Multi-axis Tool Path Research Articles

Improved Collision-Free Multi-Axis Tool-Path for Additive Manufacturing

Improved Collision-Free Multi-Axis Tool-Path for Additive Manufacturing

Collision-Free Multi-Axis Tool-Path for Additive Manufacturing

Collision-Free Multi-Axis Tool-Path for Additive Manufacturing

CNC 공작기계의 고정밀 윤곽가공을 위한 가변 윤곽오차 모델

Studies have been conducted on various contour error models applied to cross-coupling control systems, which are essential for achieving contour accuracies in multi-axis CNC systems. Most of these studies examine contour error models for straight, corner, and curved tool paths. However, there are limitations to applying these existing works in multi-axis tool paths because the straight, corner, and curved tool paths may coexist. Therefore, this paper presents a variable contour error model for cross-coupling control systems to achieve high-precision contour machining. The proposed variable contour error model allows real-time changes to the contour error model based on the tool path curvature. The proposed model was evaluated by implementing a cross-coupling control system on a PC-based three-axis CNC testbed. From the experimental results, the usefulness of the proposed model was confirmed in terms of the contour accuracy.

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.

Numerical analysis of hardness variations for a dome built without supports using directed energy deposition and multi-axis tool paths

Numerical analysis of hardness variations for a dome built without supports using directed energy deposition and multi-axis tool paths

Exploration of hardness variations for additive manufactured thin-walled components built by multi-axis tool paths

Using multi-axis tool paths in combination with a structured segmentation strategy introduces novel fabrication solutions for the direct energy deposition additive manufacturing process. However, with a piecemeal manufacturing strategy, interface regions are introduced. The goal of this research is to determine whether utilizing a multi-stage, multi-axis build strategy has an impact on the resulting hardness characteristics within the component. Surface roughness variations are noticeable when using a partitioning approach, so it is expected that hardness variations will result. The case studies consist of fabricating a set of thin wall (2 mm) hemispheres or domes. Two 45-mm nominal diameter domes are built using a wedge-based partitioning strategy. A 60-mm-diameter dome is fabricated using a rotary tool path approach. Various data collection strategies are investigated, and 300 gf or 1000 gf is recommended for the setup. It is found that the hardness across the bead thickness does not vary greatly at any point, but the hardness varies along the thin wall as the bead builds up. The interface zones have distinctly different hardness values, and the pattern is repeatable. Using fast Fourier transforms, the frequency of the noticeable surface roughness and hardness variation aligns to the interface boundary regions. This experiment illustrates that novel build solutions can be employed to eliminate the necessity of supports, but resolving a geometry issue may introduce physical and mechanical property variations within a component.

Optimization of Tool Axis Orientations in Multi-Axis Toolpaths to Increase Surface Quality and Productivity

This paper deals with a method to optimize tool axis orientations in multi-axis milling toolpaths. The method is based on calculation of the actual cutting diameter and the cutting speed during the toolpath. Subsequently, the NC code is processed by the interpolator with a machine tool kinematic model. The result is a visualization of the actual cutting speed and the real feed-rate on the toolpath. Based on these results, the vectors used to orient the tool axis along the toolpath can be effectively set up in several iterations. The toolpath are optimized to achieve a more constant cutting speedwhich lead to an improvement in surface quality and increase in productivity.

Exploration of surface roughness measurement solutions for additive manufactured components built by multi-axis tool paths

A thin-wall sphere dome set is manufactured without supports being required using a direct energy deposition additive manufacturing process. A multi-axis tool path combined with a partitioning strategy is utilized. Two partitioning strategies and a rotary toolpath build strategy are applied. The partitioned samples have a 45 mm diameter, and the rotary toolpath sample has a 60 mm diameter. The wall thickness is 2 mm for all case studies. The partitioning strategy provides an opportunity to fabricate geometries without the need for support structures, but it introduces physical properties variations. Large surface irregularities are noticed at the transition points between partitions, which escalates the roughness values drastically in these regions. The surface roughness variations within a build section and across partitions are explored in this paper. Process planning, data collection, and experimental/numerical procedures are developed and implemented to investigate the surface roughness variations (Ra measurement). Two solutions are developed: (i) a destructive testing approach (sections embedded into epoxy) and (ii) a contactless approach. The destructive testing solution uses the magnified pictures of the exposed surface edges of mount samples as input data. The other solution uses a 3D point cloud of the surface. The mount solution results show better accuracy, but the data collection process is time consuming and labour intensive. The destructive test method can detect small textures, while the contactless method is more appropriate for large-scale bead products. This research shows measuring surface roughness is challenging and further development is needed to be developed to be able to effectively measure Ra for AM built components. • Support-free hemisphere case studies are fabricated with multi-axis toolpaths. • Three partitioning process planning strategies are implemented. • Surface roughness variations can occur at the partition interfaces. • Surface roughness is measured using destructive and non-destructive methods. • The destructive measurement approach generated a high-fidelity solution. • Scanning and point cloud data solution correlated to the destructive method results.

Multi-axis tool path optimization and deposition modeling for cold spray additive manufacturing

In this study, a 3D deposition model is developed for cold spray additive manufacturing that utilizes sequential layers and a Gaussian-shaped deposition profile. The model is designed to be computationally efficient to compute for changes to the tool-path velocity. A gradient-descent-based tool path optimization algorithm is proposed to enable manufacture of arbitrary convex deposit shapes. The algorithm works by correcting the tool-path velocity to compensate for local thickness deviations due to part geometry. The combined model and optimization algorithm take STL files of the initial tool surface and targeted deposit surface as input and generate robotic g-code of the optimized tool path for a 6-axis robotic arm as output. The model is calibrated by experiments that include line sprays and particle velocimetry measurements. The path optimization scheme is evaluated by experimental test coupons in which a thick cold spray deposit is applied to a convex surface with a 0.5 mm radius of curvature.

Exploring multi-axis material extrusion additive manufacturing for improving mechanical properties of printed parts

PurposeMaterial extrusion (ME) suffers from anisotropic mechanical properties that stem from the three degree of freedom (DoF) toolpaths used for deposition. The formation of each layer is restricted to the XY-plane, which produces poorly bonded layer interfaces along the build direction. Multi-axis ME affords the opportunity to change the layering and deposition directions locally throughout a part, which could improve a part’s overall mechanical performance. The purpose of this paper is to evaluate the effects of changing the layering and deposition directions on the tensile mechanical properties of parts printed via multi-axis ME.Design/methodology/approachA multi-axis toolpath generation algorithm is presented and implemented on a 6-DoF robotic arm ME system to fabricate tensile specimens at different global orientations. Specifically, acrylonitrile butadiene styrene (ABS) tensile specimens are printed at various inclination angles using the multi-axis technique; the resulting tensile strengths of the multi-axis specimens are compared to similarly oriented specimens printed using a traditional 3-DoF method.FindingsThe multi-axis specimens had similar performances regardless of orientation and were equivalent to the 3-DoF specimens printed in the XYZ orientation (i.e. flat on the bed with roads aligned to the loading condition). This similarity is attributed to those sets of specimens having the same degree of road alignment.Practical implicationsParts with out-of-plane loads currently require design compromises (e.g. additional material in critical areas). Multi-axis deposition strategies could enable local changes in layering and deposition directions to more optimally orient roads in critical areas of the part.Originality/valueThough multi-axis ME systems have been demonstrated in literature, no prior work has been done to determine the effects of the deposition angle on the resulting mechanical properties. This work demonstrates that identical mechanical properties can be obtained irrespective of the build direction through multi-axis deposition. For ABS, the yield tensile strength of vertically oriented tensile bars was improved by 153 per cent using multi-axis deposition as compared to geometrically similar samples fabricated via 3-DoF deposition.

Spherically curved layer (SCL) model for metal 3-D printing of overhangs

Directed energy deposition (DED), equipped with 5-axis tool mechanism and no additional machining process, turned out to be able to deposit overhang/undercut features with no support directly on a part in multiple directions. When performing the deposition, two additional axes of rotating and tilting newly added to the working table where the part is typically fixed need to be precisely controlled using an advanced process management technique. The previous approach for slicing algorithm corresponding with multi-axis tool paths along the part and providing a simple stepwise two dimensional layering process of repetitive ±90 degree tilting of the base table can cause unavoidable process delay whenever the base table needs to be tilted for conforming the geometry of overhang/undercut features. Another clear and present barrier to the approach, in addition, is the physical interferences between the tool and the workpiece moving separately during the build. This study proposes a Spherically curved layer (SCL) model providing interference-free 5-axis tool-part movement, a continuous and synchronized interaction between the tool and the part each separately but precisely controlled while kept contacted together, for the build of overhangs. A methodological approach generating SCL information directly from an STL model, followed by the implementation onto various overhang problems as case studies using the proposed methodology, will be discussed in this paper.

A Generic Multi-Axis Post-Processor Engine for Optimal CNC Data Creation and Intelligent Surface Machining

This paper focuses on the development of a multi-axis post-processor engine with a curvature-based feed adaptation module, capable of extracting generic CNC data for high precision machining. The motivation of this work stems from the drawback of standard and commercial post-processors to modify their internal source codes so as to be implemented to newly-developed functions which integrate modern CNC units. The multi-axis post-processor proposed in this work operates as a stand-alone function of an artificial intelligent module that optimizes machining parameters for standard swept cut multi-axis surface tool-paths. The post-processor developed receives APT source files previously been optimized by means of a genetic algorithm that handles cutting tool selection; radial cut engagement; maximum discretization step; lead and tilt angles. The algorithm optimizes the aforementioned machining parameters towards the minimization of the number of cutter locations found in a specific APT source file as well as the surface machining error as a combined effect of chordal deviation and scallop height. The final APT output is then properly handled by the post-processor engine so as to extract the final ISO code for a double-pivoted head 5-axis CNC machine and compute optimal values for feed rate in each NC block considering the interpolation error and curvature analysis given the surface properties. To simulate and verify our proposals, the MAZAK Vortex 1000 gantry-type 5-axis CNC machine tool equipped with a Fanuc 15i CNC unit has been selected as the manufacturing resource corresponding to the final CNC output that the proposed post-processor computes. A benchmark sculptured part is created and used for the virtual material removal simulation in CATIA® V5 R18. For that part, both the proposed post-processor engine and a commercially available post-processor were employed to extract G-code data whilst it was shown that identical outputs were obtained.

Artificial immune algorithm implementation for optimized multi-axis sculptured surface CNC machining

This paper presents the results obtained by the implementation of an artificial immune algorithm to optimize standard multi-axis tool-paths applied to machine free-form surfaces. The investigation for its applicability was based on a full factorial experimental design addressing the two additional axes for tool inclination as independent variables whilst a multi-objective response was formulated by taking into consideration surface deviation and tool path time; objectives assessed directly from computer-aided manufacturing environment A standard sculptured part was developed by scratch considering its benchmark specifications and a cutting-edge surface machining tool-path was applied to study the effects of the pattern formulated when dynamically inclining a toroidal end-mill and guiding it towards the feed direction under fixed lead and tilt inclination angles. The results obtained form the series of the experiments were used for the fitness function creation the algorithm was about to sequentially evaluate. It was found that the artificial immune algorithm employed has the ability of attaining optimal values for inclination angles facilitating thus the complexity of such manufacturing process and ensuring full potentials in multi-axis machining modelling operations for producing enhanced CNC manufacturing programs. Results suggested that the proposed algorithm implementation may reduce the mean experimental objective value to 51.5%

Intelligent Optimization for Sculptured Surface CNC Tool-paths

This paper suggests the application of genetic algorithms for the intelligent generation of optimum sculptured surface CNC machining tool-paths. Two robust full quadratic mathematical models are developed relating the physical relation among machining surface deviation and resulting cutting time; quality objectives which are treated as conflicting ones. The independent variables are the tool inclination angles -lead and tilt- in the case of 5-axis machining and step-over engagement among subsequent XY passes; using a toroidal cutter. A Box-Behnken response surface design was established to prepare and conduct simulation experiments in a cutting-edge manufacturing software using a benchmark multivariable sculptured surface and a special multi-axis tool-path strategy. The genetic algorithm utilizes both models expressed as a common Pareto-based fitness function so that multi-objective optimization is achieved, yet; arriving at one optimum solution to ease the efforts of end-users and numerical control programmers. The methodology is validated by utilizing the genetic algorithm's recommendations for the settings of the machining parameters and the optimum tool-path simulation is performed to verify the operation.

Slicing algorithms for multi-axis 3-D metal printing of overhangs

A group of 3D metal printing or Additive metal manufacturing (AMM) processes, officially categorized as ‘directed energy deposition (DED)’ according to American Society for Testing and Materials (ASTM) classification, has enabled the building of full dense metallic tools and parts using metal powders precisely delivered and controlled with no powder bed. Mold making and metalworking are being taken in an entirely new direction. The overhang/undercut problem in DED processes, as much as other Additive manufacturing (AM) processes, has long remained unsolved, and the ones equipped with more than 3-axis tool mechanism turn out to be capable of depositing overhang/undercut features onto the part to be made. Multi-axis machines introduced for resolving the problem, however, require advanced preprocess software support for the process management that controls multi-axis tool paths. This study proposes slicing algorithms, sophisticatedly designed for the control of the tool paths on a 5-axis base table, to build overhang/undercut features. A methodical approach, using an auto-partitioning algorithm for generating three-dimensional layer (3DL) information, is proposed in this study, and various overhang features, as case studies, have been investigated and implemented by using the proposed method.

Multi-axis tool path generation for surface finish machining of a rapid manufacturing process

This paper proposes a completely automated, integrated tool path planning for the finish machining of freeform surfaces as a part of the hybrid metal additive manufacturing and CNC machining. This planning capability spans from a generation of b-spline freeform surfaces, to surface finish optimisation, to collision detection, to tool path generation. Two scallop height methods have been used to compare the optimal tool path strategy. Both collision detection of a tool with neighbouring surfaces and collision correction for a tool are solved using a novel extension of the bounding box, which uses body diagonal points for computation. This paper proposes a multiple screening technique to improve the computational efficiency of tool path generation calculations.

An integrated CNC accumulation system for automatic building-around-inserts

In this paper a non-layer-based additive manufacturing (AM) process named computer numerically controlled (CNC) accumulation process is presented for applications such as plastic part repairing and modification. To facilitate the CNC accumulation process, a novel three-dimensional (3D) laser scanning system based on a micro-electro-mechanical system (MEMS) device is developed for in situ scanning of inserted components. The integration of the scanning system in the CNC accumulation process enables the building-around-inserts with little human efforts. A point processing method based on the algebraic point set surface (APSS) fitting and layered depth-normal image (LDNI) representation is developed for converting the scanning points into triangular meshes. The newly developed 3D scanning system is compact and has sufficient accuracy for the CNC accumulation process. Based on the constructed surface model, data processing operations including multi-axis tool path planning and motion control are also investigated. Multiple test cases are performed to illustrate the capability of the integrated CNC accumulation process on addressing the requirements of building-around-inserts.

Digital Machining Simulation for Francis Hydro Turbine's Blade

In order to high-quality manufacture the hydro turbine blade efficiently, a series of innovative digital techniques have been developed. It includes 3-D modeling based on machining requirement, multi-axis tool path planning and generating, tool axis orientation for multi-axial NC machining of blades, machining simulation environment establishment, computer simulation for machining of a large blade to verify the gouges and collisions between machine tool, blade and fixtures. The techniques of multi-axis digital machining simulation for large-size blades can be directly applied into digital simulation processing of other sculptured surface parts, and it will completely change the traditional design and manufacturing process of turbine.

Tool-path Generation of Multi-axis Machining for Subdivision Surface

An algorithm of multi-axis NC tool-path generation for subdivision surfaces is proposed. The algorithm includes two steps: model building and tool path generation. In the section of model building, in order to obtain the deformed surface, the deformation vector is computed which is associated with the curvature and the slope of cutter location surface. In the procedure of tool path generation, the slicing procedure is adopted to get the CL points. In addition, the inversely converted method is used. The method is tested by some examples with actual machining. The results show that the method can effectively reduce the error of the scallop height for subdivision surface and obtain the better shape and quality. In addition, the computational complexity and is scalable and robust.

Parametric multi-axis tool path planning for CNC machining: the case of spur gears

Four and five axis machining strategies are difficult to standardise in the general case. General purpose CAM systems are an important tool allowing the experienced machinist to experiment with machining strategies and assess quality of the resulting tool paths. However, in the case of machine elements, such as gears, shape definition by parametric equations is most inviting for development of fit-for-purpose machining strategies and corresponding parametric tool paths without the use of CAM software. Such an approach is materialised in this paper for spur gears, drawing on discretisation of involute and trochoidal curves constituting the tooth profile, so as to satisfy scallop height constraints. The roughing stage is performed with a flat end mill, implementing slot milling along a meander type tool path. The finishing stage is performed with a bull-nose end mill, implementing peripheral milling circumferentially around the full gear profile. The algorithms were tested on a three-axis machining centre equipped with an additional 4th rotary axis to manufacture a plastic spur gear.