Tool Path Computation Research Articles

Integrating Cloud Computing, Bayesian Optimization, and Neural-Additive Modeling for Enhanced CAM Systems in 5-Axis Milling

This publication introduces the development and application of an advanced CAD/CAM/CAE system that leverages the computational capabilities of an edge-cloud infrastructure. The developed system consists of containerized technology models for various complex process planning simulation tasks in 5-axis-milling, such as toolpath calculation, cutter-workpiece-engagement, uncut chip geometry or cutting force simulations. Moreover, a Bayesian optimization (BO) algorithm is coupled with the system enabling multi-objective optimizations of the considered machining operations by varying predefined CAM-parameters. The result of the optimization consists of a set of Pareto-efficient solutions. Each solution realizes a different tradeoff between the technological objectives of the process planner. Since mastering the complexity of the design space is a major challenge in today’s CAM programming workflow, a Neural-Additive Model (NAM) is coupled with the system improving guided search through the configuration/result space. This reduces the convergence time to an optimal CAM parameter set. The coupling of the cloud computing, multi-objective optimization and artificial intelligence method with a CAM-kernel is demonstrated based on the process design of 5-axis milling operations for a blade-integrated disk (blisk).

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.

Studying the influence of the machining process on the geometrical defects of the standardized S-shape test part

In 2020, an S-shape part was proposed as a 5-axis reception test part in the new version of ISO 10791–7:2020. This test part enables the testing of machine-tool behavior that involves a high variation in tool axis orientation. This test part is formed of an S-shape fillet which is machined in flank milling with an endmill of Ø20 mm. Any defects of the machined part are influenced by the accuracy of the CAD model, the CAM tool path computation, the measurement uncertainty of the free-formed surface by a coordinate measurement machine (CMM), and machine-tool geometric behavior. This article aims to quantify the influence of all these steps on the final defects of machined parts. The proposed conclusion to our work is based on analytical and numerical study and experimental analysis. Finally, we propose an identification process for machine-tool architecture geometrical defects pertaining to the measurement of the machined S-shape part.

Determination of cutting forces based on DMG MORI CTX300 ecoline CNC lathe drive power data

Modern machine building needs demand for machines and control systems which provide higher accuracy of machining. For this purpose, setup methods are being researched and accuracy of machines and devices is being improved. The main topic of this paper is a tool path predistortion system which is necessary for improvement of shaft turning accuracy when a steady rest cannot be used on a CNC machines. Calculation of such tool path requires one to know the cutting force during turning on a CNC lathe. The research in question allowed to determine the dependence of cutting force during turning on the power consumed by the feed drive, cutting depth, cutting velocity, and feed value. An equation for further calculation applicable to a specific lathe in the turning process was derived. This equation serves as basis for adaptive turning of shafts and other parts with the aid of a mathematical model, which must account for the cutting force. Application of this formula in a CNC controlled lathe’s parametric program will provide for higher accuracy of turning without special devices.

Parallel implementation of metaheuristics for optimizing tool path computation on CNC machining

The incorporation of technological advances in industry is a must, even for traditional sectors where most companies are SMEs and investments are limited. Technology can be used to increase productivity and the quality of the manufactured product. Drilling is a common procedure in industry. It usually consists of multiple drilling of a flat surface with a tool. Usually the tool is placed on the surface to be drilled at a safe distance and then it makes the drilling in a linear fashion. Optimization of the tool path often involves reducing the movement of the tool to place it over the next point to be drilled, known as airtime. The problem of minimizing airtime for drill paths is highly complex. Most proposals to solve the problem try to adapt it to the formulation of the Traveling Salesman Problem (TSP), in which the objective is to navigate a list of nodes using the minimum global distance. In this paper, the purpose is to provide a solution to the TSP applied to tool path optimization by means of a Discrete version of the Teacher-Learner-Based Optimization (TLBO) algorithm. To improve performance, the algorithm is implemented using a parallel Computer Unified Device Architecture (CUDA) and run on a manycore Graphical Processing Unit (GPU). The results show that the parallel implementation of Discrete TLBO is faster than 9x the sequential implementation.

Real-time exact contour error calculation of NURBS tool path for contour control

The requirement of high-speed and high-precision contouring with NURBS tool path to the CNC machining process is increasing. The calculation of the contouring error (CE) of the NURBS tool path to real time is necessary for the advanced contour control like the cross-coupled controller (CCC). Based on the complexity of the CE calculation of NURBS, most studies use estimating methods to approximate the real CE in the controller. However, when the cutter is at the large curvature zones in the high-speed machining, the difference between the estimated the CE and the real one becomes large. To solve this problem, an algorithm to calculate the exact CE of NURBS tool path to real time is proposed. The calculation model of the CE of NURBS is derived. Also, the numerical calculation algorithm from Brent’s method is given to solve the CE model. Multiple solutions of CE model is discussed and real-time solution tracking method is developed to determine the intervals of the candidate solutions for numerical calculation. Contour error for control (CCE) is proposed for controller design to improve the stability of contour control, which is different from the definition of conventional control error for measurement (MCE). The proposed algorithm is validated for both the simulation and the experiment on the X–Y table. Experimental results show the effectiveness of the proposed algorithm and the actual CE is reduced significantly compared with other methods.

Use of Model-Free and Zero-Setup ComputerGuided Implant Surgical Template for Partial Edentulous Cases

This case report presents the cases of single anterior missing and posterior free-end edentulous ridge with computer-guided implant placement on the day of visit through a special tray containing fiducial markers without model scan or intraoral scan data. Cone beam CT was taken after fixing the marker embedded ready-made tray with a photopolymerized resin material by light-curing in the patient's mouth. The implant location was planned on the registered CT data in the planning software. The tool path calculation for the milling machine was conducted in the computer-aided manufacture (CAM) software. The guide was completed by milling the drill hole in the special tray as designed. Although the preparation for the conventional implant guide surgery takes considerable time, including data acquisition and 3D printing, it was possible to produce a guide on the day of the patient visit without a separate procedure other than a CT scan through this protocol. Also, the transfer of the implant surgery plan, the process of scanning and 3D printing, was omitted, thereby reducing the positional error between the CT data and the actual guide.

СПЕЦИАЛЬНАЯ СТРАТЕГИЯ ОБРАБОТКИ СЛОЖНОПРОФИЛЬНЫХ КОНИЧЕСКИХ ВИНТОВЫХ ПОВЕРХНОСТЕЙ РАБОЧИХ ОРГАНОВ ОДНОВИНТОВЫХ КОМПРЕССОРОВ

The article deals with the problems arising during the shaping of complex profile tapered helical surfaces. These surfaces form the geometry of the working bodies of single-screw miniature compressors, which have great prospects for use in mobile miniature compressor plants, which is especially important for medical and space technology, robotics, oil and gas and mining industries. Due to the fact that the capabilities of existing CAD systems do not allow obtaining three-dimensional models of these surfaces, the problem of preparing a control program for a CNC machine arises, since the calculation of the tool path in CAM systems when processing complex surfaces is impossible without a three-dimensional surface model. To solve the problem, an automated programming system was developed that implements a formalized toolpath calculation in accordance with the proposed special processing strategy for conical helical surfaces. As the initial data for calculating the toolpath, the system needs information about the tool geometry and the helical surface in a parametric form, which makes it possible to abandon the construction of a three-dimensional surface model. The results of processing prototypes for the proposed strategy are given.

Region based five-axis tool path generation for freeform surface machining via image representation

Abstract This paper inaugurates a brand new five-axis tool path generation method for freeform surface machining, which is solely based on digital image processing. By utilizing image representation, a freeform surface can be digitized into a uniform grayscale image. With this novel representation, we come up with a region based five-axis tool path scheme with remarkably enhanced utility towards freeform surface machining process. The image representation possesses sufficient geometric data for us to evaluate the surface normal distribution and split the surface area accordingly via image processing algorithms. Since each partitioned region contains a limited surface inclination range, one rotary axis is locked with a certain angle during the processing of this region. In addition, by further exploiting the potential of the image representation, the cutter contact (CC) curves are extracted purely from the image of each partitioned region. Preliminary results show that this method is more than adequate for the tool path computation. The computed tool path outperforms the benchmarks by reducing the machining time for as much as 40%, as verified in the physical cutting test.

A High-Efficiency Impeller Channel Quasi-Triangular Tool Path Planning Method Based on Template Trajectory Mapping

The manufacturing technology of an integral impeller is an important indicator for measuring the manufacturing capability of a country. Its manufacturing process involves complex free-form surface machining, a time consuming and error-prone process, and the tool path planning is considered as a critical issue of free-form surface machining but still lacks a systematic solution. In this paper, aiming at the tool path planning of the impeller channel, a quasi-triangular tool path planning method based on parametric domain template trajectory mapping is proposed. The main idea is to map the template trajectory to physical domain by using the mapping model of parametric domain to the physical domain to obtain the actual machining path. Firstly, the trajectory mapping model of parametric domain to physical domain is established using the morphing technique, and the template trajectory mapping method in the parametric domain is given. Secondly, the clean-up boundary of the impeller channel is determined in the parametric domain, and the quasi-triangular template trajectory of the impeller channel is defined. Finally, taking a certain type of impeller as an example, the quasi-triangular tool path of the impeller channel is calculated, and the tool path calculation time of this method is compared with that of the traditional isometric offset method. The result shows that the computational efficiency is improved by 45% with this method, which provides a new method for the rapid acquisition of NC machining tool path for impeller channels. In addition, the simulation and actual machining are carried out, the results show that the shape of actual cutting traces on the surface of the impeller channel is quasi-triangular, showing that this method is effective and feasible.

CMM Path Planning, Position and Orientation Optimization Using a Hybrid Algorithm

In the present paper a Hybrid Optimization Method is applied in order to determine the optimal placement of a workpiece on a coordinate measuring machine (CMM) as well as the optimal movements of the CMM probe, aiming to reduce the measurement time. Further to the review of the toolpath computation and optimization methods, the framework of the optimization problem is defined. A modeling methodology for the problem is proposed and a solving method is presented. The proposed methodology is a combination of a genetic algorithm, a quasi-Newton algorithm and a constraints-handling method. The final outcome is the determination of the best positioning location of the object as well as the best probe positioning location for the scanning. The evaluation is done comparing two methods; the first one uses a genetic algorithm while the second combines a genetic algorithm with a hill climbing method.

Optimal iso-planar cutting direction based on machine kinematic metric: A differential geometry method for freeform surface finishing tool path computation

ABSTRACTWhile machining width is an important factor of the machining time of freeform surface finishing operations, in reality the kinematic capability of the machine tool is usually the bottleneck of achieving higher feed speed and optimal machining time. The purpose of this paper is to conveniently (and approximately) determine the optimal cut direction considering the speed kinematic capability of the machine tool, without having to compute the actual tool path. We propose a mathematical instrument, called Machine Kinematic Metric (MKM), to easily evaluate infinitesimal machining time on a freeform surface based on machine kinematic consideration. It's a tensor field similar to the metric tensor in differential geometry. MKM is integrated over the part surface to approximate the cut-direction-dependent total machining time, and used to determine the optimal cut direction that minimizes the machining time. To validate the accuracy of the prediction using MKM, we apply the method and compute the machini...

Tool path generation algorithm based on covariant field theory and cost functional optimization and its applications in blade machining

In order to improve the quality of the tool path, different machining requirements have to be considered in the tool path generation process. The traditional tool path generation methods only consider one or a few requirements and ignore the others due to the lack of comprehensive mathematic framework. Tool path generated in this way normally is not fully optimized since different requirements could compete or even conflict with each other. Targeting at this issue, this paper presents a unified mathematic framework based on field theory to generate tool path for both planar and freeform surface, where the three most important factors in NC machining, i.e., the smoothness, evenness, and machining efficiency of tool path can be considered. In the proposed framework, a field-based cost functional and a gradient-field-based inequality constraint functional is established, so as to convert the multi-objective tool path computation into a functional minimization problem with inequality constraints. Then, a finite element method (FEM)-based numerical method is proposed to solve the multi-variable nonlinear optimization problem. After that, two smooth tool path generation methods are proposed with taking the step-over as constraint. To further improve the machining efficiency, this paper also provides a hybrid method that combines zigzag and spiral pattern tool path. Experiments on blade machining and simulation show that the proposed method can produce smooth tool paths, while the machining efficiency can be improved at the same time. In addition to the above advantages, the proposed mathematical framework is extensible by incorporating different machining requirements into it, making it possible to generate tool path when multi-objective is considered.

An efficient 5-axis toolpath optimization algorithm for machining parts with abrupt curvature

The kinematical behavior of 5-axis machine tool introduced by toolpath calculation has a close relation with processing efficiency and quality of parts. For the category of sculptured surface parts with abrupt curvature, such as turbine blade and fixed guide vane, the most commonly utilized spiral contouring toolpath modes usually encounter some trouble during actual machining, the reason lies in the difficult tool orientation control near the edge of such parts. However, the global optimization for the spiral toolpath means increased computation burden, and so it is time consuming. In this paper, an efficient 5-axis toolpath optimization algorithm is presented, and the objective is to smooth the rotary axes’ motion caused by drastically changed tool orientation on spiral toolpath for abrupt curvature parts machining. To reduce the computation burden, only path segments on the spiral trajectory-owned weak kinematic performance are selected for further optimizing. To obtain smoother motion for rotary axes, the specific optimization computation for the selected path segments is conducted in the Machine Coordinate System (MCS) instead of the Part Coordinate System (PCS). The optimization model is constructed and a related solution method is presented to ensure the high-performance optimization. The complete optimization algorithm is demonstrated on a spiral 5-axis toolpath for the turbine blade finish machining, and the result shows that only 25.9% optimization computation is needed compared with global optimization algorithm. And then, the actual machining experiments are carried out by using paraffin as cut material, and the machining time with optimized toolpath is decreased by 19.7% compared with initial toolpath. In addition, the surface quality of parts is significantly improved after conducting the optimization. This study proves that the proposed algorithm can significantly improve the processing efficiency and surface quality of parts with abrupt curvature and provides an efficient method to optimize the spiral 5-axis toolpath used for finish machining parts with abrupt curvature.

A tool path generation method for freeform surface machining by introducing the tensor property of machining strip width

Due to the complexity of geometry, the feed direction with maximal machining strip width usually varies among different regions over a freeform surface or a shell of surfaces. However, in most traditional tool path generation methods, the surface is treated as one machining region thus only local optimisation might be achieved. This paper presents a new region-based tool path generation method. To achieve the full effect of the optimal feed direction, a surface is divided into several sub-surface regions before tool path computation. Different from the scalar field representation of the machining strip width, a rank-two tensor field is derived to evaluate the machining strip width using ball end mill. The continuous tensor field is able to represent the machining strip widths in all feed directions at each cutter contact point, except at the boundaries between sub-regions. Critical points where the tensor field is discontinuous are defined and classified. By applying critical points in the freeform surface as the start for constructing inside boundaries, the surface could be accurately divided to such that each region contain continuous distribution of feed directions with maximal machining strip width. As a result, tool paths are generated in each sub-surface separately to achieve better machining efficiency. The proposed method was tested using two freeform surfaces and the comparison to several leading existing tool path generation methods is also provided.

Novel Incremental Sheet Forming System with Tool-Path Calculation Approach

Incremental Sheet Forming (ISF) is a prosperous forming technique since the end of the 20 th Century. Research projects are still active in this topic with the goal to understand more deeply this flexible process and to reach the full industrialisation of it. These investigations are mainly focusing on the one-side version of ISF, however only the two side variants of this process could reach the ultimate flexibility. This paper gives an overview of the recent results and inventions in the field of ISF processes. A new solution of the Two-Sided ISF processes realisation is given. A new approach to the tool-path calculation is outlined which is based on a recently patented system of the authors.

Mathematical Model and Tool Path Calculation for Helical Groove Whirling

The helical groove shape plays a key role in ensuring the adequate flute space of many screw components. In many situations, the helical groove is machined through profiled grooving cutter, which brings a huge cost. This study establishes the mathematical model of helical groove based on cross-section and presents an approach to calculate tool path using the whirling process which machines helical groove through enwrapping movements with standard cutters. Finally, a case study and the error analysis are provided to illustrate the validity of the developed models and algorithms, which offers an alternative method for further computer aided manufacturing.

Mathematical model and algorithm of toolpath optimisation on aircraft structural parts

An intelligent toolpath (processing sequence) planning for fabricating aircraft structural parts is developed to obtain a minimum-length toolpath while maintaining the required machining time. The problem is first solved in the following ways. Firstly, an abstraction of the machining process is proposed to pick up the feed/retract points of each feature to be machined as the toolpath calculation basis. Secondly, the chaotic simulated annealing method is improved through storing the optimal solution, adding the control condition and selecting each parameter reasonably during the iteration of the algorithm so as to enhance its performance. What’s more, three solution-generating methods are used chaotically to obtain a better result. Lastly, the verification is conducted on four different aircraft structural parts, and the results prove that the proposed algorithm performs very well in terms of toolpath quality and computation time.

Advanced CNC Programming Methods for Multi-Axis Precision Machining

This paper presents a method to simultaneously increase the accuracy and decrease the calculation time for complex tool path programming in multi-axis machining centers. Examples of complex parts requiring such complex tool paths include various kinds of turbine blades, pump-forcing augers, teeth surfaces, etc. It explains the creation of topological structures on the basis of analytical spline curves with floating range definitions. The method for tool path calculation accommodates the specific requirements for multi-axis milling. The algorithms developed are the foundation for the CAD/CAM software that allows for NC programming and machining on 5-axis centers employing any design model. Industrial tests reveal a 70-80% reduction of NC programming time of parts with complex surfaces, reduced machining time of approximately 40-50% using basic high-speed cutting methods and custom-made tools. The advanced methods of NC programming result in substantially increasing machining accuracy.

Global obstacle avoidance and minimum workpiece setups in five-axis machining

The state-of-the-art tool path computation algorithms for five-axis machining consider only the workpiece and clamping device for collision avoidance. However, in a real five-axis machining process, there are many other types of obstacles beyond workpiece and clamps that the tool assembly must avoid, e.g., sensors and other intrusive devices. In such cases, the only solution at present is by means of computer simulation of the machining process after the tool path has been computed. If collision is found, it requires re-computing the tool path and/or changing the setup of the workpiece. This process is then re-iterated until all the collisions are resolved. As a result, the process is time consuming and requires excessive human intervention. In this paper, we present rigorous analyses of the obstacles in five-axis machining and propose efficient numerical algorithms for calculating and representing them. Using our results, the obstacle-free tool orientations can be determined completely at the tool path planning stage, rather than relying on the simulation afterward. In addition, as a direct application of our mathematical modeling, we present a heuristic-based solution to the optimal workpiece setups problem: finding a minimum number of workpiece setups for an arbitrary sculpture part surface so that it can be machined completely on a given five-axis machine without colliding with the obstacles. We use orthogonal table–table five-axis machines as an example and work out a numerical experiment using the proposed solution.