Cutter Location Research Articles

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.

CLS Data Interpolation along Spline Curves and Post Processing for FANUC Industrial Robots

In this paper, an interpolation method along spline curves is proposed to smooth cutter location source data called CLS data. 3rd-order and 5th-order spline curves are easily implemented for interpolation. Then, a post processor is designed for an industrial robot FANUC R2000iC to produce FANUC robotic program called LS format from CLS data including linear- and circular arc-interpolated entities. The post processor works as a straightforward and cooperative interface between CAD/CAM systems and the industrial robot, so that a desirable teaching-less operation environment is realized. The validity and usefulness of the proposed methods are evaluated through simulations on FANUC RoboGuide and an actual machining experiment with the robot.

Iso-scallop tool path building algorithm “based on tool performance metric” for generalized cutter and arbitrary milling zones in 3-axis CNC milling of free-form triangular meshed surfaces

In order to generate a tool path, scallop height should be under the given precision requirement and the tool path should be as short as possible. Iso-scallop tool path generation method is traditionally used to generate the effective tool path. This paper discussed a new method to generate a iso-scallop and contour-parallel tool path for a generalized cutter and an arbitrary area on free-form surface in 3-axis CNC milling. The milling surface, originally represented as a triangular mesh, and the generalized cutter surface are converted into voxel-based depth maps. Milling zone map with the same resolution as the part depth map is used to define an arbitrary milling area. First, the points on the boundary of milling area are marked in order to build the tool path that can follow a boundary line. Second, different cutter location positions are tried in order to satisfy two conditions: milling the material from the selected boundary points within the tolerance limit and having the maximum material removal rate on the way from the previous cutter location point. The algorithm is repeated until the whole area to mill is finished. Due to the high demand of computational power, graphics processing unit is employed for the most time consuming operations.

Stability Prediction and Step Optimization of Trochoidal Milling

When machining narrow grooves, corners, and other complex cavities with trochoidal milling, the irrationally large trochoidal step usually leads to chatter, while the conservative trochoidal step constrains the machining efficiency. In this paper, a stability prediction model of trochoidal milling is established to solve these problems. An approach considering trochoidal steps and spindle speeds is presented to predict stability boundary of trochoidal milling. With considering the varying cutter-workpiece engagements, the stability of trochoidal milling process is predicted by obtaining the stability lobes of different cutter location (CL) points along the trochoidal milling tool paths. Based on the proposed stability model, a trochoidal step optimization strategy is developed to improve the machining efficiency of trochoidal milling under other parameters in a given situation. Cutting experiments are performed on the machining center GMC 1600H/2 to show the effectiveness of the proposed trochoidal milling stability model. Finally, simulations are adopted to illustrate the optimization strategy.

Preprocessor with spline interpolation for converting stereolithography into cutter location source data

The authors have developed earlier an industrial machining robotic system for foamed polystyrene materials. The developed robotic CAM system provided a simple and effective interface without the need to use any robot language between operators and the machining robot. In this paper, a preprocessor for generating Cutter Location Source data (CLS data) from Stereolithography (STL data) is first proposed for robotic machining. The preprocessor enables to control the machining robot directly using STL data without using any commercially provided CAM system. The STL deals with a triangular representation for a curved surface geometry. The preprocessor allows machining robots to be controlled through a zigzag or spiral path directly calculated from STL data. Then, a smart spline interpolation method is proposed and implemented for smoothing coarse CLS data. The effectiveness and potential of the developed approaches are demonstrated through experiments on actual machining and interpolation.

Cutter location path generation through an improved algorithm for machining triangular mesh

Direct mesh machining has been an effective technique in rapid manufacturing. Currently, the cutter location path generation is an effective method for the direct mesh machining. However, this method may cause surface defects, such as the overcut-slot, the transit-pit, and the facet defects. Therefore, the application of this method is limited for the machining accuracy issue.From the comprehensive analysis of cutter location path generation and the inspection of the machined parts by the mesh offset intersection (MOI) algorithm, the tessellation error of the offset mesh is the main factor causing the machining surface defects. To solve the problem, we propose an improved MOI algorithm to reduce the influence of tessellation error. Compared with the original surface, only the mesh vertices are considered as the points without tessellation error to the original surface. Therefore, we revise the algorithm through calculating the cutter location points only from the vertices and smoothing the tool-path in two perpendicular directions. This improved algorithm includes two sub-algorithms: a vertex-based cutter location point calculation sub-algorithm and a bi-directional spline interpolation sub-algorithm. To validate the effectiveness of the improved algorithm, the machining accuracy is investigated and verified through several testing parts. The experimental results show that the improved MOI algorithm can effectively improve the machining accuracy and avoid surface defects on the work-piece surfaces.

A Novel Tool Path Generation Method Based on the Theory of Digital Copy

In the porcelain denture manufacturing, obtaining the cutter location data is the primary step that drive NC machine to grind denture. Referring the method of copying manufacturing, this article introduced a novel cutter location data acquisition method. According to the method, used same shape probe with the grinding bur to scan a temporary mental denture along planned grinding tool path, then recorded the scanning data, namely the cutter location point following grinding porcelain denture. This article gave an experiment finally, scanned a metal molar and ground a porcelain block using the scanning data, and then obtained a perfect porcelain molar.

Uncertainty quantification for cuttings transport process monitoring while drilling by ensemble Kalman filtering

The aim in this work was to develop a method to draw our conclusions for the uncertain quantities of interest in a real problem in oilfield, namely the cuttings transport problem, given the limited data available. The cuttings transport process is subject to disturbances and is influenced by various factors in a stochastic and uncertain manner. In addition, the drilling environment is very complex to understand fully, and to model efficiently and accurately. An experiment was conducted to monitor the process in real-time via time-series measurements of distributed pressure transducers along the drillstring. A mathematical model describing the dynamic process of cuttings transport is developed, which aims to capture the dominant characteristics of the process, without attempting to model reality perfectly; modeling and measurement errors are represented by uncertainties in model inputs, parameters, and states. The proposed model is described in detail, and is incorporated in the Bayesian framework (via ensemble Kalman filtering) to make our best estimate about the location and amount of cuttings transported along the wellbore in real time, given the available data. The estimations of the uncertain process parameters are described.

Cutting force and machine kinematics constrained cutter location planning for five-axis flank milling of ruled surfaces

Abstract Five-axis flank milling has been commonly used in the manufacturing of complex workpieces because of its greater productivity than that of three-axis or five-axis end milling. The advantage of this milling operation largely depends on effective cutter location planning. The finished surface sometimes suffers from large geometrical errors induced by improper tool positioning, due to the non-developability of most ruled surfaces in industrial applications. In addition, a slender flank-milling cutter may be deflected when subjected to large cutting forces during the machining process, further degrading the surface quality or even breaking the cutter. This paper proposes a novel tool path planning scheme to address those problems. A simple but effective algorithm is developed to adaptively allocate a series of cutter locations over the design surface with each one being confined within an angular rotation range. The allocation result satisfies a given constraint of geometrical errors on the finished surface, which consists of the tool positioning errors at each cutter location and the sweeping errors between consecutive ones. In addition, a feed rate scheduling algorithm is proposed to maximize the machining efficiency subject to the cutting force constraint and the kinematical constraints of a specific machine configuration. Simulation and experimental tests are conducted to validate the effectiveness of the proposed algorithms. Both the machining efficiency and finish surface quality are greatly improved compared with conventional cutter locations. Highlights Tool position is bounded with respect to the geometrical machining error. Cutting force and kinematics during five-axis flank milling process are analyzed. An incremental adaptive flank milling tool path generation algorithm is proposed. Feed rate is smoothly assigned respecting cutting force and kinematic constraints.

A New Method of Designing the Tooth Surfaces of Spiral Bevel Gears With Ruled Surface for Their Accurate Five-Axis Flank Milling

The advantages of the five-axis flank milling of (developable) ruled surfaces include that (1) the machined surfaces could be very accurate and smooth and (2) the machining efficiency is high. Currently, spiral bevel gears are machined on the machine tools specially used for gear manufacturing. The disadvantages are that the cost is high for small batch, prototype, or repair. If a small group of spiral bevel gears are needed, the current methods are not valid. Thus, it is expected to machine the gears on five-axis computer numerical control (CNC) milling centers. Unfortunately, when tooth surfaces are designed based on the conventional gear manufacturing methods, they cannot be accurately machined in five-axis flank milling. This work is to develop the new technique for the five-axis flank milling of spiral bevel gears. First, a new method of designing the tooth surface of spiral bevel gears with ruled surface is proposed. Second, the cutter locations and orientations are calculated for five-axis flank milling the tooth surfaces. Third, the actual tooth surfaces are accurately represented with the cutter envelope surface in five-axis flank milling. It is confirmed that the difference of the actual tooth surface and the designed tooth surface is within the tolerance. Then, a pinion is generated to mesh with the gear, and the tooth contact analysis (TCA) is conducted. The good result demonstrates that the proposed method is valid, thus it can be used in industry.

Automatic generalized cutter selection for finishing of free-form surfaces in 3-axis CNC milling by “surface tolerance and tool performance metrics”

Tool selection in milling operation is an important step that dramatically influence the milling time. This paper discusses a new method to select the best cutter for different zones of a free-form surface from the list of available generalized cutters. A digital, voxel-based model is used to represent the workpiece and the available tools. First, the finishing performance is calculated for every tool and for every cutter location point. Second, the tool with maximum performance is selected for every point of the workpiece surface, and the whole milling surface is divided into zones with assigned optimal tool for every zone. Due to the high demand of computation power, a graphic processing unit is employed for the most consuming operations.

Machining error reduction by combining of feed-speed optimization and toolpath modification in high-speed machining for parts with rapidly varied geometric features

Parts with rapidly varied geometric features are usually crucial parts in high-end equipment and widely applied in the fields of aerospace, energy and power, which are difficult or inefficient to process because of the more special structure and the higher requirement of machining precision. High-speed machining technology provides an effective method for parts with rapidly varied geometric features to solve the contradiction between high demand and low machining efficiency. However, as the existence of rapidly varied geometric features, the machining toolpath for such parts is always complex free-form curve and the actual moving speed of the workbench of the NC machine tool cannot reach the feed-speed set in the NC program timely due to the drive constraint of NC machine tool. Furthermore, the machine tool would vibrate violently when machining the rapidly varied geometric features. In this way, the big machining error will be formed. A machining error reduction method by combining of feed-speed optimization and toolpath modification in high-speed machining for such parts is proposed. First, considering that the actual feed-speed cannot reach the programmed value when the toolpath curvature is too large, the feed-speed is optimized with the constraints of jerk and acceleration limitations of the feed shafts, and a feed-rate smoothing algorithm is applied. Then, the compensated cutter locations are calculated via machining-error estimation. Finally, the modified NC codes are acquired according to the optimized feed-speed and the compensated toolpath. By combining the feed-speed optimization and toolpath modification, the high precision and high efficiency machining can be realized. The experimental results demonstrate the feasibility of the proposed approach. This study provides an effective approach to reduce the machining error in high-speed machining, and is significant for improving the processing precision and efficiency of parts with rapidly varied geometric features.

Kirigami actuators.

Thin elastic sheets bend easily and, if they are patterned with cuts, can deform in sophisticated ways. Here we show that carefully tuning the location and arrangement of cuts within thin sheets enables the design of mechanical actuators that scale down to atomically-thin 2D materials. We first show that by understanding the mechanics of a single non-propagating crack in a sheet, we can generate four fundamental forms of linear actuation: roll, pitch, yaw, and lift. Our analytical model shows that these deformations are only weakly dependent on thickness, which we confirm with experiments on centimeter-scale objects and molecular dynamics simulations of graphene and MoS2 nanoscale sheets. We show how the interactions between non-propagating cracks can enable either lift or rotation, and we use a combination of experiments, theory, continuum computational analysis, and molecular dynamics simulations to provide mechanistic insights into the geometric and topological design of kirigami actuators.

Cutting and Shuffling of a Line Segment: Effect of Variation in Cut Location

We present a computational study of the impact of variation in cut location on finite-time mixing of a line segment by cutting and shuffling, which is a one-dimensional piecewise isometry (PWI), also known as an interval exchange transformation (IET). A line segment of unit length is repeatedly cut into subsegments and shuffled according to any one of a variety of permutations. To mimic practical process error, variations drawn from a normal distribution are used to perturb cut locations. Illustrative examples of the mixing behaviors and finite-time measures of mixing are used to analyze the effect of variation in cut location for different permutations of subsegment mixing order. Mixing is significantly improved under irreducible nonrotational permutations when the dynamics show a resonance-like structure without variation. Specifically, the requirement of an irrational subsegment length ratio for good mixing can be relaxed as the underlying periodic dynamics is perturbed by the stochastic variation in cut location. Thus, good mixing can occur even with only four subsegments of roughly the same length for most irreducible nonrotational permutations.

An innovative approach to NC programming for accurate five-axis flank milling of spiral bevel or hypoid gears

To transfer power, a pair of spiral bevel or hypoid gears engages. From beginning to end of two tooth surfaces engaging with each other: for their rigid property, they contact at different points; and for their plastic property, they contact at small ellipses around the points. On each surface, the contact line (or called as contact path) by connecting these points and the contact area by joining these ellipses are critical to driving performance. Therefore, to machine these surfaces, it is important to machine the contact line and area with higher accuracy than other areas. Five-axis flank milling is efficient and is widely used in industry. However, tool paths for flank milling the gears, which are generated with the existing methods, can cause overcuts on the contact area with large machining errors. To overcome this problem, an innovative approach to NC programming for accurate and efficient five-axis flank milling of spiral bevel or hypoid gears is proposed. First, the necessary conditions of the cutter envelope surface tangent with the designed surface along a designed line are derived to address the overcut problem of five-axis milling. Second, the tooth surface including the contact line and area are represented using their machining and meshing models. Third, according to the tooth surface model, an optimization method based on the necessary conditions is proposed to plan the cutter location and orientation for flank milling the tooth surface. By using these planned tool paths, the overcut problem is eliminated and the machining errors of contact area are reduced. The proposed approach can significantly promote flank milling in the gear manufacturing industry.

Trace generation of friction stir welding robot for space weld joint on large thin-walled parts

Purpose The weld joint of large thin-wall metal parts which deforms in manufacturing and clamping processes is very difficult to manufacture for its shape is different from the initial model; thus, the space normals of the part surface are uncertain. Design/methodology/approach In this paper, an effective method is presented to calculate cutter location points and to estimate the space normals by measuring some sparse discrete points of weld joint. First, a contact-type probe fixed in the end of friction stir welding (FSW) robot is used to measure a series of discrete points on the weld joint. Then, a space curve can be got by fitting the series of points with a quintic spline. Second, a least square plane (LSP) of the measured points is obtained by the least square method. Then, normal vectors of the plane curve, which is the projection of the space curve on the LSP, are used to estimate the space normals of the weld joint curve. After path planning, a post-processing method combing with FSW craft is elaborated. Findings Simulation and real experiment demonstrate that the proposed strategy, which obtains cutter locations of welding and normals without measuring the entire surface, is feasible and effective for the FSW of large thin-walled complex surface parts. Originality/value This paper presents a novel method which makes it possible to accurately weld the large thin-wall complex surface part by the FSW robot. The proposed method might be applied to any multi-axes FSW robot similar to the robot studied in this paper.

A virus-evolutionary multi-objective intelligent tool path optimization methodology for 5-axis sculptured surface CNC machining

Sculptured surface machining is a material removal operation essentially adopted to manufacture complex products. Computing optimal tool paths with reference to ideally designed CAD models is indispensable to be able to suggest machining improvements in terms of high quality and productivity. The present paper proposes a new methodology based on a virus-evolutionary genetic algorithm for enhancing sculptured surface tool path planning through an automated selection of values for standard 5-axis end milling strategies' machining parameters to be decided upon in the context of a simulation-based; software-integrated, multi-objective optimization problem. The problem involves surface machining error as the first quality objective represented via the mean value of chordal deviations that tool path interpolation yields and effective radius of inclined tools that affects scallop. Machining time is the second quality objective entering the problem to assess productivity; whereas the number of cutter location points created for each tool path evaluation is also considered. Tool type, tool axis inclination angles as well as longitudinal and transversal steps are considered as the independent parameters in the case of 5-axis machining. Results obtained by conducting evaluation experiments and simulation tests accompanied by an actual machining process provided significant insight concerning the methodology's efficiency and ability of suggesting practically viable results.

A Hybrid Wavelet Based–Approach and Genetic Algorithm to Detect Damage in Beam-Like Structures without Baseline Data

This paper proposes an optimized damage identification method in beam-like structures using genetic algorithm (GA) without baseline data. For this purpose, a vibration-based damage identification algorithm using a damage indicator called ‘Relative Wavelet Packet Entropy’ (RWPE) was implemented to determine the location and extent of damage. The procedure does not require vibration signals from an undamaged structure because the method of comparing signals from different locations in the existing state was found to be effective. To ameliorate the algorithm, GA was utilized to identify the best choice for “mother wavelet function” and “decomposition level” of the signals by means of the fundamental fitness function to optimize the algorithm. This resulted in the high accuracy of the damage identification algorithm. In addition, this method has eliminated the difficulties in selecting the type of mother wavelet function for damage identification purposes. To investigate the robustness and accuracy of the proposed method, numerical examples and experimental cases with different damage depths were considered and conducted. The results demonstrated that the proposed method has great potential in the identification of damage location and depth of cut in beam-like structures since it does not require the recorded data from an undamaged beam as a baseline for damage detection. Moreover, the relationship between damage location and depth of damage has been evaluated and results showed that the algorithm can be applied to actual structures.

Improving machined surface texture in avoiding five-axis singularity with the acceptable-texture orientation region concept

The singular phenomenon is common in five-axis machining process. Most of the existing methods try to solve the problem by deforming the tool orientations or inserting extra cutter locations after the tool path is generated, with the drawbacks that (1) the machining geometry errors are not respected and (2) irregular machined surface textures might be caused. This paper dedicates to improve the machined surface textures in the scenario of avoiding the five-axis singularities. In this paper, the acceptable-texture orientation region (ATOR) concept is proposed. If the tool orientation is picked inside the ATOR, the resulted surface texture is considered to be acceptable. Based on this concept, the tool orientations are optimized locally. For a given tool path, if the orientation curve crosses the singular circle, it is locally modified out of the circle with a bridge point locating schema and a cubic B-spline interpolation technique. Eventually, the obtained new orientation curve goes around the singular circle like a rubber band to avoid the singular problem and remains unmodified to achieve the best machined surface qualities for the rest pieces. As the process is implemented at the tool path planning stage, the machining geometry errors can also be respected.

Post-processor development of a five-axis machine tool with optimization tool radius compensation

The post-processor is an important interface that transforms cutter location data into numerical control (NC) data. The data compensation in a five-axis machine is quite complex, because of a variety of the machine centers and the computerized numerical control (CNC) system. Since most work on the five-axis post-processor method has dealt primarily with the generation of NC code, this study breaks with tradition and introduces a post-processor with optimization tool radius compensation and a general machine configuration. Furthermore, a practical method for optimizing the NC code is presented that is based on further study of tool compensation and tool wear. The proposed post-processor is validated for various five-axis machine centers using a generalized kinematic model and various cutting tool models. The results of the verification tests showed that proposed post-processor approach can be used to accurately convert the cutter location into NC codes, and the optimized NC code generated by the optimization tool radius compensation method demonstrates the practical value of the proposed approach for improving processing quality and reducing the total machining time and cost.