1 Introduction High-speed machining has become an important part and direction of modern machinery manufacturing technology. At present, the industrialized countries have begun to widely use high-speed cutting machine tools with spindle speeds of tens of thousands of revolutions per minute or even tens of thousands of revolutions per minute. China's automotive, tractor, aerospace and other industries have imported a large number of advanced production lines, machining centers and high-performance machine tools from abroad, including many high-speed cutting machine tools. Under the situation that the spindle speed of the machine tool is greatly increased, the machining performance of the traditional BT (7:24 taper) tool system has been difficult to meet the requirements of high-speed cutting. For this reason, industrialized countries have been racing to develop various new tool systems that can adapt to the needs of high-speed cutting. At present, the HSK (Germany Hohl Schaft Kegel abbreviation) tool system, the US KM tool system, and the NC5 of Japan are widely used. The Big-Plus tool system, among which the technology of the HSK system is the most mature and the most widely used. HSK tool system adopts hollow short-cone structure and two-sided clamping method. It has superior performance in terms of system rigidity, radial round runout accuracy, repeated installation accuracy, and clamping reliability. The manufacturing accuracy of the tool system directly affects its working performance. This paper analyzes the main differences between the German DIN standard and the ISO standard in the HSK tool system, and discusses the influence of the HSK tool system positioning accuracy and the connection stiffness, in order to provide reference for the development of the domestic new tool system. 2 The formulation of the HSK tool system standard began in 1987 and a special working group was established in more than 30 units of the Machine Tool Laboratory (WZL) and some tool manufacturers, machine tool manufacturers, and user companies at the Achen University of Technology in Germany. Prof. Weck initiated the research and development of a new tool system. After the first round of research, the working group submitted to the German Industrial Standards Organization in July 1990 a standard proposal for “automatic tool change hollow handleâ€. In July 1991, Germany published the draft DIN standard for the HSK tool system and proposed to the International Standardization Organization the development of relevant ISO standards. In May 1992, the International Organization for Standardization ISOT/TC29 (Tools Technical Committee) decided not to formulate the ISO standard for automatic tool change hollow shank. After the second study of the working group, Germany established the official industrial standard DIN 69893 of the HSK tool system in 1993. In May 1996, at the ISO/TC29/WG33 review meeting, the HSK tool system based on DIN 69893 was developed. ISO standard draft ISO/DIS12164. After many revisions, the official ISO standard ISO12164 for the HSK tool system was promulgated in 2001. 3 Main differences between DIN standard and ISO standard Before the official ISO standard for HSK tool system was promulgated, the HSK tool system-related products produced in various countries were designed and manufactured in accordance with the German standards DIN 69893 and DIN 69063 which specify the shape of the spindle mounting hole. However, the official ISO standard ISO 12164 of the HSK tool system has made several important improvements to the DIN standard. These differences will have a great impact on the working performance of the HSK tool system. In the HSK tool system, the quality of the taper between the shank taper and the taper of the machine spindle directly affects its performance and accuracy. Therefore, the reasonable development of the accuracy requirements of the shank taper and the spindle hole of the machine tool is the key to the HSK tool system standard must be resolved. problem. In this regard, the DIN standard and the ISO standard adopt two distinct treatment methods. Take the HSK-A shank as an example. The main control dimensions of the shank taper and spindle taper of the DIN standard are shown in Figure 1. Table 1 shows the relevant dimensions of the taper of the HSK-A63 shank and the taper of the spindle.
*D3max=D2max-2*L3 tg(2°51'45"-AT3/2)=46.534mm
*D3min=D2min-2*L3 tg(2°51'45")=46.529mm The maximum and minimum interferences at the large end d2 and the small end d3 when the taper part of the shank is matched with the taper of the main shaft are respectively
(a) Shank taper
(b) Spindle taper
(a) Tool holder taper tolerance zone
(b) Spindle cone bore tolerance zone
*D3max=D2max-2*L3 tg(2°51'45"-AT3/2)=46.534mm
*D3min=D2min-2*L3 tg(2°51'45")=46.529mm The maximum and minimum interferences at the large end d2 and the small end d3 when the taper part of the shank is matched with the taper of the main shaft are respectively
D2max=d2max-D2min=12μm
D2min=d2min-D2max=4μm
D3max=d3max-D3min=8μm
D3min=d3min-D3max=-1μm (gap)
The main control dimensions of the HSK-A shank taper and spindle taper hole specified in ISO standards are shown in Figure 3. As can be seen from the figure, in the ISO standard, the taper of the HSK shank is controlled by the diameter d2 of the large end section, the dimension l2 of the section position, the tolerance t of the profile of the taper surface, and the taper (1:9.98). The small end is not specified separately. Size and tolerances. The corresponding spindle taper hole control method is similar to the taper of the shank taper. It is also controlled by the diameter D2 of the large end section, the dimension L2 of the section, and the tolerance T and taper of the profile of the taper, but the taper is the same as the DIN standard (1: 10), small end sizes and tolerances have not been separately specified. In the ISO standard, the spindle taper and shank taper are not specified in L3, L3, D3, and D3. For ease of analysis, this paper uses "*L3", "*l3", "*D3", and "*d3" "Represents the dimensions corresponding to L3, l3, D3, d3 in the DIN standard. Table 2 shows the relative dimensions of the taper of the HSK-A63 shank and the spindle taper. Figure 4 shows the tolerance zone of the HSK-A shank taper and spindle taper. D2min=d2min-D2max=4μm
D3max=d3max-D3min=8μm
D3min=d3min-D3max=-1μm (gap)
(a) Shank taper
(b) Spindle taper
(a) Tool holder taper tolerance zone
(b) Spindle cone bore tolerance zone
D2max=d2+t=48.0 13mm
D2min=d2-t=48.007mm<br>*d3max=d2-*l3/ 9.98+t=46.540mm
*d3min=d2 -*l3/9.98-t=46.534mm
D2max=D2+T=48.000mm
D2min=D2-T=47.996mm
*D3max=D2-*L3/10+T=46.530mm
*D3min =D2-*L3/10-T=46.526mm</div>
When the taper of the shank and the taper of the spindle are matched, the maximum and minimum interferences at the large end d2 and the small end *d3 are respectively D2min=d2-t=48.007mm<br>*d3max=d2-*l3/ 9.98+t=46.540mm
*d3min=d2 -*l3/9.98-t=46.534mm
D2max=D2+T=48.000mm
D2min=D2-T=47.996mm
*D3max=D2-*L3/10+T=46.530mm
*D3min =D2-*L3/10-T=46.526mm</div>
D2max=d2max-D2min=17μm
D2min=d2min-D2max=7μm
D3max=*d3max-*D3min=14μm
D3min=*d3min-*D3max=4μm
4 The use of two standard HSK tool system performance analysis toolholder positioning accuracy and joint stiffness are two important indicators to measure the performance of the tool system. The following is a comparative analysis of the positioning accuracy and joint stiffness of HSK tool holders using DIN and ISO standards. Positioning accuracy The positioning accuracy of the HSK tool holder includes axial positioning accuracy and radial positioning accuracy. Because the HSK tool holders using the DIN standard and the ISO standard use the end face for axial positioning, both have high axial positioning accuracy (<0.001 mm), and there is no difference. Since the HSK tool holder uses a tapered surface for radial centering, its radial positioning accuracy is determined by the fitting condition of the large end of the HSK tool shank taper surface and the major end of the spindle taper hole. For HSK-A63 shank and spindle as an example, when manufactured in accordance with DIN standards, the average interference at the big end is 8 Micro; m and when manufactured according to ISO standards, the average interference at the big end is 12 Micro; m. Therefore, the use of ISO standards is more conducive to ensuring the positioning precision of the tool holder. Linking stiffness The coupling stiffness between the HSK tool holder and the spindle is closely related to the fitting condition of the HSK tool holder taper surface and the spindle taper hole, and the tension condition of the tool holder, the tool holder end surface and the spindle end surface. The deformation curve of HSK tool shank under the action of cutting load is shown in Figure 5. As can be seen from the figure, there are two states of the connection stiffness of the HSK tool holder. The A-segment curve corresponds to a lower working load and a higher shank joint stiffness (smaller deformation). The connection stiffness at this time is related to the size of the front end of the shank; the B-segment curve indicates that the working load used as the shank is increased to After a certain degree, the deformation of the tool shank increases sharply, the joint stiffness decreases, the dynamic stiffness is very low, and the workability deteriorates. This feature is related to the size of the shank taper and the fit of the shank and the spindle taper hole. D2min=d2min-D2max=7μm
D3max=*d3max-*D3min=14μm
D3min=*d3min-*D3max=4μm
Fig. 5 Deformation curves of DIN shank under static load
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