Inspection and dynamic balance of the taper handle

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Detection and dynamic balance of HSK tool taper shank Abstract: domestic HSK hollow taper shank tool system has made rapid development in recent years, but the manufacturing quality of its shank needs to be improved. Taking the hsk63-a handle and its mounting hole as an example, the shape, position and size requirements of HSK hollow taper handle are analyzed, and the quality inspection and dynamic balance calculation of HSK hollow taper handle are introduced

in modern automobile manufacturing, aircraft manufacturing, gas turbine manufacturing and other industries, in order to improve production efficiency, high-speed and ultra-high-speed cutting machines with spindle speeds of tens of thousands or even tens of thousands of revolutions per minute are widely used. At such a high speed, the 7:24 tool taper shank commonly used in traditional cutting shows a series of shortcomings, which has been difficult to meet the machining requirements of high-speed cutting. Therefore, many advanced production lines at home and abroad have widely used a new type of 1:10 short cone hollow taper handle (HSK handle) to replace the 7:24 taper handle. Because HSK tool taper shank has superior performance in stiffness, radial circular runout precision, the advanced materials adopted by C919 mainly include the third generation aluminum lithium alloy, carbon fiber composite and titanium alloy, etc., repeated installation accuracy, tool life, etc., it has been rapidly popularized. However, because the import price of various types of hollow handle tools is very expensive, we must base ourselves on domestic production and manufacturing. Developing domestic HSK hollow taper handle tool products is an important task facing China's tool industry

1 HSK interface standard and inspection of interface parts

at present, there is no formal international standard for HSK interface (only the draft iso/dis12164 standard that has not been promulgated and implemented). Manufacturers of HSK interface related products in various countries (but plastic processing technology is simple, including machine tools, tool systems, testing tools and instruments, etc.) are designed and manufactured in accordance with German standards din69893 and din69063. Din69893 specifies the shape and size of HSK handle; Din69063 specifies the shape and size of HSK taper handle mounting hole. Taking the hsk63-a handle and its mounting hole as an example, the shape, position, size requirements and detection methods of HSK taper handle and mounting hole are discussed below

1.1 in DIN standard, the size of HSK handle tool cone depends on the diameter and tolerance of two sections. Figure 1 shows the main dimensions of hsk63-a handle

Fig. 1 type and main dimensions of hsk63-a handle

in Fig. 1, the key dimensions affecting the performance of HSK tools include: ① diameter d2=48.000+0.011+0.007mm at L2 of conical handle; ② Diameter at l2+l3 d3=46.530+0.007+0.003mm; ③ The position dimension of the midpoint of the 30 ° inclined plane for clamping relative to the end face l6=18.13 ± 0.042mm. From the dimensions D2 and D3, we can get the outer conical tolerance zone of hsk63-a taper shank as shown in Figure 2. If D2 and D3 after machining meet the standard requirements, it means that the dimensional accuracy of the cone and the position accuracy of the cone relative to the end face are qualified. Because both ends of the tolerance zone are trumpet shaped, the cone root size of hsk63-a taper handle can reach 48.637 ~ 48.644mm, which is larger than the end face aperture of the installation taper hole. Therefore, before the taper handle is tensioned in the installation hole, there is a certain amount of clearance between the end faces (about 0.04 ~ 0.14mm for hsk63 taper handle); After the taper handle is tensioned, the conical surface and the end face can reach close contact and have high rigidity

Fig. 2 tolerance zone of hsk63-a handle outer cone

in production, the diameter dimensions D2 and D3 are mostly tested with special ring gauges with dial indicators (see Fig. 3). Before using the ring gauge to test the workpiece, it is necessary to calibrate the dial indicator with a standard sample cone (the cone shown in Figure 3). The dimensions of the standard sample cone are d2=48.000mm, d3=46.530mm, and the taper is 2 ° 5145 "(1:10 taper)

Figure 3 special ring gauge and standard sample cone

d2 and D3 can also be tested with pneumatic or inductive HSK comprehensive tester. Figure 4 shows the measurement principle of HSK inductance comprehensive tester. The inductance probe inputs the measured signal into the computer, and after processing by the measurement software and calculation software, the actual diameter value of D2 and D3 and the actual angle value of the cone can be directly displayed on the monitor

Figure 4 measurement principle of HSK inductance comprehensive tester

Chengdu Institute of tools has developed a variety of specifications of HSK inductance comprehensive tester (see Figure 5 for the appearance of the instrument). This instrument can be used to measure HSK taper handle or HSK taper handle mounting hole, with measurement accuracy and 4-hour stability of 0.001mm and resolution of 0.0001mm. The instrument measures accurately and quickly, and is suitable for final inspection of products

Figure 5 the HSK inductance comprehensive tester produced by Chengdu Tool Research Institute

1.2 size L6 is set to ensure that the tool handle has sufficient tension and high stiffness in the process of expanding the development of emerging markets for extruders in China's plastic machinery enterprises over the years. Dimension L6 is usually processed on the CNC lathe with high speed and small feed rate. Since the starting point and end point of L6 are in and out of the hole respectively, it is necessary to design a special inspection tool for measuring this dimension. The structure of this HSK tension inclined plane measurement inspection tool is shown in Figure 6. When calibrating or testing, first press the probe, center the sample or HSK tool handle with the cone, and then release the disc probe. The probe contacts the inclined plane under the action of spring for comparative measurement

Figure 6 HSK tension inclined plane measuring fixture

1.3 due to the thin hole wall of HSK hollow tool handle, in order to reduce the contact stress of key transmission, din69893 stipulates that the keyway at the tail end of HSK taper handle should be circular arc, and strict requirements are put forward for the position accuracy of the arc Center (see Figure 7, for hsk63, the size values in the figure are: e1=18.110mm, e2=9.15mm, r3=2.88 ± 0.02mm, b1=12.54 ± 0.04mm), and the four arcs should be tangent to the keyway width B1. In order to control the shape and position accuracy of the circular arc keyway, first ensure the dimensional accuracy and symmetry requirements of B1, and then use the special inspection tool to detect the shape and position error of the four circular arcs

Figure 7 view of HSK taper handle from the small end along the axis

1.4 in DIN standard, the type size of HSK mounting hole is determined by a diameter size and its tolerance, taper angle and its deviation. Figure 8 shows hsk63 mounting hole dimensions and their tolerance zones

figure 8 hsk63 mounting hole size and its tolerance zone

in the processing process, the taper plug gauge with dial indicator can be used to control the position of the taper hole of HSK mounting hole relative to the end face (for hsk63, the tolerance of taper hole L2 is controlled between -0.03 ~ +0.01mm). Figure 9 shows the situation of calibrating the plug gauge with dial indicator with the reference ring gauge. These gauges can be manufactured by the factory itself, but the reference ring gauge needs to be calibrated by Beijing Institute of metrology to ensure the interchangeability of HSK taper shank tools

Figure 9 HSK installation hole inspection tool

in addition to using plug gauge with meter to detect HSK installation hole, pneumatic taper plug gauge (see Figure 10) or inductive taper plug gauge can also be used for measurement, but there is no product supply in China at present, so special orders are needed

Figure 10 pneumatic taper plug gauge

2 dynamic balance of HSK tool handle

for boring and milling machine tools, if the dynamic balance of the tool handle installed on the spindle is not good, the spindle will be subjected to centrifugal force when rotating, thus reducing the stability of tool rotation, affecting the workpiece processing quality and the service life of the tool and spindle bearing. In order to counteract the effect of centrifugal force, the dynamic balance of the tool handle can be achieved by increasing or decreasing a corresponding mass at the appropriate position. For example, some HSK collets correct and offset the original imbalance u through compensation holes (or compensation planes)

2.1 calculation parameters and formulas of dynamic balance of tool handle

when calculating the dynamic balance of tool handle, the following parameters and calculation formulas should be applied: G - balance grade index (mm/s), g=e Ω; M - mass of object (g); Ω - angular velocity (/s), Ω =2pn; N -- HSK tool handle speed (r/min); M - unbalanced mass (g); R -- radius of gyration of M (mm); E -- center of gravity offset (m), e=g/Ω =u/m; U - unbalance (g · mm), u=mr=me (see Figure 11); F - centrifugal force (n), f=u Ω 2

Figure 11 calculation of unbalance U

calculation example of balance grade g

it is known that the mass of an HSK taper grip is m=1000g, and there is still residual unbalance u=3g · mm after dynamic balancing. Try to calculate the balance grade g of the chuck when it works at the speed of n=20000r/min

from e=u/m, Ω =2pn/60,

g=e Ω =2pnu/60m=pnu/30m

substituting into the numerical calculation, G ≈ 6.3mm/s can be obtained. Similarly, when the working speed n=8000r/min, G ≈ 2.5mm/s; When the working speed n=3200r/min, G ≈ 1mm/s. The above results can also be directly checked from the balance level nomogram shown in Figure 12

Fig. 12 nomograph of balance grade

it can be seen from the above results: ① when the tool handle mass m is the same, the residual unbalance u is the same, and the working speed n is different, the balance grade G is different; ② In order to make the balance level g the same at different speeds, the higher the working speed is, the smaller the unbalance u must be

2.2 recommended value of balance grade g and limited speed of HSK tool handle

when the working speed n=15000r/min, the recommended value of balance grade of hsk40 ~ hsk63 tool handle is g=6.3mm/s; When the working speed n=9000r/min, the recommended balance grade of hsk80 ~ hsk100 tool handle is g=6.3mm/s

after dynamic balancing of the tool handle and tool, the limited speed during use is shown in the table below. Tool handle specification limit speed

(r/min) tool handle specification limit speed

(r/min) hsk32hsk40hsk50hsk63hsk80hsk100 (end)

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