Cooling of motor spindles—a review

Thermally induced loads in motor spindles can cause a number of undesired effects. As a result, the process capability of spindles, and thus, the productivity of a process can decrease. Future motor spindles will be exposed to higher mechanical and especially thermal loads due to trends aiming to increase power densities and maximum speeds. These trends are amplified by increasingly powerful drive concepts and developments in bearing technology. Therefore, researchers assume that it will not be possible to raise the performance potential of spindles due to insufficient cooling of its heat sources. A series of different cooling concepts have been researched and developed in recent decades. These developments have been made for different purposes. They also differ considerably in terms of their cooling principles and cooling performance. In this article, these cooling approaches and the motivations for their development are described. Firstly, the causes of heat development in motor spindles are described in a historical context. Subsequently, the effects of heat development on the manufacturing-relevant properties of motor spindles are revealed. Finally, current deficits in the area of spindle cooling and the need for the development and transfer into industrial practice of more efficient and cost-effective cooling concepts to overcome future challenges are discussed.

Water-Tight Concrete Constructions and Directives for their Design and Realization

The paper describes problems of water-tight concrete constructions, their design, manufacture and testing of quality in accordance with regulations and directives used in the Czech Republic and abroad. Current knowledge of water-tight constructions and water-tight concrete imply that main focus is on problems of use of water-tight concrete for construction of so-called white bath and preventing crack formation in concrete. Laboratory work is focused mainly on design of concrete based on individual regulations. Subsequently, influence of various types of cement and additions partly replacing cement on properties of water-tight concrete is examined. Research of heat development during hydration at early stages of maturing is and inseparable part of the experimental work, as well as development of compressive strength, water-tightness and frost resistance of concrete