Tool Helix Angle Research Articles

A cylindrical skiving tool design method based on a conjugate surface for internal gear manufacture

Power skiving is a highly productive method for manufacturing gears, especially internal gears. However, due to the resharpening errors of the conical skiving tool, the insufficient tool life hinders the large-scale applications of power skiving. This work proposes a novel design method of the cylindrical skiving tool based on deriving the mathematical model of two-parameters conjugate tooth surface of an internal gear. The error-free cutting-edge of the skiving tool is obtained from the intersection curve of the conjugate tooth surface and the rake face with an offset along the tool axis. In the present study, a helical internal gear with 97 teeth, module of 1.5875 mm and helix angle of 23.5° is used for the design of a cylindrical skiving tool with 37 teeth. The numerical analysis results show that the tool axial offset zoff, crossed shaft angle Σ and geometric rake angle of tool γ0 result in the asymmetrical tool profile and the uneven clearance angles on both flanks. However, the change of the tool helix angle by 0.7° can obtain an even clearance angles on both flanks when zoff is −30 mm. The noninterference height of the cylindrical tool is 48 % more than the conical tool when machining the same workpiece, which means the cylindrical tool is expected to be a longer tool life. Experiments are conducted on a Profilator Type H skiving machine by using the cylindrical skiving tool by the accuracy of DIN 3. The results show the tool design method is effective and applicable to machine a gear by the accuracy of ISO1328-1 level 7.

Single and multi-objective optimization for cutting force and surface roughness in peripheral milling of Ti6Al4V using fixed and variable helix angle tools

Ti6Al4V titanium (Ti) alloy is a frequently used engineering material in industrial applications due to its superior properties. In this work, single-objective and multi-objective methods were used to optimize control factors (cutting speed, feed rate, and cutting tool helix angle) for minimal cutting force (Fc) and surface roughness (Ra) in peripheral milling of Ti6Al4V. Machinability experiments were performed using carbide end mill cutting tools with fixed and variable helix angles. Following the machinability tests performed using the L18 orthogonal array, the Taguchi technique was used as a single-objective optimization for each of the cutting forces and surface roughness. The Entropy-weighted TOPSIS approach was used in the second step to provide the optimum levels of the control factor, which minimizes both cutting force and surface roughness. The effects of control factors and interactions on thrust force and surface roughness were determined by Analysis of Variance (ANOVA) and contour plots. As a result of this study, it was determined that the helix angle of the cutting tool (84.91 % contribution) was the most effective parameter on the cutting force and the feed rate (22.71 % contribution) on the surface roughness. The cutting force and surface roughness values decreased in peripheral milling at high cutting speed, whereas the cutting forces increased, and the surface quality of the workpiece deteriorated in machining at high feed rates. The helix angle of the cutting tool has a favorable influence on the cutting force and surface roughness when milling with fixed helix tools. Cutting forces are minimized, and workpiece surface quality is improved using cutting tools with a larger helix angle. Variable helix tools with a large helix angle performed best in cutting force and surface roughness. Variable helix end mills with large helix angle (HA = 35°/38°), high cutting speed (Vc:108 m/min), and a low feed rate (f:0.04 mm/tooth) should be used in peripheral milling of Ti6Al4V Ti alloy to achieve both minimum cutting force and best surface quality. The mean cutting force and surface roughness values were obtained as 628.69 N and 0.363 μm, respectively, in the peripheral milling process performed at different levels of control factors. The cutting force was reduced to 227.52 N (34.71 % improvement) and the surface roughness value to 0.237 μm (276.32 % improvement) using the Entropy-weighted TOPSIS multi-objective optimization approach.

Generalized cutting force model for peripheral milling of wood, based on the effect of density, uncut chip cross section, grain orientation and tool helix angle

The influence of the grain angle on the cutting force when milling wood is not yet detailed, apart from particular cases (end-grain, parallel to the grain, or in some rare cases 45°-cut). Thus, setting-up wood machining operations with complex paths still relies mainly on the experience of the operators because of the lack of scientific knowledge easily transferable to the industry. The aim of the present work is to propose an empirical model based on specific cutting coefficients for the assessment of cutting force when peripheral milling of wood based on the following input: uncut chip thickness and width, grain angle (angle between the tool velocity vector and the grain direction of the wood), density and tool helix angle. The specific cutting coefficients were determined by peripheral milling with different depths of cut wood disks issued from different wood species on a dynamometric platform to record the forces. Milling a sample into a round shape (a disk) allows to measure the cutting forces toward every grain angle into a sole basic diameter reduction operation. Force signals are then post-processed to carefully clean the natural vibrations of the system without impacting their magnitudes. The experiment is repeated on five species with a large range of densities, machining two disks per species for five depths of cut in up- and down milling conditions for three different tool helix angles. Finally, a simple cutting force model, based on the previously cited parameters, is proposed, and its robustness analysed.

Investigations into the influence of tool helix angle during end milling of open straight and curved thin-wall parts

In this paper, the influence of cutting tool helix angle on performance parameters viz., milling force, part deflection, surface finish, chip morphology and micro-hardness considering open straight and curvilinear thin-walled parts is analysed. It was found that end mills with helix angle of 45° and 55° helped in achieving good surface finish and form accuracy while machining thin-wall parts. During machining, parts having concave geometry due to its inherent rigidity, generated higher milling force. But the wall deflection and form error was relatively lower in comparison with the straight wall thereby resulting in better surface finish. Also, formation of built-up-edge (BUE) at the cutting edge of end mills having 35° helix was noted which aided in surface defects. Back surface of the chips machined using 35° tools showed prominent lamella like structures but tools having higher helix angles were found to produce relatively lamella free surface.

Investigations into the influence of tool helix angle during end milling of open straight and curved thin-wall parts

In this paper, the influence of cutting tool helix angle on performance parameters viz., milling force, part deflection, surface finish, chip morphology and micro-hardness considering open straight and curvilinear thin-walled parts is analysed. It was found that end mills with helix angle of 45° and 55° helped in achieving good surface finish and form accuracy while machining thin-wall parts. During machining, parts having concave geometry due to its inherent rigidity, generated higher milling force. But the wall deflection and form error was relatively lower in comparison with the straight wall thereby resulting in better surface finish. Also, formation of built-up-edge (BUE) at the cutting edge of end mills having 35° helix was noted which aided in surface defects. Back surface of the chips machined using 35° tools showed prominent lamella like structures but tools having higher helix angles were found to produce relatively lamella free surface.

Investigation on the vibration and machined surface quality in tilt side milling of thin-walled plates

Tilting milling tools to proper angles could help significantly suppress machining vibrations and enhance machined surface quality. The aim of this study is to investigate how the two fundamental variables, tool helix angle (β) and tilt angle (θ), could influence milling vibrations and machined surface topography when milling sidewall surfaces of thin-walled plates with solid end mills. A series of side milling tests were carried out at different tilt angles utilizing tools with different helix angles, during which the accelerations, instantaneous vibration displacements, cutting forces, machined surface roughness, and topographies of the workpiece were carefully measured. The results showed that the minimum machined surface roughness across the measured surface, Ra, was 0.37 μm when β = 40° and θ = 30°. In addition, optimal tilt angles for the lowest Ra on the machined surface with tools of different helix angles are in accordance with the optimal angles for the minimum absolute value of Z-axis force Fz, rather than ones for the weakest vibrations. This result indicates that, when milling sidewall surfaces of thin-walled plates, Ra is more highly dependent on the cutting force component along the lowest stiffness direction of plates than the vibration amplitudes. The results presented in this paper are useful insights for milling process parameter optimization to improve machined surface quality in milling sidewall surfaces of thin-walled components.

Assessment of melamine-coated MDF surface finish after peripheral milling under different cutting conditions

Milling is a machining process that is widely used in the furniture industry, since a good quality surface finish is essential. Produced MDF parts usually have aesthetic importance that is affected by poor surface finish and chipping of the melamine layer that may occur during machining. In addition, higher surface roughness affects the quality required for the subsequent assembly processes because the adhesion between the part and the edge tape decreases. Despite this, there are few specific studies focused on finishing MDF milling process using CNC woodworking machines. Thus, an evaluation of the surface finish generated by peripheral milling of melamine-coated 15 mm thick MDF panels was carried out. The 2k factorial DOE was performed varying cutting speed, feed rate, and cutting motion. Four different tools were tested with different helix angles and number of teeth. The surface finish was evaluated through the measurement of the average roughness (Ra), while the chipping of the melamine edges was qualitatively evaluated. Among the main parameters, feed rate, tool helix angle and cutting motion showed a significant influence on Ra. However, the most significant influence was observed for the interaction between the number of teeth and the helix angle. Moreover, the 30° helix angle is mainly responsible for the melamine layer chipping, although the number of teeth indirectly affected the incidence of chipping. Based on the results, the end mill C-type (10° helix angle and 3 teeth) in the up milling with 2.7 m min−1 feed rate was the best combination.

Modeling of cutting forces in curvilinear peripheral milling process

Due to the increasing esthetic requirements and complex functional specifications of machined components, peripheral milling of curved geometries is becoming increasingly important in the aerospace, automotive, and the injection molds industries. However, one of the major difficulties encountered by manufacturers is that peripheral milling of the curved surfaces which is characterized by significant amount of engagement variation along the tool path causing a sudden change in cutting forces and consequently a deterioration of the surface roughness of the machined parts and lowers productivity. The present paper presents a two-dimensional machining model allowing the simulation of cutting forces including the cutting process damping in curvilinear peripheral milling. In the study, we attempt to analyze the effect of various milling parameters such as cutting speed, feed rate, axial and radial depth of cut, tool diameter, and tool helix angle on cutting forces generated by the peripheral milling of a curved surface profile. The cutting forces obtained through simulation model are compared with experimental results.

Effects of tool helix angles on machined surface morphology in tilt side milling of cantilever thin-walled plates

For milling the side wall surfaces of cantilever thin-walled plates, to tilt the tool to a proper angle could decrease the cutting force component in the direction of the lowest stiffness of the plates, and then mitigate the chatter, resulting in the improvement of the machined surface finish. The tool helix angle and tilt angle are the two major variables determining the cutting force component, accordingly having significant effects on the machined surface morphology. In this paper, these effects are investigated through experiments with solid end mills of different helix angles.With the surface roughness Ra as the quantification assessment parameter for machined surface morphologies, variations of surface morphologies not only with the tool tilt angles but also with the tool helix angles are investigated. The mathematical model expressing the relation between the tool helix angle and the corresponding optimal tilt angle is built when the quality of the machined surfaces is the best. For better understanding the effects of these two variables on the dynamic vibrations of the workpiecethat directly contributes to the formation of surface morphologies, especially chatter marks, the instantaneous vibration displacements of plates during the milling process are also measured by a laser range sensor, and the effects on the surface roughness are analyzed. This study could provide guidance for process parameters optimization in milling the sidewall surfaces of thin-walled components.

Investigation on critical cutting depth in milling of wave-transmitting Si3N4 ceramics

Wave-transmitting Si3N4 ceramics exhibits high levels of brittleness, and the milling surface inevitably exists defects. Critical cutting depth is an important reference parameter to improve the surface quality and processing efficiency in milling. A theoretical mathematical model has been proposed to predict the critical cutting depth in the study. The contact relationship between the tool cutting edge and the ceramics surface is analyzed, and the non-uniform bearing crack system is established. The micro cracks propagation critical condition has been put as the criterion of critical cutting depth. Through the model calculation, the critical cutting depth is 0.38 mm, and it is confirmed the critical cutting depth is between 0.3 and 0.4 mm with experimental results. The model predictions are consistent well with the experimental results. In addition, the theoretical model shows that the critical cutting depth decreases exponentially with the increase of the material hardness, while the increase of fracture toughness, tool helix angle and side edge rear angle, leads to critical cutting depth rising. The theoretical model can be applied to evaluate the critical cutting depth of brittle ceramics in milling.

Working mechanism of helix angle on peak cutting forces together with its design theory for peripheral milling tools

Existing researches for studying the influences of mill's helix angle on peak cutting force were mainly carried out by using simulation or experimental means. Thus, the obtained conclusions were just empirical judgments or qualitative observations, which cannot be further used for optimally designing the helix angle of mills. This paper presents a theoretical method for the first time to reveal the working mechanism of peripheral milling tool's helix angle on peak cutting force through strict analytical formulation. To facilitate well understanding the effect of helix angle, variation tendency of peak cutting force versus helix angle is comprehensively studied by analyzing the formation principle of peak cutting force from the point view of both geometrical explanation and theoretical proof. Both infinitesimal element method and differential theory are used in the investigation procedure. It is proved that the peak value of cutting forces decreases with the increase of helix angle for a single engaged cutting edge. Combining this conclusion with the overlapping effect of multiple engaged cutting edges, optimal helix angle corresponding to the minimum of peak cutting forces is analytically derived to be the function of axial depth of cut, number of flutes and cutter diameter. Experimental verifications have been carried out to validate the proposed theory.

Swept Mechanism of Micro-Milling Tool Geometry Effect on Machined Oxygen Free High Conductivity Copper (OFHC) Surface Roughness.

Cutting tool geometry should be very much considered in micro-cutting because it has a significant effect on the topography and accuracy of the machined surface, particularly considering the uncut chip thickness is comparable to the cutting edge radius. The objective of this paper was to clarify the influence of the mechanism of the cutting tool geometry on the surface topography in the micro-milling process. Four different cutting tools including two two-fluted end milling tools with different helix angles of 15° and 30° cutting tools, as well as two three-fluted end milling tools with different helix angles of 15° and 30° were investigated by combining theoretical modeling analysis with experimental research. The tool geometry was mathematically modeled through coordinate translation and transformation to make all three cutting edges at the cutting tool tip into the same coordinate system. Swept mechanisms, minimum uncut chip thickness, and cutting tool run-out were considered on modeling surface roughness parameters (the height of surface roughness Rz and average surface roughness Ra) based on the established mathematical model. A set of cutting experiments was carried out using four different shaped cutting tools. It was found that the sweeping volume of the cutting tool increases with the decrease of both the cutting tool helix angle and the flute number. Great coarse machined surface roughness and more non-uniform surface topography are generated when the sweeping volume increases. The outcome of this research should bring about new methodologies for micro-end milling tool design and manufacturing. The machined surface roughness can be improved by appropriately selecting the tool geometrical parameters.

On the multiscale tribological signatures of the tool helix angle in profile milling of woven flax fiber composites

The present study is focused on tribological and multiscale analysis for the machined surfaces of bi-directional flax fibers reinforced polypropylene composites. This is to track the multiscale effect of the helix angle of the cutting tool, related to its kinematic, on the cutting mechanisms. The results show that the helix angle has significant effect on the tribological performances which affect the tribo-contact interaction between the flax fibers and the cutting edge. The fibers orientation in the woven reinforcement has significant effect on the surface quality. The multiscale analysis reveals the pertinent scales that activate the helix angle effect.

The Machinability of CFRP with Cutting Movement of End-Milling

Recently, carbon fiber reinforced plastics (CFRP) are expected to be used more in the aerospace and automotive industries, because of their outstanding lightweight material characteristics and tensile strength [1][2]. Underlying this are problems closely related to improvement of the earth’s environment. However, a mechanical property is influenced by the difference in the distribution state of the carbon fiber, and the adhesion intensity of the binding material. Moreover, they have the characteristic of intense anisotropy, strength wise depending on the orientation of the carbon fibers [3][4]. Therefore, CFRPs are considered difficult-to-machine materials [5], because the surface finish deteriorates according to the carbon fiber orientation. Establishing the optimal cutting conditions to solve such problems also from an economical viewpoint is essential. In our study, end milling operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the relationships between the carbon fiber orientation and the machining operations were determined. We earlier evaluated the machinability from the relationship between carbon fiber orientation and tool helix angle by down-cut milling to solve these problems [6]. In this study, machining operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills by up-cut milling. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the results of this experiment were compared with the results of down-cut milling.

엔드 밀링 공정에서 순간 절삭력 계수 결정을 통한 절삭력 예측 및 크기효과 평가

This paper presents a simple procedure to obtain the instantaneous cutting force constants needed to predict milling forces. Cutting force data measured in a series of slot milling tests were used to determine the cutting force constants at different feed rates. The values of the cutting force constants were determined directly at the tool rotation angle that maximized the uncut chip thickness. Then, the instantaneous cutting force constant was obtained as a function of the instantaneous uncut chip thickness. This approach can greatly enhance the accuracy of the mechanistic cutting force model for end milling. In addition, the influences of several cutting parameters on the cutting forces, such as the tool helix angle and axial depth of cut, were discussed.

Research on Force and Temperature in Milling Ti6Al4V Titanium Alloy Based on Tool Geometry

First, quadratic regression general rotary combination experimental design is adopted in this paper. The cutting force prediction model based on tool rake angle and helix angle is established using regression analysis. And the proper cutter for milling Ti6Al4V is selected, rake angle = 12.5 °, helix angle = 34.5 °.Secondly, milling temperature during different milling process is simulated by the use of finite element simulation software. And the variation rule of milling temperature along with the rake angle and helix angle is obtained which provided the basis for the selecting tool.

Effect of Carbon Fiber Orientation and Helix Angle on CFRP Cutting Characteristics by End-Milling

Carbon Fiber Reinforced Plastics (CFRP) have outstanding lightweight material characteristics and tensile strength. The use of CFRP in aerospace industry has been successfully implemented and is expected to grow in the future. However, the mechanical properties of CFRP are affected by differences in the distribution and orientation of the carbon fibers and their adhesion to the binding material. CFRP shows intense anisotropy in strength of carbon fiber depending on its mechanical properties and the state of the carbon fiber orientation. Therefore, the tool life shortest and the surface finish quality of the material becomes unstable and eventually difficult to cut. This paper presents the effect on carbon fiber orientation and helix angle with CFRP cutting characteristics by end milling. Here, three types of orientations weremachined by straight type end mills and constant cutting conditions with a cutting speed 70 m/min, a feed rate 0.056 mm/tooth and 3 mm depth of cut. Our results showed that the tool helix angle 0° gave a better surface finish than the other tools, irrespective of the fiber orientation. The helix angle is greatly affected by the exposure of the fibers from the surface. Axial force (Fz) is negligible quantity for helix angle 0°, and cutting force is low. The carbon fiber orientation of 45° and -45° has exfoliation-like dimples.

Physical Simulation of the Cutting Process Induced by Tool Geometric Angle and Cutting Parameters

The tool geometric angle and cutting parameters have a significant influence on the titanium alloy milling process by the usage of solid carbide end mills.The physical simulation method was applied to predict the cutting force and temperature by using two comparative sets of simulation data such as the different tool gemetric angle as tool rake angle, helix angle and different cutting parameters such as spindle speed, axial depth of cut, radial depth of cut. Thus are the commonly used methods to simulate and predict the cutting process before the actual production, which can reduce product cost and time.

Modelling cutting force including thrust and tangential damping in peripheral milling process

This paper presents an analytical model to predict cutting force components, including the cutting process damping in peripheral milling. The cutting process damping is associated to the interference mechanism between the tool flank and the machined workpiece surface. It creates two components (thrust and tangential) of a dynamic cutting force. The total force model including the process damping effect is obtained through numerical integration of the local forces. The effects of cutting and tool parameters on process damping and cutting force distributions are discussed. It is shown that the average value of the process damping and the amplitude of the cutting force increase with increasing feed rate, axial and radial depth of cut, and tool diameter; but decrease with increasing cutting speed. Besides, when the tool helix angle increases, the process damping increases, and the cutting force decreases. The number of tool’s teeth does not affect the variation of the damping process and cutting forces. However, it affects the number of cycles of the periodic cutting process.

Numerical Model for Prediction of Cutting Force in Peripheral Milling Process Including Thrust and Tangential Damping

A numerical model for prediction of cutting force components in peripheral milling process, including the cutting process damping, is proposed. The cutting process damping creates two components (thrust and tangential) of a dynamic cutting force. The total force model is obtained through numerical integration of the local forces. The effects of tool parameters (diameter, helix angle, number of teeth) on process damping and cutting force distributions are discussed. It is shown that the average value of the process damping and the amplitude of the cutting force increase with increasing the tool diameter. On the other hand, when the tool helix angle increases the process damping increases and the cutting force decreases. The number of tool teeth’s has not an influence on the variation of the damping process and cutting force but an influence on the number of cycles of the periodic cutting process.