Cutter Path Generation Research Articles

Feature-Driven Next View Planning for Cutting Path Generation in Robotic Metal Scrap Recycling

Metal recycling in scrapyards, where workers cut decommissioned structures using gas torches, is labor-intensive, difficult, and dangerous. As global metal scrap recycling demands are rising, robotics and automation technologies could play a significant role to address this demand. However, the unstructured nature of the scrap cutting problem—due to highly variable object shapes and environments—poses significant challenges to integrate robotic solutions. We propose a novel collaborative workflow for robotic metal cutting that combines worker expertise with robot autonomy. In this workflow, the skilled worker studies the scene, determines an appropriate cutting reference, and marks it on the object with spray paint. The robot, then, autonomously explores the surface of the object for identifying and reconstructing the drawn reference, converts it to a cutting trajectory, and finally executes the cut. This paper focuses on the surface exploration and cutting reference reconstruction tasks, which require appropriate next view planning (NVP) algorithms. We devise three NVP algorithms enabling the robot to explore and extract desired features from the scene, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> , the drawn reference, without requiring any <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> object model. Contrasting with global or feature-agnostic NVP algorithms, our approaches guide the robot via desired local features to increase the efficiency of the exploration. We evaluate our NVP algorithms against six categories of objects both in simulation and in physical experiments. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This work is motivated by the need of extracting a desired cutting reference determined and drawn on the object by scrap yard workers. From the robot’s perspective, it must explore and reconstruct the drawing, starting from an unknown scene containing an unknown object featuring an unknown drawing. We assume that an RGB-D camera is attached to the tool-tip of the robot, and the color of the drawn path is significantly different from the object’s color. The goal of the robotic system is to explore the object surface to uncover the drawn path entirely without colliding with the object. The exploration algorithm must overcome complex object shapes and must be fast enough for practical use in scrap yards. This means conventional exploration (active vision) techniques are insufficient since they focus on exploring the entirety of the object, which is unnecessary for our task and is time-consuming. Our methods exploit the drawing information to guide the exploration for quickly determining a suitable viewpoint, which results in an efficient extraction of the entire cutting reference, without needing to explore the entire object’s surface. Our algorithms are robust against adversarial features such as discontinuous, non-smooth, or self-occluded object surfaces. Our feature-driven strategies are not limited to robotic scrap cutting as they are applicable to any viewpoint planning problem requiring high performance while extracting the local features in the scene.

A cutter path generation strategy for helical surface machining of screw rotor.

In this article, the disk mill cutter path generation strategy for the machining of complex helical surface via a currently developed minimal orientation-distance algorithm based on spatial discretization method is studied. The strategy proposed here is, first, to establish the helical surface and cutting surface in the unique coordinate system. Then, the two surfaces are divided into a series of parts by n equidistant planes, and the minimal orientation-distance algorithm is used to determine all the cutter locations. Finally, on the basis of Archimedes helical interpolation, cutter path is generated within the specified tolerance limit. The effectiveness of the proposed strategy is confirmed numerically and experimentally by a case of virtual cutting test in VERICUT software and actual machining. This strategy can be applied to a broad range of helical surface machining.

A review of cutting path algorithms for laser cutters

This paper presents a review of the literature on generating cutting paths for laser cutting machines. Firstly, the cutting path problem is defined including all relevant technical side constraints which exist plentifully in laser cutting. Secondly, a former classification method is updated to include all types of cutting path problems. Thirdly, a comprehensive review of solution methods and related applications is presented. Throughout the literature review, trends in research in cutting path generation and interesting areas for future research are identified.

Research and Development of Ultrasonic CNC Cutting Path Generation System for Nomex Composite Materials

There are a number of problems with the traditional way of machining Nomex composite materials, Ultrasonic vibration cutting as a new method can overcome most of the problems. This paper presents the machining process characteristics of ultrasonic cutting honeycomb structures of Nomex composite materials using two kinds of specials tools, and has a research on Ultrasonic machining tools posture control strategy, then proposed calculation method of generating the cutter location date. The main system was developed to meet the automatic generation cutting path of Nomex composite materials based on VS2008 and UG commercial software. The result of experiment shows this system can automatic generate rational machining path and correct NC date.

Optimization of Cutting Path for Minimizing Workpiece Displacement at the Cutting Point: Changing the Material Removal Process, Feed Direction, and Tool Orientation

The vibrations of a workpiece during machining shorten the tool life and deteriorate the surface roughness in cases where the workpieces have a low stiffness (as is the case with artificial hip joints). In this paper, we propose a method to reduce the vibrations of the workpiece at the cutting point; this method is based on an algorithm that generates a cutting path to minimize workpiece displacements. The generation of the cutting path takes into account the workpiece stiffness, cutting force vectors, the material removal process, feed directions, and tool orientation. The cutting path generation algorithm generates cutting path strategies based on the relationships among cutting force vectors, feed directions, and tool orientation, all of which are measured with machining experiments.

Analysis of drift in iso-scallop planning—machining by regions

Computer-aided manufacturing (CAM) occupies an increasingly significant role in engineering with all it has to offer in terms of new possibilities and improving designer/manufacturer productivity. Our present work is devoted to the integration of a module for automatic generation of cutter paths into a CAM program to machine freeform surfaces by end milling. The study addresses the more global issue relating to the adoption of tool path planning with constant scallop height. For present purposes, the cutter geometry is taken as given and does not enter into the study’s parameter choices. The main problem posed by planning for iso-scallop tool paths lies in the management of drift in trajectories, which leads to the path looping due to the fact that global programming over the surface remains unattainable. The proposed solution is to define surface subdivision criteria (machining by regions) enabling iso-scallop planning to be implemented in each region. We conducted our study on a three-axis numerical control machine tool.

Isoscallop of Self-Adaptive Tool Orientation with Toroidal Cutter under Optimum Orientation of MCPs

End-milling of free-form surfaces on 5-sxis NC tools is a complex problem which has been studied by a large number of research scientists. When end-milling non-convex surfaces, there is a risk of interference between the tool and the surface. This paper presents a new approach to generate gouging-free tool path for constant scallop-height machining using 5-axis toroidal milling. Based on second-order approximations of the machined strip width, we present locally optimal cutting positions for cutting directions. The largest machined strip width of iso-scallop and the corresponding gouging-avoidance tool orientation are calculated. In the cutter path generation procedures, the master cutter paths have been chosen from the minimum curvature loci of the surface. The tool path generated by this method are also compared with that of the long edge of surface as the MCP, the results of simulation show that the method can yield a reduction in line segments of tool path . Velocity curve and acceleration curve are smoother.

Optimum process parameters to produce green ceramic complex parts

The fragility of green ceramic compacts introduces considerable difficulties during green or bisque machining. This paper demonstrates methods developed to manufacture thin wall–thin floor, complex green ceramic parts to close tolerance. Hybrid finite element (FE)/mechanistic models were utilized in the development of the green machining process. An FE model was used to define cutting edge geometry and machining parameters that would reliably produce crack free parts. Mechanistic model was used to direct cutter path generation of a 5-axis milling machine having a large axial depth of cut, and to prevent edge chipping. The optimized cutter path eliminated any need for hand work before densifying the machined part.

Interactive Haptic Refinement of a Five-Axis Finishing Cut

This paper describes the design of a haptic system that allows the interactive modification of cutter orientation during five-axis finishing cuts with the aim of improving the surface finish quality and collision avoidance strategies. The system supports two haptic models that provide three degree of freedom (DOF) force feedback and 6DOF posture sensing. Details of five key functions of the system are given: (1) a rendering conversion that uses 3DOF (instead of five) force feedback haptic representation, (2) an efficient force feedback design that allows accurate results to be obtained from the user’s manipulation, (3) a fast collision detection scheme that achieves real-time feedback, (4) use of active haptic guidance to assist cutter-path generation, and (5) a design that supports both ball-end and flat-end tools with partial optimization.

Generation of cutter paths for hard material in wire EDM

A heuristic method for generating a cutter path for superhard material is presented. The cutter path should satisfy various constraints that come from physical reality in industry; for example, a constraint about undesired projections of the cut-off pieces, and that about vibration and deformation generated by the cutter. A large portion of those constraints is represented by a rooted tree called “force-support tree” in direct and concise manner, and the remaining constraints are implemented in the manipulation of this tree. The resulting method achieves to find a good cutter path very quickly.

Offset error analysis of ball-end mill for cutter-path generation from point-based surfaces

Moulds and dies with sculptured surfaces are usually finished using a three-axis computer numerically controlled milling machine with a ball-end mill. In this paper, the surface shapes are defined by a rectangular grid of surface points and the inverse offset method (IOM) is used to generate the cutter paths. The error of the offset (cutter path) points generated by the IOM due to spacing of surface points is determined. The error analysis enables an appropriately dense set of points to be chosen so that the offset surface can be generated within a specified tolerance.

Cutting path generation of linear hotwire cutter for VLM-ST

Most rapid prototyping (RP) processes adopt a solid CAD model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually, the stacked layers form a physical part of the model. A new thick-layered RP process, the transfer-type variable lamination manufacturing process using expandable polystyrene foam sheets (VLM-ST), has been developed to reduce building time by employing thick layers and to improve the surface finish of parts with a sloping surface. This paper describes the method to generate the unit shape layer (USL), the cutting path data of the four-axis hotwire cutter for the VLM-ST process. The USL is the basic unit of cutting and building in the VLM-ST process and it is also the basic unit of cutting path data of each layer. The USL includes data such as layer thickness, positional coordinates, side angles of each layer, and reference shape. The method to generate the USL is as follows: (1) the mid-slice of each layer is generated from the CAD model, (2) each mid-slice is converted into a simply-connected domain, (3) the rotation angle of the hotwire of the cutting system is calculated for each layer, and (4) the reference shape of each layer is generated for manual stacking. The procedure to generate the cutting path data of the linear hotwire cutter for VLM-ST was practically applied and verified for various three-dimensional shapes.

Extraction of simple and concatenated features from a wire frame model using IGES data

The manufacturing information for a part is required for automated process planning, the link between CAD and CAM. Extraction of manufacturing features for a part from its CAD model is the first step in automated process planning. Most of the CAD models are transferred from one system to another through the neutral file format IGES. The software developed in C++ extracts both simple and concatenated features for prismatic parts from IGES files. The final results obtained are a set of manufacturing features along with their dimensions and positions, which can be used directly for downstream applications such as process planning, NC part programming and cutter path generation. The working of the system and algorithms used for feature extraction are explained with examples.

Optimization of CNC isoscallop free form surface machining using a genetic algorithm

Isoscallop machining with edge-based master cutter path (MCP) essentially ensures uniformity of surface roughness over entire surface of part but may not necessarily ensure minimization of machining time. In the present work, it has been shown that there is a provision for minimizing machining time while implementing Isoscallop machining, by optimizing the orientation of the primary or Master Cutter path (MCP) through application of a GA. The results indicate a substantial reduction in total machining time for the proposed approach compared to those obtained through previously reported cutter path generation strategies.

Selection of master cutter paths in sculptured surface machining by employing curvature principle

In the Isoscallop strategy of sculptured surface machining, one of the surface edges is generally chosen as the Master Cutter Path (MCP)—from which other cutter paths are derived such that the roughness produced is uniform. In this paper, the MCPs have been chosen from the maximum or minimum curvature loci of the surface. Those loci that divide the surface into distinct zones of similar curvature are adopted as MCPs. Secondary cutter path generation is carried out employing standard isoscallop formulation and problems associated with multiple MCPs have been identified and addressed. MCPs along the locus of maximum convex curvature lead to a considerable reduction in machining time while those for minimum curvature (maximum flatness) yield a reduction in CL data file size.

Cutter path orientations when high-speed finish milling inclined hardened steel

The use of high-speed milling (HSM) for the production of moulds and dies is becoming more widespread. Critical aspects of the technology include cutting tools, machinability data, cutter path generation and technology. Much published information exists on cutting tools and related data (cutting speeds, feed rates, depths of cut, etc.). However, relatively little information has been published on the evaluation of cutter paths for this application. Most of the research focuses on cutter path generation with the main aim on reducing production time. Work concerning cutter path evaluation and optimisation on tool wear, tool life and relevant workpiece machinability characteristics are scant. This paper investigates and evaluates the different cutter path orientations when high-speed finish milling inclined hardened steel, at a workpiece inclination angle of 75°. The results demonstrate that employing a vertical downward orientation achieved the longest life. However, in terms of workpiece surface roughness, vertical upward orientation is generally preferred.

A composite B-spline method for cutter path generation on free-form surfaces

This paper presents a composite B-spline method for cutter path generation on free-form surfaces on a point-by-point basis, with appropriate radial offset and interference checking along the cutter path. It is aimed at developing a more efficient and accurate free-form surface machining method for an open-architecture CNC system with B-spline interpolation capability. In this method, the cutter paths over the free-form surface are composed of a sequence of B-spline segments. The length of each spline segment is determined by the desired deviation, within some given tolerance, from the curve of the surface over which the cutter path is to be generated. If the spline segment does not satisfy the specified dimensional tolerance, control points of the spline segment are adjusted to modify the curve shape according to the required accuracy. As a result, the deviation between the actual cutter paths and the desired surface curves will always fall within the allowable tolerance. In addition, by adjusting the position of the control points, the adjacent spline segments are made at least C1 geometrically continuous. The distance between adjacent cutter paths in the side step direction is determined by checking the scallop height between them. To make the cutting process more efficient, a modified adaptive iso-parametric curve generation approach is employed. The resulting cutter paths are more compact and accurate compared with those from commonly used cutter path generation techniques.

Three-Axis NC Cutter Path Generation for Subdivision Surface with Z-Map

In this paper we propose methodologies and algorithms of NC cutter path generation for subdivision surfaces. We select Loop surface as the subdivision surfaces. A path plan including rough cut and finish-cut is developed based on the LoD (Level of Detail) property of subdivision surface. We generate a coarse mesh that covers the limit surface to implement the rough cut. For finish-cut we use ball-end mills and offset cutter contact data to generate cutter location data. In these two steps we use a Z-map model and a collision detection/correction method is presented for the interference-free of these two steps. We implement our methods and present machining results. All of these two kinds of cutter paths are computed rapidly and automatically.

Cutter path strategies in high speed rough milling of hardened steel

Advances in machine tool technology have led to high speed milling for the production of moulds and dies to become more prevalent. Critical aspects of the technology include cutting tools, machinability data, cutter path generation and machine tools. Much published information exists on cutting tools and related data (cutting speeds, feed rates, depths of cut, etc.), however, relatively little information has been published on the evaluation of cutter paths when high speed rough milling hardened steel. The aim objective of the paper is to investigate the feasibility of employing high axial depths of cut (10 mm ⩽ axial depth of cut ⩽ 20 mm) when high speed rough milling hardened AISI H13 steel in order to achieve high volume of metal removed at the expense of low machining time. In conclusion, where long tool life, high volume of metal removed, short machining times and high volumetric removal rates were concerned, raster cutter path strategy was the most favourable at all high axial depths of cut employed.

Design, evaluation and optimisation of cutter path strategies when high speed machining hardened mould and die materials

The use of high speed milling (HSM) for the production of moulds and dies is becoming more widespread. Critical aspects of the technology include cutting tools, machinability data, cutter path generation and technology. Much published information exists on cutting tools and related data (cutting speeds, feed rates, depths of cut, etc.). However, relatively little information has been published on the optimisation of cutter paths for this application. Most of the research work is mainly focused on cutter path generation with the main aim on reducing production time. Work with regards to cutter path evaluation and optimisation on tool wear, tool life, surface integrity and relevant workpiece machinability characteristics are scant. Therefore, a detailed knowledge on the evaluation of cutter path when high speed rough and finish milling is essential in order to improve productivity and surface quality. The paper details techniques used to reduce machining times and improve workpiece surface roughness/accuracy when HSM hardened mould and die materials. Optimisation routines are considered for the roughing and finishing of cavities. The effects of machining parameters notably feed rate adaptation techniques and cutting tools are presented.