Guide

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…

Tool spindles are cooled by water (with corrosion inhibitor), air or oil in order to protect the spindle components from overheating and to maintain temperature-dependent material characteristics.The coolant is fed through the cooling coil, a wide milled "internal thread" in the housing around the motor spindle. The coolant heated by the waste heat from the spindle is cooled in suitable cooling units so that it can be fed back through the cooling coil again. In doing so, the correct composition of the coolant must be observed because the cooling coil could be destroyed or blocked through the effects of corrosion. 

The main spindles in machine tools are predominantly driven by electrical motors.As an alternative, there is also the option to use a hydromotor for the drive.Conventional machines with older construction styles are often driven by an unregulated electrical motor, which is tied to a speed as a result of the physical principle of operation, with the mains frequency and the number of pole pairsIf the spindle is to have several speed settings, a transmission is required between the motor and the spindle. Different types of transmission can be used depending on the requirements for the speed range and the accuracy…

DIN 31051 defines improvement as a "combination of all technical and administrative measures as well as the management measures required to increase functional reliability of the unit under consideration, without changing its required function".Similarly to the repair procedure, the improvement procedure encompasses "calculations, schedule planning, customising, provision of personnel, equipment and materials, creation of work plans" and the implementation of the improvement.   After the improvement measures have been implemented, a renewed functional check is essential to assure the correct functionality.The area of spindle improvement encompasses, for example, the conversion from steel balls to ceramic balls in spindle bearings in order…

DIN 31051 defines inspection as "measures for determining and assessing the current condition of the object being considered, including determining the causes of wear and deriving the necessary steps for future use".The inspection procedure encompasses the creation of "a plan for determining the current condition" and the implementation of this plan. Furthermore, the results of the determination of the current condition are assessed and a fault analysis created.  A decision is made about further measures on the basis of this assessment.   This includes maintenance, improvements or further measures.The scope of spindle inspection includes the adoption of measurement data such as spindle…

According to DIN  31051 maintenance is defined as "combination of all technical and administrative measures as well as the management measures during the life-cycle of the object being considered, required to maintain its fully functional condition or to return it to this condition so that it can perform the required function".Spindle maintenance includes servicing, inspection, repair and improvement.   When devising maintenance, consideration is given to the internal and external requirements of the company, as well as the repair strategies, and repair objectives are tailored to the objectives of the company.BILDSpindle maintenance is often offered under spindle servicing as a service….

Electrical motors are most commonly used as spindle drives.  Depending on the requirements on the machine tool, 3 different types of rotational electrical motors can be employed here:  The DC motor, the synchronous motor and the asynchronous motor. Externally excited DC motors have high torsional stiffness under load when regulated and can vary their speed significantly. For this reason they have long been employed as the main drives in machine tools. The stationary exciter field is generated in the motor stators in separately excited DC motors. The conductor windings are located on the rotor of the motor and must therefore be…

Alongside the mounting of the feed spindle and the rotary table, as well as the guides on the work table, the mounting of the main spindle is one of the most important components in the machine tool and is responsible for accepting and transferring the forces.The spindle mounting must fulfil the requirements for machine tools. These can be expressed as high working accuracy and high performance over an extended period of time, with low manufacturing and operating costs.In order to fulfil these requirements, spindle mountings have the following features:Exact positioning with low feed forces through low friction and low stick-slipCompliance…

The spindle run-time defines the operating time of the working spindle in the machine tool. The run-time is the number of hours for which the spindle has rotated within the course of processing, similar to the mileage of a car. This determines the value of the spindle when sold.The servicing intervals are based on the run-time as this provides the time for which the spindle has actually been stressed, in contrast to the switch-on time. In modern machines the run-time is automatically logged and recorded for evaluation. In production engineering the run-time can be compared with the switch-on time in…

The service life of the tool spindle is largely dependent on the service life of the spindle bearings, the components most affected by wear. The nominal service life calculation for roller bearings is based on fatigue theory. During operating times the roller surfaces of the bearing are subjected to cyclical compressive stresses, which result in the failure of the bearing after a foreseeable period due to fatigue. Moisture, inadequate lubrication or contamination, which result in wear and rust formation, are largely disregarded by this theory.  For this reason, the calculated service life does not generally apply reliably to practical situations.Alongside the…