About the book
In proportion to the increase of requirements for the effectivity and accuracy of contemporary products, demand for the quality of the products manufactured is also continually going up. In the aspect of design and choice of optimal machines, we more often meet with virtual prototyping and computer analysis of the functional properties of a designed machine. Productivity, accuracy and reliability belong among the basic criteria for a manufactured machine.
The productivity of a machine is characterized by the number of manufactured parts along with the size of the machined area and the volume of material taken up. Productivity is limited by the mean thickness of the chips and is in dependence of cutting and feed speed. Moreover, the cutting speed depends mostly on the frequency of rotation of the working headstock of the machine tool. This is the reason for ongoing increase in terms of revolution frequencies, the ever more frequent application of headstock with integrated drive, so-called “motor headstock” and the shift from classic to high-speed machining.
The basic condition for achieving the required machine tool accuracy, as well as that of the machined parts, is the rigidity of the "machine - tool - preparation – workpiece" system. Apart from rigidity, this system is influenced by the geometric accuracy of the machine, the technological approach, the strategy for measuring the workpiece and the servicing of the machine. With classical machine tools construction, this refers to the serial structure of arranging the motion axes, where the total rigidity of the system is limited by the machine’s weakest construction node. With machining tools with moving rotation, it is generally the motion axis carrying the workpiece, or the tool carrier - again the headstock.
It is clear that such productivity and machine tool works precision depends mostly on the quality of the headstock and all of the factors described above. Both of these criteria act in a contradictory manner. With the requirement for increased headstock frequency and feed speed, production does increase, but at the same time the positional rigidity of the work headstock and of the motion mechanisms (under the requirement for small mass) – in other words, machine work precision – decreases. From the viewpoint of productivity and accuracy of work we can regard the headstock as the heart of the whole machining tool, influencing the quality of work to a decisive degree.
Among other important quality criteria is the mechanical construction or modularity of the machine tool or of the production system. The modular state of the construction is an important precondition for the competitiveness of the product on the market. The basis of this concept is the system of modules from which various configurations can be created, in line with the specific demands of the client. On the side of the producer the manufacture of the machines will be made more effective, while on the other hand the client will be paying for a functioning machine that he really needs and uses.
An inseparable component in the selection of a suitable machine is risk management and current analysis of the functionality and reliability of the machine’s work. We are able, on the basis of such an analysis, continue with computer optimization of the mutual spatial arrangements of "machine - tool – preparation- workpiece" system so as to configurably achieve the maximum work safety of the existing machine.