Wyniki wyszukiwania - BazTech

1

Measurements of temperature of CNC machine tool ball screw utilising IR method

Zapłata J.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 3

769--777

EN

In numerous papers it is proposed to use IR measurements of feed axis ball screw temperature distribution in order to compensate CNC machine tool thermal errors. The paper aims to validate reliability of the IR measurements in application to the feed axes ball screws. The identification of key factors influencing the accuracy of the IR measurements of ball screw temperature distribution has been conducted. A test-bench utilizing a ball screw assembly with built-in temperature sensors was introduced and the experimental data are presented along with conclusions.

2

Sensorless compensation system for thermal deformations of ball screws in machine tools drives

Kowal M.

Archives of Mechanical Technology and Materials

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2016

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Vol. 36

1--6

EN

The article presents constructional, technological and operational issues associated with the compensation of thermal deformations of ball screw drives. Further, it demonstrates the analysis of a new sensorless compensation method relying on coordinated computation of data fed directly from the drive and the control system in combination with the information pertaining to the operational history of the servo drive, retrieved with the use of an artificial neural networks (ANN) -based learning system. Preliminary ANN -based models, developed to simulate energy dissipation resulting from the friction in the screw-cap assembly and convection of heat are expounded upon, as are the processes of data selection and ANN learning. In conclusion, the article presents the results of simulation studies and preliminary experimental evidence confirming the applicability of the proposed method, efficiently compensating for the thermal elongation of the ball screw in machine tool drives.

3

Investigation of Ball Screws for Feed Drive

Sobolewski J.

Journal of Machine Engineering

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2013

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Vol. 13, No. 4

86--95

EN

The paper presents a method which enables the ball screw choice for machine tools feed drive with increasing cutting speed. It has been proven, that when the velocity deflection in the ball/balltrack area of the transitive phase of ball motion reaches a certain level, the repetitive shocks (impact forces) are generated. Digital simulation of these forces for variable length screws shaft and ball diameters in function of rotational speed has been performed. The research proves that impact forces increase not only as rotational velocity increases, but also with the increase of the ball diameters. The cases of the harmful accordance of the feed drive resonance vibrations with the frequency of the balls entering the load have been examined.

4

Ball Screws Selection for CNC Feed System

Sobolewski J. Z.

Machine Dynamics Research

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2011

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Vol. 35, No. 2

72-79

EN

Ball screws are used in the feed systems of the Numerical Control (NC) machines tools working with constantly higher cutting speed. When the speed of the balls reaches certain level, the repetitive shocks (impact forces) generated by the balls in the "transient" phase of the balls' motion increases vibration and noise. The frequency of impact forces should not be equal to the resonance frequency of driving system. Otherwise it could cause an incorrect work of the system, even could damage the ball screw mechanism. Digital simulation of these forces for definite screw and ball diameters in function of rotational speed has been investigated. The feed system resonance frequency for variable payload masses, balls diameters and the ball screw shafts length has been examined.

5

The problems of ball screws rigidity estimation

Sobolewski J., Małkiński J.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

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2006

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z. 4/63

13-20

EN

Rigidity is the main criterion for application of ball screws in NC machine tools feed systems. One of rigidity components is the balls/balltrack area rigidity, dependent on Hertz deflections. hoever, due to machining errors, the ball screws rigidity are considerably lower than the theoretical ones. On the basis of mathematical model developed by the authors, a computer simulation of the influence of machining errors on contact deflections was carried out. It proved that the rigidity of balls/balltrack area depends not only on accuracy grade but also on geometrical parameters of the thread. Measurements of ball screws rigidity were executed and the results were compared with the results of computer simulation. This effected a verification of computational model and a determination of the confidence level of calculations. A coefficient known as the geometry correction factor was introduced in order to estimate the influence of machining errors on lowering the level of rigidity. This coefficient was compared to the correction factor of accuracy applied in ISO norms for estimating ball screws rigidity.

6

Vectorial dimensioning and tolerancing of ball screws

Humienny Z., Kiszka K., Sobolewski J.Z.

Prace Naukowe Instytutu Technologii Maszyn i Automatyzacji Politechniki Wrocławskiej. Konferencje

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2000

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Vol. 76, nr 35

51-58

EN

The implementation of vectorial dimensioning and tolerancing (VDT) for dimensioning and tolerancing of ball screw with focus on balls screw nut and recirculation inserts is discussed. The VDT concept is based on substitution of real workpiece surfaces by imaginary geometrical ideal features. Location vector, orientation unit vector, tolerances of their components and tolerated substitute size define the substitute element. The VDT approach changes significantly rules of geometrical tolerancing based on ISO 1101 and provides firm foundations for workpiece dimensional and geometrical accuracy. The classical dimensioning and tolerancing of the nut and ball recirculation elements is briefly given. Next generation of drawing with table according to the VDT rules and proposed principles of transformation are discussed. The VDT eliminates unclear cases of dimensioning and tolerancing and univocally defines geometry of the mating nut and ball recirculation element. It should be stressed that elimination of some unclear cases of classical dimensioning tightens manufacturing requirements. Correct VDT substantially facilitates verification of geometrical nut requirements with the coordinate measuring technique.