron level.Originality/valueThis research contributes to the field by providing valuable guidance for achieving superior results in milling FFF parts. This study includes a concise summary of the theoretically relevant insights, presents verification of the key factors by qualitative analysis and offers optimal milling parameters for 3D-printed thermoplastics based on systematic experiments.

Tsunami inundation and flow velocity within a partially sheltered structural array

ABSTRACT This work examines tsunami run-up processes within a building array partially sheltered by a high-elevation, finite length, seawall. Work was performed using numerical modeling of 2D shallow water equations with varying seawall length, wave height, time scale, and structure size. Inundation depth and flow velocity were output at many locations of interest throughout the structural array. The most important influence on results when compared to the no-wall case was the sheltering or clearance angle as defined from the end of the wall. Behind the wall, inundation depth and cross-shore velocity declined significantly as sheltering angles increased (more sheltered). Alongshore inundation velocity (parallel to the seawall) increased strongly with increasing sheltering angle. A longer wave time scale resulted in significant increase in inundation depth and velocity especially at locations sheltered by the wall. Larger structure size or blockage ratio also led to increased inundation depth and flow velocity. However, varying wave height gave little change in inundation and velocity patterns. These results will serve to provide a better understanding of the wave inundation within a coastal urban region in a tsunami event when the seawall is breached, as well as the influence of coastal structure size and spacing on the tsunami inundation.

Analysis of Transient Instability on a 132KV Transmission grid Power System Using 4th Order Runge kutta Technique

This study examines the transient response of synchronous machines in a 132kV transmission grid power system utilizing 4th order Runge Kutta algorithms. In order to determine the critical clearance angle (CCA) and critical clearing time (CCT) of the transmission grid, a three-phase fault was intentionally introduced. Data were gathered from the Transmission Company Nigeria (TCN) for the specific purpose of analysis and simulation. The Electrical Transient and Analysis Program (ETAP 19.1) is utilized with circuit breaker and relay time settings of (0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.2) to examine the differential variations in generator rotor angles, alterations in generator bus voltage, and changes in system frequency. The obtained results demonstrate that the 4th order Runge Kutta numerical technique is stable and accurate. It exhibits a fast response critical clearing time (CCT) of 0.02s and a critical clearing angle of 76.9 degrees, which is very close to the expected value of 81.5 degrees. The average critical angle was determined from the simulated results. Additionally, a lower percentage error of -51% was observed at the moment of disturbance. The 4th order Runge-Kutta numerical technique is superior due to its sustainability, faster computation, and stability in the presence of transient disturbances, as demonstrated in the study case. It is crucial to promptly and accurately coordinate the circuit breakers and protection relays in order to rapidly clear a symmetrical 3 phase fault at any bus. This will improve the stability margin of the network.

Molecular dynamics simulation of the effect of tool parameters on nano-cutting of polycrystalline γ-TiAl alloys

As one of the most promising lightweight high-temperature structural materials in the future, the surface quality of γ-TiAl alloys has a great influence on the performance of the workpieces, and the tool parameters are an important factor affecting the machining results. In this study, molecular dynamics simulations of the nano-cutting process of polycrystalline γ-TiAl alloys with different tool parameters were carried out. The results show that increasing the tool rake angle and decreasing the tool edge radius within a certain range helps to reduce the average cutting force, cutting force fluctuation, cutting temperature, and stabilize the cutting process, while the change of the tool clearance angle has less influence on the cutting process. In contrast, negative rake angle cutting is more likely to produce grain rotation and grain boundary steps in the processed substrate and increase the processed surface roughness than positive rake angle cutting; increasing the tool rake angle within a certain range will weaken the elastic recovery effect of the substrate. During cutting at a positive rake angle, whether a portion of the substrate is prone to slip toward the surface of the substrate, thereby reducing the surface quality, depends on the relative state of grain orientation and force applied in the substrate.

Non-interference slow tool servo turning method for complex surfaces with large undulation changes

Complex curved surface parts are integral to the mechanical industry, demanding precise machining techniques. Multi-axis slow tool servo turning has emerged as an efficient method due to its high precision and quality. However, the challenge of severe tool flank interference arises, especially on surfaces with large undulation changes. Conventional methods, such as increasing tool clearance angles or adding extra tool axes, detrimentally affect machining precision and stability. To address this, a non-interference toolpath planning method is proposed for complex surfaces with large undulation changes. The approach begins with establishing geometric models of the single-point diamond turning tool and typical complex surfaces, followed by analyzing the mechanism and evolution of tool flank interference. By considering geometric parameters and vector relationships, the practical tool clearance angles are calculated. And then a criterion for subregion division is introduced and the non-cutting stroke is designed, accounting for the maximal acceleration of machine tool axis. Multi-pass toolpaths are generated to navigate different subregions while avoiding interference by transforming spindle rotation direction. Furthermore, a method is proposed to optimize toolpath stitching in practical machining regions, ensuring continuous and smooth transitions while maintaining machining precision and surface quality. Experimental validation, conducted on a hyperbolic paraboloid surface with large undulation changes, demonstrates a significant reduction in surface roughness (Sa) from 380.503 nm to 75.664 nm—a reduction of 80.115 %. The proposed method not only enhances machining precision and surface quality but also extends tool life and improves working conditions. This research offers vital guidance for non-interference toolpath planning in engineering practice.

Numerical analysis of machinability and surface alterations in cryogenic machining of additively manufactured Ti6Al4V alloy

Metal additive manufacturing (AM) technology has been utilized in many industries including automotive, aerospace, and medical. AM Ti6Al4V (Ti64) alloy is highly noticed for production of medical instruments such as dental implants and the machining process is mostly needed during the production or post-processing of these components. Numerical model, as a powerful tool, can be efficiently used for analyzing the machining process. A customized model was employed using a user-written subroutine in this work to evaluate machinability and microstructural changes in cryogenic machining of AM Ti64 alloy. For this purpose, the microstructural changes were simulated as the new numerical outputs. The numerical results of cutting forces, temperature, nano-hardness, and alpha lamellae thickness (grain size) were successfully verified by corresponding experiments from literature. Then, the impact of tool geometry (including rake and clearance angles, cutting edge radius, and nose radius) on the machinability performance was examined. It was found that, the variation of clearance and rake angles were more effective on depth of the hardened layer compared to the other parameters. Thickness of alpha lamellae phase near the machined surface and depth of the affected layer by nano-hardness changes were changed from 0.9 to 1.58 µm, and from 18 to 40 µm, respectively. Overall, it was concluded that the variation of insert positioning made by tool holder (change in rake and clearance angles) was an effective parameter on the process outputs when machining AM Ti64 alloy.

Finite element explicit dynamics simulation of an impact cutting mechanism analysis of Populus tomentosa branches

The branch impact failure mechanism has gradually received attention from scholars, along with the application of impact cutting methods in plantation forest pruning. In this paper, the impact cutting failure mechanism of Populus tomentosa branches was mainly studied. The impact cutting process of branches was simulated by using Finite Element Method (FEM)-based explicit dynamics. The stress change and deformation characteristics in the branch failure process were studied. A theoretical model of branch impact cutting mechanism with branch diameter, cutting clearance, and branch angle as the main factors was proposed. The model describes the branch cutting damage process and the changing characteristics of cutting force. A branch failure state equation was proposed to describe the branch impact cutting failure patterns. The forest experiment was conducted to validate the branch impact cutting mechanism and the branch failure state equation. This work fills a vacancy of relevant theory and provides a theoretical basis for the future development of forestry and agricultural equipment using impact cutting.

Effect of repetitive nano-cutting tool parameters on surface quality and subsurface damage of γ-TiAl alloy

In this paper, the molecular dynamics simulation of the repeated nano-cutting of single crystal γ-Tial alloy was carried out by selecting different geometric parameters of the second cutting tool by single factor experiment. The cutting force, friction coefficient, subsurface defects, dislocation evolution and surface roughness of the second cutting were analyzed systematically. The results show that when the tool rake angle is 15°, the surface roughness is lower and the surface quality is better. The influence of different second cutting tool rake angle on the surface roughness is not strong. When the rake angle of the second cutting tool and the radius of edge are constant, the average normal cutting force decreases with the increase of the clearance angle of the tool. Under the machining parameters in this paper, the critical clearance angle of the second cutting of single crystal γ-TiAl alloy is between 10° and 15°. When the tool clearance angle is greater than the critical clearance angle, the average cutting force and the machined-surface roughness no longer change significantly. With the increase of the radius of the second cutting tool, the chip decreases, the subsurface defect increases, and the surface roughness of the machined surface also increases with strong regularity.

Study on the mechanism of multidimensional cutting teeth and the influencing factors of rock breaking efficiency.

The innovative cutting mechanism of multi-dimensional teeth presents a groundbreaking approach to drill bit design, particularly optimizing drilling efficiency in challenging geological formations such as interlayers and gravel-rich layers within the Changqing Oilfield. Nevertheless, compared to conventional flat-tooth PDC drill bits, several aspects of the cutting mechanism and design parameters for multi-dimensional teeth require further elucidation. This article employs a linear cutting finite element model to establish cutting models for traditional flat teeth and two distinct types of multi-dimensional teeth, designated as Ridge and Benz. It systematically investigates the influence of varying cutting parameters on the effectiveness of rock-crushing within the multi-dimensional tooth-cutting mechanism. This study conducts laboratory-based single-tooth rock-crushing experiments to validate the numerical simulation results. Furthermore, applying principles derived from soil plastic mechanics contrasts the stress states experienced by rocks during the rock-crushing process between multi-dimensional teeth and conventional flat teeth, shedding light on the rock-crushing mechanism employed by multi-dimensional teeth. This research categorizes PDC cutting teeth on the drill bit into two groups: those near the center and those near the outer shoulder. A linear cutting model for teeth positioned near the outer shoulder is developed to analyze the impacts of different rake angles, side clearance angles, and welding errors on the tooth helix angle and the rock-crushing efficiency of the Benz tooth. This comprehensive study is a valuable reference for tailored drill bit design and holds potential for publication in a prestigious scientific journal.

Experimental studies on the characteristics of chisel picks in coal cutting for bucket wheel excavators

Chisel pick is a basic and important rock cutting tool, and the performance of chisel pick directly affects rock mining. In this paper, a rock cutting device was developed for chisel picks cutting experiments. The influence of the depth of cutting, width of chisel pick, rake angle, back clearance angle and tip fillet radius on the cutting performance such as cutting force, normal force, and specific energy has been comprehensively studied. In addition to the general conclusions, the experimental results show that the back clearance angle has an influence range on the cutting, and the ratio of the normal force to the cutting force decreases with the increase of the rake angle; the tip fillet radius greatly improve the mean cutting force and specific energy. The experimental results will provide data support for the design of chisel picks on rock excavation machinery and a more reasonable chisel pick cutting rock mechanics model.

Material deformation mechanism of lamellar twined high–entropy alloys during machining

The effects of sample structure and tool geometry are studied under cutting simulation to verify the deformation, removal mechanisms, and subsurface defection of lamellar twined CoCuFeNiPd alloys. These findings suggest that the twin boundary spacing (TBS) and twin inclination angle (β) are the main determinants of surface wear characteristics and cutting-induced surface harm. The maximum cutting force achieved with TBS = 8a and β = 90°. The high friction coefficient with the sample has TBS = 8a and β = 90°, showing that the tool’s moving in the substrate is strongly restricted. Furthermore, the surface topography is not sensitive to the TBS and β. The best-machined surface is achieved with TBS = 3a and 4a under twin inclinations of 0° and 30°. The effect of edge radius (R), rake angle (γ), and clearance angle (α) on the deformation behavior is examined. The negative of γ, small α, or larger R results in a higher cutting force, a worse subsurface, and a lower cutting pile-up height. With a positive γ, a large α or small R has a larger average friction coefficient, which implies a higher resistance rate. The tool with a smaller R or positive γ can improve the machined surface’s smoothness.

Finite element investigation of cutting speed effects on the machining of Ti6Al4V alloy

In modern times, titanium alloy has a great application prospect in the medical field. Still, the pitiful machinability of titanium alloy material brings incredible difficulty to its ultra-precision cutting. This work presented the effect of parametric sensitivity analysis of the orthogonal cutting process using the finite element method, which dramatically enhances the cutting performance of Ti–6AL–4V. The simulation results are attained by applying Abaqus® explicit 6.14 software. The mechanical reaction of two-dimensional finite element models has been examined for cutting forces. Additionally, the impacts of rake angle, clearance angle, and nose radius on the stress distribution in orthogonal cutting of Ti–6AL–4V have been investigated. Also, to make certain numerical accuracy, the Johnson–Cook constitutive models for Ti6Al4V alloy are implemented. In the end, FE simulation outcomes were supported by the reported results in the literature.

PROFILING OF CUTTING TEETH OF A GEAR SHAPING HEAD

This paper investigates a possibility of the use of the mathematical model of the cutting edge profile developed for turning form cutter in the profiling the cutting edge of the tooth of a gear gushing head. The corresponding cutting tooth of the gashing head was carried out with Mathcad commercial software package accounting for the rake and clearance angles. The use of the same mathematical model increases the degree of automation of the design of various types of form cutting tools, which is the goal of many research work in the field of tool design and its manufacturing. In order to apply the mathematical model of the tuning form tool during the profiling of cutting teeth of a gear gashing head, arrays of coordinates of the points of the involute profile of the tooth are formed accordingly. This was carried out accounting on the difference in the motions of cutting edge of the tuning form tool and that of a gear gushing head. Moreover, the obtained results allow to conclude that the developed generalized mode can be used not only for great gushing tools but also for gear generating tools as gear shaper cutters.

Performance analysis of a novel small-scale radial turbine with adjustable nozzle for ocean thermal energy conversion

Ocean thermal energy is acknowledged as one of the most promising ocean renewable energy sources in low latitude sea areas. In the ocean thermal energy conversion system, the turbine plays a significant role, and it is responsible for converting the working medium enthalpy into the shaft output power. The present study is focused on the performance analysis of a novel radial inflow turbine with an adjustable nozzle in the OTEC system in order to adapt to the changing operating conditions of the turbine, which vary with the change in seawater temperature. At the design point, the predicted overall isentropic efficiency is 86.5%, and the shaft output power is 15.3 kW, slightly higher than the expected 15 kW. Furthermore, a parametric study is performed, respectively, for the nozzle vane stagger angle and the nozzle-impeller radial clearance to explore the favorable geometric parameters for different conditions. The turbine’s overall efficiency increases slightly with deceasing nozzle-impeller radial clearance, and the variation of the nozzle vane stagger angle is much more influential on the turbine shaft power and overall efficiency. The optimum stagger angle point moves from 32° to 36° gradually with the increase in nozzle-impeller clearance. Finally, the feasibility of an adjustable nozzle for the turbine under off-design conditions was verified by combining the radial clearance and nozzle stagger angle.

Investigation of machining quality indicators and effect of tool geometry parameters during the machining of difficult-to-machine metal

Producing high-quality surfaces from hard and brittle metals presents a formidable challenge that calls for a meticulous machining strategy and an effective cutting tool. The mechanism of tool failure, chip formation behavior, and micro-morphology of the machined surface are crucial factors in determining a correlation between the used parameters and the machined surface quality. Among the metrics employed to assess the effectiveness of the tool. However, the determination of optimum machining parameters requires the repetition of precise experimental investigations with every change in the cutting conditions. The current research work proposes a set of suggestions for choosing the optimal tool parameters based on the micro-morphological characteristics of the tool and the machining performance indicators. A WC-Co ball end mill tool was used for the machining of an H13 tool steel workpiece to establish the relationship between changes in tool geometrical parameters and the machining performance indicators. Tool geometry with a rake angle of 3°, a clearance angle of 10°, and a helix angle of 32° was found to have the least wear band length at 56 μm. Moreover, the impact of tool geometry on the quality of the surface produced through machining was also investigated.

Machining fiber-reinforced glass-epoxy composites with cryo-treated and untreated HSS cutting tools of varying geometries

Depending on the expanding application areas of glass fiber reinforced composite materials, quality machining of such materials also receives increasing interest. However, since the cutting tools used for machining such composites generally have standard geometric properties, both the life of the cutting tool and the quality of the machined composite workpiece are adversely affected by. In this study, the performance and the most optimum drilling geometries of untreated (UT) and cryo-treated&tempered (DCT&T) HSS cutting tools used for machining of fiber-reinforced glass-epoxy composites were investigated. Moreover, Taguchi experimental design was employed to reduce the number of experiments, and also the analysis of variance (ANOVA) and regression analysis were performed. Furthermore, XRD analysis and microhardness tests were applied to UT and DCT&T HSS cutting tools. From the highest and lowest delamination factor (Fd) values obtained using UT and DCT&T HSS drills, it was understood that DCT&T HSS drills achieved better results by 0.8% and 0.7%, respectively. According to average surface roughness (Ra) values obtained, the performances of DCT&T HSS drills were 14.76% (for the highest Ra value) and 2.69% (for the lowest Ra value), better than UT HSS drills. When the highest and lowest cutting force values were compared, it was seen that the cutting force values obtained using DCT&T HSS drills were 24.54% and 16.15% less than the cutting force values obtained using UT HSS drills, respectively. According to the S/N ratios for the cutting forces, the most optimum geometries of the cutting tool were found to be 128° point angle, 33° helix angle and 8° clearance angle, respectively. With respect to S/N ratios for Fd values, the most optimum geometries of the cutting tool were found to be 118° point angle, 26° helix angle and 8° clearance angle, respectively. Based on S/N ratios for Ra values, the most optimum geometries of the cutting tool were found to be 128° point angle, 26° helix angle and 8° clearance angle, respectively. On the other hand, as a result of the regression analysis, R2 values obtained over 90% show that the regression models are quite successful. Besides, it was observed (from SEM and thermal camera images) that the epoxy resins in the chips produced at high spindle speeds melted because of high temperature, which indicated that the integrity of the composite workpieces started to deteriorate.

Intelligent Tapping Machine: Tap Geometry Inspection.

Currently, the majority of industrial metal processing involves the use of taps for cutting. However, existing tap machines require relocation to specialized inspection stations and only assess the condition of the cutting edges for defects. They do not evaluate the quality of the cutting angles and the amount of removed material. Machine vision, a key component of smart manufacturing, is commonly used for visual inspection. Taps are employed for processing various materials. Traditional tap replacement relies on the technician's accumulated empirical experience to determine the service life of the tap. Therefore, we propose the use of visual inspection of the tap's external features to determine whether replacement or regrinding is needed. We examined the bearing surface of the tap and utilized single images to identify the cutting angle, clearance angle, and cone angles. By inspecting the side of the tap, we calculated the wear of each cusp. This inspection process can facilitate the development of a tap life system, allowing for the estimation of the durability and wear of taps and nuts made of different materials. Statistical analysis can be employed to predict the lifespan of taps in production lines. Experimental error is 16 μm. Wear from tapping 60 times is equivalent to 8 s of electric grinding. We have introduced a parameter, thread removal quantity, which has not been proposed by anyone else.

Dynamic characteristics analysis of an aeroengine rotor system subjected to aerodynamic excitation

This paper aims to investigate the dynamic characteristics of an aeroengine rotor subjected to aerodynamic excitation. Firstly, the dynamic model of the turbo-shaft engine rotor system is established by means of finite element (FE) method, taking into account the blade-tip clearance-induced aerodynamic force and oil-film force induced by squeeze film damper. Next, the critical speeds and mode shapes of the rotor are achieved by calculation, simulation and experiment to illustrate the validity of the established model. Then, using bifurcation diagram, rotating orbit and time-domain waveform, the dynamic responses of the turbo-shaft engine high-pressure (HP) rotor with aerodynamic excitation are analyzed, and the effects of blade-tip clearance, inlet and outlet angles on the dynamic responses of the rotor are discussed, respectively. The numerical results reveal that the system maintains a stable-periodic motion at low-speed region. In contrast, at high-speed region, there is a noticeable appearance of instability. Besides, the magnitude of the response decreases with the growth of the blade-tip clearance. The growth of the inlet angle will result in an increase of the magnitude of the response, and the magnitude of the response reduces with the growth of the outlet angle. The aerodynamic force at resonance is greater than that at non-resonance. The research results can assist in understanding the dynamic characteristics of the rotor subjected to aerodynamic excitation, and provide theoretical guidance for the structural design of an aeroengine rotor system.

Improving the work process efficiency of a tillage module for pre-sowing tillage

The formation of a differentiated structure of the arable horizon during the pre-sowing processing of the grant is a relevant task that can be solved by designing appropriate soil-processing technical means. A scientific hypothesis has been put forward, according to which increasing the efficiency of the process of forming a differentiated structure of the arable horizon can be achieved by improving the design and substantiating the structural and technological parameters of the tillage module for pre-sowing tillage. Numerical simulation was carried out in the Simcenter STAR-CCM+ software package using the Lagrangian multiphase model employing the discrete element method. Calculation of second-order regression equations and statistical processing of the obtained data was carried out in the Wolfram Cloud software package. As a result of the simulation of the improved design of the tillage module, which includes one drum, plowshare, casing, and cleaner, it was found that it performs the operation of separation and redistribution of soil aggregates with almost the same efficiency as the basic design with 2 drums and plowshare. As a result of the simulation of the work process of the improved tillage module, regression equations of the content of the 10–30 mm fraction in the 0–4 cm soil layer and the content of the 0–10 mm fraction in the 4–8 cm soil layer from the research factors were obtained. The chosen factors of influence were a casing outlet clearance, casing inlet clearance angle, cleaner inclination angle, drum rotation frequency, unit movement speed, and processing depth. Solving the problem of multi-criteria optimization, the rational structural and technological parameters of the tillage module for pre-sowing tillage were calculated

Transient synchronous stability analysis and enhancement control strategy of a PLL-based VSC system during asymmetric grid faults

The stability of a voltage source converters (VSC) system based on phase-locked loop (PLL) is very important issue during asymmetric grid faults. This paper establishes a transient synchronous stability model of a dual-sequence PLL-based VSC system during low voltage ride-through by referring to the equivalent rotor swing equation of synchronous generators. Based on the model, the synchronization characteristics of the VSC system under asymmetric grid faults are described, and the interaction mechanisms, as well as the transient instability phenomena of positive and negative sequence PLL during asymmetric faults are explained. Using the equal area criterion, the influences of sequence control switching action, detection delay, and interaction between the positive and negative sequence PLL on the transient synchronous stability of the VSC system are analyzed, respectively. In addition, a transient stability assessment criterion based on the critical fault clearance angle and time and an enhancement control strategy based on the improved positive and negative sequence PLL are proposed. Finally, the analytical results are validated through simulation and experiments.