Summary ： Using UG software to model and virtual assembly the clutch press mechanism of offset press. The UG-based kinematics module describes the process of creating motion simulation. Using the measurement function in the kinematics module, a method for analyzing the center distance between rollers is given.
Keywords: offset press; clutch pressure mechanism; motion simulation; UG
introduction
UG is a high-end software that integrates CAD / CAE / CAM and is oriented to the manufacturing industry. It is widely used in mechanical design, engineering simulation and digital manufacturing. Its motion analysis module (Scenario For Motion) can be used to build a motion mechanism model, perform interference analysis of the mechanism, track the movement trajectory of parts, and analyze the displacement, velocity, acceleration, force, and torque of components in the mechanism. The clutch pressure mechanism is the key mechanism to complete the image transfer and realize the printing process on the offset press. The center distance between the rubber cylinder and the plate cylinder and the center distance between the rubber cylinder and the impression cylinder are important dimensional parameters. Center distance can only get the ideal printing pressure]. Generally, the methods for analyzing the center distance between the rollers include drawing method and computer-aided programming method. Because there are many adjustment links in the mechanism, such as the adjustment of the roller of the support base, the adjustment of the supporting teeth in the swing lever mechanism, and the irregular shape of the cam and the bearing sleeve, the calculation and programming of the above method is relatively difficult Large, causing many inconveniences to the agency ’s analysis. Using UG software analysis, if you want to understand the parameter values ​​when the parts and components are in different positions, you only need to change the assembly dimensions of the parts and components in the assembly model, and they will automatically link to the motion analysis model and run the motion simulation to get the needs. the result of. This article takes the mechanical "three-point support" clutch pressure mechanism of an offset press as an example, and uses UG software to model and simulate the mechanism.
1 "Three-point support" clutch pressure mechanism
"Three-point support" clutch pressure mechanism diagram [3 see Figure 1. Its working principle is to realize the separation and contact between the cylinders by changing the center distance between the rubber cylinder 12 and the plate cylinder 13 and the rubber cylinder and the impression cylinder 10. In Figure 1, the plate cylinder axis o and the impression cylinder axis o. The roller bearing is installed in the wallboard hole, and the position of the axis of the roller shaft remains unchanged. The rubber roller shaft o is installed in the rolling bearing, and the rolling bearing is installed in the hole of the bearing sleeve 15. The bearing sleeve is supported by two fixed support roller members 14, 16 and a floating support roller member 11 to determine its center position. Because the outer contour of the bearing sleeve is designed as a special contour curve, when the bearing sleeve rotates along the support roller, the axis position of the rubber roller shaft changes, which serves the purpose of changing the center distance between the rollers. When closing the pressure, the closing cam and connecting rod mechanism drive the bearing sleeve to rotate counterclockwise, so that the rubber cylinder is in contact with the plate cylinder and the impression cylinder in sequence. The process of decompression is reversed.
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According to the above, the change of the center distance between the rollers is mainly caused by the change of the center position of the bearing sleeve, so that the position of the shaft center of the bearing and the rubber roller shaft installed in the hole changes. The change of the center distance between the rollers is mainly determined by the outer contour size of the bearing sleeve. When the machine needs to be debugged or when the thickness of the printed paper changes, the center distance can also be finely adjusted by rotating the eccentric shaft on the roller of the support base. Fig. 2 is a schematic diagram of the structure of a roller component of a supporting seat supporting a bearing sleeve, which is mainly composed of an eccentric shaft, a roller seat, a roller and a bush. In Figure 2, O1 is the center of rotation of the eccentric shaft, O2 is the center of cooperation between the eccentric shaft and the roller, and O3 is the center of the marked hole position on the eccentric shaft. The roller seat is connected with the wall panel and rotates the eccentric shaft. The roller changes its position with the rotation of the eccentric shaft and plays the role of radial adjustment. If the eccentricity O1O2 is set to a, the radial adjustment range of the roller is 0 to 2a.
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2 Parts modeling and assembly of clutch pressure mechanism
Run the UG software and enter the Modeling module to model the parts solidly. In this mechanism, the outline dimensions of the cam and bearing sleeve are all discrete coordinate values. The coordinate points of the parts can be first generated into a data file, and the Spline / Through points / Points from File command can be used to read the data file and draw the outline. The instruction generates parts drawings of the clutch and the pressure cam and the bearing sleeve. Figure 3 shows the solid model of the pressure-off cam.
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After constructing the solid model of the part, enter the assembly module (Assemblies) and perform virtual assembly on each component and part of the clutch pressure mechanism. Because it is necessary to analyze the influence of the eccentric shaft in the support seat roller parts (14 and 16 in Figure 1) at different positions on the center distance between the rollers, the angle assembly parameters are set when the support seat roller parts are assembled. As shown in FIG. 2, the side surface of the roller base is set as the reference plane A, the surface passing through the axis direction of the eccentric shaft and passing through the center O1 and the center O3 is the reference plane B, and the angle pairing parameters are set for the surfaces A and B during assembly. Set the maximum position of the eccentric direction away from the A surface in Figure 2 as 0 °. When the eccentric shaft 1 rotates counterclockwise around the roller base 2 and the set angle is positive, the angle when the marked hole on the eccentric shaft turns to the O3 'position It is 60 °, and when the eccentric position 02 is at the lowermost end, the angle value is 180 °.
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3 Create a motion simulation
After simplifying the assembly master model, enter the Motion Simulation module (Motion Simulation). Creating a motion simulation includes creating links, motion pairs, and defining motion drives.
3.1 Create connecting rod
Build auxiliary curves for the related parts of Curve on Curve Joint (including cam, cam follower swinging roller, bearing sleeve, upper left support roller and lower left support roller) to ensure that the corresponding curve position is on the assembly drawing In the CCP, add the constructed curves to the reference sets of their parts. According to the movement relationship of the clutch pressure mechanism, refer to the name of the parts shown in Figure 1, and establish each link (Link) as follows:
(1) L001: Construction curve of the closing pressure cam 1 and its contour.
(2) L002: Swing lever 3, swinging roller construction curve of closing cam follower, supporting teeth 4.
(3) L003: Swing arm 7 and pawl 5.
(4) L004: Tie rod 9.
(5) L005: bearing sleeve 15 and its construction curve, rubber roller 12.
(6) L006: Plate cylinder 13, impression cylinder 1O.
3.2 Definition of motion pair, 3D contact (3D Contact) and damping (Damper)
According to the actual working conditions, define the sports pair as follows:
(1) J001: L001 is fixed to the ground, and a rotary pair (Revolute) is constructed.
(2) J002: L002 is fixed to the ground to construct a cylindrical pair (Cylindrica1).
(3) J003: L003 is fixed to the ground to construct a revolute.
(4) J004: L003 and L004 establish a universal joint motion pair (Universa1).
(5) J005: L004 and L005 establish a revolute pair (Revolute).
(6) J006: L006 is fixed to the ground, and a sliding pair is constructed.
(7) J007: The definition line of the pressure cam 1 and the swinging roller of the follower is on the curve (Curve on Curve).
(8) j008: The definition line of the bearing sleeve and the upper left support seat roller is on the line.
(9) J009: The definition line of the bearing sleeve and the lower left support seat roller is on the line pair.
(10) G001: To build a 3D contact (3DContact) between the supporting teeth and the pawls.
(11) D001: Swing arm motion pair J003 defines damper (Damper).
3.3 Define Motion Drive
(1) J00l's motion drive selects constant speed, and the speed is set to 1 (°) / s.
(2) The motion drive of J009 chooses constant speed, and the motion parameters are all set to 0. This motion pair is mainly used to set the marker (Marker).
4 Analysis of center distance between rollers
Build mark points A001, A002, A003 at the center of the rubber cylinder, plate cylinder, and impression cylinder, enter the measurement function of the packaging option, select the minimum distance type, and set the measurement Me001 (rubber cylinder) The distance from the center of the plate cylinder) is the marking point A001 and A002, and the MeO02 (the distance between the center of the rubber cylinder and the impression cylinder) is A001 and A003. Run the motion simulation and set both Time and Steps to 360. After the simulation is complete, click List Measurements. The resulting data is plotted as a graph, see Figure 5 (a). As can be seen from Figure 5 (a), when the closing pressure cam rotates to 237 °, the closing pressure action is completed. At this time, the center distance Rr-p between the rubber cylinder and the plate cylinder is 220.896 mm, and the center between the rubber cylinder and the impression cylinder The distance Rr-i is 220.908mm. The above measured value is the value when the eccentric position on the eccentric shaft is far from the corresponding roller, that is, the value when the eccentric position is 0 °. Change the assembly angle of the eccentric shaft and the roller seat in the support base component to 180 °, the position of the roller changes accordingly, and re-execute the motion simulation. The corresponding center distance between the rollers is shown in Figure 5 (b). As can be seen from 5 (b) in the figure, when the cam turns to 235 °, the closing action is completed, the center distance between the rubber cylinder and the plate cylinder is 220.872 mm, and the center distance between the rubber cylinder and the impression cylinder is 219.126 mm. As mentioned above, simply changing the assembly parameters of the corresponding parts and components in the assembly master model will automatically link to the movement master model to run the motion simulation to obtain the corresponding value, which is unmatched by several other analysis methods .
5 Conclusion
UG software was used to model the clutch press mechanism of the offset press, and the creation process of connecting rod and kinematic pair during kinematics simulation was described. Using the UG motion analysis module to analyze the center distance between the rollers of the clutch pressure mechanism, the required results are obtained. Compared with other analysis methods, it has the characteristics of simple, intuitive, less workload and convenient modification. Provide an effective method for the analysis of such institutions.
references:
[1] Zhang Bo, Wang Suping, Zhou Lei. UG NX2 basic tutorial IM]. Beijing: Tsinghua University Press, 2005.
[2] Wang Wenhui. Determination of printing pressure in lithography [J]. Printed Magazine, 2004 (2): 72-74.
[3] Qian Junhao. Printing machinery rM]. Beijing: Chemical Industry Press, 2005.
[4] Hu Xiaokang. UG NX4 motion analysis training course IM]. Beijing: Tsinghua University Press, 2006.
[5] Zhang Chiyun. Application of UG MOTION in the analysis of car transmission IJI. Journal of Shanghai University of Engineering Science, 2005, 19 (4): 327-329. (end)
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