Chatter Avoidance in Parallel Turning With Unequal Pitch Angle Using Observer-Based Cutting Force Estimation

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Shinya Sakata ◽  
Takashi Kadota ◽  
Yuki Yamada ◽  
Kenichi Nakanishi ◽  
Hayato Yoshioka ◽  
...  
Keyword(s):  
Cutting Force ◽  
Pitch Angle ◽  
Machine Tools ◽  
Prediction Models ◽  
Chatter Vibration ◽  
Force Estimation ◽  
Angle Difference ◽  
The Stability ◽  
Stability Limits ◽  
Turning Test

Parallel turning is garnering attention as one of the most important technologies for multitasking machine tools. This is because a potential exists to enhance the stability limits compared to the turning operation using a single tool when cutting conditions are properly selected. Although stability prediction models for parallel turning have been developed in recent years, in-process monitoring and in-process chatter techniques are almost not discussed. In this study, to suppress chatter vibration, an unequal pitch turning method was proposed. In this method, the upper tool was controlled based on the optimum pitch angle calculated from spindle speed and chatter frequency. Chatter frequency was identified from estimated cutting force by a disturbance observer (DOB). From the result of the parallel turning test, it is clear that chatter vibration can be avoided by controlling the upper tool based on optimum pitch angle. Meanwhile, the pitch angle difference that can suppress chatter had a certain range. Subsequently, the robustness of the optimum pitch angle difference is experimentally evaluated by both the continuous moving test and the stepwise moving test of the pitch angle.

Chatter Suppression in Parallel Turning With Unequal Pitch Using Observer Based Cutting Force Estimation

2017 ◽  
Author(s):  
Shinya Sakata ◽  
Takashi Kadota ◽  
Yuki Yamada ◽  
Kenichi Nakanishi ◽  
Hayato Yoshioka ◽  
...  
Keyword(s):  
Cutting Force ◽  
Pitch Angle ◽  
Machine Tools ◽  
Prediction Models ◽  
Chatter Vibration ◽  
Force Estimation ◽  
Chatter Suppression ◽  
The Stability ◽  
Stability Limits ◽  
Turning Test

Parallel turning attracts attention as one of the important technologies for the multi-tasking machine tools. This is because there is a potential to enhance the stability limits compared to turning operation using single tool when cutting conditions are properly selected. Although stability prediction models for parallel turning have been developed in recent years, in-process monitoring technique of chatter is almost out of focus. In this study, to suppress chatter vibration, unequal pitch turning method was proposed. In this method, the upper tool was controlled based on optimum pitch angle calculated from spindle speed and chatter frequency. Chatter frequency was identified from estimated cutting force by disturbance observer. From the result of parallel turning test, it is clear that chatter vibration can be suppressed by controlling the upper tool based on optimum pitch angle.

Integrated Chatter Monitoring Based on Sensorless Cutting Force/Torque Estimation in Parallel Turning

2017 ◽  
Vol 11 (2) ◽  
pp. 215-225 ◽  
Author(s):  
Yuki Yamada ◽  
◽  
Takashi Kadota ◽  
Shinya Sakata ◽  
Junji Tachibana ◽  
...  
Keyword(s):  
Cutting Force ◽  
Disturbance Observer ◽  
Prediction Models ◽  
Estimation Methods ◽  
Torque Estimation ◽  
Frequency Components ◽  
Internal Information ◽  
The Stability ◽  
Stability Limits ◽  
Cutting Point

Parallel turning technology is considerably important in future multi-tasking machine tool because it has the potential to enhance the stability limits, compared to turning operations using a single tool. Although stability prediction models for parallel turning have been developed recently, the technique of in-process monitoring of chatter is almost out of focus. In this study, the monitoring of chatter based on the sensorless cutting force/torque technique was evaluated in the parallel turning and cutting of the same surface of an elongated workpiece. Two cutting force/torque estimation methods were evaluated: a conventional disturbance observer (DOB) using internal information from a servomotor and a multi-encoder-based disturbance observer (MEDOB) using load-side position/angular information as well. In the DOB-based monitoring, chatter frequency components were observable regardless of the guideway type and drive system. However, chatter monitoring may be difficult when the angle of the servomotor is changed slightly because of the damping properties of the sliding guideway. In the MEDOB-based monitoring, the waveform of the estimated cutting force reflected the vibrational state at the cutting point well, and the extraction of chatter frequency components became easier regardless of the guideway type.

scholarly journals Investigating Multiscale Phenomena in Machining: The Effect of Cutting-Force Distribution Along the Tool’s Rake Face on Process Stability

2015 ◽  
Author(s):  
Tamás G. Molnár ◽  
Tamás Insperger ◽  
S. John Hogan ◽  
Gábor Stépán
Keyword(s):  
Cutting Force ◽  
Distributed Delay ◽  
Chip Thickness ◽  
Rake Face ◽  
Center Manifold Reduction ◽  
Force System ◽  
Force Magnitude ◽  
Stability Lobe ◽  
The Stability ◽  
Stability Limits

Regenerative machine tool chatter is investigated in a nonlinear single-degree-of-freedom model of turning processes. The nonlinearity arises from the dependence of the cutting-force magnitude on the chip thickness. The cutting-force is modeled as the resultant of a force system distributed along the rake face of the tool. It introduces a distributed delay in the governing equations of the system in addition to the well-known regenerative delay, which is often referred to as the short regenerative effect. The corresponding stability lobe diagrams are depicted, and it is shown that a subcritical Hopf bifurcation occurs along the stability limits in the case of realistic cutting-force distributions. Due to the subcriticality a so-called unsafe zone exists near the stability limits, where the linearly stable cutting process becomes unstable to large perturbations. Based on center-manifold reduction and normal form calculations analytic formulas are obtained to estimate the size of the unsafe zone.

Stability as a constraint in sagittal plane human force exertion modeling

1998 ◽  
Vol 1 (1) ◽  
pp. 23-39
Author(s):  
Carter J. Kerk ◽  
Don B. Chaffin ◽  
W. Monroe Keyserling
Keyword(s):  
Muscle Strength ◽  
Ankle Joint ◽  
Coefficient Of Friction ◽  
Sagittal Plane ◽  
Biomechanical Model ◽  
Whole Body ◽  
The Stability ◽  
Joint Center ◽  
Static Conditions ◽  
Stability Limits

The stability constraints of a two-dimensional static human force exertion capability model (2DHFEC) were evaluated with subjects of varying anthropometry and strength capabilities performing manual exertions. The biomechanical model comprehensively estimated human force exertion capability under sagittally symmetric static conditions using constraints from three classes: stability, joint muscle strength, and coefficient of friction. Experimental results showed the concept of stability must be considered with joint muscle strength capability and coefficient of friction in predicting hand force exertion capability. Information was gained concerning foot modeling parameters as they affect whole-body stability. Findings indicated that stability limits should be placed approximately 37 % the ankle joint center to the posterior-most point of the foot and 130 % the distance from the ankle joint center to the maximal medial protuberance (the ball of the foot). 2DHFEC provided improvements over existing models, especially where horizontal push/pull forces create balance concerns.

scholarly journals Prediction and Stability Assessment of Soft Foundation Settlement of the Fishbone-Shaped Dike Near the Estuary of the Yangtze River Using Machine Learning Methods

2021 ◽  
Vol 13 (7) ◽  
pp. 3744
Author(s):  
Mingcheng Zhu ◽  
Shouqian Li ◽  
Xianglong Wei ◽  
Peng Wang
Keyword(s):  
Extreme Learning Machine ◽  
Prediction Models ◽  
Good Prediction ◽  
Foundation Settlement ◽  
Machine Method ◽  
Settlement Prediction ◽  
Soft Foundation ◽  
Simulation Results ◽  
Learning Machine ◽  
The Stability

Fishbone-shaped dikes are always built on the soft soil submerged in the water, and the soft foundation settlement plays a key role in the stability of these dikes. In this paper, a novel and simple approach was proposed to predict the soft foundation settlement of fishbone dikes by using the extreme learning machine. The extreme learning machine is a single-hidden-layer feedforward network with high regression and classification prediction accuracy. The data-driven settlement prediction models were built based on a small training sample size with a fast learning speed. The simulation results showed that the proposed methods had good prediction performances by facilitating comparisons of the measured data and the predicted data. Furthermore, the final settlement of the dike was predicted by using the models, and the stability of the soft foundation of the fishbone-shaped dikes was assessed based on the simulation results of the proposed model. The findings in this paper suggested that the extreme learning machine method could be an effective tool for the soft foundation settlement prediction and assessment of the fishbone-shaped dikes.

Stability of Milling Operations With Asymmetric Cutter Dynamics in Rotating Coordinates

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Alptunc Comak ◽  
Orkun Ozsahin ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Machine Tools ◽  
High Speed ◽  
End Mill ◽  
Spindle Shaft ◽  
Milling Operations ◽  
Stability Model ◽  
Principal Directions ◽  
The Stability ◽  
Rotating Coordinates

High-speed machine tools have parts with both stationary and rotating dynamics. While spindle housing, column, and table have stationary dynamics, rotating parts may have both symmetric (i.e., spindle shaft and tool holder) and asymmetric dynamics (i.e., two-fluted end mill) due to uneven geometry in two principal directions. This paper presents a stability model of dynamic milling operations with combined stationary and rotating dynamics. The stationary modes are superposed to two orthogonal directions in rotating frame by considering the time- and speed-dependent, periodic dynamic milling system. The stability of the system is solved in both frequency and semidiscrete time domain. It is shown that the stability pockets differ significantly when the rotating dynamics of the asymmetric tools are considered. The proposed stability model has been experimentally validated in high-speed milling of an aluminum alloy with a two-fluted, asymmetric helical end mill.

scholarly journals Cutting Force Prediction Models by FEA and RSM When Machining X56 Steel with Single Diamond Grit

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 326
Author(s):  
Lan Zhang ◽  
Xianbin Sha ◽  
Ming Liu ◽  
Liquan Wang ◽  
Yongyin Pang
Keyword(s):  
Cutting Force ◽  
Coefficient Of Friction ◽  
High Speed ◽  
Prediction Models ◽  
Pipeline Steel ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Cutting Force Prediction ◽  
Force Prediction ◽  
Diamond Wire Saw

In the field of underwater emergency maintenance, submarine pipeline cutting is generally performed by a diamond wire saw. The process, in essence, involves diamond grits distributed on the surface of the beads cutting X56 pipeline steel bit by bit at high speed. To find the effect of the different parameters (cutting speed, coefficient of friction and depth of cut) on cutting force, the finite element (FEA) method and response surface method (RSM) were adopted to obtain cutting force prediction models. The former was based on 64 simulations; the latter was designed according to DoE (Design of Experiments). Confirmation experiments were executed to validate the regression models. The results indicate that most of the prediction errors were within 10%, which were acceptable in engineering. Based on variance analyses of the RSM models, it could be concluded that the depth of the cut played the most important role in determining the cutting force and coefficient the of friction was less influential. Despite making little direct contribution to the cutting force, the cutting speed is not supposed to be high for reducing the coefficient of friction. The cutting force models are instructive in manufacturing the diamond beads by determining the protrusion height of the diamond grits and the future planning of the cutting parameters.

Mit Einzelzähnen schneller zum Verschleiß*/Faster to wear with single teeth

2019 ◽  
Vol 109 (01-02) ◽  
pp. 8-13
Author(s):  
H.-C. Möhring ◽  
R. Eisseler ◽  
H. Ghassemi ◽  
Keyword(s):  
Machine Tools ◽  
Circular Saw ◽  
Single Tooth ◽  
The University ◽  
Turning Test

Standzeittests an Kreissägewerkzeugen sind in der Regel zeit- und materialintensiv. Am Institut für Werkzeugmaschinen (IfW) der Universität Stuttgart wird der Aufwand mithilfe von Einzahnversuchen deutlich verringert. Die Versuche basieren auf einem Leistendrehtest, der sich an die ehemalige VDI-Richtlinie VDI 3324 anlehnt und auf Drehmaschinen durchgeführt werden kann. Durch einfach gestaltete, wechselbare Leisten entsteht eine für das Sägen typische Schnittunterbrechung und es können beliebige Werkstoffe berücksichtigt werden.   Live time tests on circular saw tools are usually time-consuming and material-intensive. At the Institute for Machine Tools (IfW) of the University of Stuttgart, the required effort can be significantly reduced by conducting single tooth tests. The tests are based on a block turning test which adopts the former VDI guideline VDI 3324 and can be used on lathes. Simply designed and exchangeable blocks allow the typical cut interruption for sawing and consider any materials.

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