Tool Path Generation Research Articles

Point cloud based tool path generation for corrective machining in ultra-precision diamond turning

The increasing demand for machining non-rotational optical surfaces requires capable and flexible cutting tool path generation methods for ultra-precision diamond turning. Furthermore, the recent interest in on-machine metrology and corrective machining requires efficient as well as accurate algorithms capable to handle point cloud based surface data. In the present work, a new computation method for the tool path generation is proposed that focuses on three-axes corrective machining. It is based on the principle of defining the surface to be machined by a point cloud of given density, since surface measurement data is usually available as point cloud. Numeric approximation techniques are used to compute the surface normal vectors and calculate the resulting positions of the cutting tool path preserving a uniform radial axis motion for face turning. Investigations are performed in order to quantify the error between the calculated tool path and the exact analytical solution. The error dependencies are analyzed regarding the local surface slope and numerical parameters. Error values below 1 nm are achieved. In addition, form deviation results prove the method’s capability for corrective diamond turn machining.

Tool Path Generation Algorithm Based on Rough Machining of Jade Carving Surface

To improve the quality of tool paths in surface machining, different machining requirements are considered in the tool path generation algorithm. In the traditional tool path generation algorithm, due to the lack of a unified mathematical calculation framework, these requirements often need to be considered separately, but they often compete with each other, so that different requirements cannot be satisfied at the same time and the tool path cannot achieve the optimal. To resolve this issue, an extensive tool path generation algorithm framework for arbitrary surfaces was proposed. The proposed algorithm transforms the tool path calculation framework into a constrained functional optimization problem by establishing an optimization function based on the potential energy field and an inequality function based on the gradient field in the machining area. By establishing finite element approximation, the functional optimization problem is transformed into a numerical optimization problem, which reduces the difficulty of solving. According to the machining requirements of die surface such as tool path smoothness, line width constraint and cutting direction constraints were transformed into the constraints of potential energy field isopotential line, and the method of generating reciprocating cutter path and cutter contact path isosection cutter path was proposed by optimizing the method. It is evident from the simulation and machining experiments results that continuous and smooth tool paths can be generated by using this algorithm, and machining quality and machining efficiency can be improved. By adding different machining requirements into the framework, a tool path with different optimization objectives can be generated.

Tool path generation and optimization for freeform surface diamond turning based on an independently controlled fast tool servo

Diamond turning based on a fast tool servo (FTS) is widely used in freeform optics fabrication due to its high accuracy and machining efficiency. As a new trend, recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller. However, the tool path generation strategy for the independently controlled FTS is far from complete. This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining. Different from the conventional integrated FTS control system, where control points are distributed in a spiral pattern, in this study, the tool path for the independent FTS controller is generated by the ring method and the mesh method, respectively. The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces. To demonstrate the feasibility of the proposed tool path generation strategies, cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared. As a result, after tool path optimization, the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method, and from 191 nm to 103 nm for the micro-lens array by using the mesh method, respectively.

Uniform Coverage Tool Path Generation for Robotic Surface Finishing of Curved Surfaces

We provide a novel solution to the problem of robot tool path generation to uniformly cover the surface area of a curved surface with varying curvatures by using a circular, flat finishing tool. We first develop a local contact shape descriptor using tools from differential geometry to estimate the contact shape and its area between the finishing tool and the workpiece surface under an applied normal force. Based on this varying contact area as the tool moves on the surface, we describe a tool path planning strategy that provides full and uniform coverage of a free-form or curved surface with the least amount of overlap. As opposed to fixed spacing paths with point contact in most existing approaches, we provide a novel path generation method where the interval spacing between neighboring path segments is determined by the contact area, which is position-dependent and varies along the surface in accordance with its principal curvatures. An efficient bisection method is employed in the proposed off-line path planning strategy. Numerical studies were conducted for ruled and general curved surfaces to compare the contact areas and coverage of the resulting path with paths generated using two other approaches from the literature. Real-time surface finishing experiments with a six degree-of-freedom robot equipped with a surface finishing tool were also conducted for both these surfaces to validate the proposed approach. Results from the numerical studies and experiments are presented and discussed.

Research on the Negative Multistage Incremental Forming of Straight-Wall Parts Based on the Extrusion from the Forward and Reverse Side of the Sheet

Because the forming area involved in traditional reverse multistage incremental forming is only located inside the model, the sheet-metal thinning rate is relatively large. Particularly, the straight-wall parts with a narrow internal space cannot be formed using traditional multistage incremental forming. Therefore, a negative multistage incremental forming that extrudes the sheet from the forward and the reverse side of the straight-wall part is proposed in this paper. In this method, firstly, the auxiliary surface is generated to divide the straight-wall part model into three forming regions; secondly, the first- and second-stage forming are carried out from the forward side of the straight-wall part with support, respectively; Thirdly, the third-stage forming is carried out from the forward side of the straight-wall part without support. The software system for auxiliary-surface generation, the straight-wall parts partition, each intermediate-stage-forming model, and each stage-forming toolpath generation was developed by using C++, VC++, and OpenGL library. In order to verify the feasibility of the proposed method in this paper, the forming experiments of a 1060 aluminum sheet were conducted using traditional reverse multistage forming and the proposed method in this paper, and the forming effects were compared and analyzed. The results show that compared with traditional reverse multistage incremental forming with forward-side extrusion, the multistage incremental forming method with the forward and the reverse-sided extrusion proposed in this paper can increase the area of the sheet participating in the deformation and avoid the problem of excessive thinning of sheet thickness, especially suitable for the straight-wall part model with narrow internal space.

Large-scale Robotic Fabrication of Polychromatic Relief Glass

This research investigates a new digital fabrication method for large-scale polychromatic glass elements. Glass elements with locally differentiated properties usually require manual labor or are limited to film applications of secondary materials that are incapable of producing material texture and relief in glass. To create mono-material glass elements for buildings with customized color, opacity, and relief present in the same glass element, this research investigates a novel robotic multi-channel printing process for industrial float glass. Mono-material polychromatic glasses do not require any additional material and can be fully recycled. This paper presents a design-to-production workflow for the construction scale within feasible cost. Investigations include kilning and material considerations, multi-channel tool and fabrication setup, tool path generation, process parameter calibration, and large-scale prototyping. The co-occurrence of locally varying opacities, colors, material textures, and relief within one glass element enabled by the presented robotic fabrication method could allow for novel optical and decorative features in facades and windows.

Incremental Sheet Forming Simulation of Aluminum Alloys for Industry Level Production

The Single point incremental sheet forming process known as a SPIF process. Which got a great attraction among other existed sheet metal forming processes because of their flexibility to manufacture complex products. The aluminum alloy material mechanical properties are adopted and integrated into the finite element (FE) code. The tool paths for the truncated cone shape are modeled in Fusion 360 software, and the coordinates are converted into 3D punch tool coordinates by the tool path generation framework tool for modeling the numerical simulation. In numerical modeling, three kinds of mesh settings are used to construct the mesh for producing consistent results. Afterward, the obtained results are tested against the experimental observations and the desired parts dimensions to verify the accuracy of the established FE model. Thickness variations in the formed parts are discussed in detail in terms of the thinning part, thinning location, and its size in percentage. A comparison of tested geometries displays that reduction in thickness tends to be uniform in the wall region and small fluctuation noticed near the tool retraction location. Overall, the statistical results of the SPIF process are well in contract with the experimental measurements. In terms of geometry dimensions and thickness reduction. In addition, the surface roughness was noticed to be increased when the step size is more extensive, and on the other hand, the machining time tends to be more if the contour step size is small in the SPIF process.

Generating direct diamond shaping tool paths using special-purpose computer-aided-machining post-processor

ABSTRACT Ultra-precision direct diamond shaping (DDS) is an attractive method for manufacturing highly accurate and complex features. DDS employs 4 of the 5-axes in an Ultra-Precision Machine (UPM) with a conventional diamond tool to machine features on a workpiece mounted on a rotary axis. It has been proven to be effective and flexible in manufacturing intricate features, from microfluidics to Fresnel lenses. However, a significant technical hurdle in the practical implementation of DDS is the complexity of its non-conventional tool path generation. Current practices in generating DDS tool paths rely on programming and significant mathematical manipulation. This is not only time consuming but also requires the user to overcome a steep learning curve. Moreover, conventional Computer-Aided Machining (CAM) software does not support DDS tool paths, but instead supports tool path generation for common machining processes like milling and turning. This paper discusses the use of a special-purpose post processor to bridge the compatibility gap between CAM and DDS tool path generation. The mathematics and logic of converting CAM milling tool paths to DDS would be discussed. Finally, the post processor was experimentally verified using a case study.

Simultaneous optimization of curvature and curvature variation for tool path generation in high-speed milling of corners

Simultaneous optimization of curvature and curvature variation for tool path generation in high-speed milling of corners

Five-axis iso-error numerical control tool path generation for flat-end tool machining sculptured surface

Five-axis iso-error numerical control tool path generation for flat-end tool machining sculptured surface

Adaptive tool path generation for flank milling of thin-walled parts based on force-induced deformation constraints

Adaptive tool path generation for flank milling of thin-walled parts based on force-induced deformation constraints

Smooth Flank Milling Tool Path Generation for Blisk Surface with Barrel Cutters

Smooth Flank Milling Tool Path Generation for Blisk Surface with Barrel Cutters

Data-driven metal spinning using neural network for obtaining desired dimensions of formed cup

A data-driven metal spinning process was developed to systematically generate tool paths to obtain desired dimensions such as height and thickness of formed parts for various sizes of blank disks and tools without preparing big data. An artificial neural network was modeled using tool-path parameters, the sizes of the blank disks and tools, and the height and thickness of the formed parts. The tool-path parameters to obtain the desired dimensions were iteratively calculated by the steepest descent method using a Jacobian submatrix. This method was applied to a multi-pass conventional spinning process, and thickness of spun cups was successfully controlled.

CAM Planning for Automatic Support Removal with Robotic Chiseling

In this paper, a new CAM planning strategy for removal of support structures is presented. Since such a task is usual in post-processing of parts fabricated with additive manufacturing, the developed approach is about a toolpath planning algorithm suitable for generic robotic cells that can be equipped with a chiseling holder. The 6-axis toolpath generation was used to define spatial paths of the tool tip and proper orientation of the chisel tool. The chisel can be orientated with a certain angle to the machined surface ensuring a gouge-free and collision-free positioning. Removability of different support structures was experimentally validated.

Process Development for the Freeform Deposition of a Glass Fiber Reinforced Photopolymer

Continuous fiber additive manufacturing is a rapidly growing field of research and industry. The development of freeform polymer extrusion systems has also seen some interest in the last few years. In this paper, developments to a system combining the concepts of continuous fiber additive manufacturing and freeform extrusion are discussed. The system is able to produce freeform glass fiber reinforced photopolymer extrusions, using 5-axis toolpaths executed by an industrial robot. A simple method of freeform toolpath generation using manual specification of nozzle posture is presented. Process parameters are then identified, and a series of tests to determine suitable values of critical process parameters are described. Results of these tests indicate that, using suitable settings, freeform glass fiber reinforced extrusions can be produced with moderate geometric accuracy, fiber volume fractions in excess of 30 %, and void contents of below 1 %. In addition, using suitable nozzle posture and offset values, fused segments can be extruded in parallel, which will allow for the manufacture of struts comprising multiple joined extrusions.

Field-Based Toolpath Generation for 3D Printing Continuous Fibre Reinforced Thermoplastic Composites

We present a field-based method of toolpath generation for 3D printing continuous fibre reinforced thermoplastic composites. Our method employs the strong anisotropic material property of continuous fibres by generating toolpaths along the directions of tensile stresses in the critical regions. Moreover, the density of toolpath distribution is controlled in an adaptive way proportionally to the values of stresses. Specifically, a vector field is generated from the stress tensors under given loads and processed to have better compatibility between neighboring vectors. An optimal scalar field is computed later by making its gradients approximate the vector field. After that, isocurves of the scalar field are extracted to generate the toolpaths for continuous fibre reinforcement, which are also integrated with the boundary conformal toolpaths in user selected regions. The performance of our method has been verified on a variety of models in different loading conditions. Experimental tests are conducted on specimens by 3D printing continuous carbon fibres (CCF) in a polylactic acid (PLA) matrix. Compared to reinforcement by load-independent toolpaths, the specimens fabricated by our method show up to 71.4% improvement on the mechanical strength in physical tests when using the same (or even slightly smaller) amount of continuous fibres.

A supervised community detection method for automatic machining region construction in structural parts NC machining

In structural part NC machining, part faces need to be grouped to form various machining regions to support machining sequencing, parameter planning and toolpath generation. However, existing automatic machining region construction methods are usually only acceptable for parts in specific fields due to the heavy dependence on domain-specific expert defined rules or strategies. This research proposes a data-driven method that learns the knowledge required by machining region construction directly from the historical data. The task is first converted to machining region community (MRC) detection from the attributed graph of the 3D part model. As existing supervised community detection methods in network science need to know the total MRC number in advance which is unpractical in this task, a new concept named affiliation similarity (AS) is defined to describe the overlap of the MRC affiliations of multiple nodes, then with which a new MRC detection algorithm that does not require any information of the MRC number is established. The maps from the face nodes to the AS information is modeled using graph neural networks (GNN) which are trained using the data samples constructed based on the historical process files. A case study using the data of aircraft structural part NC machining from real industry is carried out and the result shows the proposed method is practical in automatic machining region construction. More importantly, it is believed that the proposed method is convenient to be extended to parts of other domains by modifying the node attributes, redesigning the GNN structures and retraining the GNN models with corresponding dataset.

Tool Path Generation for Linear Cutting Using Step File (ISO 10303) Data Structure

The ISO 10303 also known as the Standard for the Exchanged Product data (STEP) that describes how to represent and exchange the product manufacturing information. STEP’s data structure incorporates three-dimensional data of product design elements and manufacturing details which allows users to access 3D product model/information via different CAD applications. These product data model if exploited fully can be used in CAD/CAM and CNC system to perform machining simulation or physical machining operation. The paper describes the interface system development of tool path generation for linear cut using STEP file as input file. The system must be capable of identifying, extracting, processing the geometric data from STEP file and generate tool path according to G-code ISO 6983. A machined block sample with straight slot profile is designed from a 3D CAD modeler and saved in the STEP file format. This file was then upload into the Interface system to auto generate a G-code. The simulation and physical machining using 3-axis CNC milling as to validate the output.

A smooth tool path generation method for ultraprecision turning discontinuous multi-freeform-surfaces with high machining efficiency

The typical tool path of turning freeform surfaces is spiral. Usually, this kind of tool path only can deal with continuous surfaces within a circular area. If the designed surfaces are not continuous, the spiral tool path will break, which will lead to a significant increase in servo following error of ultraprecision lathe during machining. In order to reduce the servo following error, the processing speed needs to be significantly reduced, which will greatly decrease the machining efficiency. To solve this problem, a smooth tool path interpolation algorithm in the non-cutting area for ultraprecision turning discontinuous multi-freeform-surfaces is proposed. In addition, more than circular area, this method can generate smooth tool paths for discontinuous generic surfaces of quasi-revolution based on the optimized space Archimedean spiral. Finally, the effectiveness and adaptability of the method are proved through two examples.

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.