Numerical and experimental modeling of the thermal flow in a modern rotary transfer machine

2021 ◽  
pp. 1-23
Author(s):  
Francesco Robusto ◽  
Dario Croccolo ◽  
Massimiliano De Agostinis ◽  
Stefano Fini ◽  
Giorgio Olmi ◽  
...  
Keyword(s):  
Relative Displacement ◽  
Numerical Control ◽  
Heat Sources ◽  
Thermal Flow ◽  
Complete Model ◽  
Rolling Bearings ◽  
Temperature Variations ◽  
Friction Heat ◽  
Working Day ◽  
Thermal Sources

Abstract The aim of this study is to estimate the relative displacement between the spindle nose and the clamping vice in a rotary transfer machine due to temperature variations. The study was focused on the relative displacements caused by temperature variations produced by two heat sources: the environment around the machine and the 3-axis computer numerical control station during the duty cycle. Regarding the last point, an analytical model was developed, in order to account for different thermal sources inside the 3-axis module (e.g. ball screws, rolling bearings and guideways friction heat, as well as heat generation in the motor). The complete numerical model was calibrated and successfully validated. Comparison was run between numerical results and experimental data in the framework of trials involving a newly developed transfer machine. Finally, the complete model, considering the combination of both the heat sources, has made it possible to estimate spindle nose-clamp relative displacement during a typical working day, highlighting that the radial displacement risks affecting seriously the accuracy of a workpiece.

scholarly journals A new model for predicting the mechanical efficiency of ball screws based on the empirical equations for the friction torque of rolling bearings

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401880017 ◽  
Author(s):  
Chang-Guang Zhou ◽  
Hu-Tian Feng ◽  
Yi Ou
Keyword(s):  
Rotational Speed ◽  
Axial Load ◽  
High Speed ◽  
Mechanical Efficiency ◽  
Friction Torque ◽  
Numerical Control ◽  
Measuring System ◽  
Empirical Equations ◽  
Rolling Bearings ◽  
New Model

Based on the empirical equations for the friction torque of rolling bearings, this article proposes a new model for predicting the friction torque and mechanical efficiency of ball screws. Meanwhile, a novel measuring system is constructed to obtain the mechanical efficiency of ball screws, where both the axial load and rotational speed are stable and adjustable. The experimental results at a rotational speed of 1000 r/min agree well with the theoretical values calculated by the present method, which show that the mechanical efficiency of ball screws increases with increasing axial load. Moreover, the model built in this article is more applicable to a relatively high-speed condition. The new model can be easily used to obtain the friction torque and mechanical efficiency for ball screws, which is essential for improving the performance of ball screws and the computer numerical control machine tools.

Mixed Convection Heat Transfer From Thermal Sources Mounted on Horizontal and Vertical Surfaces

1990 ◽  
Vol 112 (4) ◽  
pp. 975-987 ◽  
Author(s):  
S. S. Tewari ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Mixed Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Finite Width ◽  
Heat Sources ◽  
Wide Range ◽  
Thermal Sources

An experimental study is carried out on the fundamental aspects of the conjugate, mixed convective heat transfer from two finite width heat sources, which are of negligible thickness, have a uniform heat flux input at the surface, and are located on a flat plate in the horizontal or the vertical orientation. The heat sources are wide in the transverse direction and, therefore, a two-dimensional flow circumstance is simulated. The mixed convection parameter is varied over a fairly wide range to include the buoyancy-dominated and the mixed convection regimes. The circumstances of pure natural convection are also investigated. The convective mechanisms have been studied in detail by measuring the surface temperatures and determining the heat transfer coefficients for the two heated strips, which represent isolated thermal sources. Experimental results indicate that a stronger upstream heat source causes an increase in the surface temperature of a relatively weaker heat source, located downstream, by reducing its convective heat transfer coefficient. The influence of the upstream source is found to be strongly dependent on the surface orientation, especially in the pure natural convection and the buoyancy dominated regimes. The two heat sources are found to be essentially independent of each other, in terms of thermal effects, at a separation distance of more than about three strip widths for both the orientations. The results obtained are relevant to many engineering applications, such as the cooling of electronic systems, positioning of heating elements in furnaces, and safety considerations in enclosure fires.

Experimental Characterization and Numerical Simulation of Plumes Above Thermal Sources: Transport of a Passive Contaminant

2010 ◽  
Author(s):  
Rene´ Devienne ◽  
Jean-Raymond Fontaine ◽  
Talel Maalej
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Heat Sources ◽  
Experimental Characterization ◽  
Tracer Gas ◽  
Industrial Ventilation ◽  
Analytical Formulae ◽  
Thermal Sources

Industrial ventilation problems are linked with plumes above heat sources. This paper proposes an experimental study of dynamic, thermal and concentration fields that develop from cylindrical complex or rectangular sources. The metrology allows the measurement of local velocities and temperatures but also of the concentration of a tracer gas (helium). The results are compared with the classical analytical formulae, more particularly in the proximal field and also to results issued from simulation.

Dissipative Behaviour of Metallic Materials in Low Stress Cyclic Loading

2006 ◽  
Vol 3-4 ◽  
pp. 253-258
Author(s):  
Francois Maquin ◽  
Fabrice Pierron
Keyword(s):  
High Cycle Fatigue ◽  
Temporal Integration ◽  
Heat Diffusion ◽  
Temperature Fields ◽  
Heat Sources ◽  
Metallic Materials ◽  
Heat Diffusion Equation ◽  
Spatio Temporal ◽  
Metallic Specimen ◽  
Thermal Sources

In order to fully understand the thermomechanical phenomena involved in high-cycle fatigue, a method for determining the dissipative thermal sources in a loaded metallic specimen from the spatio-temporal integration of the heat diffusion equation is proposed. Temperature fields obtained through a focal array infra-red camera are processed with this technique. After a refined analysis of the sensitivity of the method, preliminary tests have shown that it is possible to detect a burst of heat sources within the first couple of cycles for the specimen tested above a certain level of tensile stress. This behaviour is thought to be related to the microplasticity level.

scholarly journals Modeling of Heat Phenomenon in Rolling Kinematic Pairs Using the Finite Element Method

2021 ◽  
Vol 11 (14) ◽  
pp. 6447
Author(s):  
Jan Kosmol
Keyword(s):  
High Speed ◽  
Fem Simulation ◽  
Rolling Bearing ◽  
Heat Sources ◽  
Geometric Form ◽  
Simulation Studies ◽  
The Finite Element Method ◽  
Rolling Bearings ◽  
Fem Simulations ◽  
High Speed Cutting

In the spindles of HSC (High Speed Cutting) machines with rolling bearings, higher temperatures in the bearings can be expected, which may affect the resistance to movement of the bearing itself. Therefore, to estimate these resistances, it is necessary to know the temperatures of the bearing components. The article presents the results of FEM simulation tests of temperature distribution in a rolling bearing. These studies were focused on assessing the influence of such features as the distribution of heat sources, the geometric form and size of the contact areas of the balls with the raceways, the conditions of heat convection to the environment and heat conduction inside the bearing. It has been recognized that FEM simulations for the default conditions offered by most commercial FEM systems can lead to out-of-the-box results. As part of the experimental research, conclusions from the simulation studies were verified.

scholarly journals Thermal Sources of Errors in Surface Texture Imaging

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2337 ◽  
Author(s):  
Karol Grochalski ◽  
Michał Wieczorowski ◽  
Paweł Pawlus ◽  
Jihad H’Roura
Keyword(s):  
Surface Topography ◽  
Environmental Conditions ◽  
Internal Heat ◽  
Thermal Stabilization ◽  
Surface Irregularity ◽  
Heat Sources ◽  
Axis Direction ◽  
Thermal Chamber ◽  
Internal Heat Sources ◽  
Thermal Sources

This paper presents the influence of thermal phenomena on areal measurements of surface topography using contact profilometers. The research concerned measurements under controlled and variable environmental conditions. The influence of internal heat sources from profilometer drives and their electronic components was analyzed. For this purpose, a thermal chamber was designed and built. Its task was to maintain and control environmental conditions and, at the same time, separate the profilometer from external disturbances. Heat sources and temperature values for elements and systems were determined. It further enabled for the calculation of the displacements in axes as a function of temperature. The largest displacement in the probe due to internal heat sources for the considered cases occurred in the X-axis direction. Its value reached 16.2 μm. However, the displacement in the probe in the Z-axis direction had the greatest impact on the measured surface topography. These displacements for a thermally unstable profilometer reached 7.9 μm in Z, causing results even 90% greater than in the case of a device without such problems. The time after which a proper topography measurement can be started was also determined basing on obtained data. This time for tested profilometers was between 6 and 12 h. It was found that performing thermal stabilization of the profilometer significantly reduced surface irregularity errors. The stabilization time should be determined individually for a specific type of device.

scholarly journals FEM-Analysis of 2D Micromachined Flow Transduers based on aGe-Thermistor Arrays and a Double Bridge Readout

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3561
Author(s):  
Almir Talic ◽  
Samir Cerimovic ◽  
Roman Beigelbeck ◽  
Franz Kohl ◽  
Thilo Sauter ◽  
...  
Keyword(s):  
Leading Edge ◽  
Fem Analysis ◽  
High Accuracy ◽  
Thermal Flow ◽  
Excess Temperature ◽  
Temperature Variations ◽  
Air Gaps ◽  
Flow Velocity Field ◽  
Planar Surfaces ◽  
Thin Film Devices

This paper reports on a design and simulation study aiming at high-accuracy 2D micromachined thermal flow transducers. The scope is restricted to micromachined devices featuring a square-shaped membrane incorporating central symmetric thin-film devices. A microthermistor array probed spatial excess temperature variations while the main heat supply was alternatively established by optional heating resistors or by pronounced self-heating of the thermistor devices. Proper device designs enable leading edge transducer performance without sophisticated signal conditioning schemes. We found that a high azimuthal uniformity of flow magnitude transduction is tantamount to a precise azimuthal accuracy. The most advanced result gave a maximum azimuthal aberration of 0.17 and 1.7 degrees for 1 m/s and 10 m/s, respectively, while the corresponding magnitude uniformity amounted to 0.07% and 0.5%. Such excellent specifications exceed the need of ordinary meteorological applications by far. However, they are essential for, e.g., precise non-contact measurements of 2D relative movements of two quasi-planar surfaces via the related Couette flow in intermediate air gaps. The simulations predicted significantly better device characteristics than achieved by us in first experiments. However, this gap could be attributed to imperfect control of the flow velocity field by the measurement setup.

Compensation for Thermal Deformation of a Compact Lathe in Cutting Operations Using a Coolant Fluid with Temperature Measurements at a Few Specific Points

2019 ◽  
Vol 13 (4) ◽  
pp. 527-538
Author(s):  
Yoshiaki Ishino ◽  
Hiroshi Tachiya ◽  
Yoshiyuki Kaneko ◽  
◽  
Keyword(s):  
Fluid Flow ◽  
Work Environment ◽  
Thermal Deformation ◽  
Thermal Conditions ◽  
Numerical Control ◽  
Coolant Fluid ◽  
Heat Sources ◽  
Modified Equations ◽  
Cnc Lathe ◽  
Calibration Coefficients

We previously designed a compact computer numerical control (CNC) lathe that arranges its heat sources so as to reduce their thermal deformation. However, a compact lathe often undergoes large deformation owing to unexpected thermal conditions arising out of the work environment or from operation of the lathe itself. Hence, we propose a method to determine equations predicting thermal deformation in a CNC lathe from temperatures measured at a few specific points. These equations enable one to effectively compensate for lathe thermal deformation. However, they cannot be applied to cutting operations involving a coolant fluid because the coolant fluid flow may lead to a complicated thermal deformation scenario. In this study, we attempted to more accurately compensate for thermal deformation, for cutting operations involving a coolant fluid, by adding simple calibration coefficients to the prediction equations. We applied the modified equations to a numerically controlled controller and validated our approach for cutting operations using a coolant fluid under various conditions.

Observations of the spatial structure of interstellar hydrogen

1967 ◽  
Vol 31 ◽  
pp. 45-46
Author(s):  
Carl Heiles
Keyword(s):  
High Resolution ◽  
Spatial Structure ◽  
Velocity Dispersion ◽  
Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

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