Flank Milling Research Articles

Tool path planning for flank milling of non-developable ruled surface based on immune particle swarm optimization algorithm

Aiming at the tool position optimization problems in flank milling of non-developable ruled surface with conical tools, a new method based on immune particle swarm optimization (IPSO) and least squares (LS) is proposed. The geometric features of the non-developable ruled surface are analyzed and the error measurement function under each tool position is used as the objective function of the intelligent algorithm. It means that the sum of the distances from the discrete points on the axis of the conical tool to the design surface is the minimum by adjusting the cutter axis and the offset distance to the design surface. The initial tool position is determined by two-point offset method. On this basis, the objective function is optimized by the immune particle swarm optimization algorithm to obtain the optimized tool position. Since the geometric decomposition method is adopted, the optimization is essentially a local optimization, so the least squares method is further used for global optimization, and the overall optimized tool position is obtained. The simulation results show that the machining error is reduced by 86% and the validity of the method is verified by machining experiments finally.

Flank-Milling of Integral Blade Rotors Made in Ti6Al4V Using Cryo CO2 and Minimum Quantity Lubrication

Abstract This paper presents the machining of integral blade rotors (IBRs) made in Ti6Al4V using CO2 as cryogenic cooling. This kind of component is typical in gas turbines, pumps, and other rotary machines. A flank milling technique using polycrystalline diamond (PCD) tools and CO2+minimum quantity lubrication (MQL), denominated CryoMQL, is here presented as an alternative to conventional oil emulsions. The proposed approach implies a balance between technical and environmental issues. Cryogenics makes feasible the use of PCD tools avoiding problems derived from the reactivity of Ti6Al4V alloy with this type of cutting tool, which is directly related to cutting temperature. One key aspect is that CO2 has to be supplied and injected onto the cutting zone avoiding the risks of dry-ice formation, and the consequent clogging of both pipes and nozzles. For this purpose, a new device for CO2 delivery was developed, using gas and liquid CO2 simultaneously.

High-precision machining technology based on analytical method for integral impeller with flank milling

The paper first introduces R offset tool axis error calculation method. In order to reduce the maximum machining error, the paper presents a new geometric model of tool axis vector for flank milling non-developable ruled surfaces and machining error exact analytical solution is derived. Its main advantage is that the theoretical machining error of each point on the straight generatrix can be calculated. MATLAB software simulation and actual NC machining experiment are conducted to validate the effectiveness of the proposed algorithm. The measurement experimental results show that the actual maximum machining error is basically consistent with the theoretical calculation error, and the machining error can be reduced compared with the previous literature algorithm.

The control of machining errors of tool path for unequal diameter flank milling of globoidal cam

The profile error is inevitable in the machining process of globoid cam. In order to tackle the problem of normal vector anisotropy in unequal diameter machining, the offset point optimization algorithm is served to optimize the tool position according to the error transfer relationship of equidistant surfaces and the characteristics of unequal diameter tool path generation. In this paper, a bidirectional search algorithm is devised to minimize the deviation between unequal diameter machining tool path surface and fitting ruled surface. The optimal numerical solution with high accuracy is obtained by genetic algorithm. And then the end points of the tool axis are regarded as the initial data. Inverse interpolation of the NURBS (Non-Uniform Rational B-Spline) interpolation is utilized to reconstruct the ruled surface of the flank milling tool path. The simulation results verify the effectiveness of the proposed approach. Compared with the existing methods, the presented one reduces the machining error greatly.

Influence of dynamic loads in joints on dimensional stability

In small arms manufacturing the lock dimensional chain final link precision is secured with manual file fitting and removing the tolerance intentionally left on the recoil lugs. The manual process reduces the contact stiffness of the lock components, and the final link dimension (between the cylindrical gauge end that simulates a cartridge, and the breeching lock face) set during the assembly is distorted when the breech lock components are exposed to shot impact loads. For this reason, the cylindrical cartridge dummy used for the initial assembly is sized to allow for subsequent plastic deformation at the breech lock component interfaces. The deformation value is determined experimentally on an ad hoc basis. Polynomial expressions have been obtained experimentally for the interface plastic deformation vs. relative positioning errors and surface finish relation for parts made of typical military steel grades. To study the relation between the interface surface machining methods and contact stiffness flat specimens, 50RA steel quenched to HRC 40…45 (the roughness Rz is 10…15 μm) were machined as follows: peripheral pregrinding; flank milling; file crosswise (at 45°) movements. The results generated after processing the measurements made with a HOMMEL TESTER W55 instrument show that finish flank milling yields the best results.

Modal parameter determination and chatter prediction for blade whirling: a comparative study based on symmetric and asymmetric FRF

Whirling has been adopted for the cost-effective machining of blade-shape components in addition to traditional end milling and flank milling processes. To satisfy the requirements of rotary forming in the blade whirling process, the workpiece must be clamped at both ends in suspension and rotated slowly during machining, which complicates the dynamics. This study aims to identify the dynamic characteristics within the blade whirling operation and present strategies for stability prediction. In this study, the dynamic characteristics of a whirling system are modeled by assuming symmetric and asymmetric parameters. Theoretical prediction frequency response function (FRF) results are compared with experimental results. Moreover, semi-discretization stability lobe diagrams (SLDs) obtained using the dynamic parameters of these models are investigated experimentally. The results show that the asymmetric model is more suitable for describing the whirling system, whereas the symmetric model presents limitations associated with the frequency range and location of measuring points. Finally, a set of airfoil propeller blade whirling operations is conducted to verify the prediction accuracy.

Precision and energy-efficient ball-end milling of Ti6Al4V turbine blades using particle swarm optimization

ABSTRACT Ti6Al4V is extensively employed in the aviation, biomedical, and energy industries due to its high strength at elevated temperatures, low thermal conductivity, and high corrosion/creep resistance. However, these intrinsic properties have brought many technical challenges during the machining process of turbine blade shape. However, the recent advancements in flexible and precision machining in the state-of-the-art turn-mill machine tools can enable the manufacturing of high-quality turbine blades. In this study, a methodology is developed for the precision and energy-efficient machining of Ti6Al4V turbine blades on turn-mill machine tools. The stock-to-part manufacturing procedure includes the initial turning operation on bar stock, rough flank milling, and final surface finish milling. The developed method encompasses five stages. Utilizing a reconfigured Particle Swarm Optimization algorithm, a 3D Pareto optimal solution set is generated to evaluate trade-offs between surface roughness, specific cutting energy, and material removal rate. Also, the effect of different inclination angles is analyzed, and the optimization method is repeated with varying lead and tilt angles. This work shows that the surface roughness can be effectively reduced by including inclination angles into optimization while improving the machining process's energy efficiency.

Simulation-based surface roughness modelling in end milling

The surface topography often is an important quality criterion for the manufacturing of milled workpieces as it often defines their functional behaviour. In machining both, the kinematics of the process and the stochastic influences deriving from the machine tool, workpiece and the surrounding environment affect the workpiece’s surface roughness. This paper presents a simulation-based method for flank milling, which considers kinematic and stochastic influences including run-out errors and tooth length variations. The simulation results are used in combination to predict the surface roughness depending on the chosen process parameters. Hence, also making in possible to choose appropriate process parameters to achieve a defined surface roughness.

Collision-free and smooth joint motion planning for six-axis industrial robots by redundancy optimization

Abstract Planning collision-free and smooth joint motion is crucial in robotic applications, such as welding, milling, and laser cutting. Kinematic redundancy exists when a six-axis industrial robot performs five-dimensional tasks, and there are infinite joint configurations for a six-axis industrial robot to realize a cutter location data of the tool path. The robot joint motion can be optimized by taking advantage of the kinematic redundancy, and the collision-free joint motion with minimum joint movement is determined as the optimal. However, most existing redundancy optimization methods do not fully exploit the redundancy of the six-axis industrial robots when they conduct five-dimensional tasks. In this paper, we present an optimization method to solve the problem of inverse kinematics for a six-axis industrial robot to synthesize the joint motion that follows a given tool path, while achieving smoothness and collision-free manipulation. B-spline is applied for the joint configuration interpolation, and the sum of the squares of the first, second, and third derivatives of the B-spline curves are adopted as the smoothness indicators. Besides, the oriented bounding boxes are adopted to simplify the shape of the robot joints, robot links, spindle unit, and fixtures to facilitate collision detections. Dijkstra's shortest path technique and Differential Evolution algorithm are combined to find the optimal joint motion efficiently and avoid getting into a local optimal solution. The proposed algorithm is validated by simulations on two six-axis industrial robots conducting five-axis flank milling tasks respectively.

Manufacturing of Screw Rotors Via 5-axis Double-Flank CNC Machining

We investigate a recently introduced methodology for 5-axis flank computer numerically controlled (CNC) machining, called double-flank milling (Bo et al., 2020). We show that screw rotors are well suited for this manufacturing approach where the milling tool possesses tangential contact with the material block on two sides, yielding a more efficient variant of traditional flank milling. While the tool’s motion is determined as a helical motion, the shape of the tool and its orientation with respect to the helical axis are unknowns in our optimization-based approach. We demonstrate our approach on several rotor benchmark examples where the pairs of envelopes of a custom-shaped tool meet high machining accuracy.

Smoothing method of generating flank milling tool paths for five-axis flat-end machining considering constraints

Gouging and collision avoidances, tool path smoothness, and geometric deviation should be considered concurrently when generating a five-axis flank milling tool path. The tool orientations of the generated tool path, which can achieve smooth rotary axis motions of the machine tool, can improve the machining quality. Tool orientation planning for five-axis ball-end machining does not affect the position of the ball center point. However, different from ball-end cutters, tool orientation adjustments for flat-end machining will affect the cutter reference point position, which may cause local gouging between the bottom circular edge of the flat-end cutter and the constraint surfaces of the workpiece or excess uncut material left. Hence, generating a smooth flank milling tool path for five-axis flat-end machining which meets all the requirements is a challenge. To deal with this problem, a method of smoothness flank milling tool path generation for flat-end cutters considering constraints is developed in this research, which can minimize the angular accelerations of the rotary axes. B-spline curves are used to represent the displacements of the rotary axes so that the rotary axes’ motions along the tool path can be directly smoothed. The sum of the squares of the first, second, and third derivatives of the cutter reference point trajectory and the two rotary axes’ displacement curves are then utilized as the smoothness indicators for the five-axis tool paths. The method of tool orientation and positioning adjustments for flat-end cutters based on the differential rigid body motion is also presented, ensuring the bottom circular edge of a flat-end cutter is tangent to the constraint surfaces of the workpiece along the tool path. Besides, the discrete vector model is utilized to represent the workpiece geometry, and intersection points between the discrete vectors and the tool swept envelope are calculated to determine the geometric deviation for a flank milling tool path. Finally, a multi-objective optimization problem with constraints is established to generate flank milling paths with flat-end cutters. Numerical examples and machining tests are carried out to confirm the validity and effectiveness of the proposed approach.

A hybrid approach for cutting force prediction in flank milling based on analytical and 3D finite element method

Flank milling is one of the most widely used milling processes characterized by high machining efficiency. However, due to the low thermal conductivity and high-temperature strength of nickel-based superalloy Inconel 718, flank milling of Inconel 718 is still an extremely difficult and challenging task in which the milling cutter suffers large cutting force and excessive tool wear. Therefore, prediction of cutting force in milling process has caused due attention and became a major concern in manufacturing process. The present work is thus aimed at developing a new cutting force model for flank milling, which might try to eliminate the drawbacks of pure analytical force model, data-based reasoning method (DBRM), and full three dimensional (3D) finite elements (FE) model. The hybrid cutting force model is conducted by discretizing cutting edge into fragments based on infinitesimal method and regarding each fragment as a 3D oblique cutting FEM model. With the integration of 3D predicted cutting force along the axis considering the run-in and run-out effect of each cutting edge, the predicted cutting force can be obtained. Finally, the predicted results showed a good agreement with that of experimental.

Principal symmetric meshes

The isolines of principal symmetric surface parametrizations run symmetrically to the principal directions. We describe two discrete versions of these special nets/quad meshes which are dual to each other and show their usefulness for various applications in the context of fabrication and architectural design. Our discretization of a principal symmetric mesh comes naturally with a family of spheres, the so-called Meusnier and Mannheim spheres. In our representation of principal symmetric meshes, we have direct control over the radii of theses spheres and the intersection angles of the parameter lines. This facilitates tasks such as generating Weingarten surfaces including constant mean curvature surfaces and minimal surfaces. We illustrate the potential of Weingarten surfaces for paneling doubly curved freeform facades by significantly reducing the number of necessary molds. Moreover, we have direct access to curvature adaptive tool paths for cylindrical CNC milling with circular edges as well as flank milling with rotational cones. Furthermore, the construction of curved support structures from congruent circular strips is easily managed by constant sphere radii. The underlying families of spheres are in a natural way discrete curvature spheres in analogy to smooth Möbius and Laguerre geometry which further leads to a novel discrete curvature theory for principal symmetric meshes.

Effect of machined surface texture on fretting crack nucleation under radial loading in conformal contact

This paper presented the influence of machined surface texture on fretting cracks behaviors of Titanium alloy Ti–6Al–4V under radial loading in conformal contact. The contacted holes of specimen were machined with combined helical and flank milling before fretting fatigue tests, and a special fretting fatigue test apparatus was proposed to focus on conformal contact fretting fatigue (CCFF) test under radial loading. The test results showed that all the specimens failed at the contact area where characterizes an inner obtuse angle between the material flow direction (or cutting direction) and the direction of the tangential component of the contact force. The area with higher surface skewness and kurtosis values was also prone to nucleate fretting fatigue crack. These results suggested that the corresponding machining conditions in hole-making and surface strengthen processes should be adjusted to guide the production of surface texture properties, in terms of obtaining desirable lower skewness and kurtosis features to relieve nucleation of fretting cracks. Additionally, the debris in conformal contact tended to aggregate towards the partial slip zone (PSZ) due to the conformal geometry and form a compacted layer in the gross slip zone (GSZ) subjected to radial loading. These characteristics exacerbated and alleviated fretting damage in the PSZ and GSZ, respectively. In this research, a set of suitable milling parameters for the hole flank milling process in terms of prolonging fretting fatigue life were also defined.

Digital-twin-driven geometric optimization of centrifugal impeller with free-form blades for five-axis flank milling

Centrifugal impeller (CI) manufacturing is moving toward a new paradigm, with the objective to improve efficiency and competitiveness through Industry 4.0 and smart manufacturing. Making a CI developable and ruled has become a crucial technology to obviously improve machining efficiency and save costs although it may bring negative effects on aerodynamic performance accordingly. Hence, it is extremely challenging to consider and balance both machinability and aerodynamic performance in the process of CI geometric optimization. Digital Twin (DT) provides an attractive option for the integrated design and manufacturing due to multi-dimension and real-time. This paper breaks traditional procedures and presents a DT-based optimization strategy on the consideration of both machining efficiency and aerodynamic performance, as well as builds a reified 5-dimensional DT model. The virtual model consists of three sub-functional modules, including geometric modeling, machining optimization and aerodynamic performance evaluation. A tool-path generation method for CI five-axis flank milling is proposed to improve machining efficiency. The negative influences on aerodynamic performance and internal flow field are simulated and analyzed. Reinforce Learning is introduced to determine the optimization decision-making. Machining experiment and performance test with respect to various CI workpieces are conducted to provide immediate feedback to DT model. Real world and virtual world are combined to make CI geometry dynamically updated and iteratively optimized, which is desirable and significative to effectively shorten cycles and save costs in CI development.

Correction to: Five-axis flank milling stability prediction by considering the tool-workpiece interactions and speed effect

Correction to: Five-axis flank milling stability prediction by considering the tool-workpiece interactions and speed effect

Five-axis flank milling stability prediction by considering the tool-workpiece interactions and speed effect

Chatter is one of the challenging topics in the field of metal cutting. The dynamic characteristics of five-axis milling system are complex and variable. Especially in high-speed milling process, the influence of the tool-workpiece interactions and speed effect on milling stability is more obvious. It is necessary to investigate the influence of various interaction effects on milling stability. In this paper, the dynamical model of spindle system was established, and then the model was applied to investigate the influence of gyroscopic effect and centrifugal force on the dynamical characteristics of the tool tip. In order to solve the chatter problem of five-axis flank milling, the extended dynamical model of five-axis flank milling which considers the tool-workpiece interactions and speed effect was established. Based on the established milling dynamical model, the influence mechanism of the spindle system-tool-workpiece interaction effects on five-axis flank milling stability was investigated. The stability lobe diagrams of five-axis flank milling which contains the tool-workpiece interactions and speed effect can be obtained. Experimental results show that the proposed five-axis flank milling dynamical model can predict the milling state more reliable than the traditional ones. The research results are of great significance in preventing five-axis flank milling chatter.

Reparameterization of Ruled Surfaces: Toward Generating Smooth Jerk-minimized Toolpaths for Multi-axis Flank CNC Milling

This paper presents a novel jerk minimization algorithm in the context of multi-axis flank CNC machining. The toolpath of the milling axis in a flank milling process, a ruled surface, is reparameterized by a B-spline function, whose control points and knot vector are unknowns in an optimization-based framework. The total jerk of the tool’s motion is minimized, implying the tool is moving as smooth as possible, without changing the geometry of the given toolpath. Our initialization stage stems from measuring the ruling distance metric (RDM) of the ruled surface. We show on several examples that this initialization reliably finds close initial guesses of jerk-minimizers and is also computationally efficient. The applicability of the presented approach is illustrated by some practical case studies.

Tool path planning for five-axis flank milling of free-form surfaces

Tool path planning for five-axis flank milling of free-form surfaces

Kinematics Test and Evaluation of Tool Axis Direction Error for Five-axis Machine Tools

This paper presents a kinematics detection and evaluation method for tool axis direction error of five-axis machine tools. By measuring the trajectory errors of two tool center positions corresponding to two different tool lengths, the tool axis direction error can be obtained by combining the two measurements. Compared with the evaluation method in ISO10791.6.2014 which can only evaluate the tool center position errors corresponding to a single tool length, the proposed method can infer the processing accuracy corresponding to different tool lengths and to evaluate the comprehensive accuracy of five-axis flank milling. The proposed method is verified through simulations and experiments on a five-axis gantry machine tool.