Straight Flute Research Articles

Experimental and statistical damage analysis in milling of S2‐glass fiber/epoxy and basalt fiber/epoxy composites

AbstractS2‐glass fiber reinforced plastics (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) have emerged as crucial materials due to their exceptional mechanical properties, and milling of composite materials plays an important role in achieving desired properties. However, they have proven challenges due to relative inhomogeneity compared with metals, resulting unpredictability in quality of milling operations. The objective of this work is to investigate the effect of cutting parameters, tool geometry and tool surface materials on the surface quality of composites using burrs as a metric. S2‐GFRP and BFRP composites were produced by the vacuum infusion method. Helical and straight flute end mills were manufactured from high‐speed steel (HSS) and carbide rounds, and half of them were coated with titanium nitride using reactive magnetron sputtering technique. Taguchi L18 orthogonal array is used to determine the effect of tool material, tool angle, coating, cutting direction, spindle speed, and feed rate on the machining quality of S2‐GFRPs and BFRPs with respect to burr formations. Milling experiments were conducted under dry conditions and then the burrs were imaged to calculate the total area and length. Statistical analysis was also performed to optimize the machining parameters and tool type for ensuring the structural integrity and performance of the final composite parts. The results showed that the selection of tool material has the most significant impact on the burr area and length of the machined surface. The novel image analysis allows to analyze the extent of the burr size with a desirable operation speed for industrial applications.Highlights Aerospace grade S2‐Glass (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) were manufactured. Carbide and HSS end mills were fabricated and coated with titanium nitride protective layer. FRPs were machined at various process parameters designed by Taguchi method. Distinctive image processing was firstly used to compute milling induced Burr area and length. Statistical analysis was performed to quantify the contribution of parameters and optimize milling.

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.

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.

Effect of cutting flute design features on primary stability of immediate implant placement and restoration: a dynamic experimental analysis.

Self-tapping implants with self-cutting flutes may influence primary stability, especially for the immediate implant placement and restoration protocol in which implants are affixed to the bone in the apical portion. Screw geometry differs between brands, and the effect of apical design on its clinical outcomes remains unclear. This study is aimed at investigating the influence of cutting flute shape (spiral, straight, and without flute) on primary stability by using a dynamic experimental test. Six types of dental implants were designed using computer-aided design and computer-aided manufacturing technology, consisting of three types of cutting flute shapes along with two types of screw features. A dynamic mechanical test was performed using a cyclic loading scheme. The mechanical behaviors of resistance to lateral load (RLL), maximum force, and energy dissipation were compared between groups. In the dynamic test, implants without cutting flute also exhibited higher values in RLL, maximum force, and energy dissipation. The aggressive thread implant with straight flute displayed higher RLL and had a significantly higher values in RLL (p = 0.033) at the threshold point of bone-implant interface breakdown. The implants without cutting flutes exhibited higher primary stability. Straight flute design would improve RLL for aggressive thread implant.

Influences of screw design features on initial stability in immediate implant placement and restoration

BackgroundSelf-tapping screws have been extensively used for dental implants. Their biomechanical behavior is highly associated with their clinical success, particularly for screws used for immediate implant placement and restoration, because occlusal forces can directly affect the loading transfer at the bone–implant interface after implantation. The effect of implant design on the initial stability of self-tapping screws remains unclear. This study explored the biomechanical behaviors of implant stability in standardized implants with different design features. MethodsSix types of dental implants were designed using computer-aided design/computer-aided manufacturing technology, including three types of cutting flute shapes (spiral, straight, and non–self-tapping) combined with two types of screw features. Peak insertion torque values were first recorded; initial stability levels were subsequently evaluated in terms of the maximum force and resistance to lateral loads using an electrodynamic test system. FindingsThe peak insertion torque values, maximum force, and resistance to lateral loads of the non–self-tapping groups were higher than those of the self-tapping groups by 17%–90% (p < 0.01). The peak insertion torque values of the Straumann implant with a spiral flute was higher than that of the original straight flute by 20% (p < 0.001). However, compared with the original spiral flute, the Nobel Biocare implant with straight flute had a 23% higher maximum force (p = 0.016) and 24.5% higher resistance (p = 0.012) under lateral loading. InterpretationChanging the flute design would affect initial implant stability. Non–self-tapping implants exhibited superior initial stability than did self-tapping implants.

The effects of cutting conditions and tool geometry on mechanics, tool wear and machined surface integrity when routing CFRP composites

Carbon-fibre-reinforced plastic (CFRP) composite materials are highly susceptible to tool-wear-induced interlayer delamination and superficial carbonization when subjected to routing, particularly under high cutting speeds (> 100 m/min) and high feed rates (> 0.40 mm/rev). This study modelled orthogonal, mono-oblique, and dual-oblique cuttings in routing CFRP composite workpieces with a consideration of the bending-moment-induced deflections in the cutting tools, and the effects of the cutting conditions on the delayed tool wear, vibrations and the produced machined surface integrity. The interactions of the cutting conditions and the alterations in the cutting edges are discussed and analysed, particularly the quality of the machined surfaces in their forms and topographies. The tool geometries of helical and cross-flute routers outperformed straight-flute routers in preserving tool life, by allowing the cutting forces generated by the primary cutting edges to counteract those generated by the secondary cutting edges, and in so doing, reduce the forces more effectively. Nonetheless, the straight flute router produced a smooth surface without the pulled-out fibres, smearing, or material adhesion produced by the other routers. Statistical methods were used to analyse the relative contributions of the various operating parameters for the least power consumption. We also sought to clarify the cutting mechanisms underlying the observed cutting forces and tool flank wear, as well as to interpret their effects on the machined surface texture, roughness, and topography. In addition, a detailed discussion of fibre fracture mechanisms and subsurface alterations on the matrix material are provided.

Strength, failure and microstructure development for friction stir welded AA6061-T6 joints with different tool pin profiles

The influence of seven different tool pin profiles was investigated to appraise the tensile, flexural strength, fracture behavior, and microstructure evolution in friction stir welded similar AA6061-T6 joints. Results indicate that each tool pin profile affects the material flow/intermixing in different ways; consequently, the weld nugget feature and grain size in the stir zone (SZ) were also observed to be different. Relatively finer grains with homogenous microstructure in SZ were observed for joints prepared using cylindrical grooved with straight flutes (CGF) and cylindrical grooved (CG) tool pins. The highest tensile strength and flexural load were observed for joints obtained with CGF tool pin followed by CG tool pin. A relationship between average yield strength of the joint and inverse square root of average SZ grain size was established for these joints. EBSD analysis revealed that the SZ is the mixture of low angle grain boundaries and high angle grain boundaries (HAGBs) and the fraction is controlled by different pin profiles. The HAGBs and high shear texture components B/B¯ and C were found predominant in welds prepared with CGF and CG tool pins. Fractographic analyses showed the presence of numerous dimples in sound bonded regions indicating the ductile fracture; however, tearing/rupture and shear failure were witnessed near the vicinity of the tunnel region.

Effect of implant design on the initial biomechanical stability of two self-tapping dental implants

BackgroundThis study evaluated the effect of two self-tapping implants on implant stability in immediate implantation. MethodsTwo types of self-tapping implants, straight flute (STF) and spiral flute (SPF) designs, were studied. Two synthetic bone blocks with varying densities (0.32 g/cm3 and 0.16 g/cm3) were chosen to simulate the bone quality of the anterior maxilla. Insertion torque values were measured by a torque testing machine during implant insertion. Four biomechanical tests were performed: resonance frequency analysis was conducted using the Osstell device, and the strengths of screw push-in, lateral bending, and pull-out were evaluated using an MTS machine. The strength for each design feature was obtained by averaging the results of 10 trials. In total, 40 specimens were tested for each bone density. Statistical difference was determined by one-way analysis of variance followed by Bonferroni post hoc multiple tests between groups. FindingsThe STF and SPF groups exhibited similar insertion torque values (p = 0.525 in low-density bone, and p = 0.99 in high-density bone). A significant difference (p < 0.001) was observed in the push-in test between the two groups when low-density bone was tested. The SPF group exhibited a significantly higher lateral bending force (p = 0.001) and a higher stiffness (p < 0.001) than the STF group in high-density bone. The SPF design attained higher (p < 0.001) ISQ numbers than the STF design, but all numbers were below 60. InterpretationImplant stability can be influenced by the apical fixture design of self-tapping implants in immediate implantation.

New tool for reduction of harmful particulate dispersion and to improve machining quality when trimming carbon/epoxy composites

Conventional machining of carbon fiber reinforced plastic composites (CFRPs) generates minute chips that get suspended in air causing a hazard compromising operator safety. This study investigates the influence of cutting parameters (feed speed, cutting speed, radial depth of cut, tool geometry and tool wear) during trimming of CFRP on the form and quantity of harmful particles dispersed. Also, performance of two classical PCD tool geometries (two straight flutes, two helix flutes) have been compared with newly designed (in collaboration with ASAHI Company) four serrated straight flutes for the purpose of dust emission reduction. The quantification of the number of harmful particles was estimated using laser spectroscopic dust monitor. The results reveal that, trimming with a combination of higher feed speed and lower cutting speed can reduce the dispersion of harmful particles. Further, the four serrated straight flutes recorded the least number of harmful particles compared to the conventional tools.

Improved dynamic cutting force modelling in micro milling of metal matrix composites Part I: Theoretical model and simulations

Cutting force modelling for micro machining is of great importance for better understanding of the cutting mechanics in the process. As precision machining of metal matrix composites (MMCs) is much more complex than machining homogeneous materials, the accurate prediction of cutting force is critical to control the cutting performance and tooling life. This paper presents an improved theoretical dynamic cutting force model in MMCs micro milling process by using straight flute PCD end mills. The theoretical model is modified and improved based on the conventional milling force modelling while taking account of various factors including tooling geometries, the material microstructure, size effect and chip formation in the cutting process. An innovative expression on dynamic cutting force in micromachining MMCs is presented through the multiscale modelling and analysis. The cutting force coefficients are further defined through instantaneous cutting force signals analysis. Simulation results under varied cutting process variables are presented against a series of MMCs micro milling trials, which indicate that the improved dynamic cutting force model can predict the cutting force accurately and reveal more details on the cutting force variations in the process due to the material inhomogeneous nature. In addition, the optimal process variables can be readily explored through the dynamic force modelling and simulations so as to further improve the cutting performance.

Improved dynamic cutting force modelling in micro milling of metal matrix composites part II: Experimental validation and prediction

The effects of cutting dynamics and the particles' size and density cannot be ignored in micro milling of metal matrix composites. This article presents the improved dynamic cutting force modelling for micro milling of metal matrix composites based on the previous analytical model. This comprehensive improved cutting force model, taking the influence of the tool run-out, actual chip thickness and resultant tool tip trajectory into account, is evaluated and validated through well-designed machining trials. A series of side milling experiments using straight flutes polycrystalline diamond end mills are carried out on the metal matrix composite workpiece under various cutting conditions. Subsequently, the measured cutting forces are compensated by a Kalman filter to achieve the accurate cutting forces. These are further compared with the predicted cutting forces to validate the proposed dynamic cutting force model. The experimental results indicate that the predicted and measured cutting forces in micro milling of metal matrix composites are in good agreement.

An investigation into tapping of Al6061/SiC metal matrix composite with straight flute HSS machine tap

The present study deals with tapping of Al6061/SiC metal matrix composite. Stir casting technique was used for the fabrication of composite. Castings were produced by varying weight percentages of SiC (5%, 7.5% and 10%) of 23μm size in Al6061. The tapping experiments were conducted for the machinability study of Al6061/SiC metal matrix composite using M8 x 1.25 HSS machine taps. The tapping operation was performed under dry condition with different cutting speeds. Torque required for tapping was measured using piezoelectric based 4-component drill tool dynamometer. Surface morphology and profile of thread surfaces were analysed using Scanning Electron Microscope (SEM) and metallurgical microscope. Estimation of progressive flank wear of machine taps was undertaken using profile projector. The performance of HSS machine tap was evaluated in terms of tapping torque, tool flank wear, and surface characteristics of thread surfaces. The flank wear of uncoated HSS machine tap increased with the increase in weight percentage of SiC in Al/SiC composite for a particular cutting speed. Further, when the matrix materials were reinforced by the same kind and the same weight percentage of SiC particles, the flank wear of the tool was found to increase with cutting speed. In addition, the damage caused to thread profiles increased with the increase in cutting speed and weight percentage of SiC.

An experimental investigation on surface generation in ultraprecision machining of particle reinforced metal matrix composites

Ultraprecision machining of metal matrix composites (MMCs) is observed as a scientific challenge, due to their hard-to-machine property and often the poor surface finish. This paper presents an experimental investigation on surface generation in ultraprecision machining of Al/B4C/50p MMCs. The machining trials using straight flute polycrystalline diamond (PCD) tools are conducted on a high precision micro milling machine. Side milling is adopted under varied cutting conditions. Metrology assessments on the workpiece surface roughness, topography, texture and defects/features are undertaken using a ZYGO 3D surface profiler and a scanning electron microscope (SEM). Experimental results indicate that process parameters and their contributions play essential roles in the machining process. By applying the optimal process parameters, e.g. cutting speed of 188.496 m/min, feed rate of 10 μm/rev and axial depth of cut of 150 μm, a better surface generation with surface roughness Ra < 20 nm can be obtained in ultraprecision machining of Al/B4C/50p particulate MMCs.

Phonetic characterisation of musical articulation: The case of txistu

ABSTRACTThis article presents a description, in strictly phonetic terms, of the tonguing of a straight flute: the txistu. First, it identifies the linguistic articulation most resembling tonguing, which is not, as often claimed, dentoalveolar [] or [t], but prepalatal []. Next, it examines different phases of tonguing, around the major moments of (consonantal) shutting and (vowel) opening. Throughout the paper, a variety of experimental phonetics materials and techniques are used, such as MRI imaging, endoscopy, electropalatography and spectrography.

Influence of machining parameters on surface quality during high speed edge trimming of carbon fiber reinforced polymers

CVD diamond-coated carbide tools could provide an economical alternative for trimming CFRPs components compared to their PCD tools counterpart. Nevertheless, there are still some technical issues to understand related to wear resistance and surface quality. In this work, a CVD tool with six straight flutes was used to investigate the relationship between surface roughness, surface damage, tool wear, cutting force and cutting parameters during the high speed trimming of CFRPs. Statistical techniques for identifying and selecting the best cutting conditions for CVD tool are developed. In terms of tool wear, results show that the best operational condition to minimize the tool wear is achieved at lower feed rates and higher cutting speeds. Experimental results show also that a 0° ply orientation represents the worst case and produces the maximum tool wear. Furthermore, a strong correlation between the feed force and the tool wear was observed. It was found that the surface roughness decreases as a reciprocal function of cutting length. This decrease was due to the matrix burning/sticking and the thermal damage related to the low thermal conductivity of CFRP. In such situation, Ra becomes inappropriate indicator for roughness evaluation. On the other hand, it wasn’t seen any type of delamination or fiber pull-out on the trimmed surface of all coupons for the three tool life tests. Accordingly, delamination can be avoided using high fixture rigidity, high quality of CFRP laminates, a suitable cutting tool and stable operational conditions.

A Method to Generate the Spiral Flutes of an Hourglass Worm Gear Hob

All of the cutting edges on an hourglass worm gear hob have different shapes and spiral angles. If the spiral angles are small, straight flutes are typically adopted. However, for hobs with multiple threads, the absolute values of the negative rake angles on one side of the cutting teeth will greatly affect the cutting performance of the hob if straight flutes are still used. Therefore, spiral flutes are typically adopted to solve this problem. However, no method to determine the spiral flute of an hourglass worm gear hob has been proposed until now. Based on the curved surface generating theory and the hourglass worm forming principle, a method for generating the spiral flute of the planar double enveloping hourglass worm gear hob is proposed in this paper. A mathematical model was built to generate the spiral flute. The rake angles of all cutting teeth of the hob are calculated. The laws of the rake angles of the cutting teeth for four hobs with different threads from one to four threads were analyzed when straight flutes and spiral flutes are adopted. The laws between the value of the negative rake angles of the hob with four threads and the transmission ratio were studied. The most appropriate transmission ratio for generating the spiral flute was obtained. The machining of the spiral flutes was simulated using a virtual manufacturing system, and the results verify the correctness of the method.

Behaviour and performance style in present day canto sul tamburo from the Giuglianese area: continuity and change

Within the tradition of the singing and dancing accompanied by the traditional frame-drum of Campania Region, there are different identifia-ble area styles. Beyond several common traits, these styles are distinguished by different types of performative structure concerning both vocal-instrumental and cho-reutic performance. The style of Giuglianese-domiziana area is easily recognizable being characterized by the use of sisco, a small straight flute. The aim of this study is to verify the relevance of the Giuglianese style with its different performative inno-vations and the wide variety of performance contexts (from ritual occasions to concert performances on stage). By means of examples, it will outline the essential features which characterize the performance practice of canto sul tamburo in Giugliano. Particular attention will be devoted to the different modes of self-represe-ntation that are mainly constitute by a large number of self-produced CDs, and a great flowering of video on YouTube and Facebook groups which play a crucial role in today's aware-ness of the local actors.

DETERMINATION OF OSCILLATOR CIRCUIT PARAMETERS OF A MATHEMATICAL MODEL OF THE DYNAMICS OF THE CUTTING PROCESS WITH A METAL CUTTING TOOL

Objectives. The development of a mathematical dynamic system model is necessary for analysing vibrational motion during the metal cutting processes. The mathematical model of the dynamic system is considered to be defined if the system parameters that unambiguously determine its state are known and the alteration of its state over time is specified. Considering the above mentioned, each study of vibrational motion must be preceded by a determination of the parameters of the oscillator circuits of the mathematical model. The working part of the metal cutting tool consists in a shank having a complex profile, which makes such calculations very difficult to carry out. There are no sufficiently rigorous and, at the same time, acceptable formulae for engineering practice in the literature data. Therefore, data on the characteristics of the metal cutting tool – in particular, its stiffness and moment of inertia – scatter significantly. The aim of the study is to obtain calculated dependences that meet these requirements and determine the limits of their applicability for different cutting tool diameter ranges. Methods. Approaches referring to the theory of elasticity are used for the calculations. Results. Engineering formulae for the calculation of stiffness and polar moment of inertia of the metal cutting tool are obtained; in particular, three- and four-blade taps with straight flutes as well as drills. It is established that to increase the dynamic stability of the metal cutting tool, it is necessary to increase the moment of inertia of the section. This can be achieved by increasing the diameter of the core.As the flute helix angle increases, the stiffness of the tool decreases significantly. High stiffness of the metal cutting tool can be achieved by employing a flute with a variable helix angle. Conclusion. The calculated dependences allow the parameters of the Machine-Device-Tool-Part (MDTP) system to be set with an acceptable accuracy when analysing metal processing dynamics using metal cutting tools. The influence of the sharpening angles on the moment of inertia is demonstrated; the account given for the latter will significantly increase the reliability of the results of the analysis of the process dynamics.

A Feasibility Study of Laser-assisted Titanium Implant Drilling for Periprosthetic Fracture Repair

This paper studies the feasibility of hand drilling through a titanium implant located in the femur. This is hypothesized to be achievable via laser-assisted drilling with carbide tools. A series of tests were conducted to measure the thrust force and torque with different shaped drill bits under dry- and laser-assisted drilling (using a 200-watt fiber laser), respectively. These drill bits included 2-flute and 3-flute twist drills and a straight flute drill that is clinically available. Results showed that the 2-flute drill outperformed the other two in both thrust force and torque. The laser can further reduce the forces of 2- and 3-flute drill bits by over 10%, but has a negative impact on the straight-flute one. This paper also discusses results from a clinical perspective, current limitations, and future work.

CFD simulation for internal coolant channel design of tapping tools to reduce tool wear

This paper presents the analysis and controlled modification of the coolant flow in tapping processes by means of Computational Fluid Dynamics (CFD). First, a conventional straight flute tapping tool was analyzed and the results of the CFD simulation show, that the cutting edges are not sufficiently supplied with coolant. Therefore, the design of the internal coolant channels was modified based on these simulation results. To validate the CFD simulation, experimental tests were performed, using an optimized tool. The applied modifications lead to a reduction of the tool wear and an increase of the tool's performance of about 36% was achieved.