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Finite element analysis of the dynamically created portal in the huge machine tool of “travelling column” type

Dounar Stanislau, Iakimovitch Alexandre, Jakubowski Andrzej

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

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nr 65 (137)

29--37

EN

In this paper, a special configuration for the huge multipurpose machine tool of “travelling column” type was investigated by the finite element analysis. Internal degrees of freedom of a bulky system consisting of the ram, stock, column, sledge and bed, were implemented by the hydrostatic guides. A simulation of coupling two assembled columns into the portal structure was completed. The results of this work showed that temporal joining raises the spindle static rigidity by 1.39–1.91 times depending on the direction (mostly longitudinal – along the X-axis). The simulation also revealed the robustness of a whole-machine resonance pattern (11.7–39.0 Hz) to “column–to–portal coupling”. Eight types of eigenmodes were analyzed for frequency intervals from 0 to 80 Hz. A decrease by 2.9 times of the resonance peaks of a frequency response function was observed in the case of a portal structure creation. In case of columns-to-portal transition, stable cutting just at resonance frequencies (resonance overriding) becomes allowable. Overall, the “Portal” structure is recommended for intermittent cutting machining by raised high spindle unit at frequencies below 40 Hz.

2

Dynamic finite element analysis of rotor-shaft fastening into a heavy precise lathe

Dounar Stanislau, Jakubowski Andrzej

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

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nr 66 (138)

37--45

EN

The results of finite element analysis of large machined rotor fastened into heavy precise lathe are reported. Many design changes are simulated to improve the dynamic rigidity of the machining. Three radial eigenmodes detrimental to the accuracy were revealed: rotor-stock bending at 17.7 Hz (“half-wave”), rotor-lathe bending at 36.1 Hz (“full-wave”), and “support rocking” at 68.1 Hz. The frequency response functions and dynamic rigidities were evaluated. Three compliance issues were revealed: angular flexibility of the spindle console, low stiffness of the lathe bed (with boots), and an excessively slender tailstock. It is proposed to transform the spindle chuck into a table with additional hydrostatic backing, fill the bed cavities with concrete, and redesign the tailstock as a counter-spindle unit. This will decrease the amplitude of the main rotor resonance by 6.3 times and upshift the frequency near two-fold from 17.7 to 35 Hz. The renovated lathe should be able to machine a rotor without a lunette system or overriding the main resonant frequency.

3

Finite Element Method analysis of the deformation of the shaft and supports of a large, precise lathe – Cutting force excitation

Dounar Stanislau, Iakimovitch Alexandre, Jakubowski Andrzej

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2020

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nr 62 (134)

91--98

EN

In this paper, Finite Element Method (FEA) harmonic analysis of the changes caused by raising the centerline of a large, precise lathe is presented. Two standalone dynamic subsystems (“Rotor Shaft” and “Support”) are revealed and the resilience of the “Rotor Shaft” to the raising procedure is stated. The three subsystems of the “Support” class are much more dynamically pliable, only the main eigenmodes of the shaft and supports are excited in the 0…100 Hz range (MR1“Half-wave” and MS1…3 “Radial pecking”). Mounting the lunette suppresses the MR1 peak by a factor of two; therefore the lunette is strongly recommended, with an optional tuned-mass damper (TMD). The support’s resonant frequencies MS1…3 are more deleterious for precision; they should be omitted or weakened using TMD’s that are attached to the supports. For the above conditions, raising the centerline (up to 600 mm) may be included in the lathe renovation program.

4

FEA-analysis of shaft and supports deformations for huge precise lathe. Statics and resonances

Dounar Stanislau, Lakimovitch Alexandre, Ausiyevich Andrei, Jakubowski Andrzej

New Trends in Production Engineering

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2018

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Vol. 1, Iss. 1

341--348

EN

Load bearing system simulation is provided for a huge lathe to be renovated. Static and modal analyses are done by FEM. Focus was centerline rising, needed for larger rotor shaft machining. Forces between shaft and three supports were applied. Shaft static stiffness is lowered at 1.15 times only for 600 mm centerline rising. Supports have lost its rigidity at 1.42 times. Concrete pouring into bed cavities is recommended for supports flexibility limitation such as tailstock reinforcement. Robustness of bottom resonances is revealed both for rotor shaft (14.5-18.2 Hz) and supports (42.7-55.4 Hz). Centerline rising is allowed on 300 mm at least. It gives possibility to machine extremely large (up to ø2750 mm) shafts.