In order to determine the uniform reasonable balance quality grade G for high-speed rotary tools, a working group was established under the leadership of the precision tools professional committee of the German government and the association of machine manufacturers (VDMA).Members of the research group come from related industries and technical fields, such as cutting tools, machine tools and balance machine manufacturing industry, user industry, universities and research institutions.Based on their research results, the guidance specification (FMK -- Richtlinie) for "balancing requirements for high-speed rotary tool systems" was proposed.

The specification has three main points:

(1) it is considered that the requirements for the tool balance quality level are a range defined by the upper limit and the lower limit, and the unbalance of the tool greater than the upper limit will have a negative impact on the processing and less than the lower limit indicates that the unbalance requirements are too strict, which is both technically and economically unreasonable and unnecessary.

(2) the size of the dynamic load of the spindle bearing is taken as the evaluation scale of the tool balance quality, and G16 is stipulated as the unified upper limit value.Due to the diversity of cutting conditions and factors affecting the machining effect, the evaluation scale of the machining effect as the tool balance is not universally applicable, and the size of the spindle bearing dynamic load caused by the tool imbalance is and

Unbalance is directly related to the parameters, so the size of the dynamic load of the spindle bearing is proposed as the basis for the establishment of uniform balance requirements.According to VDI plus 56(DIN/ISO10816) "mechanical vibration evaluation standard", can make the spindle bearing to produce the maximum vibration speed (1 ~ 2.8mm/s) unbalance as the tool system allowable unbalance upper limit.When the LMM/s or 2.8 mm/s vibration velocity as the evaluation scale, different weight of HSK an 63 handle within a certain range speed allowed by the balance of the upper limit of quality grade G three curves (b) show that the upper limit of G and tool quality, speed, and the selected spindle vibration velocity, and scattered in a wide range.The working group selected HSK tool shank of different specifications with vibration speed of 1.2mm/S, 2mm/S, rotation speed range of 10000-40000r /min and weight of 0.5-10kg to calculate the upper limit value of 27 G, in which the maximum G value reached 201 and the minimum G value was only 9.To comprehensively consider the security requirements of high speed rotary tool and ease of use, the working group proposed a compromise tool system balance level requirements, the selection of G16 as the upper limit of unity, so besides cannot satisfy a G9 value can be calculated to satisfy all G value covering the scope of the processing conditions (i.e. speed for l0000 ~ 40000 r/min, the cutting tool system is 0.5 ~ 12 kg weight, vibration speed of 2 mm/s).

(3) the lower limit for determining the reasonable unbalance of the tool system is the eccentricity (in units) of the tool system installed on the spindle of the machine tool, which is usually 2 ~ 5 m(depending on the specific situation of each machine tool) according to the existing machine tool manufacturing level

Different).Setting eccentricity as the lower limit indicates that it is not meaningful to balance the allowable residual eccentricity eper(m) of the tool system to less than 2~5 m.When the rotation speed is below 40000r/min, the allowable residual eccentricity eper value (m)(or residual unbalance GMM /kg per unit weight) corresponding to the upper limit value G16 is greater than the repeated positioning accuracy of tool change system (eper=4 m only when the rotation speed is equal to 40000r/min).Therefore, the upper limit of G16 and lower limit of 2 ~ 5 m(or GMM /kg) can not only prevent the adverse impact of excessive unbalance on the spindle, but also has technical and economic rationality.In addition, the requirements of the G16 meet the requirement that the tool balance grade in the EDINENISO15641 is better than that of the G40.

The guidelines also require that the tool's internal cooling holes be symmetrically distributed.The tool and tool spindle can be used as a system to balance if necessary. That is to balance the spindle and tool (or tool system), and then load the tool into the spindle and balance the system as a whole.