Encoders convert mechanical movement into electrical signals.  This conversion is carried out optically, magnetically or mechanically. Encoders are subdivided into rotary and linear depending on the movement involved. Rotary encoders are used in the field of tool spindles to measure the rotational speed.Encoders work with very small (incremental), counting or absolute material measures as line patterns, magnetisation or contacts.Absolute encoders directly assign a position to each measured value. No reference value is required and it is also possible to drive directly to a particular position after the machine has been at a standstill.Incremental encoders require a reference value from which…

With the fixed-floating bearing arrangement of the roller bearings, most often the tool interface side bearing on the outer and inner ring is set, so that there can be no movements. At the other end of the shaft another roller bearing is set on the spindle shaft, whereby the outer ring is designed to be free to slide within the housing. This type of mounting is suitable for spindle mounting, although to a very limited degree because it is not possible to apply the essential pre-tensioning force to the spindle bearing. 

With bearings lubricated with grease, correct commissioning primarily determines the durability, service life and the performance of the spindle bearing. An optimum grease distribution run will optimise the characteristic value of the rotational speed, reduce the operating temperature in the bearing, achieve a long service life and ensure high operational reliability. During the grease distribution run, the grease is displaced from the running track and the base oil which is continuously added can build up the separating oil film between the balls and the running tracks required for lubrication.The grease distribution run can be split into short intervals and continuous…

The HSK mount is used for clamping tools (milling, drilling). Due to its positive characteristics with regard to accuracy and stiffness, the HSK interface per DIN 69893 has found widespread use in the area of machining. In addition, its suitability for high rotational speeds and the possibilities for rapid tool change have lead to supremacy over the SK interface. The hollow shank taper interface achieves its significantly higher radial and axial stiffness, compared with the steep taper interface, through its flatness. In addition, the flexural rigidity of a hollow shank taper is far greater than that of steep tapers or…

With most repair work, the vertically or horizontally positioned spindle must be removed from the machine tool. In doing so, it is critical that installation or removal work is only carried out once the machine has been released for this and that safety measures are complied with.  The oil and coolant lines are disconnected first and reconnected last.If it is necessary to ship the spindle, ensure that all open connections for lubrication and sealing air are sealed by suitable means. This prevents the ingress of foreign objects and moisture, which could damage the sensitive precision bearing. Shipping should be carried…

In machine tools, the main spindle realises the rotational cutting movement. In doing so, the cutting movement can be carried out both by a rotation of the workpiece (lathes) as well as by a rotation of the tool (drilling or milling machines).   The design of the spindles differs depending on the application, the speed range and the development stage. As a result, from machine to machine, differentiation is made between a directly driven and indirectly driven spindle. In the case of directly driven spindles, the motor is integrated on or at the spindle shaft (motor spindle) with the tool interface. …

A motor spindle is a directly driven spindle, where the motor, which is normally a three-phase asynchronous motor, is located directly on the main spindle between the spindle mounts.  Here, the rotor is shrink-fitted directly onto the spindle shaft. The heat arising from the high power losses is partially dissipated via liquid cooling, or occasionally via air cooling over the stator. Compared to conventional drives, motor spindles are characterised by a high degree of torsional stiffness and most commonly belt-driven or gear-driven designs. Further advantages of the motor spindle are the compact construction of the motor, the quiet and precise running…

A rotary feedthrough provides gases and liquids with a sealed transition from a fixed object to a rotating object or between two rotating objects.In the machine tool spindle, the rotary feedthrough is attached above the floating bearing and feeds the coolant for the tool into the shaft. In wet processing, this is oil or water-based coolant and in dry processing it is air.  With minimum quantity lubrication, where the coolant is precisely metered to suit the machining and the workpiece, an oil-air mix is used as coolant.As a result, the rotary feedthrough is exposed to high rotational speeds and variable…

Rotor and Stator of Motor Spindles: Fundamentals and SignificanceMotor spindles are crucial components in machine tools used for precision machining tasks such as milling, drilling, or grinding. A fundamental physical aspect that governs the functioning of these spindles lies in the interaction between the rotor and stator. This essay illuminates the functions, structure, and importance of these two key elements.1. The Rotor: The rotor constitutes the rotating part of the motor spindle and bears the tool. Typically made from high-strength materials like alloyed steel or ceramics, the rotor withstands the stresses encountered during machining operations. Its rotation generates the necessary…

Single-row angular contact ball bearings with a contact angle between 12° and 25° are termed spindle bearings. They comprise solid inner and outer rings as well as solid window cages and cannot be dismantled. In comparison to other bearings, they can be better lubricated thanks to their smaller contact surfaces. For this reason, spindle bearings are used for mounting high-speed main spindles in machine tools, and are distinguished from conventional angular contact bearings by their accuracy and the smaller contact surfaces for the balls.  In order to guarantee a defined rolling behaviour of the balls, spindle bearings always require pre-tensioning…