Tool Orientation Research Articles

Accurate Optoacoustic and Inertial 3-D Pose Tracking of Moving Objects With Particle Filtering

In industrial environments, the determination of the positions and orientations of tools in complex manual assembly processes allows an automated monitoring about the fulfillment of the process and a quality control. This contribution presents an optoacoustic indoor localization system based on combined distance and inertial measurements that is able to undertake this positioning task. In doing so, an accurate distance measurement is achieved with ultrasound and infrared. This novel system is able to localize multiple moving objects attached to transmitters simultaneously by measuring the unilateral distances to room-fixed receivers and fusing these measurements with inertial navigation system data (acceleration, angular velocity, and magnetic field) in a particle filter (PF). In doing so, the PF is determining the objects’ poses by using the accelerometer and gyroscope data for a pose prediction in a propagation step and by utilizing the distance measurement and magnetometer data for an estimation correction. A commercially available, optical reference system is used to record the dynamics of human hand movements in an assembly scenario in order to analyze these dynamics for a system performance evaluation. Subsequently, the novel, an optoacoustic system is tested by applying these dynamics to an electrical linear axis on which a transmitter is fixed. Compared to the reference system, the median position error achieved is below 2.6 cm and the median orientation error is less than 10.0°, even when going beyond the hand movement dynamics recorded previously.

A novel convex hull method for optimum multi-point 5-axis tool positioning for machining of complex sculptured surfaces

The Point-In-Convex-Hull-Control (PICHC) method is presented for the calculation of the optimum tool orientation during the 5-axis simultaneous CNC machining of sculptured surfaces. More specifically, this novel exact multi-point algorithm minimizes the clearance and/or overclosure of the contact surface between the tool and the workpiece and maximizes the material removal rate. It can be used in sculptured surfaces, where conventional algorithms allow up to two points of tool-workpiece contact, leading to suboptimal material removal rate. The proposed method allows a third contact point which makes an ideal matching of the tool-workpiece surface and its application is validated both numerically and experimentally in two case studies that are published in the literature. In the first case study, the PICHC method is compared with an exact algorithm, whereas in the second case study, it is compared with an evolutionary optimization algorithm coupled with a commercial software. The numerical and experimental results, apart from being more accurate and less computationally demanding than other commercial software algorithms, prove the suitability, versatility, and robustness of the developed methodology, which can be extended to describe and control more advanced machining problems, either stand-alone or within an API.

A Robotic Deburring Methodology for Tool Path Planning and Process Parameter Control of a Five-Degree-of-Freedom Robot Manipulator

Industrial robotics is a continuously developing domain, as industrial robots have demonstrated to possess benefits with regard to robotic automation solutions in the industrial automation field. In this article, a new robotic deburring methodology for tool path planning and process parameter control is presented for a newly developed five-degree-of-freedom hybrid robot manipulator. A hybrid robot manipulator with dexterous manipulation and two experimental platforms of robot manipulators are presented. A robotic deburring tool path planning method is proposed for the robotic deburring tool position and orientation planning and the robotic layered deburring planning. Also, a robotic deburring process parameter control method is proposed based on fuzzy control. Furthermore, a dexterous manipulation verification experiment is conducted to demonstrate the dexterous manipulation and the orientation reachability of the robot manipulator. Additionally, two robotic deburring experiments are conducted to verify the effectiveness of the two proposed methods and demonstrate the highly efficient and dexterous manipulation and deburring capacity of the robot manipulator.

Industrial Robot Accuracy Degradation Monitoring and Quick Health Assessment

Robot accuracy degradation sensing, monitoring, and assessment are critical activities in many industrial robot applications, especially when it comes to the high accuracy operations which may include welding, material removal, robotic drilling, and robot riveting. The degradation of robot tool center accuracy can increase the likelihood of unexpected shutdowns and decrease manufacturing quality and production efficiency. The development of monitoring, diagnostic and prognostic (collectively known as prognostics and health management (PHM)) technologies can aid manufacturers in maintaining the performance of robot systems. PHM can provide the techniques and tools to support the specification of a robot’s present and future health state and optimization of maintenance strategies. This paper presents the robotic PHM research and the development of a quick health assessment at the U.S. National Institute of Standards and Technology (NIST). The research effort includes the advanced sensing development to measure the robot tool center position and orientation; a test method to generate a robot motion plan; an advanced robot error model that handles the geometric/nongeometric errors and the uncertainties of the measurement system, and algorithms to process measured data to assess the robot’s accuracy degradation. The algorithm has no concept of the traditional derivative or gradient for algorithm converging. A use case is presented to demonstrate the feasibility of the methodology.

Determination of 5-axis tool orientation using analogy between parametric surface and form shaping function

This paper describes a method to determine tool orientation in a 5-axis machine tool. In simultaneous 5-axis machining, the tool orientation must be determined uniquely from infinite options based on a strategy implemented with computer-aided manufacturing (CAM) software. In general, tool orientation is determined by constraining several conditions, such as avoiding singularities and collisions between the tool and the workpiece and creating a smooth tool trajectory. This paper proposes a new method using an analogy between a parametric surface and the form-shaping function of the target machine tool. This paradigm means that the constraint process of tool path generation can be converted to geometric problems on the surface comparable to the form-shaping function. For example, an intersection line between the surface and a plane provides a constraint that fixes specific axes on the machine tool. This method furthermore has good compatibility with the tool configuration space (C-space). That is, the parametric space composed of two parameters of the parametric surface is synonymous with the C-space. First, the proposed method is illustrated, and then two cases without collision avoidance and one case based on C-space are demonstrated.

Kinematics performance oriented smoothing method to plan tool orientations for 5-axis ball-end CNC machining

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.

Accurate real-time interpolation of 5-axis tool-paths with local corner smoothing

5-axis machining tool-paths, when programmed in workpiece coordinates, translational and rotational tool motion in terms of Cartesian tool center points (TCPs), and unit tool orientation vectors (ORI). This paper presents a computationally efficient real-time trajectory generation algorithm for 5-axis machine tools to interpolate translational and rotational tool motion synchronously for accurate 5-axis machining. Finite Impulse Response (FIR) filters are used to generate jerk limited motion trajectories in real-time. Linear translational motion of the tool center point (TCP) is interpolated by FIR filtering of Cartesian velocity pulses in G01 blocks. In order to generate constant speed tool axis rotation, spherical linear interpolation is used, and unit tool orientation vectors (ORI) are filtered directly in the spherical coordinates. Precise tool motion synchronization is realized by matching time-constants of FIR filters utilized for translational and rotational interpolation. Non-stop path interpolation is achieved by locally blending consecutive linear G01 commands. Instead of fitting geometric blending curves and solving feed scheduling problem, smoothing functionality of FIR filtering is used, and a direct 1-step path smoothing algorithm is proposed for real-time implementation. The algorithm considers path blending errors in Cartesian (Euclidian) as well as in spherical (orientation) coordinates due to transient response of the FIR filter. As a result, both tool-tip and the tool-orientation errors are controlled accurately. Effectiveness of the developed algorithms are validated in simulations and also experimentally on an open-NC controlled 5-axis machine tool.

Tool orientation optimization considering cutter deflection error caused by cutting force for multi-axis sculptured surface milling

Multi-axis milling (especially five-axis) is in the ascendant for high precision manufacturing of a product with a sculptured surface such as ship propeller, owing to its multi-axis linkage and resulting outstanding superiorities. Needs of a faster-improving manufacturing level of sculptured surface milling are derived by higher performance requirement of complicated equipment, which makes the planning of tool orientations more significant and challenging. This paper builds a tool orientation optimization model with inclusion of the influence of deflection error caused by cutting force to achieve better machining precision controlling in five-axis sculptured surface milling. The basic idea of the optimization method is described firstly, followed by the prediction of cutter deflection error. Then determining processes of the related subset to restrain the tool orientations are developed. Lastly, comparative experiments are designed and performed through milling a propeller rotor possessing numerous blades in a five-axis machining center. By comparison with several other tool orientation methods, the average values and volatility of deflection error are both suppressed better utilizing the optimization modeling. The experiment results reflect that it is insufficient to consider single geometric constraint or kinematic constraint, and greater attention should be paid to the role of cutter deflection caused by cutting force in planning the tool orientations.

Smooth flank milling tool path generation for blade surfaces considering geometric constraints

In practical machining, flank milling path generation methods of blade surfaces should concern machine axes’ motions to improve machined surface quality, as well as the gouging-avoidance with the hub surface and the geometric deviation constraints. The smoothness of the tool orientation in the part coordinate system cannot assure the smooth rotary axis motions of a five-axis machine tool, since the conversion of tool orientation from the part coordinate system to the machine coordinate system is nonlinear. A flank milling path is represented with the cutter reference point trajectory and the displacement curves of the two rotary axes in this research, so that the machine axes’ motions along the tool path can be directly smoothed when generating the path. The point-to-surface distance function is adopted to evaluate the geometric deviation, and an algorithm based on the differential evolution algorithm is presented to solve the distance function robustly. The sum of the squares of the first, second, and third derivatives of the cutter reference point trajectory and the two rotary axes’ displacement curves are adopted as the smoothness indicators. Then, a flank milling path generation model for blade surface smoothing the machine axes’ motions and considering the hub surface gouging-avoidance and geometric deviations constraints is developed. Numerical examples and machining experiments for five-axis flank milling of a blade surface are given to confirm the validity and effectiveness of the proposed approach.

A Gouge-Free Tool Axis Reorientation Method for Kinematics Compliant Avoidance of Singularity in 5-Axis Machining

Abstract When a cutter traverses a region local to the singularity in 5-axis machining, the stability of machine tool motion may be violated and inevitably lead to a reduction in machining quality and accuracy. In this paper, the underlying cause of the singular machine behaviors is first investigated by differentiating tool path motions, on the basis of the tool path motion expressions in part and machine coordinate systems. A further investigation indicates abrupt kinematic changes to be inevitable when the rotary axes approach a singularity. To eliminate such possible singular risks in 5-axis machining, a local tool path modification method is proposed by adjusting the two rotary axes out of a singular configuration. The critical kinematics smoothing and the consequent gouging concerns resulting from reorientation are comprehensively incorporated in the process of singularity avoidance, by means of a novel tool orientation optimization model. Specifically, the algorithm starts with the determination of an appropriate adjustment range in a simple yet effective manner, and then the primary rotary axis is adjusted in a constrained region away from zero, so as to avoid singularity. After that, the second rotary axis is accordingly adjusted, with no gouging requirements being violated. In this way, singularity problems in 5-axis machining are solved, and both the machine axes kinematics and surface gouging errors are under control. Machining simulation and laboratory experiments were conducted to validate the effectiveness of the proposed method.

Advanced CAD/CAM Techniques for 5-Axis Machining of Free-Form Surfaces

This paper presents some advanced techniques on CAD modelling and CAM programming for 5-axis machining of free-form surfaces. In the CAD stage, based on surface partitioning, the design surface can be created with separate regions such as convex, concave and saddle. Point-based techniques are used to create the original surface and the boundary curves of the regions. Some other CAD/CAM techniques for determining tool sizes and tool orientations are also proposed to generate gouge-free tool paths for each region. A simple B-spline surface was given as an example to demonstrate the proposed techniques implemented in Creo Parametric. The points on the design surface and on the boundaries were generated by a Matlab program developed by the author.

Assembly Tool Manufacturing and Optimization for Polylactic Acid Additive Manufacturing

Paper focuses on additive manufacturing of assembly tool for hole selection. One of the most important part in design and optimization process in additive manufacturing for assembly tool is material selection and technology. In this case was chosen plastic material know as poly-lactic-acid. Polylactic acid has low shrinkage and huge potential in assembly tooling and assembly fixture manufacturing. Main benefits are in use of additive manufacturing for this purpose because of huge manufacturing variability and time savings in case of frequent design changes. From filament fused fabrication technology stand point is important to determine right manufacturing orientation of part. Main material benefit is bio-degradability and recyclability. Current trend in manufacturing is bio materials, clean manufacturing and ecofriendly products. Correct orientation of assembly tool will optimize manufacturing process in one way. Article is aimed on manufacturing precision in each orientation of part on build late. With right orientation of part in additive manufacturing process is determined exact precision of assembly tool manufacturing. For measurement was used coordinate-measuring machine. In this case measurements and precision checking are made only in exact spots where is needed the most precise distance

An irredundant G01 tool path generation method for five-axis machining considering tool tip and orientation errors

Five-axis machine tool is widely used in freeform surface machining. The freeform surface’s tool path is usually discretized as G01 segments and the freeform surface machined with linear interpolation in five-axis machine. Due to the two additional rotary axes, there are the nonlinear coupling relationship between the workpiece coordinate system (WCS) and machine coordinate system (MCS). Hence, there are many uncertain errors produced by the nonlinear coupling relationship, especially via linear interpolation. In order to represent the motion trajectory accurately and generate G01 tool path appropriately, this paper proposes an irredundant G01 tool path generation method for five-axis machine. Firstly, a new tool tip error (TTE) definition is given to reflect the influence of the rotation axis on the tool tip. And then, a new tool orientation error (TOE) definition is given to mirror the tool orientation error caused by rotary axis’ linear interpolation. Finally, an adaptive iterative method (AIM) is proposed to obtain irredundant G01 tool path. By using this method, the G01 tool path can be generated based on the given error limits and the proposed method is verified both in the simulation and experiment. The results show that the proposed method can significantly reduce the number of G01 segments and limit the actual error.

Topology optimization for multi-axis machining

This paper presents a topology optimization approach that incorporates restrictions of multi-axis machining processes. A filter is defined in a density-based topology optimization setting, that transforms an input design field into a geometry that can be manufactured through machining. The formulation is developed for 5-axis processes, but also covers other multi-axis milling configurations, e.g. 2.5D milling and 4-axis machining by including the appropriate machining directions. In addition to various tool orientations, also user-specified tool length and tool shape constraints can be incorporated in the filter. The approach is demonstrated on mechanical and thermal 2D and 3D numerical example problems. The proposed machining filter allows designers to systematically explore a considerably larger range of machinable freeform designs through topology optimization than previously possible.

Contour error–bounded parametric interpolator with minimum feedrate fluctuation for five-axis CNC machine tools

In this paper, a new generalized parametric interpolation method is proposed for optimized five-axis machining with the consideration of both the machine contour errors and the feedrate fluctuation elimination. An analytic processing is presented for linearization of contour errors with respect to feedrate limit. For machine configuration, explicit analytical modeling of the contour error and the tracking error with respect to feedrate is presented; thus, the error constraint problem is nicely converted to a kinematic constraint problem. On this basis, an accurate feedrate upper limit with confined contour errors is further determined by using a shifted Frenet frame with linear computational complexity. With the consideration of both the motion smoothness and machining efficiency, a time-based optimization algorithm is proposed for time-optimal feedrate scheduling. For eliminating the feedrate fluctuation, a new real-time interpolation algorithm is developed for free derivation between the path parameter and the arc length for smoothed five-axis tool path generation. Laboratory testing experiments were conducted for validation and were presented in the paper. And the experimental results indicate that the proposed feedrate interpolation method is capable of confining both the tool tip contour error and tool orientation contour error simultaneously, as well as maintaining a satisfactory interpolation performance in both computation efficiency and accuracy. The presented methods can be used for five-axis machining and the feedrate optimization of complex part machining.

Влияние ориентации инструмента на силы резания при концевом фрезеровании

This article presents the results of single-factor modeling and analysis of the influence of tool orientation with regard to the tilt angle and lead angle, on cutting forces when finish milling by a ball end cutter. The program NX 10 is used to build boundaries and contact areas of the tool and the workpiece, and the SIMULIA ABAQUS software is used to create a three-dimensional finite element model and determine the cutting forces. Graphs that describe dependencies of the cutting forces on the tool rotation angle are obtained for different orientations of the tool axis relative to the surface normal. The computational results will allow transition to the two-factor analysis of the influence of tilt angle combinations on the cutting forces and the determination of the optimal tool orientation during five-axis milling with maximum productivity.

Modification of Tool Orientation and Position to Compensate Tool and Part Deflections in Five-Axis Ball End Milling Operations

Tool-workpiece deflection is one of the major error sources in machining thin walled structures like blades. The traditional approach in industry to eliminate this error is based on modifying tool positions after measuring the error on the machined part. This paper presents an integrated model of cutting force distribution on the tool–blade contact, automatic update of blade static stiffness matrix without resorting to time-consuming finite element solutions as the material is removed, the prediction and compensation of static deflection marks left on the blade surface. The main focus of the paper is to compensate the deflection errors by respecting the maximum form errors, collision of tool/machine/workpiece, cutting speed limit at the tool tip, and ball end—blade surface contact constraints. The compensation has been carried out by two modules. The first module adjusts the tool orientation along the path to reduce the error by constructing an optimization problem. This module is computationally inexpensive and results in about 70% error reduction based on the conducted experiments. The modified tool path resulted from the first module is fed to the second module for further reduction of the form errors if needed at the violated cutter locations; hence it takes less computational time than the stand alone approach proposed in the literature. The proposed algorithms have been experimentally validated on five-axis finish ball end milling of blades with about 80% reduction in cutting force induced form errors.

An interference-and-chatter-free tool orientation planning method for five-axis NC machining

Five-axis machine tools are widely applied in machining parts with complex structure or geometric shape because of the two additional rotary axes. Meanwhile, the solution space of the tool orientations is significantly enlarged. Interference is considered in most traditional methods to compute feasible tool orientation space. However, since the surface quality requirements keep increasing, machining stability should be seriously confirmed. This paper proposes a new tool orientation planning method by considering both interference and chatter avoidance. Interference-free tool orientation space is first computed at each cutter location point (CLP). Then the machining stability is evaluated to eliminate the tool orientations leading to machining chatter from the interference-free tool orientation space. Based on this interference-and-chatter-free tool orientation space, a tool orientation smoothing strategy is implemented. The proposed method is tested by two cases and the experimental comparison results show that interference and chatter avoidance can be achieved. [Submitted 26 January 2018; Accepted 27 March 2018]

An Analytical Decoupled Corner Smoothing Method for Five-Axis Linear Tool Paths

Nowadays, the tool path in five-axis machining is usually described with linear segments. Tangential and curvature discontinuities of the linear tool path lead to poor machining efficiency and quality. Due to the complexities in constraining approximation errors and synchronization of tool tip position and tool orientation, it still remains a challenge to smooth five-axis linear tool path in real-time. To solve this problem, this paper developed an analytical decoupled corner smoothing method by inserting an asymmetric cubic B-spline and a pair of symmetric quartic spherical Bezier curves for tool tip position and tool orientation, respectively. The maximal approximation errors for tool tip position and tool orientation are fully constrained in the blending procedures. Tool tip position and tool orientation are synchronized by adjusting the blending lengths and angles, which guarantees the C 2 continuity of the tool path. The blending and synchronous scheme are analytical. Therefore, the proposed method can be employed in real-time. To verify the proposed method, simulations and experiments on a five-axis machine tool are conducted, the results demonstrate the feasibility and efficiency of the proposed method.

An interference-and-chatter free tool orientation planning method for 5-axis NC machining

Five-axis machine tools are widely applied in machining parts with complex structure or geometric shape because of the two additional rotary axes. Meanwhile, the solution space of the tool orientations is significantly enlarged. Interference is considered in most traditional methods to compute feasible tool orientation space. However, since the surface quality requirements keep increasing, machining stability should be seriously confirmed. This paper proposes a new tool orientation planning method by considering both interference and chatter avoidance. Interference-free tool orientation space is first computed at each cutter location point (CLP). Then the machining stability is evaluated to eliminate the tool orientations leading to machining chatter from the interference-free tool orientation space. Based on this interference-and-chatter-free tool orientation space, a tool orientation smoothing strategy is implemented. The proposed method is tested by two cases and the experimental comparison results show that interference and chatter avoidance can be achieved. [Submitted 26 January 2018; Accepted 27 March 2018]