Kinematical performance prediction in multi-axis machining for process planning optimization (original) (raw)
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Kinematic performances in 5-axis machining
This article presents a predictive model of the kinematical behaviour during 5-axis machining. This model highlights differences between the programmed tool-path and the actual follow-up of the trajectory. Within the High Speed Machining context, kinematical limits of the couple CNC-machine-tool have to be taken into account in the model. The originality of the model is the use of the inverse-time method to coordinate machine-tool axes, whatever their nature (translation or rotation). The model reconstructs the actual relative velocity tool-surface from each axis velocity profile highlighting trajectory portions for which cutting conditions are not respected.
Kinematical performances in 5-axis machining
This article presents a predictive model of the kinematical behaviour during 5-axis machining. This model highlights differences between the programmed tool-path and the actual follow-up of the trajectory. Within the High Speed Machining context, kinematical limits of the couple CNC-machine-tool have to be taken into account in the model. The originality of the model is the use of the inverse-time method to coordinate machine-tool axes, whatever their nature (translation or rotation). The model reconstructs the actual relative velocity tool-surface from each axis velocity profile highlighting trajectory portions for which cutting conditions are not respected.
5-axis High Speed Milling Optimisation
Manufacturing of free form parts relies on the calculation of a tool path based on a CAD model, on a machining strategy and on a given numerically controlled machine tool. In order to reach the best possible performances, it is necessary to take into account a maximum of constraints during tool path calculation. For this purpose, we have developed a surface representation of the tool paths to manage 5-axis High Speed Milling, which is the most complicated case. This model allows integrating early in the step of tool path computation the machine tool geometrical constraints (axis ranges, part holder orientation), kinematical constraints (speed and acceleration on the axes, singularities) as well as gouging issues between the tool and the part. The aim of the paper is to optimize the step of 5-axis HSM tool path calculation with a bi-parameter surface representation of the tool path. We propose an example of integration of the digital process for tool path computation, ensuring the required quality and maximum productivity.
Free-form surfaces are used for many industrial applications from aeronautical parts, to molds or biomedical implants. In the common machining process, CAM software generates approximated tool paths because of the limitation induced by the input tool path format of the industrial CNC. Then, during the tool path interpolation, marks on finished surfaces can appear induced by non smooth feedrate planning. Managing the geometry of the tool path as well as the kinematical parameters of the machine tool are two key factors for quality and productivity improvements. The aim of this paper is to present a unified method to compute the trajectory directly on the surface to be machined avoiding CAM approximations and producing a smoother trajectory. This paper proposes an interpolation of the trajectory based on the free form surface mathematical model while considering the kinematical limitations of a high speed milling machine (velocity, acceleration and jerk). The amelioration of the data exchange between CAD/CAM and CNC opens new ways to optimize the manufacturing process. The Direct Trajectory Interpolation on the Surface (DTIS) method allows to obtain both a higher productivity and a better surface quality. Machining experiments carried out with an Open CNC on a 5-axis high speed milling machine show the benefits of the proposed method compared to the classical strategies available with an industrial CNC.
Model for performance prediction in multi-axis machining
This paper deals with a predictive model of kinematical performances in 5- axis milling within the context of HSM. Capacities of each axis as well as some NC unit functions can be expressed as limiting constraints. The proposed model relies on each axis’ displacement in the joint space of the machine-tool and predicts the most limiting axis for each trajectory segment. Thus, the calculation of the relative feed rate tool- surface can be performed highlighting zones for which the programmed feed rate is not reached and so, it constitutes an indicator for trajectory optimization. The efficiency of the model is illustrated through an example.
Optimization of 5-axis high-speed machining using a surface based approach
Computer-Aided Design, 2008
This paper deals with optimization of 5-axis trajectories in the context of high-speed machining. The objective is to generate tool paths suited to high speed follow-up during machining in order to respect cutting conditions, while ensuring the geometrical conformity of the machined part. For this purpose, the optimization of the tool axis orientations is performed using a surface model for the tool path, which allows integrating kinematical limits of the machine tool as well as classical geometrical constraints. The illustration of the optimization through an example highlights the gain in machining time, thereby demonstrating the feasibility of such an approach.
Tool path generation, simluation and optimization of a five-axis milling machine
2004 IEEE Region 10 Conference TENCON 2004., 2004
This paper presents the algorithms to generate and simulate non-linear tool path of the five-axis milling machine. The simulator is based on rD representation and employs an inverse kinematics approach to derive the corresponding rotational and translation movement of the mechanism. The simulator makes it possible to analyze an accuracy of a 3D tool path based on a prescribed set of the cutter location (CL) points as well as a set of the cutter contact (CC) points and the tool inclination angle. The resulting trajectory of the tool path is not unique and depends on the initial set up of the machine which in turn is problem dependent. Furthermore, the simulator can be used to simulate the milling process, verif, the final cut and estimate the errors of the actual tool path before the real workpiece is actually cut with the real machine. Thus, it reduces the cost of iterative trial and error. Tool path generation and simulation is verified by a series of cutting experiments performed by means of the proposed software and the accuracy of milling is estimated. It has been shown that the proposed graphical 3D software presents an efficient interactive approach to the modification of a tool path based on an appropriate set of transformations as well as verification of the tool path optimization algorithms. The result of the simulation has been tested using the Maho600E S-Axis Milling Machine at Computer Integrated Manufacturing Laboratory at the Asian Institute of Technology.
Kinematic Behaviour Modeling of the Axes of a Machining Center in High Speed Milling
Advanced Materials Research, 2013
In the context of high speed milling ''HSM'', the feed rate does not always reach the programmed value during the machining process which implies an increase of machining time and non compliance with the programmed feed rate. This phenomenon leads to productivity issues and an underestimation of the cost of machining for the industry. The aim of this study is to identify the kinematic behaviour of the machine tool during any type of discontinuity between linear and circular contours in different combination by taking into account the specific machining tolerances. In order to achieve this, a model of the law of the axes motion and the actual trajectory at discontinuities is necessary. This method is based on the subdividing of the trajectory into elementary geometries according to the type of interpolation (circular or linear). The proposed method can estimate the cycle time with a maximum error of 5% between the actual and the prediction cycle time. Finally, an experimental study was carried out on a high speed machine. It is based on elementary tests in order to analyze the axes behavior during any type of discontinuity and to validate the developed models.
International Journal of Mechanical Sciences, 2019
When adopting 5-axis machine to mill the parts, it is desired to avoid the drastic change of tool orientation for improving the kinematics performance of 5-axis machining while ensuring no machining interferences. For this purpose, a kinematics performance oriented smoothing method is proposed to plan the tool orientations, which is focused specifically on minimizing the angular accelerations imposed on the rotary axes of 5-axis machine. In this method, with several specified representative tool orientations (RTOs), two B-spline curves, which represent the displacements of the rotary axes, are used to join smoothly the RTOs together and then to determine the tool orientations at other areas. The solutions for the two B-spline curves are achieved by solving a least-square objective function which minimizes the angular accelerations of the rotary axes. To restricting simultaneously the interpolated tool orientations in the geometric feasible domains (GFDs) of tool motion, a simple alternate strategy of first smoothing the tool orientation and then checking the machining interference is developed so that tool orientation planning and its geometric constraints are decoupled and the complicated constraint optimization process of tool orientation can be greatly simplified. Since the proposed method works in the machine coordinate system (MCS), it can not only ensure the smooth motions of the rotary axes without the machining interferences, but also can generate directly the rotary axis orders. Finally, the proposed method is validated by the experiments.
The International Journal of Advanced Manufacturing Technology, 2015
In modern machining applications, with the developments in computer-aided manufacturing (CAM) technology, predictive modeling of milling operations has gained momentum. However, there is still a big gap between CAM technology and process modeling which limits its use in machining strategy development and parameter selection. In this paper, an approach is proposed for the use of process models and simulation tools in this direction. Cutting force and stability simulations are used in identification of feasible regions of cutting parameters and comparison of machining strategies for productivity. Cutting force simulation throughout a toolpath is performed through extended Z-mapping approach, where a previously developed generalized cutting force model is utilized. Stability diagrams are generated in frequency domain. Dynamic programming (DP) approach is adapted for machining strategy comparison, which takes into account several constraint curves such as chatter stability, cutting torque, spindle power, tool deflection, and surface roughness. The proposed approach was applied on a case study to demonstrate the use of process models in machining strategy and parameter selection in 5-axis milling.