Analysis method of spindle deflection of the hotte

2022-09-23
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Machine tool spindle deflection analysis method

machine tool spindle deflection analysis method Abstract: PDM system based on Web optimal layout design of grinder bed structure based on dynamic characteristics SMT basic terms explanation safety operation instructions for plate shears mkl7150 16/2 seven axis five linkage CNC powerful forming grinder three problems need to be solved for China's superhard tools to enter the international market large angle inclined plane laser cutting process operation of CNC EDM fast wire cutting machine tool Make (Part 1) connection and adjustment between FANUC CNC system and machine tool teguk shows metal processing 18 kinds of Wuyi 135 diesel engine block valve tappet hole machining modular machine tool W200HD boring and milling machine CNC system fault maintenance bearing failure analysis method in CIMT2007 (I) Implementation and application of PDM Project in Hangzhou gear box factory new injection molding process of embedded numerical control system based on ARM microprocessor -- injection compression molding technology new robot drag chain system surface quality coefficient implementation of PDM, acceleration of enterprise informatization development basic structure and advantages and disadvantages analysis method of deep groove ball bearing analysis spindle machine tool support processing 0.0002l calculation structure bearing this paper uses the method of statistics, calculation and actual measurement analysis and comparison, This paper discusses the allowable deflection of the spindle of modern machine tools (including numerical control, precision and general machine tools), and demonstrates the limitations of the commonly used allowable deflection formula in application. Introduction the rigidity of the spindle components of modern machine tools is the main index to reflect the structural performance of the spindle components. It comprehensively reflects the deformation of the spindle and bearing

this paper discusses the allowable deflection of the spindle of modern machine tools (including numerical control, precision and general machine tools) by means of statistics, calculation and measured analysis and comparison, and demonstrates the limitations of the commonly used allowable deflection formula in application

preface

the stiffness of the spindle components of modern machine tools is the main index reflecting the structural performance of the spindle components. It comprehensively reflects the deformation of the spindle and bearing, and is directly related to the machining accuracy of machine tools. The high-speed spindle is one of the key components of machine tools, so when designing the spindle components of high-precision CNC machine tools, it should meet the requirements of high stiffness. The stiffness of the spindle components is usually measured by the displacement in the direction of the force exerted by a certain force on the front end of the spindle. This is called the displacement of end deflection. It is an important parameter for designing the initial automatic control hydraulic material testing machine to use the electro-hydraulic servo valve to form the control system to calculate the spindle components. The allowable deflection has a decisive impact on the stiffness of the spindle components, so it determines the use performance of the machine tool

I. [y]=0.0002l source

at present, there is no unified regulation on the allowable value of the stiffness of the spindle components. Most of them take the displacement at the end of the main shaft, the rotation angle at the front bearing, the rotation angle at the gear mesh and the maximum cutting width without chatter, etc., which are often controlled by some empirical data and formulas. Among them, the following contents are often used to control the displacement of the spindle end [2][3]:

1 The displacement of the spindle end of the finishing machine tool shall not exceed one third of the allowable radial runout of the spindle

2. The end deflection of spindle for general machine tools [y]=0.0002l

allowable deflection is widely used in China. At present, this empirical formula is also quoted in various school textbooks. As we all know, the teaching content of most relevant textbooks in China comes from the former Soviet Union, and almost all of them adopt the early discussions on the allowable deflection of shafts and spindles by liechetov and Archer Kang, the authorities of machine tool research in the former Soviet Union

literature [5] suggests that the ratio of the maximum deflection of most shafts in machine tools (excluding the spindle in this section) to the length between bearings is in the range of 0.0001---0.0005. Generally not more than 0.0002

literature [6] also introduces that the general criteria for determining the allowable deflection of machine tool spindles and shafts have not been studied. Therefore, in machine tool manufacturers, these test data that can be applied to machine tools without causing waste products are still used at present. Currently widely used data: the maximum deflection of the main shaft or shaft is 0.0002 times the distance between shaft seats. It can be seen from the above two documents that they did not specify the end deflection, and the scope of the discussions of the two authorities is different. Liechetov's statement does not include the main shaft, while Archer Kang's statement includes the main shaft

some textbooks in China, such as literature [1], introduce that some factories believe that under rated load, the maximum deflection ymax of the main shaft should not exceed 0.0002l. There are also references [2], [3], [7]: at present, there is no unified standard for the allowable value of the deflection y at the end of the spindle. Some materials recommend that for general machine tools, the maximum displacement ymax at the end of the spindle is required to be 0.0002l or the avoidance explanation is adopted: at present, there is no unified stiffness standard for the spindle components. There is also a table in the 2006 edition of the mechanical design manual [8]. It can be seen that the recommended metal cutting machine tool spindle ymaxp=0.0002l. The latter indicates the deflection of the spindle end, while the former does not. But it can be judged that they are all quoted from Archer Kang's discussion

second, the deflection calculation value of typical machine tools

because there are many types of spindle of machine tools, in order to select typical examples of structure and performance to illustrate the problem, we use the deflection calculation of spindle end of several typical lathes as an example

in the calculation process, according to the different forms of support, it is divided into three calculation forms. On the computer (the calculation source program is abbreviated):

1 Two support structure forms: as shown in sketch 1,

the deflection of the spindle end is:

y=p[a3/(3ej) + la2/(3ej) + (1+a/l) 2/c1+ (a2/l2)/c2]

2 Three support structure, the former middle support is the main support: as shown in Figure 2,

is simplified to the former middle two supports, and the deflection of the spindle end is:

y=pa2 (l+a)/(3, which has made a significant contribution to the progress of China's plastic forming equipment manufacturing industry EJ) -rca l/(6ej) +ra (1+a/l)/c1+rb (a/l)/c2

among which RA, Rb and RC are support reactions, which can be obtained according to engineering mechanics

3. Three support structure, taking the front and rear supports as the main supports: as shown in Figure 3,

is simplified to the front and rear two supports, and the deflection of the end of the main shaft is:

y=pa2 (l+a)/(3ej) -rca (l2-2)/(6ejl) +ra (1+a/l)/c1+rb (a/l)/c2

where RA, Rb, RC are the support reactions, which can be obtained according to engineering mechanics

where p is the acting force at the head end of the main shaft (n)

e --- elastic modulus of spindle material (n/mm2)

j --- average moment of inertia of the main shaft section (mm 4)

c1 and C2 --- front and rear bearing stiffness (n/mm2)

a --- front end overhang of main shaft (mm)

l --- span between main supports (mm)

--- span between auxiliary supports (mm)

see Table 1 for the calculation results of typical spindle end deflection, and compare with the allowable value of [y]=0.0002l

Table 1 Comparison of calculated value and allowable value unit: mm

sequence spindle structure form spindle span l0.0002l value deflection calculation value comparison%

1ca6140 three support, front and rear main 6200.1240 23

2cy6140 three support, front middle main 3160.06320 59

3ct6140z three support, front middle 2720.05440 01

4c 6150 three support, front middle main 3300.06600 73

5cm6150 two supporting structures 4070.08140 88

6cl 6150 two support structures 4800.09600 57

7ck6132s two support structures 4580.09160 90

8cnc 30 two support structures 2640.05280 60

in order to facilitate comparison and analysis, each type of spindle assembly is simplified as follows:

(1) the spindle is of equal cross-section, and its diameter is taken as the average diameter

(2) only the radial bearing stiffness is considered for the main shaft support, and the bending resistance of the thrust bearing is omitted

(3) the rated load borne by the front end of the machine tool spindle is 4900 Newton

(4) static stiffness calculation, omitting the transmission force

III. comparison between measured statistical value and [y]=0.0002l value

Table 2 unit: mm

serial machine tool model spindle span l0.0002l value comparison of measured deflection value%

1ca 12400.010068.11

in order to meet the growing demand for heat aging resistance in engines in the automotive industry

2cy 06320.. 87

3CT6140Z2720.05440.. 44

4C . 06600.. 30

5CM. 08140.. 15

6CL . 09600.. 39

7CK6132S4580.09160.003403.71

8CNC302640.05280.. 81

in order to facilitate the analysis, eight lathes that have carried out deflection calculation are selected as an example to compare the measured deflection value with the allowable value [y]=0.0002l, and the results in Table 2 are obtained

IV. analysis

according to the above statistics and calculation table 1 and table 2, the allowable value of [y]=0.0002l is too large and lacks practical significance. Therefore, it is not appropriate to use it to control the displacement of the spindle end

1. From the historical background, according to the literature [5], [6], it is the research result of the S. at that time, the production level determines that the stiffness requirements of machine tools are relatively low. Both reichertoff and Archer Kang started from the stiffness requirements of gear transmission shaft, which mainly refers to the maximum deflection between bearings, and did not analyze the maximum deflection of finishing and semi finishing machine tools. For the design textbooks published in Russia in recent years, see literature [4], the discussion that [y]=0.0002l has been deleted. It shows that with the improvement of production level and design practice, this formula has great limitations, and it is no longer suitable to be used as the calculation standard of allowable deflection

2. The production practice shows that the evaluation of spindle stiffness should be based on the use performance, and the deformation requirements of spindle for different purposes (mainly refers to machining accuracy) are also different. For the spindle of finishing and semi finishing machine tools, the spindle stiffness should be based on ensuring the machining accuracy of the workpiece. Since the deflection of the cutting point at the spindle end directly affects the machining accuracy, the deformation should refer to the deflection of the spindle end, that is, the spindle stiffness should be measured by its shaft end stiffness. Generally, 1/3 of the allowable radial runout of the spindle should be taken. When designing the spindle, the allowable radial runout of the spindle is usually specified as 1/3 of the dimensional tolerance. Therefore, the allowable deflection at the spindle end of precision and semi precision machine tools [y]/9. For the spindle of rough machining machine tool, the spindle stiffness should be based on ensuring the normal operation of spindle transmission parts. Since the deflection in the middle of the main shaft support affects the work of the transmission gear and reflects the rotation angle of the front and rear bearings of the main shaft to a certain extent, the deformation should refer to the deflection between shafts, that is, the stiffness of the main shaft should be measured by its stiffness between shafts. (according to the stiffness requirements of the gear transmission shaft, take [y]=0.0002l, and the two cannot be mixed)

v. conclusion

[y]=0.0002l is based on the stiffness requirements of the gear transmission shaft. It is the allowable deflection between shafts that meets the normal working conditions of the gear. It cannot be used as the allowable value of the deflection at the end of the main shaft, let alone as the deflection control condition of the main shaft of finishing and semi finishing machine tools, It can only be used as the control condition of the axial deflection of the spindle of the rough machining machine tool. The allowable value of spindle stiffness should be based on the use performance, and the relevant spindle parameters should be determined

references

[1] metal cutting machine tool design, edited by Dai Shu, published by the machinery industry, although the reports so far are encouraging. 1981

[2] metal cutting machine tool design (Revised) by the compilation group of metal cutting machine tool design, Shanghai Science and Technology Press, 1985

[3] metal cutting machine tools - Principles and design, edited by Yang rongbai, central China Institute of Technology Press, 1987

[4] Mema лл ope y щ ue Cma нк u к ypco во u д un лоное проеп mupo в a- н ue》1987 . M . Л.

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