Tool Path Patterns Research Articles

Application of Linear Mixed-Effects Model, Principal Component Analysis, and Clustering to Direct Energy Deposition Fabricated Parts Using FEM Simulation Data.

The purpose of this study is to investigate the effects of toolpath patterns, geometry types, and layering effects on the mechanical properties of parts manufactured by direct energy deposition (DED) additive manufacturing using data analysis and machine learning methods. A total of twelve case studies were conducted, involving four distinct geometries, each paired with three different toolpath patterns based on finite element method (FEM) simulations. These simulations focused on residual stresses, strains, and maximum principal stresses at various nodes. A comprehensive analysis was performed using a linear mixed-effects (LME) model, principal component analysis (PCA), and self-organizing map (SOM) clustering. The LME model quantified the contributions of geometry, toolpath, and layer number to mechanical properties, while PCA identified key variables with high variance. SOM clustering was used to classify the data, revealing patterns related to stress and strain distributions across different geometries and toolpaths. In conclusion, LME, PCA, and SOM offer valuable insights into the final mechanical properties of DED-fabricated parts.

Generation of cubic Hermite spline-based trochoidal milling toolpath by introducing a coefficient factor in machining curved slots

Trochoidal milling has become popular in high-speed milling due to its ability to reduce cutting force, enhance thermal dissipation, and prolong tool life. Among other toolpath patterns, the cubic Hermite spline offers significant advantages in generating trochoidal milling toolpath in machining complex and curved slots. However, determining those two different relation coefficients in the polynomial function of cubic Hermite spline remains complicated and empirical. This paper introduces a coefficient factor to simplify the determination process, which only requires the position and tangent vector parameters of each endpoint pair. The coefficient factor combines an instantaneous in-process slot width (IISW)-related width factor and a tangent vector direction-related direction factor. Two complex-curved slots are used to validate the performance of the proposed method. The results show that this method is straightforward and effective in generating trochoidal milling toolpaths for machining complex-curved slots while matching the slot geometry. Additionally, compared with a direct 5-axis trochoidal milling (one-step slotting strategy) in trochoidal milling of 3D slots on both serial and hybrid machining tools, a two-step slotting strategy (3-axis trochoidal milling and a successive 5-axis perpetual milling) is preferable in improving machining efficiency.

A novel method for trochoidal milling tool path tailoring based on curvature variation

Trochoidal milling has gained popularity in high-speed milling owing to its ability to reduce cutting force, accelerate thermal dissipation, and increase tool life. Nevertheless, it has the drawbacks of poor cutting efficiency and longer machining time due to decreased cutter-workpiece engagement (CWE). This paper studied the tailoring of trochoidal milling tool path curves subjected to improve machining efficiency by controlling curvature variation while meeting predefined CWE angle criteria. The relationship between the instantaneous CWE angle and the curvature variation of the tool path curve was quantitatively established. Then, a negative exponential function-based governing function was introduced to regulate the curvature variation. Finally, the proposed method was experimentally validated via trochoidal milling of curved slots by evaluating machining efficiency and surface quality. The results showed that compared with the circular, elliptical, and polynomial tool path, the tailored tool path-related average CWE angle increased by 40.5 %, 17.9 %, and 6.3 %; while the machining efficiency improved by 25 %, 16 %, and 14 %, respectively. Although the surface quality (surface roughness varies within 5 % and flatness raised by 27 %) is worse than that of the other three tool path patterns, benefiting from the highly improved machining efficiency, it is still applicable in high-efficiency rough milling of components.

A Methodological Framework for Assessing the Influence of Process Parameters on Strand Stability and Functional Performance in Fused Filament Fabrication.

With an ever-increasing material and design space available for Fused Filament Fabrication (FFF) technology, fabrication of complex three-dimensional structures with functional performance offers unique opportunities for product customization and performance-driven design. However, ensuring the quality and functionality of FFF-printed parts remains a significant challenge, as material-, process-, and system-level factors introduce variability and potentially hinder the translation of bulk material properties in the respective FFF counterparts. To this end, the present study presents a methodological framework for assessing the influence of process parameters on FFF strand stability and functional performance through a systematic analysis of FFF structural elements (1D stacks of FFF strands and 3D blocks), in terms of dimensional deviation from nominal geometry and resistivity, corresponding to the printability and functionality attributes, respectively. The influence of printing parameters on strand stability was investigated in terms of dimensional accuracy and surface morphology, employing optical microscopy and micro-computed tomography (mCT) for dimensional deviation analysis. In parallel, electrical resistance measurements were carried out to assess the effect of different process parameter combinations and toolpath patterns on functional performance. In low-level structural elements, strand height (H) was found to induce the greatest influence on FFF strand dimensional accuracy and resistivity, with higher H values leading to a reduction in resistivity of up to 38% in comparison with filament feedstock; however, this occurred at the cost of increased dimensional deviation. At higher structural levels, the overall effect of process parameters was found to be less pronounced, indicating that the translation of 1D strand properties to 3D blocks is subject to a trade-off due to competing mechanisms that facilitate/hinder current flow. Overall, the proposed framework enables the quantification of the influence of process parameters on the selected response variables, contributing to the development of standard operating procedures and recommendations for selecting optimal process parameters to achieve the desired process stability and functional performance in FFF.

Effect of novel tool path pattern on mechanical properties of friction stir welded AA6061 alloy

Effect of novel tool path pattern on mechanical properties of friction stir welded AA6061 alloy

Impact of the novel square wave tool path pattern on AA6061-T6 friction stir welding

ABSTRACT The proposed study deals with the joining of AA6061 T6 alloy using a novel geometric square wave tool path pattern for adequate mixing of materials with increased stirring time and enlargement of the deformation zone. Experiments were conducted based on the process parameters to imply the stirring effect like rotation speed 1200 rpm, weaving rate 100 mm/min; and specific step sizes (1.0, 1.5, and 2.0 mm). Results show that the Percentage of variation for achieving the higher tensile strength of 11.3%, micro vickers hardness of 12.8% with a step size of 1 mm compared to the linear weldment. The SEM morphologies of the weldment clarify the formation of IMCs like spheroidal cementite with the zeolitic structure for resulting in higher hardness value. The EDAX results confirm the formation of intermetallic precipitates like Mg2Si that leads the precipitation hardening and grain boundary strengthening.

Strength Enhancement in Fused Filament Fabrication via the Isotropy Toolpath

The fused filament fabrication (FFF) process deposits thermoplastic material in a layer-by-layer manner, expanding the design space and manufacturing capability compared with traditional manufacturing. However, the FFF process is inherently directional as the material is deposited in a layer-wise manner. Therefore, the in-plane material cannot reach the isotropy character when performing the tensile test. This would cause the strength of the print components to vary based on the different process planning selections (building orientation, toolpath pattern). The existing toolpaths, primarily used in the FFF process, are linear, zigzag, and contour toolpaths, which always accumulate long filaments and are unidirectional. Thus, this would create difficulties in improving the mechanical strength from the existing toolpath strategies due to the material in-plane anisotropy. In this paper, an in-plane isotropy toolpath pattern is generated to enhance the mechanical strength in the FFF process. The in-plane isotropy can be achieved through continuous deposition while maintaining randomized distribution within a layer. By analyzing the tensile strength on the specimens made by traditional in-plane anisotropy toolpath and the proposed in-plane isotropy toolpath, our results suggest that the mechanical strength can be reinforced by at least 20% using our proposed toolpath strategy in extrusion-based additive manufacturing.

Generic Tool path planning method of T-spline surface CNC milling

T-spline is a new surface modeling technology, which has superior advantages in complex shape representation over traditional NURBS and mesh surfaces. However, the research in CAM field is insufficient, which hinders the further promotion of this technology. To fit the complex topology of T-spline surface, a general tool path planning method of T-spline surface CNC milling is proposed based on the commonly used zig-zag or contour-parallel toolpath pattern. This method utilizes the 2-dimensional scallop height model to calculate side step, the iso-scallop height method to generate tool paths, the minimum energy method to smooth them, and Hermite curves to join them as one tool path, which can realize the milling of T-spline surface model with arbitrary topology. Finally, a T-spline CAM prototype system is successfully developed to implement simulation analysis and machining experiments to verify the algorithms above. And the results of simulations and experiments prove this method can generate a smooth tool path with uniform iso-scallop height distribution, short length, smooth corner transition, and one retraction, which can achieve better finish machining effect.

귀중품 포장 블록용 폴리우레탄 소재의 NC 가공조건 결정에 관한 연구

Polyurethane is used for packaging valuables. However, it is challenging to cut polyurethane while maintaining the exact form of the workpiece because of its high elasticity. Therefore, it is essential to precisely determine the machining parameters for maintaining the form accuracy rather than the processing speed. In this study, the machining conditions that could maintain the contact surface accuracy were determined so that the packaging block could stably support the contents. Based on the characteristics of the Taguchi technique and experimentally applied initial machining conditions, the optimum machining conditions such as the spindle speed, feed rate, step over, and tool path pattern, considering the machining stability and machined surface integrity, were determined.

Optimization of Cutting Data and Tool Inclination Angles During Hard Milling with CBN Tools, Based on Force Predictions and Surface Roughness Measurements.

This work deals with technological considerations required to optimize the cutting data and tool path pattern for finishing the milling of free-form surfaces made of steel in a hardened state. In terms of technological considerations, factors such as feed rate, workpiece geometry, tool inclination angles (lead and tilt angles) and surface roughness are taken into account. The proposed method is based on calculations of the cutting force components and surface roughness measurements. A case study presented in the paper is based on the AISI H13 steel, with hardness 50 HRC and milling with a cubic boron nitride (CBN) tool. The results of the research showed that by modifications of the feed value based on the currently machined cross-sectional area, it is possible to control the cutting force components and surface roughness. During the process optimization, the 9% and 15% increase in the machining process efficiency and the required surface roughness were obtained according to the tool inclination angle and feed rate optimization procedure, respectively.

Region-based toolpath generation for robotic milling of freeform surfaces with stiffness optimization

Abstract Because of industrial robots’ relatively low stiffness, many research efforts have been performed to improve the robot stiffness by optimizing the robot posture. For freeform surfaces with large curvature, however, the expected high stiffness posture may undergo excessive changes that exceed the robot joint speed limit. Therefore, the stiffness optimization may not achieve the expected results in actual machining owing to the limitation of robot kinematics and conventional toolpath pattern. To address this problem, a region-based toolpath generation method is proposed to improve robot stiffness in this study for robotic milling of freeform surfaces. To provide the possibility of higher stiffness robot posture, not only the redundant degree of freedom (DOF) of the robot but also the orientation of tool axis during machining is optimized. Under the influence of surface curvature and position, the change of high stiffness posture has regionality. A surface subdivision method is proposed to divide the surface into multiple sub-regions, so that actual robot posture with better stiffness can be obtained. For each sub-region, the feed direction of toolpath is optimized to further enhance robot stiffness. Simulations and experimental studies are conducted, and show that the proposed toolpath generation method can improve the robot stiffness in freeform surface machining.

Tool path generation for a car rear door die: UMO versus rest milling tool paths

Tool path generation for sculptured surfaces that contain many concave and convex features involves gouging and undercut problems. Past research has paid little attention to tool path generation for hard materials, which require careful and precise planning. In this paper, a comparison is made between traditional unit machining operation (UMO) and rest milling-based tool paths for the various machining steps (roughing, semi-finishing and finishing) of a car’s rear door, designed by NURBS surfaces. The experimental work involves the machining of two dies in a 3-axis CNC machine. Each die comprises two parts: punch (convex) and die (concave). Various tool path patterns (contour, zig-zag, zig, concentric zig-zag) are generated and compared via NX8 software. The results show a great saving of time and less tool consumption by using a rest milling technique over UMO techniques.

Experimental evaluation of interfacial adhesion strength of cold sprayed Ti-6Al-4V thick coatings using an adhesive-free test method

Cold spray (CS) is a rapidly growing solid-state additive material deposition technique often used for repair of high-value metallic components. This study aims at evaluating the interfacial adhesion strength of cold sprayed Ti-6Al-4V (Ti-64) coatings deposited onto Ti-64 substrates for repair applications. An adhesive-free test method, referred as modified Collar-Pin Pull-off Test was developed based on Sharivker's (1967) original design, in order to overcome the limitations of existing test approaches (both adhesive-based and adhesive-free). This method was designed to allow measurement of adhesion strength of high strength coatings such as CS Ti-64, where adhesion strength is higher than 70–90 MPa. A parametric study was performed to assess the effect of coating thickness, scanning speed, track spacing, toolpath pattern, and substrate surface preparation on the coating adhesion strength. A finite element model was also used to evaluate the stress distribution during the pull-off test, and to check the validity of the proposed test method. The proposed adhesive-free test method was found to be capable of measuring coatings with adhesion strengths beyond the upper limit of conventional adhesive-based methods such as ASTM C633. Among the investigated cases, the highest value of coating adhesion strength was measured around 122 MPa, in the case of CS Ti-64 deposited on ground Ti-64 substrates.

Analytical Characterization and Experimental Validation of the Material Extrusion Wave Infill for Thin-Walled Structures

Abstract The wave infill for material extrusion (MEX) of the thin-walled structure (TWS) is presented. The wave infill, a lightweight truss-like porous core structure sandwiched between two outer walls, is an efficient toolpath pattern for the MEX of TWS. Analytical models for predicting the stiffness, load capacity, fabrication time, and mass were established for two orthogonal in-plane and layer-to-layer variations inherent in MEX wave infill parts. Rectangular prism, four-point flexural bending specimens representing the in-plane and layer-to-layer orientations with wave infill were fabricated by MEX of polyamide-12 (Nylon-12) material. From these specimens, fabrication time and mass were measured, and four-point flexural tests were conducted to measure the stiffness and load capacity of the beam. Analytical models were compared with the experimental measurements to identify their predictive capabilities. Stiffness for in-plane and layer-to-layer orientations was predicted well with the relative root-mean-square error (RRMSE) of 7% and 6%, respectively. Load capacity in in-plane and layer-to-layer orientations had the RRMSE of 23% and 22%, respectively. Fabrication time and mass were predicted well with a RRMSE of 7% and 6%, respectively. The methods established in this study are the foundation for optimal design and MEX of wave infill TWSs with generalized loads.

A Neural Network Based Process Planning System to Infer Tool Path Pattern for Complicated Surface Machining

Die and mold are necessary for the manufacture of present industrial products. In recent years, the requirement of high quality and low cost machining of complicated surfaces has increased. However, it is difficult to generalize process planning that depends on skillful experts and decreases the efficiency of preparation in die and mold machining. To overcome an issue that is difficult to generalize, it is well known that neural networks may have the ability to infer a valid value based on past case data. Therefore, this study aims at developing a neural network based process planning system to infer the required process parameters for complicated surface machining by using past machining information. The result of the conducted case studies demonstrates that the developed process planning system is helpful for determining the tool path pattern for complicated surface machining according to the implicit machining knowhow.

Five-Axis Milling of Large Spiral Bevel Gears: Toolpath Definition, Finishing, and Shape Errors

In this paper, a five-axis machining process is analyzed for large spiral-bevel gears, an interesting process for one-of-kind manufacturing. The work is focused on large sized spiral bevel gears manufacturing using universal multitasking machines or five-axis milling centers. Different machining strategies, toolpath patterns, and parameters are tested for both gear roughing and finishing operations. Machining time, tools’ wear, and gear surface are analyzed in order to determine which are the best strategies and parameters for large modulus gear manufacturing on universal machines. The case study results are discussed in the last section, showing the capacity of a universal five-axis milling for this niche. Special attention was paid to the possible affectations of the metal surfaces, since gear durability is very sensitive to thermo-mechanical damage, affected layers, and flank gear surface state.

Study on Ball End Milling of Inclined Surfaces for Ultra High Molecular Weight Polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) is a polyethylene with a molecular weight ranging from one million to seven million. UHMWPE is often used for constructing sliding parts such as artificial knees, hip joints, and gears owing to its self-lubrication, wear resistance, biocompatibility, and light weight structure. High accuracy and smooth surfaces are required for UHMWPE parts. Cutting operations of UHMWPE are particularly suitable for small numbers of products and to realize high shape accuracy. This paper describes some surface properties due to ball end mill operations of inclined surfaces. Some inclined workpieces are fixed by jigs and various cutting conditions are analyzed. Two tool path patterns, namely contour line and raster line (scanning line), are also evaluated for various cutting conditions by surface observations and surface roughness measurement.

Friction stir weave welding (FSWW) of AA6061 aluminium alloy with a novel tool-path pattern

In this present work, a novel tool-path movement has been implemented in the friction stir welding of AA6061-T6 plates and termed as Friction stir weave welding (FSWW). The aim of this new process is to enhance the weld quality in terms of tensile strength and microstructure properties by the selection of effective process parameters, such as tool-path movements (Step size), spindle speed and weaving rate. The investigation results proved that the tensile strength of AA6061-T6 alloy joints were remarkably affected by the newly developed tool-path pattern. A three factor, three-level Box–Behnken design matrix was used to minimise the number of experiments. A response surface methodology technique was used for developing the objective function. TOPSIS technique was applied to optimise the FSWW process parameters. The optimised results were validated with the derived experimental results.

Tool path pattern and feed direction selection in robotic milling for increased chatter-free material removal rate

Robotic milling becomes increasingly relevant to large-scale part manufacturing industries thanks to its cost-effective and portable manufacturing concept compared to large-scale CNC machine tools. Integration of milling processes with industrial robots is proposed to be well aligned with the aims and objective of the recent fourth industrial revolution. However, the industrial robots introduce position-dependent and asymmetrical dynamic flexibility, which may reflect to the tool tip dynamics under several conditions. Under such circumstances, the stability limits become dependent on the machining location and the feed direction. In this respect, selection of machining tool path patterns is crucial for increased chatter-free material removal rates (MRR). This paper proposes an approach to evaluate and select tool path patterns, offered by the existing CAM packages, for increased chatter-free MRR. The machining area is divided into number of machining locations. The optimal feed direction is decided based on the absolute stability at each region considering the asymmetrical and position-dependent tool tip dynamics. Then, the alternative tool path patterns are evaluated and the corresponding optimum feed direction is decided for increased chatter-free material removal. The application of the proposed approach is demonstrated through simulations and representative experiments.

Ultrasonic-Vibration-Assisted Micromachining of Sapphire

Sapphire is an attractive engineering material for the cover glass of smartphones and wristwatches because of its high hardness and resistance to corrosion, wear, and heat. However, the high rate of tool wear and brittle chippings around the holes are serious problems associated with drilling sapphire. To enhance the accuracy and efficiency of the drilling process on sapphire, this paper presents a novel tool-path strategy using helical milling along with various tool path patterns. Experimental results show that the proposed method successfully reduces brittle chippings around the holes.