Trajectory Of Tool Tip Research Articles

Investigation on two-dimensional ultrasonic vibration plane turning method based on elliptical plane swinging strategy along short axis

In the ultrasonic elliptical vibration cutting (UEVC) process, the surface morphology suffers from the large fluctuation of ridge height and residual height, which has restricted the development of UEVC technology. Therefore, on the basis of the elliptical plane swinging strategy along a short axis, a surface topography improvement method (i.e., swing ultrasonic elliptical vibration turning (SUEVT)) for two-dimensional ultrasonic vibration plane turning is proposed in this study. The core idea of the method is to swing the ultrasonic elliptical vibration plane along the short axis to form a machining inclination angle, which reduces the ridge height of the machined morphology to a certain extent, thereby optimizing the surface microstructure and reducing the surface roughness. First, this study establishes a mathematical model of the tool tip trajectory of ultrasonic elliptical vibration under different swing angles, theoretically analyzes the influence of swing angles on the tool tip trajectory and surface topography, and provides a theoretical basis for revealing the surface topography formation mechanism of SUEVT. Second, an engineering practice scheme of SUEVT is proposed, and a processing experiment platform is built. Finally, cutting experiments of SUEVT for TC4 titanium alloy were conducted, studying the influence of swing angles on surface topography and roughness and assessing the feasibility of the method. Results showed that compared with ultrasonic elliptical vibration turning (UEVT), SUEVT has certain advantages in improving surface morphology. When the swing angle of SUEVT is 15°, the surface roughness decreases the most, reaching 19.00 %. Under the condition of SUEVT θ = 15°, the surface roughness decreases first and then increases with the increase in spindle speed, while it is proportional to the feed speed and ultrasonic power. The method proposed in this study can provide new methods and new ideas for ultrasonic elliptical vibration high surface quality machining.

Design and Study of Machine Tools for the Fly-Cutting of Ceramic-Copper Substrates.

Ceramic-copper substrates, as high-power, load-bearing components, are widely used in new energy vehicles, electric locomotives, high-energy lasers, integrated circuits, and other fields. The service length will depend on the substrate's copper-coated surface quality, which frequently achieved by utilising an abrasive strip polishing procedure on the substrate's copper-coated surface. Precision diamond fly-cutting processing machine tools were made because of the low processing accuracy and inability to match the production line's efficiency. An analysis of the fly-cutting machining principle and the structural makeup of the ceramic-copper substrate is the first step in creating a roughness prediction model based on a tool tip trajectory. This model demonstrates that a shift in the tool tip trajectory due to spindle runout error directly impacts the machined surface's roughness. The device's structural optimisation design is derived from the above analyses and implemented using finite element software. Modal and harmonic response analysis validated the machine's gantry symmetrical structural layout, a parametric variable optimisation design optimised the machine tool's overall dimensions, and simulation validated the fly-cutterring's constituent parts. Enhancing the machine tool's stability and motion accuracy requires using the LK-G5000 laser sensor to measure the guideway's straightness. The result verified the machine tool's design index, with the Z- and Y-axes' straightness being better than 2.42 μm/800 mm and 2.32 μm/200 mm, respectively. Ultimately, the device's machining accuracy was confirmed. Experiments with flying-cut machining on a 190 × 140 mm ceramic-copper substrate yielded a roughness of Sa9.058 nm. According to the experimental results, the developed machine tool can fulfil the design specifications.

Study on surface morphology of titanium alloy curved thin-walled parts by longitudinal-torsional composite ultrasonic assisted milling

In order to obtain titanium alloy curved thin-walled parts with better surface quality, longitudinal-torsional composite ultrasonic assisted milling (LTCUAM) was studied. The tool tip trajectory model and the surface roughness model of LTCUAM were established. It was found that LTCUAM could obtain lower surface roughness than common milling (CM) through analyzing the theoretical model. Finally, the effects of milling parameters and acoustic parameters on surface morphology were studied by orthogonal test and single factor test. The experimental results indicated that the surface roughness Ra and the surface arithmetic average height Sa value decreased in different degrees after LTCUAM. However, various milling parameters and acoustic parameters had different effects on the reduction of Sa and Ra. With the increase of ultrasonic amplitude, both Sa and Ra displayed a trend of decreasing first and then increasing. With the increase of spindle speed, both Sa and Ra decreased first, then increased and then decreased. With the increase of the feed per tooth, both Sa and Ra basically showed an increasing trend. The results demonstrated that better surface texture and surface quality can be obtained with lower feed per tooth, medium ultrasonic amplitude and spindle speed.

Surface feature and material removal in ultrasonic vibration-assisted slot-milling of Ti–6Al–4 V titanium alloy

The continuous optimization of processing technology and evaluation methods is an important way to achieve high processing quality and processing efficiency for difficult-to-process materials. To solve the problem of frequent defects in the slot, the ultrasonic vibration-assisted slot-milling (UVASM) technology was developed for processing titanium alloy. Simultaneously, comparative experiments were carried out between UVASM and conventional slot milling (CSM), in terms of surface features of slot bottom and slot sidewall, cutting force, tool trajectory, chip morphology, and micro-hardness. The results show that uniform vibration micro-texture could significantly improve surface topography of slot bottom in UVASM, while numerous tool feed trajectories and observable machining defects detract from the surface quality in CSM. The UVASM can greatly reduce material spalling and edge breakage, thereby maintaining a smooth and regular edge profile of the slot sidewall. The tool tip trajectories of the two machining methods are highly corresponding to the machining textures of the slot sidewall surface. There is a high-frequency and small-amplitude force fluctuation signal on the axial force waveform in UVASM, which can reduce the instantaneous maximum milling force and milling force in the stable stage by 8.7 and 12.2%, respectively. The UVASM has a better chip breaking effect and surface anti-scratch effect, and the UVASM can obtain higher surface micro-hardness and deeper plastic deformation layer than those CSM. In summary, the multi-dimensional evaluation of slot processing status has been completed, and the processing quality of the slot has been improved.

Experimental Study on Ultrasonic-Assisted End Milling Forces in 2195 Aluminum-Lithium Alloy.

To achieve high-quality machining of the 2195 aluminum-lithium alloy, this paper presents an experimental study on the effect of milling processing parameters on milling forces and surface topography, during which conventional milling and longitudinal-torsional ultrasonic vibration milling of the 2195 Al-Li alloy were performed. The characterization of the tool tip trajectory illustrates some of the advantages of ultrasonic machining, which include variable depth of cut and tool chip pulling. The differences in milling forces between conventional milling and longitudinal-torsional ultrasonic vibration machining were compared using orthogonal tests, and the effect of ultrasonic vibration on milling forces was investigated in detail. The maximum reduction of milling force Fy in the feed direction under the influence of torsional vibration is 62% and 54% for larger feed per tooth and cutting depth, respectively. The high-frequency impact generated by the longitudinal vibration not only reduces the chip accumulation on the surface, but also smooths out the tool-tooth scratches and creates a regular surface profile. In addition, the characteristics of the milling force signals of the two machining methods were analyzed, and the analysis of the spectrum of the collected milling forces revealed that the ultrasonic vibration caused the high-frequency components of the milling forces Fy and Fz. The orthogonal result analysis and single-factor result analysis verified the superiority of ultrasonic machining, provided parameter selection for subsequent aluminum-lithium alloy machining, and bridged the gap of longitudinal torsional ultrasonic vibration machining of 2195 aluminum-lithium alloy in the study of milling force.

Blazed grating enables highly decoupled optically variable devices fabricated by vibration-assisted diamond texturing.

Optically variable devices (OVDs) are well received for anti-counterfeiting and decorative applications. In this study, new strategies to develop highly decoupled OVDs were proposed and demonstrated based on the fast patterning of blazed gratings by vibration-assisted diamond texturing. A unique surface generation mechanism was revealed as a combined cutting and forming process. One facet of blazed grating is generated by the cutting motion defined by the tool tip trajectory. The other facet is formed by the tool flank face, which establishes the blaze angle. This process is able to generate high-resolution, structurally colored graphics by modulating cutting velocity to control the grating distribution. Due to the unique surface generation mechanism, the orientation of the created blazed gratings is intrinsically perpendicular to the cutting direction. Thus, it enables the flexible control of concentration directions of diffracted light by tuning the orientation of blazed gratings. We designed and demonstrated two types of highly decoupled OVDs based on vibration-induced blazed gratings. The orthogonal-type OVD utilizes the azimuth angle dependence of blazed gratings to encode two images in orthogonal cutting directions. The in-plane-type OVD utilizes the optimized diffraction efficiency of blazed gratings in a given diffraction order to encode two images in opposite cutting directions. The fabricated OVDs are presented and compared with optical simulation results based on an extended scalar diffraction theory.

A novel method for effecting flexible guided wave propagation in elliptical vibration cutting

As a key part of elliptical vibration cutting (EVC) technology, a two-dimensional ultrasonic elliptical vibration cutting (UEVC) device has become a prevalent area of importance and research interest. This paper dissects through the conventional structural design and creatively proposes the UEVC device with flexible guided wave propagation. The device resolves the problems of poor coupling efficiency of two-way excitation signal, complex structure design, non-orthogonal, and the difficulty in controlling the ellipse trajectories of the tool tip. It has been confirmed that a flexible guided wave exhibits an effective unidirectional propagation and lateral load decoupling ability via establishing its system dynamic response and frequency impedance characteristics. Here, we explain the coupling mechanism of the two-way flexible guided wave in the UEVC device. Results suggested that the experimental measurement of the impedance for the cutting device and the individual transducer shows that the cutting device with the transducer and the tool bar connected by the flexible guided wave has a lower impedance increase ratio compared to the individual transducer, and hardly influence the tool bar mode of the cutting device. At the same time, the tool tip trajectory of the cutting device having a phase difference of 90° showed a satisfactory “elliptical” shape, while the microstructure processed by the tool tip ellipse trajectory with a phase difference of 60° reached a burr-free state. Theoretical and experimental findings reveal that the flexible guided waves exhibit excellent weak coupling characteristics in the non-transmitting direction. This is convenient to the independent, orthogonal and stable propagation of signals in the two directions. Based on flexible guided wave propagation technology, our findings provide theoretical foundation and application value for the design of a two-dimensional UEVC device.

Surface texture generation using high-feed milling with spindle speed modulation

This paper presents a new surface texturing technique using ball-end milling with high feed speed and spindle speed modulation. The ratio between feed-rate and cutting tool radius is in the range of 0.2–0.4, which is much larger than the ratio in conventional milling. Sinusoidal modulation signal is added, so the spindle speed becomes time-varying in order to generate different texture profiles. The cutting tool kinematics are modeled considering the tool-tip run-out and deflection due to cutting forces. The effects of amplitude and frequency of the modulation signal on tool-tip trajectories and surface textures are simulated and analyzed. The relationship between the micro features of the surface texture and the process parameters are investigated. Surface texturing experiments are conducted based on the proposed technique, and tribology tests are performed on the textured surface. It is shown that the textured surfaces present frictional anisotropy, which depends on the process conditions and modulation parameters. The proposed technique is able to achieve fast generation of various surface textures without additional instrumentation, and the final texture geometry is controllable based on the presented kinematics model.

Effect of double-excitation ultrasonic elliptical vibration turning trajectory on surface morphology

To explore the formation law and influence factors of three-dimensional geometry in axial turning surface, the turning experiment of 7075 aluminum alloy was carried out by using double excitation three-dimensional ultrasonic elliptical vibration method. Based on the theory of turning kinematics, the tool tip trajectory model of three-dimensional ultrasonic elliptical vibration turning (3D-UEVT) was established, and the related mechanism in surface residual height, surface topography formation characteristics, and turning transmission was given. Through single factor simulation and turning test, the influence of spindle speed, feed speed, amplitude, and phase difference on the surface microstructure and roughness of workpiece was analyzed contrastively. The results show that, compared with the traditional turning, the double excitation ellipse assisted turning can affect the surface topography and quality of the workpiece by causing the dynamic change of the cutting angle of the tool tip and the residual height of the material. Combined with the analysis of simulation and experimental results, it is found that the ideal microstructure and roughness can be obtained with low speed, slow feed, small amplitude, and small phase difference. Meanwhile, the tool workpiece separation characteristics, surface topography, roughness, and surface defect level can be effectively improved under the three-dimensional ultrasonic elliptical assisted vibration.

Performance analysis of the longitudinal-torsional ultrasonic milling of Ti-6Al-4V

Titanium alloy is a typical difficult-to-cut material due to its high strength and high stiffness. To solve the problem of the low efficiency and poor surface quality in the milling of titanium alloy, this paper proposes a novel longitudinal-torsional ultrasonic vibration milling (LTUVM) process. An ultrasonic horn with spiral slots was designed to convert the longitudinal vibration into longitudinal-torsional vibration. The tooltip trajectory was modeled, and the finite elements analysis was used to analyze the cutting mechanism of LTUVM. The simulation results indicate a kind of separation cutting characteristics in every vibration cycle, which is beneficial to reduce the cutting force and improve the surface finish compared with the single longitudinal ultrasonic vibration milling (SLUVM). Then, cutting tests were conducted on Ti-6Al-4V to evaluate the performance of LTUVM. Experimental results demonstrated that the LTUVM could reduce the cutting force by 46–86% compared with the conventional milling (CM) and the SLUVM due to its separation cutting characteristics. Moreover, the surface morphology was analyzed, and a fractal dimension (FD) method was proposed to characterize the regularity and fragmental property of the machined surfaces. The surface morphology analysis results showed that the LTUVM can be used as a novel high-efficiency and high-quality surface texturing method for Ti-6Al-4V. The textured surface of the LTUVM has the superiority of high integrity and periodicity, which could be applied to effectively tune the tribological property of surface.

Research on the tool tip trajectory deflection control and cutting characteristics of elliptical vibration cutting based on guided wave transmission

Chip and surface roughness (Ra) are the two main problems in ultra-precision machining. In the current research on elliptical vibration cutting (EVC), little is known about the impact of high-frequency tool tip ellipse trajectory deflection on the quality of cutting surfaces. In this paper, effective control of the tool tip ellipse trajectory deflection is achieved by adjusting phase difference. We also explain how tool tip ellipse trajectory changes affect chip and surface roughness. Firstly, an EVC device is optimized to obtain orthogonal vibration output of the tool tip based on the guided wave transmission technique. Secondly, we establish an elliptical trajectory deflection control model of the tool tip. Analysis of the control model shows that (1) when the tool tip amplitude and phase difference are simultaneously adjusted, the tool tip trajectory can be controlled at an angle of deflection with the same elliptical shape; (2) when only phase difference is adjusted, control of the tool tip trajectory is achieved at an angle of deflection with a different elliptical shape. At a phase difference below 90°, elliptical trajectory of the tool tip is considered positive, while at an angle exceeding 90°, the reverse is true. Analysis of cutting characteristics of the tool tip ellipse trajectory deflection controlled by phase difference adjustments and finite element simulation indicate that as the phase difference increases, the continuity of the chip and Ra first becomes better then poorer due to friction force reversal effect. At a phase difference of 60°, elliptical trajectory of the tool tip is positive with an appropriate dynamic plunging angle for optimized quality of the cutting surface. Overall, test results of our cutting experiment are consistent with theoretical reports demonstrating the feasibility and effectiveness of the current work.

High-Speed Rotary Ultrasonic Elliptical Milling of Ti-6Al-4V Using High-Pressure Coolant

High-speed rotary ultrasonic elliptical milling (HRUEM), as a novel ultrasonic vibration cutting method, has been introduced in milling the alloy Ti-6Al-4V. The application of ultrasonic vibration in high-speed milling can help open the cutting contact area intermittently. New cutting effects will happen with full use of the separation effect brought by ultrasonic vibration and the cooling effect brought by a high-pressure coolant (HPC). On the basis of that, this paper firstly introduces HPC into HRUEM of Ti-6Al-4V in the open literature and analyzes the tool-workpiece separation cooling mechanism in HRUEM, including kinematic analysis of tool tip trajectories, tool-workpiece separation principles and high-pressure coolant effects. We have conducted a comprehensive experimental study and the results show when HPC is increased to 200 bar, compared to conventional milling (CM), the tool life in HUREM can be extended by 6.6 times at 80 m/min, 4.2 times at 120 m/min and 2.4 times at 160 m/min. The maximum material removal volume (MRV) for a given new end mill in HRUEM is increased by 657% approximately. When the cutting speed is 80 m/min, the cutting temperature of the workpiece in HRUEM is reduced by 24.1% compared to that of CM. By applying the combination of HPC and tool-workpiece periodic separation, we can significantly enhance the cooling and lubrication efficiency in HRUEM and also inhibit the tool wear mode of adhesive wear typically occurred in CM.

Investigation on the Tool Wear Suppression Mechanism in Non-Resonant Vibration-Assisted Micro Milling.

Excessive tool wear during hard and brittle material processing severely influences cutting performance. As one of the advanced machining technologies, vibration-assisted micro milling adds high-frequency small amplitude vibration on a micro milling tool or workpiece to improve cutting performance, especially for hard and brittle materials. In this paper, the tool wear suppression mechanism in non-resonant vibration-assisted micro milling is studied by using both finite element simulation and experiment methods. A finite element model of vibration-assisted micro milling using ABAQUS is developed based on the Johnson cook material and damage models. The tool-workpiece separation conditions are studied by considering the tool tip trajectories. The machining experiments are carried out on Ti-6Al-4V with a coated micro milling tool (fine-grain tungsten carbide substrate with ZrO2-BaCrO4 (ZB) coating) under different vibration frequencies (high, medium, and low) and cutting states (tool-workpiece separation or non-separation). The results show that tool wear can be reduced effectively in vibration-assisted micro milling due to different wear suppression mechanisms. The relationship between tool wear and cutting performance is studied, and the results indicate that besides tool wear reduction, better surface finish, lower burrs, and smaller chips can also be obtained as vibration assistance is added.

Design, Analysis, and Control of a Two-Dimensional Vibration Device for Vibration-Assisted Micromilling

In this article, a new two-dimensional piezoelectric actuator driven vibration stage is proposed and prototyped. A double parallel four-bar linkage structure with double-layer flexible hinges is designed to guide the motion and reduce the displacement coupling effect between the two directions. The compliance modeling and dynamic analysis are carried out based on the matrix method and Lagrangian principle, and the results are verified by the finite-element analysis. A closed-loop control system is developed and proposed based on the LabVIEW program consisting of a data acquisition device and capacitive sensors. Machining experiments have been carried out to evaluate the performance of the vibration stage and the results show good agreement with the tooltip trajectory simulation results, which demonstrates the feasibility and effectiveness of the vibration stage for vibration-assisted micromilling.

Improved dynamic cutting force modelling in micro milling of metal matrix composites part II: Experimental validation and prediction

The effects of cutting dynamics and the particles' size and density cannot be ignored in micro milling of metal matrix composites. This article presents the improved dynamic cutting force modelling for micro milling of metal matrix composites based on the previous analytical model. This comprehensive improved cutting force model, taking the influence of the tool run-out, actual chip thickness and resultant tool tip trajectory into account, is evaluated and validated through well-designed machining trials. A series of side milling experiments using straight flutes polycrystalline diamond end mills are carried out on the metal matrix composite workpiece under various cutting conditions. Subsequently, the measured cutting forces are compensated by a Kalman filter to achieve the accurate cutting forces. These are further compared with the predicted cutting forces to validate the proposed dynamic cutting force model. The experimental results indicate that the predicted and measured cutting forces in micro milling of metal matrix composites are in good agreement.

Comparative investigation of tool wear mechanism and corresponding machined surface characterization in feed-direction ultrasonic vibration assisted milling of Ti–6Al–4V from dynamic view

This paper mainly investigated the wear mechanism of universal coated carbide tools in feed-direction ultrasonic vibration-assisted milling (UVAM) of Ti–6Al–4V alloy through theorical analysis and experimental approaches, where the external ultrasonic vibration excitation was imposed on the workpiece. The rapid intermittent machining features, the generation mechanism of ultrasonic-frequency pulse cutting force and alternating friction, ultrasonic-frequency dynamic impact effect of resonant workpiece and considerable changes in tool trajectory and relative cutting speed in UVAM were analyzed from perspective of tool-workpiece dynamics and kinematics. Due to the ultrasonic-frequency friction between the tool and the workpiece, the minimum quantity lubrication (MQL) with biodegradable cutting fluid was firstly introduced in UVAM to improve the lubrication/cooling performance between tool and workpiece/chips interfaces. Three different machining methods, general milling, feed-direction UVAM and feed-direction UVAM&MQL, were sequentially carried out to comparatively investigate the tool wear mechanism and characterize tool wear and machined surface features. The corresponding machined surface quality including surface topography, surface profile and surface roughness under different tool wear states were presented to evaluate the tool wear condition. The results indicated that the tool wear mechanism in workpiece feed-direction UVAM system was dominated by ultrasonic-frequency dynamic load, where ultrasonic-frequency cutting force, ultrasonic-frequency friction, ultrasonic-frequency vibration impact and cutting inflection points of tool-tip trajectory worked together on the cutting edges. And the tool wear morphology in feed-direction UVAM was mainly characterized by tool-tip fracture, impact crack, friction traces and fatigue crack. The results of machined surfaces indicated that compared with the surfaces obtained in CM and general UVAM, the UVAM&MQL method could significantly improve the finished surface quality, which can also improve the tool wear to a certain extent.

Effect of vibration assistance on chatter stability in milling

Vibration-assisted machining is a process in which external vibration at certain amplitude and frequency is superimposed to the original cutting motion. It has been demonstrated that vibration assistance is able to improve tool life and surface quality in milling process. This research presents an analytical model in predicting the chatter stability in vibration-assisted milling process. The tool-workpiece separation caused by the modified tool tip trajectory with assisted vibration is investigated. The instantaneous uncut chip thickness and varying time delay are obtained numerically. A dynamic model with varying time delay caused by the vibration assistance is developed, and semi-discretization method is used to determine the chatter stability with different frequencies and amplitudes of vibration assistance. The simulations are validated by experimental results, and it is shown that the vibration assistance does not improve the critical depth of cut, but generates new stability lobes between the original two adjacent lobes corresponding to no vibration assistance. The results provide guidance in determining appropriate milling and vibration assistance parameters to ensure the process stability.

Synchronization of tool tip trajectory and attitude based on the surface characteristics of workpiece for 6-DOF robot manipulator

• Propose a method to extract surface characteristics for B-spline curve fitting. • Reduce the calculation complexity and obtain a smooth fitting curve. • Use the tool tip and corresponding attitude to get the tool reference at each sampling. • Use a rotation matrix and the direction to synchronize the pose with position. This study proposes a method to extract feature points from the surface characteristics according to the machining accuracy of a 6-Degrees-of-Freedom (6-DOF) robot manipulator, which makes the fitting of the B-spline curve easier and decreases the amount of calculation for the approximation process. The tool tip trajectory is defined via B-spline curve fitting. Many robotic controllers use two Non-Uniform Rational B-Spline (NURBS) curves to represent the trajectories of the tool tip and tool axis but these double trajectories are not synchronous. In order to synchronize the orientation with the tool tip trajectory, this study uses a rotation matrix and a machining direction vector to plan the attitude of the tool. Before the attitude is planned, interpolation is used to generate the motion command for the tool tip using the S-Curve feedrate profile. The trajectory of the tool tip is further used to calculate the synchronized tool reference using a rotation transformation. Finally, the tool tip trajectory and the corresponding synchronized tool reference are used to determine the machining position and the orientation information. One of the experimental results shows that the proposed method can simultaneously sustain a 10 μm machining accuracy with a significant decrease in the computation load from 1113 s to 31 s.

Radial Throw in Micromilling: A Simulation-Based Study to Analyze the Effects on Surface Quality and Uncut Chip Thickness

This paper presents a simulation study toward analyzing the effect of radial throw in micromilling on quality metrics and on the deviation in tool-tip trajectory from its prescribed pattern. Both the surface location error (SLE) and the sidewall (peripheral) surface roughness are analyzed. The deviation in tool-tip trajectory is evaluated considering the flute-to-flute variations in the uncut chip thickness and changes in the tooth spacing angle. Radial throw indicates the instantaneous radial location of the tool axis, thereby capturing all salient features of tool-tip trajectory deviations, such as the general elliptical form of the radial motions. This is in contrast to the concept of run-out, which is a scalar quantity (total indicator reading) indicating the total displacement or change in the radial throw measured from a perfect cylindrical surface for one complete rotation of the axis. As such, measurement and analysis of radial throw is essential to understanding micromachining processes. In our previous work, we described an experimental approach for accurate determination of radial throw when using ultra-high-speed micromachining spindles. In this work, we present a simulation-based study to relate radial throw parameters and form to SLE, sidewall surface roughness, flute-to-flute variations of uncut chip thickness, and changes in tooth spacing angle for a two fluted micro-endmill. As expected, our study concludes that the magnitude, orientation, and form of radial throw all significantly affect the studied quality metrics, tooth spacing angle, and the flute-to-flute chip thickness variations. Specifically, the presence of radial throw with an elliptical form induces up to 50% variation in SLE, up to 20% variation in sidewall surface roughness, up to 60% variation in tooth spacing angle deviations, and up to 50% variation in flute-to-flute chip thickness. As such, the presented simulation approach can be used to assess the direct (kinematic) effects of the radial throw parameters on the quality metrics and chip thickness variations.

A recurrent convolutional neural network approach for sensorless force estimation in robotic surgery

Providing force feedback as relevant information in current Robot-Assisted Minimally Invasive Surgery systems constitutes a technological challenge due to the constraints imposed by the surgical environment. In this context, force estimation techniques represent a potential solution, enabling to sense the interaction forces between the surgical instruments and soft-tissues. Specifically, if visual feedback is available for observing soft-tissues’ deformation, this feedback can be used to estimate the forces applied to these tissues. To this end, a force estimation model, based on Convolutional Neural Networks and Long-Short Term Memory networks, is proposed in this work. This model is designed to process both, the spatiotemporal information present in video sequences and the temporal structure of tool data (the surgical tool-tip trajectory and its grasping status). A series of analyses are carried out to reveal the advantages of the proposal and the challenges that remain for real applications. This research work focuses on two surgical task scenarios, referred to as pushing and pulling tissue. For these two scenarios, different input data modalities and their effect on the force estimation quality are investigated. These input data modalities are tool data, video sequences and a combination of both. The results suggest that the force estimation quality is better when both, the tool data and video sequences, are processed by the neural network model. Moreover, this study reveals the need for a loss function, designed to promote the modeling of smooth and sharp details found in force signals. Finally, the results show that the modeling of forces due to pulling tasks is more challenging than for the simplest pushing actions.