**1.1. Headstock – The heart of the machine tool**

50 Performance Evaluation of Bearings

the types of lubrication used.

Economics, production and service efficiency

**Figure 1.** Factors influencing the Quality of Machine Tools, [4].

Flexibility MACHINE TOOL

parameters of the machine.

experience in this field.

system, e.g. [1] and [2].

Industrial design

*K*

Total Machine Stiffness

 *n*

*i i machine K*

1

1

the individual bearings, their number, pre-load magnitude, manufacturing precision, and

The stiffness of the SBS depends on the stiffness of the bearings and the spindle itself. There are several methods that can be employed for determining the static stiffness of the spindle

High utility value

Effect on the working environment

Easy control and safety of the work

Speed capability of bearings *N = nmax.dmid* 

QUALITY

However, one problem which has not yet been solved is the calculation of the stiffness of the bearings, (or nodes of bearings) in the individual housing. Accurate calculation of the stiffness of the bearing nodes requires the determination of the static parameters of each bearing. From a mathematical point of view, this can be solved by using a system of nonlinear differential equations, which requires the use of computers. To simplify the design, we need a static analysis which provides the basis for the dynamic characteristics of the mounting, and of the machine itself. Designers often prefer the conventional and proven methods of mounting*,* without taking into account the technical and technological

MACHINE TOOL HEADSTOCK

Work accuracy **Productivity** 

For the design engineer, it is important to be able to undertake a quick evaluation of various SBS variants at the preliminary design stage. The success of the design will depend on the correct choice of suitable criteria for the SBS, and if the design engineer has adequate The headstock, whether tool or workpiece carrier, has a direct influence on the static and dynamic properties of the cutting process, Figure 2. The spindle-bearing system (SBS) stiffness affects the surface quality, profile, and dimensional accuracy of the parts produced. It also has a direct influence on machine tool productivity because the width of cut influences the initiation of self-induced vibration; it is directly proportional to machine tool stiffness and damping.

Complex analysis of the SBS is very difficult and complicated, [5]. The analysis requires an advanced understanding of mathematics, mechanics, machine parts, elasto-hydrodynamic theory, rolling housing techniques, and also programming skills. The results of our research into SBS have been divided into three parts:

**Figure 2.** CNC profile milling machine, Carl Hurt Maschines, Germany; Work nodal point – 3x7013ACGA/P4, Opposite nodal point – 2x7013ACGA/P4

