Kv factor

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The k v factor (speed gain factor ) clarifies the positioning accuracy of a movement axis in mechanical engineering . It indicates the relationship between the process speed and the difference between the target and actual position of the machine , similar to the slip .

The K v factor is therefore also a measure of the rigidity of the drive. It is caused by inertia and loss .

calculation

The K v factor of a machine tool describes the ratio of the current speed (in ) of a moving part, usually the tool or workpiece , to the positional deviation, also known as the following error, in :

his unit is

The following error as a measure of the position deviation during the movement denotes the difference between the position setpoint and the position actual value . The k v factor is thus :

application

In positioning systems , for example in machine tools, the k v factor influences the accuracy with which the machine works:

  • The k v factor can be used to predict how large the position deviation will be at a certain speed. The more precisely a contour is to be traversed with a constant k v factor, the slower the movement must be; If a maximum following error is specified, the k v factor can be used to determine the maximum travel speed at which it is allowed to travel in order not to exceed it.
Influence of the k v factor on the following error
  • At constant speed, a higher k v factor leads to a lower positional deviation or a lower following error, i.e. H. for higher positioning accuracy (see Fig.).
  • If, on the other hand, the contour is to be traversed more quickly with the same accuracy, the k v factor must be increased. However, the load capacity of the machine must be known, since too large a k v factor leads to vibrations and instability of the drive system, which has a negative effect on the machining result and the machine.

A circular test can be used to check the positioning accuracy of a machine tool and to identify incorrectly set k v factors.

In control technology , in which these machines are analyzed (also hydraulic machines), it often appears in a block diagram , see also signal flow diagram . In automation technology and machine tool development, it is therefore a key factor influencing size, see machining movement .

Examples

In official information, the k v factor relates to the speed at which the positional deviation reaches 1 mm. Average values ​​are 5 m / (min * mm), whereby the maximum values ​​can be up to 16 m / (min * mm). With feed drives , the order of magnitude of the k v value is 0.6 to 4.8 m / (min * mm).

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