Spiral Flute Research Articles

Machining method and experiment for segmental spiral flute rake faces of hourglass worm gear hob

Machining method and experiment for segmental spiral flute rake faces of hourglass worm gear hob

On the Lubricity and Comparative Life Cycle of Biobased Synthetic and Mineral Oil Emulsions in Machining Titanium Ti-6Al-4V at Low Cutting Speed

The paper discusses an instrumented tapping test method using a CNC machine tool to compare the lubricity of MWFs by cutting threads in a Ti-6Al-4V alloy at low speed. The method uses a spiral flute tap size typical of industrial practice. A soft synchronous tap holder and spindle mounted dynamometer were incorporated on the machine to measure torque and thrust force. The tapping test method was demonstrated on three groups of MWFs that were commercially available and classified by ASTM E2523-13:2018. The method developed stable results free of chip clogging in tool flutes which could otherwise mask their comparative lubricity. The fully synthetic (FS) group displayed the best lubricity and within this group the FS from renewables (FS-bio) was the best overall. The method was shown to be effective in mitigating biasing effects on lubricity performance due to the generous tool chamfer angle tolerance and was practical and economical to implement. The significance of the results is discussed enabling an understanding of friction effects in tapping using a soft synchronous tap holder. A life cycle assessment of each MWF group found total Greenhouse Gas emitted from the FS group was 17% of the hydrocarbon group whilst FS-bio emitted just 7%.

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.

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.

Design and correction method of spiral flute rake face of an hourglass worm gear hob

Design and correction method of spiral flute rake face of an hourglass worm gear hob

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.

Theoretical research of dynamic characteristics of Tc bearing of measurement while drilling

In this paper, through analyzing Tc bearing by the theory of Hydrodynamic lubrication, the unsteady Reynolds equation of Tc bearing under the dynamic-state condition is initially established. The formula of Tc bearing’s liquid-film dimensionless stiffness coefficient and damping coefficient is derived. Furthermore, two kinds of the distribution curves of Tc bearing’s liquid-film dimensionless stiffness coefficient, damping coefficient against Tc bearing’s eccentricity ratio and width-diameter ratio are displayed respectively, and the stability criterion of liquid film is worked out and the angular speed of instability of bearing shaft is calculated. Overall, conclusions are drawn: downhole system improves the entire system’s stability by enhancing the stiffness of bearing shaft itself. The improvement of the stability of bearing shaft itself, which can be done by altering the structure of Tc bearing and adopting better spiral flutes and ellipse groove can strengthen the whole system’s stability. The high width-diameter ratio of Tc bearing increases the liquid film’s stiffness coefficient and damping coefficient of Tc bearing. The rotational rate of rotary table is lower than half of that of the supporting system of Tc bearing.

Numerical Simulation for Peripheral Milling of Aero-Aluminum Alloy Based on 3D FE Model

In this paper, an advanced 3D FE model was established using ABAQUS Explicit to simulate the process of milling aluminum-alloy 7075-T7451. Taking the end edge and the side edge of single flute into consideration, the model simulated the interaction between the spiral flute and wokpiece at full depth of cut. In addition, by defining automatic element deletion criterion and locally refining mesh, this model realized chip separating from workpiece without defining of cutting layer. The simulation results were compared with experimental data to verify the correctness of the simulation model.

Influence of welding parameters and tool pin profile on microstructure and mechanical properties along the thickness in a friction stir welded aluminum alloy

Microstructure, second-phase particles and mechanical properties of the joint along the thickness of plate during friction stir welded 2219 aluminum alloy thick plate using different shapes pin were investigated in this paper. The top presented larger equiaxed recrystallized grain structure and finer second-phase particles compared to the middle and bottom. Thermo-mechanically affected zone and boundary were more optically distinct on the advancing side in comparison with the retreating side. Grain size and particles were much finer and dispersed using the first tool with three spiral flute or at the lower rotational speed of 300rpm. The strength and ductility in top slices was slightly higher than that in middle and bottom, increased with increasing traverse speed from 60 to 100mm/min or the decrease of rotational speed from 500 to 300rpm using the first tool. The mechanical properties using the second tool was lower than that of first tool, which was consistent with the hardness curves.

Study of local heat transfer in a spirally fluted tube

Local Nusselt numbers in a spirally fluted circular tube are presented. Thermochromic liquid crystals and shroud-transient technique are used to measure spatially-resolved surface temperature distributions, which are used to deduce local Nusselt numbers. The Reynolds number Re ranges from 30,000 to 70,000, a spiral angle θ is fixed at 60° and the dimensionless streamwise distance z/d ranges from 0 to 4.5. The results show that in general, the local Nusselt numbers monotonically decrease with a distance away from both windward and leeward crests of the spiral flute and reach a minimum value near its valley for all Re's and z/d's tested. The local Nusselt numbers in the spirally fluted tube are maximum 179–89.3% higher for Re = 30,000–70,000 near the windward crest at z/d = 4.5 than the fully developed values in the smooth tube. It is also found that the average Nusselt numbers are 52–23.7% higher for Re = 30,000–70,000 than the fully developed values in the smooth tube.

Numerical Analysis on Convection Heat Transfer of Pulsating Flow in a Spiral Fluted Tube

The mechanism of heat transfer enhancement of pulsating flow in a spiral fluted tube was researched by CFD (computational fluid dynamics) software FLUENT. Numerical results showed that pulsating flow leads to cyclical fluctuation of outlet pressure and the extent of fluctuation increases with increasing the pulsating flow frequency. Moreover, the pulsating flowing causes whirlpools near the spiral flute and the vortices generate, drift, and fall off periodically. The optimum pulsating frequency in the spiral fluted tube is 6HZ and the optimum amplitude A is equal to 0.7 approximately when the Reynolds number is 1683.

Key Techniques and Advances of Grinding/Milling Spiral Flutes on NC Machines with Multi-Axis Linkage

Introduced systematically the forming principles and mathematical modeling of grinding/ milling spiral flutes with numeric control machines, overviewed the functions of multi-axis linkage and the determination technique of the number of the linkage axes, discussed the conversion technique of NC—STEP-NC code in programming with EXPRESS, presented advances of controlling systems with high performance. Much attention was paid to the explanation of the error modeling and the tool interference in the real machining with the error-compensation techniques. Trends were envisioned on key technique study of the forming principles for the spatial spiral flutes, function of multi-axes, tool interference in the real machining and simulation of the operation processing, as well as automatic generation of NC codes and the connection /compatibility of the codes with the mainline NC systems, in future.

Fabrication of Spiral Micro-Coil Utilizing LIGA Process

We developed a method for fabricating a three-dimensional spiral micro-inductor with high inductance using the LIGA process. The spiral inductor created had a diameter of 0.5mm, and a length of 1mm. The width of the spiral line was 10µm, the pitch was 20µm, and the number of turns was 15. It was made of plated copper. The master was a brass round bar coated with PMMA resist. Deep X-ray lithography was employed to fabricate a master for a metallic mold at the NewSUBARU synchrotron radiation facility, University of Hyogo. The inductor core was made of resin by injection molding. It has a spiral micro flute on the surface. We chose the worm injection molding technique in order to avoid the parting line across the spiral line. The worm injection molding was the method─for demolding the work such as that used in loosening a screw.

00/02829 Cooled expansion in gas turbines: a comparison of analysis methods

Local Nusselt numbers in a spirally fluted circular tube are presented. Thermochromic liquid crystals and shroud-transient technique are used to measure spatially-resolved surface temperature distributions, which are used to deduce local Nusselt numbers. The Reynolds number Re ranges from 30,000 to 70,000, a spiral angle θ is fixed at 60° and the dimensionless streamwise distance z/d ranges from 0 to 4.5. The results show that in general, the local Nusselt numbers monotonically decrease with a distance away from both windward and leeward crests of the spiral flute and reach a minimum value near its valley for all Re's and z/d's tested. The local Nusselt numbers in the spirally fluted tube are maximum 179–89.3% higher for Re = 30,000–70,000 near the windward crest at z/d = 4.5 than the fully developed values in the smooth tube. It is also found that the average Nusselt numbers are 52–23.7% higher for Re = 30,000–70,000 than the fully developed values in the smooth tube.

Turbulent Flow in Integrally Enhanced Tubes, Part 1: Comprehensive Review and Database Development

Abstract Thermal performance improvements through passive and active enhancement methods have been studied intensely for over three decades. Heat exchangers with single-phase lube-side flow are one of the important applications where passive surface-modification methods are popularly employed. Ribs, indentations, spiral flutes, and coil inserts are some common surface modification techniques that are relatively easy to manufacture, are cost effective for many applications, and can be used conveniently for retubing existing heat exchangers. This article describes a comprehensive database that was developed to provide easy access to existing single-phase tube-side heat transfer and pressure drop data for different enhanced tube designs, in a consistent and useful manner. The database contains four files: (1) friction factor data, (2) heat transfer data, (3) tube characteristics, and (4) features of the experiments used by each data source, such as fluid type, boundary conditions, tube material, and tube type. The friction factor database contains nearly 5,000 data points, and the heat transfer database contains more than 4,700 data points. The data encompass more than 360 different tube geometries from over 35 investigations. The information can be used by practicing engineers for validatating and /or developing prediction methods, or to compare or estimate the performance of a specific tube design.

Spiral Flutes

Spiral Flutes