Cutter Contact Research Articles

UG secondary development of path generation of straight profile toroidal worm finishing tool

Abstract Due to the complexity of the right and left tooth surfaces of the straight profile toroidal worm, it is difficult in 3D modeling and NC programming. Based on the equal residual height algorithm, this paper deduces the calculation formula of the cutter contact and cutter point of the tooth surface of the straight profile toroidal worm by using the round nose milling cutter, calculates the cutter point coordinates and rotation angles of each point of the tooth surface of the straight profile toroidal worm through the UG secondary development interface and Visual Studio software, and generates the numerical control code on this basis. The machining simulation and experiment show that the machining efficiency and error of the straight profile torus worm machined by the tool path prepared by the equal residual height method are better than that of the isoparametric method.

A novel tool path planning method for 5-axis single-point diamond turning

5-Axis single-point diamond turning adds two linked axes based on 3-axis single-point diamond turning, which can smoothly and continuously process complex surfaces. Compared to 3-axis turning, tool path planning for 5-axis single-point diamond turning is a complex decision-making process, which is a novel problem in the existing studies and a difficulty in multi-axis turning. In this study, a novel path planning method for 5-axis single-point diamond turning is proposed. Firstly, the mapping relation from scallop height to the distribution of cutter contact (CC) points is established in the non-uniform rational B-spline (NURBS) parameter space, thereby the planning of CC points is quickly achieved under fewer constraints. Furthermore, the local interference and global interference generation mechanism of 5-axis single-point diamond turning are revealed by geometrical analysis, combining diamond tool parameters and tool shank parameters. By transforming the motion of the cutter axis posture in 3D space into swings in two planes, the posture accessibility diagram of the cutter axis is efficiently constructed. Finally, the feasibility and effectiveness of the tool path planning method are verified by 5-axis single-point diamond turning experiment. And the contour accuracy is improved through the quadratic planning of the CC points (the contour accuracy after compensation is 3.2 μm compared to normal one 9.6 μm). This study extends the traditional 3-axis turning to 5-axis turning, providing a new perspective for the machining of complex surfaces.

An integrated method for compensating and correcting nonlinear error in five-axis machining utilizing cutter contacting point data

In current five-axis computer numerical control (CNC) machining, the use of minute linear path segments as an approximation for the ideal cutter contacting (CC) point trajectory is still prevalent. However, introducing rotation axes leads to a deviation of the actual CC point trajectory from the ideal, resulting in nonlinear errors. An integrated method is proposed in this paper for compensating and correcting both the contour error, associated with the approximation of the part surface by the ideal CC point trajectory and the nonlinear error of the CC point trajectory based on the information in the CC point data. By analyzing the spatial relationship between the tool posture and the CC point path during the five-axis linear interpolation process, two adjacent machining tool positions containing CC point data information are selected as the starting and ending points of the five-axis linear interpolation machining. The ideal tool center point and the actual CC point are calculated during the interpolation process, as well as the distance and the unit vector in the perpendicular direction between the actual CC point and the ideal CC point trajectory segment. In the comprehensive error compensation and correction phase, the obtained unit vectors are used as direction vectors for error compensation, and the tool center point during interpolation is first compensated and corrected. This ensures the actual CC point and the contour curve are on the same plane. The compensation direction for contour error is calculated using the start/end tool axis vectors and the ideal CC point trajectory vectors. The size of the contour error approximating the contour curve is calculated through the chord error. A second compensation and correction are applied to the tool center point for interpolation, ultimately achieving comprehensive compensation and correction of nonlinear errors. The data calculations were conducted in the MATLAB environment using actual machining data. After compensation and correction, the contour error was reduced by 76%, the nonlinear error of the CC point trajectory decreased to below 0.88 μm, and the comprehensive nonlinear error of the CC point trajectory was reduced from 19 to 1.5 μm, a reduction of 93%. This demonstrates significant practical value in enhancing the accuracy of five-axis CNC machining. Through actual machining verification, after using the method described in this paper, the average surface roughness decreased from 1.133 to 0.220 μm, and the maximum surface roughness decreased from 6.667 to 1.240 μm. This significantly demonstrates that the compensation and correction method proposed in this paper can significantly improve the surface quality of machined parts.

Mechanical Properties and Influencing Factors of Shield Cutting Existing Station Supporting Piles

Based on the shield-cutting existing station supporting piles project of Zhengzhou metro line 6, the process and mechanism of concrete in the process of pile cutting were analyzed by establishing a three-dimensional model of concrete with a cutter. The magnitude and variation rules of cutting force, penetration force, and tangential force were explored. The variation rules of cutting force with four factors of cutting speed, cutting depth, cutter width, and tool rake angle were explored. The correctness of the numerical model and results were verified by the theoretical analysis method. Finally, the significance of the influencing factors of pile cutting was studied by means of range analysis and variance analysis using the orthogonal test method, and the cutter parameters were optimized. The cutting mechanism is that the front concrete is compressed and crushed to produce a dense core. The cutting force increases rapidly to its maximum value in a short time during the cutting process. The cutting force is always larger than the penetration force and tangential force. The cutter contact force basically remains unchanged with the change in cutting speed; however, it increases with the increase in cutting depth and cutter width. The significant order of the three influencing factors is cutting depth, cutter width, and rake angle. It is suggested that the cutting depth be adjusted preferentially, followed by the cutter width. And the principle of rake angle should be considered last.

Assessment of the morphological properties of secondary semi-finished wood-fibre products obtained from production waste

This paper presents the results of an assessment of the morphological characteristics of semi-finished wood-fibre products obtained from waste fibreboard using a rotary cutting machine by dry grinding. The work has established the influence of machine design parameters, such as the gap between the rotor and stator cutters and the angle of the stator cutter contact with the raw materials, on the mass fraction of small fibres and fines in wood-fibre pulp. These parameters determine the main structural characteristics of boards and ensure fibre bonding. The paper describes the collision of single secondary wood fibres that leads to the development of primary cracks, contributing to external and internal fibrillation in the absence of high temperatures and pressure without using chemical additives or water and steam.

A novel regional force control strategy based on seven-axis linkage grinding system to improve blade machining accuracy

The aero-engine blade has the characteristics of large curvature and uneven allowance distribution, which makes it difficult to ensure its machining accuracy during processing. The existing research mainly realizes the removal of blade allowance through constant contact force control strategy, which is difficult to achieve accurate removal of uneven allowance. This paper proposes a novel regional force control strategy based on seven-axis linkage grinding system. The ideal contact force is obtained according to the curvature and allowance distribution at each cutter-contact (CC) point, and the coefficient kp is calibrated by orthogonal grinding tests considering the initial rapid wear of the hollow ball abrasive belt. The ideal contact force is controlled by the regional force control strategy, which is composed of the regional division and the seventh axis controller. Considering the system response time and the distribution of the ideal contact force, the ideal contact force is divided into several regions through regional division algorithm, and then the actual contact force is controlled in real time during processing by the designed seventh axis controller to ensure the stability of the seventh axis. The force control accuracy with the seventh axis controller has increased by 63.7 % on the whole profile of the blade than that without the controller. The comparative robotic grinding experiment results show that the surface profile accuracy values at the four profile areas are improved by 57.6 %, 59.2 %, 70 % and 61.7 % than that with the passive compliance control (PCC) method, respectively.

Numerical simulation of rock breaking by PDC cutter with finite-discrete-infinite element method

To better reveal the rock damage evolution law during rock breaking by Polycrystalline Diamond Compact (PDC) cutter, the Finite-Discrete-Infinite Element Method (FDIEM) was adopted to establish the 3D models for rock breaking by PDC cutter pressing and cutting. It was found that the cutter tip was the starting point of crack initiation during rock breaking by PDC cutter pressing. When the pressing depth was about 2 mm, the tensile breaking ratio of the rock was the highest, which was the most conducive to rock breaking. During rock breaking by PDC cutter cutting, the boundary of the area where the cutter contacts with rock was the starting point of micro-crack initiation. The volumetric fracture mainly occurred in the rock surface area in front of the cutter, and the comminuted fracture mainly occurred in the rock in contact with the front of the cutter. A new method based on crack density has been proposed to evaluate rock damage during rock breaking by PDC cutter. The results proved the feasibility and reliability of the FDIEM in simulation of rock breaking by PDC cutter, which can provide a method guidance for the studies on other types of rock breaking tools.

Posture Optimization in Robotic Flat-End Milling Based on Sequential Quadratic Programming

AbstractRobotic flat-end milling of complex surfaces offers advantages such as high flexibility and high machining efficiency. In the process of planning the toolpath based on the cutter contact path, the robot functional redundancy and the tool orientation need to be solved carefully. This paper presents a posture optimization method for robotic flat-end milling. Taking the weighted sum of the machining width and the toolpath smoothness performance criterion as the objective function, an optimization model considering the joint limits and gouging avoidance is established. An efficient algorithm based on sequential quadratic programming is proposed to solve this nonconvex problem. During the execution of the algorithm, the machining width is efficiently calculated by an iterative method based on conformal geometric algebra, while its derivatives are approximated analytically. Simulations and experiments demonstrate that the presented technique can resolve the tool axis direction and the robot redundancy effectively to increase the machining width and improve the toolpath smoothness, thus reducing the time for machining and improving the surface quality.

Automatic Generation of Interference-Free and Posture-Smooth Toolpath for Robotic Belt Grinding of Complex Workpieces

Robotic belt grinding has shown great potential to achieve automatic machining of high-precision parts. However, its productivity in machining complex parts has been greatly limited by the problem that interference-free and posture-smooth toolpath planning is still a time-consuming and labor-intensive job. Therefore, this work presents a fully automatic and practical approach to facilitate interference-free and posture-smooth toolpath planning for robotic belt grinding of complex parts. With this approach, the interference correction spaces in two common belt grinding modes, namely, wheel face grinding and wheel edge grinding, are first established, where various types of interferences and their corresponding correction strategies are modeled. Then, two B-spline posture curves, which represent the rotational motion and translational motion of the workpiece for correcting interference throughout the entire cutter contact curve, are presented. With the two B-spline curves, a toolpath planning algorithm for robotic belt grinding of complex parts is further developed based on surface partitioning and iteratively correcting interference and smoothing grinding postures. The effectiveness and practicability of the proposed approach are validated by simulations and experimental studies, which demonstrates that the authors’ approach can significantly improve the toolpath planning efficiency and ground surface quality for complex parts as compared with the leading commercial computer-aided manufacturing (CAM) software.

Toolpath planning method with the constraint of cutting force fluctuation in slow tool servo turning for complex curved surface parts

Parts with the complex curved surface are commonly used in high-end equipment. The machining quality of the curved surface parts is important for the property of high-end equipment. With position control of the main spindle, i.e., the C axis, the slow tool servo (STS) turning is a very promising technique to effectively machine complex curved surface parts. However, the turning machining quality is restricted by the cutting force fluctuation in finishing turning. Hence, the STS turning toolpath generation approach with the constraint of the cutting force fluctuation is proposed in this study. As the cutting force is proportionate to the cutting area, the cutting area for turning complex curved surfaces is analyzed and calculated. Then the functional relation between the cutting force fluctuation and the feed rate is derived. Based on the geometrical characteristic of the first revolution of the toolpath, the feed rate is optimized with small cutting force fluctuation to derive the cutter contact points (CCPs) in the cylindrical coordinate system. From the validation experiment results, it can be seen that the cutting force fluctuation, the profile tolerance, and the surface roughness of parts are effectively reduced, and the surface roughness of the part machined with the proposed toolpath planning method is 17.625 nm. Thus, this study provides guidance for toolpath generation with the constraint of the fluctuation of the cutting force in STS turning for a complex curved surface.

A Novel Toolpath for Robotic Adaptive Grinding of Extremely Thin Blade Edge Based on Dwell Time Model

High precision and high efficiency in robotic grinding of aero-engine extremely thin blade edges is a challenging problem. In this article, a novel toolpath planning method is proposed based on the derived dwell time calculation model and the developed interpolation algorithm. The dwell time of each cutter contact point is solved based on the matrix method by consideration of the revised material removal model and machining allowance distribution. To optimize the previous interpolation algorithm based on geometric intersection, an arc length and Taylor binary expansion optimization are proposed to plan cutter contact points according to the dwell time and the curvature changes of blade edges. Subsequently, the tool orientation is corrected based on a double-vector controlling method to avoid the processing interference. Simulation results show that the proposed interpolation algorithm has improved the path coverage by 17.6%, and its computational efficiency is 34 times higher than that in previous algorithm. The comparative robotic grinding experiment results show that the proposed toolpath has improved the surface profile accuracy of blade edge to 0.042 mm, and its machining accuracy is 14.3–46.2% higher than that of other methods.

Design of surface micro texture in the cutter-chip contact area of a cemented carbide cutter

Placing micro textures on a cutter surface can enhance the cutter-chip and cutter-workpiece contact, improving the cutter performance and machined surface quality. However, both the proper placement of micro textures and careful modeling of their density function are required for optimizing the cutting performance. In this study, a ball end milling cutter was utilized to demonstrate how these can be achieved. Initially, the theoretical cutter-chip contact length of the was calculated based on the chip curl theory and the theoretical cutter-chip contact area was obtained by combining the theories of cutter contact area and micro texture placement. Then, a mathematical model describing the micro texture distribution was established using a uniform density function, which allowed the determination of the specific distribution model for the micro textures. Finally, both simulations and experiments were used to validate the accuracy of the theoretical solution for the cutter-chip contact area and the uniformity of the micro texture density function. The results showed that the theoretical cutter-chip contact area and the uniform micro texture density mathematical model are consistent with the simulation and experimental results. The results reported in this paper provide a theoretical basis for the accurate preparation of micro textures.

A Rapid Approach of Computing Multi-axis Tool Accessible Space for General Cutter Model by Utilizing Programmable Graphics Pipeline

Computation of tool accessible space (TAS) is key to interference-free toolpath planning for multi-axis machining complex parts. However, most existing solutions are difficult to guarantee efficiency and accuracy simultaneously, and are only applicable to certain types of tools. Hence, this article proposes a rapid and accurate TAS computation approach for general cutters based on programmable graphics pipelines of modern graphics-processing unit (GPU). With this approach, a concept of MID (maximum interference distance)-space that quantitatively describes interference states between obstacles and a general cutter model is first proposed. Then, an MID model between obstacles and the general cutter model is presented. And a GPU-enhanced MID computing algorithm is developed based on new features of graphics pipelines. Moreover, an algorithm for batch computing TASs is presented based on GPU instancing. Experimental studies show that compared with traditional GPU-based methods, since our approach enables TASs computation of all cutter contact points to be completed in batches by running the graphics pipeline only once, the computation efficiency is improved by nearly 11 times. Besides, since the accuracy of our approach does not rely on the resolution of GPU rendered image, and also because the actual MID is identified precisely, the accuracy can be guaranteed very effectively. More encouragingly, our approach is general for various cutters, including special-shaped cutters, which greatly facilitate generating interference-free toolpath as well as optimizing tool postures globally for multi-axis machining complex parts.

A study of interferential tool position correcting algorithms in 3D impeller variable-axis rough plunge milling

Plunge milling has significantly improved the rough machining efficiency of 3D impeller channels. However, in conventional plunge milling cutter position planning, interferences occurring at the end of every cutter position due to the sudden increase of radial depth is inevitable. This can seriously compromise the service life of the machine tool and cutter, and also reduce the efficiency at the interferential phase. This study optimised the tool path cutter axis vector of conventional rough machining of 3D impeller variable-axis plunge milling, thus making the angle between the normal vector of workpiece surfaces at the cutter contact point, and the cutter-axis vector of the adjacent tool position, gradually increase from the outlet to inlet on a very small scale. Based on this, an iterative algorithm for the tool centre position and cutter safety height was obtained, thus making the hub allowance of the optimised tool path for plunge milling as small as possible without affecting subsequent machining by avoiding the interferential phenomenon. Finally, the proposed method was verified by relevant numerical examples.

An Energy Efficiency Tool Path Optimization Method Using a Discrete Energy Consumption Path Model

As the energy cost accounts for about one-third of the total manufacturing cost, there is great significance in evaluating and managing energy consumption in manufacturing processes. The energy consumption during multi-axis end milling, which represents a large part of the industrial energy costs, is usually extraordinarily large, especially for complex free-form surfaces requiring multi-finish-machining. To obtain the most efficient tool path, the tool orientation is adjusted to obtain the largest cutting stripe width at each cutter contact point. However, the use of excessive driving energy consumption and cutting energy to obtain the largest cutting stripe width may reduce the energy efficiency of the tool path. To solve this problem, the geometry features of the tool path are analyzed firstly, and the global energy consumption analysis, which includes a cutting energy analysis and driving energy analysis, is conducted. The discrete energy consumption path model is constructed to find the most energy-efficient tool orientation sequence for a tool path. Finally, contrast experiments are carried out to validate the proposed method.

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.

Machining-path mapping from free-state to clamped-state for thin-walled parts

Thin-walled parts with curved surface are widely used in industrial applications and the high-quality machining is still a major problem because of the low stiffness. By using the machining-path obtained from the design model of thin-walled parts with curved surface, the machining accuracy requirement may easily not be met due to the springback of clamping deformation when the machining process is finished. It is a novel idea that when the machining-path mapping from free-state to clamped-state is realized based on the clamping deformation, the final machining-path of thin-walled parts can be re-designed to directly ensure the machining accuracy requirement after the fixture is released. Based on the concomitant thought of curved surface and the elastic deformation theory of thin shell in this study, the mathematical model for the machining-path mapping from free-state to clamped-state is established for the thin-walled parts with curved surface. Then, the corresponding relationship of cutter contact (CC) points is calculated by grid mapping. Finally, the machining-path for the thin-walled parts with curved surface is re-designed under the clamped-state. Taking a thin-walled cylinder workpiece as an example, the experiment results show that the proposed method can achieve the avoiding purpose for the machining error caused by clamping deformation. These research achievements are of vital importance for realizing high-quality machining of the thin-walled parts with curved surface.

A novel selected force controlling method for improving robotic grinding accuracy of complex curved blade

Nonlinear time-varying contact state is a crucial factor to prevent the traditional robotic belt grinding method from precision machining of blade. In this case, a novel selected force controlling method (SFC) with consideration of regional division (RD) based on machining allowance is proposed for improving robotic grinding accuracy of complex curved blade, on basis of the self-developed adaptive impedance controller. Ideal normal grinding force at each cutter-contact (CC) point is calculated by principal curvature radius and regional allowance of blade surface. Then, the CC points with similar ideal normal grinding force are divided into one region along grinding path based on the force threshold. Furthermore, an adaptive impedance controller with neural network online compensation algorithm (AICNN) is developed, and the verification test results of grinding four profile areas of intake side, exhaust side, convex and concave, indicate that the force control accuracy with AICNN has increased by 80.33%, 50.58%, 82.65% and 69.01% than that without the controller, respectively. Based on this, the grinding experiment of typical turbine blade is conducted with SFC, and the surface profile accuracy values at the four profile areas have evidently improved by 48.79%, 35.67%, 59.54%, and 66.90% than that with conventional grinding (CG), respectively.

Assessment of Inoculation Methods of Thielaviopsis paradoxa (De Seynes) Höhn into Oil Palm Seedlings under Greenhouse Conditions.

Oil palm (Elaeis guineensis Jacq. and Elaeis Oleifera Cortes) is one of the most important oil crops in the world. Colombia is the fourth-largest oil palm producer worldwide. However, oil palm diseases are a significant factor affecting yield. Thielaviopsis paradoxa (De Seynes) Höhn is a pathogen that affects young palm trees, causing spear rot. Four disease establishment methods were studied to replicate, in a controlled environment, the symptoms of the disease found in the field. Young palm trees were inoculated with a suspension of endoconidia using either local infiltration, drip, scissor cut, or direct contact with agar blocks bearing mycelia and conidia. The effects of the inoculation methods were studied in dose-method-disease severity experiments conducted in a greenhouse under controlled conditions. All four methods resulted in T. paradoxa infections and the development of symptoms of the disease. The disease severity was correlated with the method and dose of inoculation. In trials to test Koch’s postulates, T. paradoxa was isolated from areas of disease progression in the inoculated trees, but the teleomorph Ceratocystis paradoxa (Dade) Moreau was not observed. A photographic record of the infection process at different times post-infection was compiled. Given that establishing the disease through artificial inoculation is essential for assessing plant pathogenesis, this study determined that the local infiltration method (1 × 106 endoconidia mL−1) and a 3–7 day incubation period were critical for the development of symptoms as severe as those observed in natural infections in the field.

Velocity effect sensitivity analysis of ball-end milling Ti-6Al-4 V

Ball-end cutters are widely used in industries of dies, molds, and aerospace, which have the problem of poor machined surface quality due to the low cutting speed near the tool-tip. With the increase in the complexity of parts, it will become more and more difficult to avoid the tool-tip participating in the cutting. In this paper, the velocity effect sensitivity of the ball-end cutter is analyzed, and several key positions, including the intersection points of the CWE boundaries, are selected to describe the cutting speed in three dimensions. The relationships between the cutting speed of the critical points and important variables such as the machining inclination angle and the feed direction were investigated. The optimal range of feed direction is obtained when the tool-tip engages in the contact circle. The core aim of the feed direction selection is to make the tool engagement area in a high position by changing the feed direction, to avoid surface damage and improve the quality of the machined surface. Finally, an experimental study was carried out, and the results corroborate the effectiveness of the selection method. In the experiment, it was also found that cutting-out from the cutter contact position can improve the surface quality in the directions of non-optimal range, and the milling force and chips shape will vary with the change of the feed direction.