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Computer aided design of the label taking mechanism of beer labeling machine

the labeling machine is an important equipment in the beer production line. Its main function is to stick the trademark paper evenly on the surface of beer bottles. Among them, the marking mechanism is the most complex and has high motion requirements, which is the difficulty in the design of labeling machine. The working principle of the bid taking mechanism is shown in Figure 1. In the process of taking the mark, the rotary table 1 rotates at a uniform speed around the o0 point, and a disc cam 2 is fixed under the rotary table. When the sector gear 3 rotates with the rotary table 1, the curve of the cam 2 can control the sector gear 3 to automatically move around the O1 point through the pin shaft 4. The standard plate 5 and the gear 6 are fixedly connected together and rotate with the rotary table. Its rotation around the O2 point is driven by the sector gear 3 called "tiger skin pattern". The label paper is installed on the label plate 7, which is fixed in the position shown in the figure. If the composite motion of the marking board 5 can make the marking board roll purely along the length L of the marking board 7, the marking operation can be completed satisfactorily

1. Turntable 2 Cam 3 Sector gear 4 Pin shaft 5 Gear 6 Take the standard plate 7 Standard plate

Figure 1 working principle of the standard taking mechanism

therefore, the design work of the label taking mechanism of the labeling machine is mainly as follows: (1) when the rotary radius r of the turntable and the length L of the standard plate are given, the optimal values of the radius R and eccentricity e of the standard taking plate are calculated; (2) Calculate the cam curve that meets the motion requirements

because the motion relationship of the above mechanism is very complex, manual design can only be solved by trial and error, and the best design parameters cannot be obtained, so it is difficult to ensure the operation effect of the whole mechanism. Therefore, this paper adopts the method of computer-aided design, develops the corresponding software, and successfully solves the above problems

1 analysis of motion error in the calibration process

if the calibration plate is pure rolling along the calibration plate, the motion trajectory of the rotation center O2 of the calibration plate should be cycloid, as shown in Figure 2

Figure 2 Analysis of motion error in the bidding process

in the figure,

x = R, the sales volume of the current year exceeds 100 million yuan t-esint (1)

y = r-ecost (2)

among them, -l/2R ≤ t ≤ L/2R. However, the actual motion trajectory of the rotation center O2 of the standard plate is a circle, so there is an error with the motion requirements. Due to the symmetry of the mechanism, only studying the position shown in the figure (t ≥ 0) can get (3)

(4)

2 problem solution

due to the mechanism, the motion error is inevitable. When there is an error in the X direction, the standard plate will slip on the surface of the standard plate; When there is an error in the Y direction, the standard plate will squeeze the standard plate. Therefore, the radius R and eccentricity e of the standard plate should be correctly selected in the design to minimize the error, that is (5)

where: α 1、 α 2 is the weight factor coefficient, which represents the error coefficients in the X and Y directions respectively, and α 1＋ α 2＝1。 Since the standard plate is elastically supported in the Y direction, the standard plate is allowed to produce a certain range of normal displacement, which is usually taken as α 1＞ α 2。

because equation (5) defines a problem of functional extremum, and it needs to solve nonlinear equations, it is very difficult. Therefore, this paper adopts the optimization algorithm. Take R and E as variables and equation (5) as objective function to solve. When calculating the objective function, take t as the variable, scan the range of 0 ~ l/(2R) with a certain step length, and calculate the maximum value. There is no one-dimensional search method here, mainly because of the fear that the calculation will fail due to the complex functional relationship. However, in the actual calculation, the speed is still very fast, and there is no need to wait

3 calculate the cam curve

as shown in Figure 3, set when O2 rotates at P {XP, YP} point with the rotary table

xp = rsin θ pyp＝Rcos θ P

where: θ Is the corner of the turntable

according to formula (1) and formula (2), get

xp = RTX esintx (6)

yp = r-r-ecosty (7)

according to formula (6) and formula (7), find TX, ty, so that

tp = α 1tx＋ α 2ty (8)

can be found θ The cam curve can be easily obtained after the corresponding relationship between P and TP is completely determined according to the angle of T, the transmission ratio between sector tooth 3 and gear 5, and the position of the pin hole

Figure 3 Calculation of the rotation angle of the standard plate

4 software programming

in order to realize the above design calculation, a computer-aided design software is developed with ads under the AutoCAD environment. The software is divided into the following modules: (1) the user input module mainly provides an interface for users to further listen to the Council's opinion data, including the length of the standard plate, the radius of rotation of the turntable, the number of gear teeth and other geometric parameters, As well as the maximum radius and eccentricity of the standard plate, it also includes the expansion of the control scope, the echo of the shopping mall, the production cost and many other factors, such as small values and weight coefficients α 1、 α 2, etc. (2) The R and e calculation module calculates the values of R and E by using the optimization algorithm according to the user input data, and displays the calculation results on the screen. (3) The cam curve calculation module calculates the cam curve according to the above calculation results and the input data, and saves the calculation results in the data file. (4) According to the above data, the dynamic simulation module simulates and displays the moving process of the marking, and can display the normal and tangential errors in the moving process. (5) The drawing module is used to draw cam curve, mechanism schematic diagram, motion error analysis and other graphic display

5 application example

Qingdao machine tool factory is a professional manufacturer of beer equipment. In production, the factory needs to develop a labeling machine with a length of the standard plate l = 130mm. The rotating radius of the turntable of the labeling machine is r = 135mm, the number of sector teeth Z1 = 64, the gear Z2 = 18, the center distance a = 103.5mm, the eccentricity of the pin shaft H = 50mm, the offset angle of the pin shaft f = 9.75 °, the minimum radius r = 40mm, the maximum radius r = 80mm, and the minimum spacing d = 38mm, Maximum spacing d = 40mm. The calculation results of the computer aided design software used in this paper are: radius r = 56.11mm, spacing d = 40mm. α 1＝1、 α When 2 = 0 (no sliding), the maximum normal error is 0.726mm, and the tangential error is zero; α 1＝0．9、 α 2 = 0.1, the normal error is 0.692mm, and the tangential error is 0.296mm; α 1＝0．5、 α 2 = 0.5, the normal error is 0.357mm, and the tangential error is 1.476mm; α 1＝0、 α When 2 = 1 (no extrusion), the normal error is zero, and the maximum tangential error is 2.941mm. This data has been applied in the design of labeling machine. (end)

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