Wyniki wyszukiwania - BazTech

1

Problemy określenia sztywności przekładni śrubowych kulkowych

Małkiński J., Sobolewski J. Z.

Przegląd Mechaniczny

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2008

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nr 2

36-40

2

Simulation investigation of ball screws for high speed transmitting systems

Sobolewski J. Z., Małkiński J., Pieniecki P.

Journal of Machine Engineering

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2008

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Vol. 8, No. 4

59--67

EN

The ball screws are used in feed systems in CNC machines working with constantly higher cutting speed. When the speed of the balls reaches certain levels, the repetitive chock (impact forces) generated by the balls in the "transient" phase of the balls' motion and forces acting in the return channel cause damage to the recirculation ball system. A simulation of impact forces for variable length of transient phase in function of the rotational speed was made. The static axial rigidity is a very important factor to be considered in defining ball screws performance and exerts a major influence on positioning accuracy of NC machine tools. One of rigidity components is the balls/balltrack area rigidity, dependent on Hertz's deflections. However, due to machining inaccuracies, the ball screws properties (especially rigidity) are considerably lower than the theoretical ones. A coefficient known as the geometric correction factor makes it possible to predict the rigidity of the ball screw. A computer simulation of the influence of machining inaccuracies on contact deflections, rigidity and servo drive resonance was carried out. It was examined what rotational speeds set off the harmful phenomenon of the agreement of the frequency of the arrangement of the impact forces with the frequency of the servo drive system resonance. The presented method allows for the calculation of the impact forces, total rigidity and resonance of NC machine feed system, in the preliminary phase of technical project.

3

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.