Approach For Tool Path Generation Research Articles

NURBS-based path planning for aerosol jet printing of conformal electronics

Conformal printing offers a promising capability to integrate complex electronic functionality with intricate objects consisting of curved surfaces. However, motion planning to support these printing configurations presents a challenge, in part due to conventional reliance on tessellated surface representations that limit the accuracy and scalability of the printing process. In this paper, we introduce a direct approach to conformal aerosol jet printing on topographically complex surfaces, represented using non-uniform rational B-splines (NURBS). Using the NURBS surface definition directly offers a scalable and continuous approach for toolpath generation, which is well-aligned with standard computer-aided design practices. We select a patch that directly corresponds to the area of interest on the NURBS surface and extract the associated surface points. These surface points are then appropriately connected to generate the machine code (G-code) for a 3-axis printing system. We demonstrate this capability by printing a strain gauge on a curved model of a wind turbine blade. Our approach offers a promising avenue for manufacturing printed electronics with diverse applications that require conformal printing. This approach is particularly valuable for incorporating printed circuits on intricate underlying structures, including structural health monitoring for aerospace and civil infrastructure applications.

Tool path generation with a uniform residual error distribution considering tool contour error for ultra-precision diamond turning

Tool path generation strategy plays a crucial role in improving the efficiency and surface quality of ultra-precision diamond turning mainly by influencing residual errors. However, current approaches in tool path generation have not achieved a uniform distribution of residual error due to the unexplored and significant impact of tool contour error on residual error. Therefore, this study introduces a novel tool path generation algorithm for ultra-precision diamond turning, aiming for a uniform residual error distribution with consideration of tool contour error. The tool contour is measured off-machine, fitted, and modeled to achieve its actual cutting-edge contour at a submicron scale. An estimation model is established to calculate residual error on the machined surface considering the tool contour error. A tool path generation approach is then proposed to achieve uniform residual error distribution by adaptively controlling stepovers. Then the proposed stepover is smoothed by cubic Hermite polynomial interpolation to avoid undesired tool path fluctuations. To further improve the machining accuracy, a spiral tool path is generated with proper discretization parameters to control chord error. Finally, a prototype software system is developed to optimize the tool path as well as predict the residual and machining error across the entire machined surface. Experiment results demonstrate a significant reduction of approximately 40 % in both residual error and machining error compared to unoptimized results.

A novel approach for adaptive skeleton toolpath generation

Industry 4.0 is revolutionizing manufacturing through the integration of automation and real-time data sharing in cyber-physical systems. At the forefront of this revolution is large-format additive manufacturing. In large-format printing, parts are often designed to be an even number of beads wide to produce a completely dense part. However, voids can still arise. This is often due to the part not being an even number of bead widths wide in some areas, or in geometry containing acute angles, as the process of generating closed contours cannot completely fill the space. Voids can be tolerated in smaller models, but in large-format additive manufacturing they may cause mechanical defects. To fill these voids, open loop paths called skeletons are often used, but they are typically limited by the physical constraints defined in the slicing software. To address this, researchers at Oak Ridge National Laboratory have extended skeleton toolpaths via an adaptive methodology. These adaptive skeletons were found to better fill void spaces through manipulation of physical parameters of the build process and were calculated as part of the slicing process.

Toolpath planning method with the constraint of cutting force fluctuation in slow tool servo turning for complex curved surface parts

Parts with the complex curved surface are commonly used in high-end equipment. The machining quality of the curved surface parts is important for the property of high-end equipment. With position control of the main spindle, i.e., the C axis, the slow tool servo (STS) turning is a very promising technique to effectively machine complex curved surface parts. However, the turning machining quality is restricted by the cutting force fluctuation in finishing turning. Hence, the STS turning toolpath generation approach with the constraint of the cutting force fluctuation is proposed in this study. As the cutting force is proportionate to the cutting area, the cutting area for turning complex curved surfaces is analyzed and calculated. Then the functional relation between the cutting force fluctuation and the feed rate is derived. Based on the geometrical characteristic of the first revolution of the toolpath, the feed rate is optimized with small cutting force fluctuation to derive the cutter contact points (CCPs) in the cylindrical coordinate system. From the validation experiment results, it can be seen that the cutting force fluctuation, the profile tolerance, and the surface roughness of parts are effectively reduced, and the surface roughness of the part machined with the proposed toolpath planning method is 17.625 nm. Thus, this study provides guidance for toolpath generation with the constraint of the fluctuation of the cutting force in STS turning for a complex curved surface.

A Multiaxis Tool Path Generation Approach for Thin Wall Structures Made with WAAM

Wire Arc Additive Manufacturing (WAAM) has emerged over the last decade and is dedicated to the realization of high-dimensional parts in various metallic materials. The usual process implementation consists in associating a high-performance welding generator as heat source, a NC controlled 6 or 8 degrees (for example) of freedom robotic arm as motion system and welding wire as feedstock. WAAM toolpath generation methods, although process specific, can be based on similar approaches developed for other processes, such as machining, to integrate the process data into a consistent technical data environment. This paper proposes a generic multiaxis tool path generation approach for thin wall structures made with WAAM. At first, the current technological and scientific challenges associated to CAD/CAM/CNC data chains for WAAM applications are introduced. The focus is on process planning aspects such as non-planar non-parallel slicing approaches and part orientation into the working space, and these are integrated in the proposed method. The interest of variable torch orientation control for complex shapes is proposed, and then, a new intersection crossing tool path method based on Design For Additive Manufacturing considerations is detailed. Eventually, two industrial use cases are introduced to highlight the interest of this approach for realizing large components.

An efficient tool-path planning approach for repair of cylindrical components via laser cladding

Laser metal deposition (LMD) is extensively used for repairing and remanufacturing mechanical components. Amongst these components, the vast majority comprise of cylindrical and planar geometries. In recent remanufacturing work, it is a challenge to generate a deposition tool-path directly from point cloud data of a damaged surface. Additionally, the acquisition of high resolution point cloud data that is necessary to carry out a high precision repair presents another problem since it is a time-consuming process. Hence, this paper explores a novel approach for tool-path generation for the repair of cylindrical components directly from point clouds via LMD technology. The presented method discounts the surface reconstruction and registration steps and directly generates tool-path from the damaged point cloud data. In this paper, a comparison is drawn between the traditional framework of reverse engineering and the proposed approach. Following, a tool-path generation method is presented, which incorporates enhancing the resolution or information density of the point cloud data. Finally, the results are validated through a robot laser cladding system (RLCS), which carries out autonomous repair based on the tool-path algorithm. The proposed method is demonstrated to repair a cylindrical fixed bend.

Stability optimal selection of stock shape and tool axis in finishing of thin-wall parts

In 5-axis milling of thin-wall parts, flexibility of the in-process-workpiece (IPW) governs static and dynamic deflections. Thus, the stock shape left around the part and the tool axis are crucial for stability. This paper presents a methodology for selection of stock shape and tool axis for improved stability. Constant stock finishing is compared to variable stock, where a novel tool path generation approach is used to achieve the desired semi-finish shape. Effect of stock shape on IPW structure is simulated in FEM and benefits are shown. The proposed method is experimentally verified on case studies.

Theoretical and Experimental Investigation of Surface Topography Generation in Slow Tool Servo Ultra-Precision Machining of Freeform Surfaces.

Freeform surfaces are featured with superior optical and physical properties and are widely adopted in advanced optical systems. Slow tool servo (STS) ultra-precision machining is an enabling manufacturing technology for fabrication of non-rotationally symmetric surfaces. This work presents a theoretical and experimental study of surface topography generation in STS machining of freeform surfaces. To achieve the nanometric surface topography, a systematic approach for tool path generation was investigated, including tool path planning, tool geometry selection, and tool radius compensation. The tool radius compensation is performed only in one direction to ensure no high frequency motion is imposed on the non-dynamic axis. The development of the surface generation simulation allows the prediction of the surface topography under various tool and machining variables. Furthermore, it provides an important means for better understanding the surface generation mechanism without the need for costly trial and error tests. Machining and measurement experiments of a sinusoidal grid and microlens array sample validated the proposed tool path generation and demonstrated the effectiveness of the STS machining process to fabricate freeform surfaces with nanometric topography. The measurement results also show a uniform topography distribution over the entire surface and agree well with the simulated results.

Toolpath generation for the manufacture of metallic components by means of the laser metal deposition technique

In this paper, a novel toolpath generation approach is proposed for concentric laser metal deposition (LMD) technology, which is an additive manufacturing (AM) process. The toolpaths define the movements to be carried out by the deposition head to manufacture the part through a layer-by-layer construction process. In this way, the characteristics of the generated deposition strategy directly affect the quality of the construction, that could lead to geometric distortions and irreparable defects. This work introduces a toolpath generator that provides several capacities with respect to the previous works: (1) an optimized hybrid deposition strategy that combines contour curves and zigzag filling patterns and ensure a uniform Z growth for each layer by a constant overlap parameter, (2) a multi-axis movement strategy that guarantees the deposition on the previous layer in overhang walls, and (3) a non-planar slicing strategy that adapts the layers to the variable vertical growth in single-bead wall structures with variable inclinations and multi-axis deposition strategy. The effectiveness of the generated toolpaths was proved through the implementation and validation on LMD technologies by the construction of different three-dimensional geometries.

Smart tool path generation for 5-axis ball-end milling of sculptured surfaces using process models

Abstract Efficient 5-axis milling of free form surfaces required smart parameter selection and tool path generation approaches. Current computer-aided manufacturing (CAM) technology offers limited flexibility and assistance for such purposes, where purely geometrical issues are considered. Consequently, the generated tool path may be off the high-performance milling parameters. In 5-axis milling, the efficient process parameter set usually vary along the tool path due to varying engagement conditions because of inherent reasons. In this paper, a novel approach is proposed for identification of efficient surface milling parameters according to the variation of cutting forces and stability along the tool path, and then continuously implementation of these parameters for smart tool path generation, obeying the geometrical requirements. The proposed approach is applied on representative cases relevant to industrial applications to demonstrate the benefits. It is shown that, use of process simulations in tool path planning and generation offers significant benefits in decreasing the total cycle time in 5-axis milling.

A region-based tool path generation approach for machining freeform surfaces by applying machining strip width tensor

In freeform surface machining, the cutter should move along the feed directions with maximal machining strip widths (MSW) as much as possible to improve machining efficiency. However, since the optimal feed directions usually vary among different regions over a complex freeform surface, only local optimal machining result could be achieved by most existing tool path generation methods which consider the whole surface as one machining region. This research proposes a tensor-based approach to generate regional tool paths for more globally optimal machining result. A rank-two tensor is first constructed to enable the evaluation of the MSW over the whole feed direction space at the cutter contact point (CCP). To make this MSW tensor usable for generic APT cutters, the concept of effective cutting surface (ECS) is raised. The tensor is then obtained by modeling the geometric approximation between the ECS and the part surface around CCP. A MSW tensor field is then induced over the entire part surface. The regional distribution of the optimal feed directions is associated with the degenerate points within the tensor field. Then, the surface may be divided into several machining regions by constructing inside boundaries starting from the trisector degenerate points. At last, tool paths will be separately calculated in each sub-surface. Since the optimal feed directions in each sub-surface vary continuously, the cutter movements can follow the optimal feed directions closely based on the generated regional tool paths which refer to shorter tool path length and machining time. Two parts with freeform surface are selected from the real industry as test cases and the comparisons to other traditional methods are also provided.

Spiral tool path generation based on symbolic computation for machining of non-axisymmetric curved surface

Bent mandrel, which consists of non-axisymmetric curved surface (NACS), has been widely used as precise mold in automobile industry, shipping industry, and aviation industry. To improve the versatility and efficiency of turning method of the NACS with fixed rotational center, a machining method of non-axisymmetric curved surface using symbolic computation is proposed in this paper. A spiral tool path generation approach in non-axisymmetric turning process (NATP) is developed as well to deal with the error of part-to-part repeatability in existed machining model. The actual cutter-contact points are obtained from the approach of spiral sweep process using equal-arc-length segment principle in polar coordinate system. The tool offset, which is used to avoid the interference between tool and workpiece, is also considered in the machining model. In the NATP, the model of CNC lathe is established based on machine kinematics, and the inserted cutter is mathematically modeled considering both its geometrical model and the positioning of the insert. Depending on the spindle rotational angle, the synchronized control of X-axis, Z-axis, and C-axis is adopted to generate the tool path of the NATP. NC program has been generated using symbolic computation method according to the presented model, including calculation of cutter-location points and generation of 2D tool path of cutting process. With the approach of a bent mandrel taken as an example, the experiment results have verified that the machining method is appropriate for the NACS

An artificial neural network approach for tool path generation in incremental sheet metal free-forming

This research considers a specific incremental sheet metal free-forming process, which allows for individualized component manufacturing. However, for a reasonable application in practice, an automation of the manual process is mandatory. Unfortunately, up to now, no general tool path generation strategies are available when free-forming processes are to be utilized. On this account, for the investigated driving process, a holistic concept for deriving tool paths for the production of sheet metal parts directly from a digital component model is presented adopting an artificial neural network architecture. Consequently, for the very first time an automated part production is possible in incremental sheet metal free-forming applications. For this, a suitable network input and output structure is designed. Balanced sample data sets are generated for appropriate training. An associated network topology is determined and undergoes a training and testing phase. The influence of different training algorithms, network configurations, as well as training sets have been studied in relation to a feedforward network structure with backpropagation. Finally, the proposed computer integrated manufacturing system is subject to validation and verification by automated sheet part production, which is followed by concluding remarks on the capabilities and limits of the concept.

Tool path generation for ultra-precision polishing of freeform optical surfaces in an off-axis three-mirror imaging system

The optical performance of the off-axis three-mirror imaging system can be greatly improved using freeform surfaces. This article focuses on the polishing of the primary mirror and tertiary mirror in an off-axis three-mirror imaging system. The primary mirror and tertiary mirror are fabricated on one monolithic substrate and described by non-uniform rational B-spline–based freeform surfaces. The separated and integrated polishing strategies are presented for polishing the two mirrors on the four-axis computer numerical control polishing platform. A tool path generation approach is proposed for polishing of the non-uniform rational B-spline–based freeform surface. Three kinds of the tool paths are given for ultra-precision polishing of the primary mirror and tertiary mirror with the freeform surfaces. The concentric circle path and the approximately concentric circle path are generated for polishing two mirrors separately, while the spiral path is calculated for integrated polishing of two mirrors simultaneously. The polishing tool posture along the planned tool paths is also analyzed. The ultra-precision polishing experiments of the primary mirror and tertiary mirror on the four-axis computer numerical control polishing platform are performed to verify the proposed approach for tool path generation.

Automatic tool path generation from structuralized machining process integrated with CAD/CAPP/CAM system

Nowadays, machining process information from CAPP cannot yet be directly interpreted and utilized in CAM systems. It is the NC programmers who decipher the information and link up CAPP and CAM, which is inefficient. In order to reduce the tool path editing and programming time, this paper describes the implementation of an automatic tool path generation from the structuralized machining process (SMP). An intelligent agent named KMAIMOD was developed to automate SMP analysis and tool path generation based on operation controlled template (OCT) and feature machining volume semantics (FMVS). The framework of CAD/CAPP/CAM integration was introduced for automatic tool path generation. Then the working principle and machining process data analysis of KMAIMOD was proposed. And three categories of FMVS construction with machining elements were discussed to automatic determine machining position and range. In the experiments, some part models are utilized to verify the approach for automatic tool path generation, and the experimental results are analyzed at length to show the application effectiveness of the method.

Research on inverse evaluation mechanism in toolpath generation based on global interpolation simulation

Free form surfaces are primarily designed and manufactured by CAD/CAM/CNC system. In traditional way, toolpath generation approaches always consider machining precision and efficiency by constraining scallop height and toolpath lengths. However, toolpath lengths do not exactly reflect the actual machining time because the feedrate usually fluctuates along different toolpath during CNC interpolating period, which indicates that the total machining efficiency is coupled with both toolpath generation and interpolation. Therefore, the toolpath generation and interpolation systems should not be independent, and the conventional unidirectional information flow from CAM to CNC should be replaced by a new mechanism with information exchange and mutual optimization. This paper proposes an inverse evaluation mechanism with feedback information from CNC to CAM system. The feedback information is obtained by off-line interpolation simulation for each toolpath and evaluation of the total machining time for the entire surface. With the feedback information, CAM is able to optimize the toolpath or choose the best one among candidate solutions. As the evaluation mechanism should be under the same interpolation algorithm, an interpolation algorithm with axis kinematic/dynamic constraints is also introduced. The simulation results with different free form surfaces show that the proposed mechanism can economically improve the machining efficiency without increasing system cost.

Optimization of tool-path generation for material extrusion-based additive manufacturing technology

In this study, we propose a tool-path generation approach for material extrusion-based additive manufacturing (AM) that considers the machining efficiency and fabrication precision, which are inherent drawbacks of general AM techniques compared with conventional manufacturing methods. The proposed approach aims to tackle the generation of direction-parallel tool-paths for the interior filling of simple connected areas, which comprises three main steps: (1) determining the inclination of reference lines; (2) generating and grouping tool-path segments into individual sub-paths; and (3) linking sub-paths based on specific requirements. These three modules interact to affect the efficiency and precision of AM significantly. In order to find an optimal inclination, we first analyze the impacts on the fabrication efficiency and manufacturing accuracy with different inclinations. A comparatively accurate building time model is developed subsequently to obtain the optimal tool-path inclination, but without compromising the machining precision, based on the analysis of a geometrical accuracy model. The proposed approach employs different inclinations in distinct layers according to specific manufacturing scenarios and technological requirements. After determining the reference lines, the tool-path segments are selected and grouped based on some characteristics (e.g., the number of intersections between reference lines and boundaries) to make up individual sub-paths, which are then connected to a zigzag-shaped path with short line segment connections. In the module for sub-path linking, some strategies are introduced to decrease the number of useless tool-paths, i.e., uncut paths, which could jeopardize the manufacturing quality by frequently turning the print head on and off. In addition, parametric curves are used to link the final sub-paths to avoid deceleration/acceleration processes in the end/starting parts of the sub-paths. The proposed approach has been used in practice to generate tool-paths for a wide range of models and the results verify its effectiveness and obvious advantages.

A new STL model-based approach for tool path generation in CNC incremental forming

A new tool path generation method for sheet metal computer numerically controlled incremental forming was proposed based on the stereolithography model, considering the factors of sheet thickness variation, surface smoothness, and extruding direction. The new cutter contact surface modeling algorithm based on the non-equidistant offset was presented, which can be adapted to the sheet thickness variation so as to guarantee a reasonable gap between the forming tool and support. Moreover, a spiral tool path generation algorithm was introduced by considering the scallop height in both z-axis direction and circumferential rotation direction, so that a smoother surface can be obtained. In addition, the algorithm for keeping the tool direction perpendicular to the wall surface was also presented. Finally, the case study shows that the proposed method can automatically generate smooth and continuous spiral tool path with constant scallop height. The developed software system runs steadily and reliably.

Feature-based tool path generation approach for incremental sheet forming process

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Although tool path plays an important role in the ISF process, there is only limited development in the tool path generation strategy and the conventional contour based strategies have been proven to cause problems in surface quality and geometric accuracy. This paper presents a new feature-based tool path generation algorithm for incremental sheet forming process. In this algorithm, tool paths are generated according to the specified critical edges. To obtain a better understanding of forming mechanism using the new tool path generation method, the thickness distribution, geometric accuracy and surface quality of the ISF formed shapes by using the feature-based tool path approach are compared with the traditional ISF tool path method based on three case studies including a truncated cone with double bottoms, a non-symmetrical cone and a car fender. The results suggest that the new tool path stretches the sheet in a different way and results in different thickness distributions. The results of these case studies also demonstrate the advantages of the feature based tool path generation especially in surface quality, geometric accuracy and forming time.

A hybrid and adaptive tool-path generation approach of rapid prototyping and manufacturing for biomedical models

In this paper, a hybrid and adaptive tool-path generation approach, which is able to improve geometrical accuracy and build time of rapid prototyping/manufacturing (RP/M) for complex biomedical models, is presented. Firstly, NURBS (Non-Uniform Rational B-Spline)-based curves were introduced to represent the boundary contours of sliced layers to keep the high-fidelity information of original models. Secondly, a hybrid tool-path generation algorithm was then developed to generate contour and zigzag tool-paths. The contour tool-paths are used to fabricate the boundary and neighbouring regions of each sliced layer to preserve geometrical accuracy, and zigzag tool-paths for the internal region of the layer to simplify computing processes and speed up fabrication. Thirdly, based on developed build time and geometrical accuracy analysis models, algorithms were designed to generate an adaptive speed of the RP/M's nozzle/print head for the contour tool-paths to address the geometrical characteristics of each layer, and to identify the best slope degree of the zigzag tool-paths towards achieving the minimum build time. Finally, five case studies of biomedical models with different geometrical characteristics and complexity were used to verify and demonstrate the improved performance of the approach in terms of processing effectiveness, geometrical accuracy and algorithm robustness.