Valve cam mechanism kho tài liệu bách khoa

ME-430 INTRODUCTION TO COMPUTER AIDED DESIGN Valve Cam Mechanism Pro/ENGINEER Wildfire 3.0 Dr Herli Surjanhata There are parts that will be used in this mechanism analysis: • shaft_mount.prt — the ground body • camshaft.prt (rotating body) • rocker.prt (oscillating body) • valve_guide.prt (ground body) • • valve.prt (sliding body) rocker_shaft.prt (rotating body) PART: SHAFT_MOUNT.PRT PART: CAMSHAFT.PRT PART: ROCKER.PRT PART: ROCKER_SHAFT.PRT PART: VALVE.PRT PART: VALVE_GUIDE.PRT CREATE AN ASSEMBLY – rocker_arm.asm Create a new assembly called rocker_arm Uncheck Use default template The New File Options dialog box appears Select System of Units of mmns_asm_design Under Parameters, fill DESCRIPTION and MODEL BY with Rocker Arm Assembly and your name OK The assembly should have default datum planes – ASM_FRONT, ASM_RIGHT, and ASM_TOP Click to open rocker_shaft.prt Select to assemble the rocker_shaft.prt at default location Click to finish the assembly operation Click and open rocker.prt, Keep default setup for assembly Apply the following constraints between rocker_shaft and rocker – see below • Align the axis of the rocker.prt with the axis of the of rocker_shaft.prt Align constraint • Align OFFSET the FRONT datum plane of the rocker.prt with the ASM_FRONT datum plane of the rocker_arm.asm assembly Align constraint The offset distance is 25 mm The result of the assembly is shown below Save the assembly The rocker_arm.asm will be sub-assembly for total valve_cam assembly 10 Note that Dynamic Oscillations is listed under Result Set Accept Measure vs Time as the Graph Type (Create new measure) The Click Measure Definition dialog box opens 38 Enter Valve_Position under Name, and select Position under Type Use the arrow button to select PNT1 on valve.prt Accept the WCS as the Coordinate System Select Magnitude under Component, and Each Time Step under Evaluation Method Click OK to accept the definition and return to the Measure Results dialog box 39 PNT1 – Datum point of the valve On the Measure Results dialog box, select Valve_Position in the Measures list and click measure) (Copy selected Select copy_of_Valve_Position, and click (Edit selected measure) The Measure Definition dialog box opens Change the Name entry to Valve_Velocity, and select Velocity for the Type Click OK to accept the definition 40 On the Measure Results dialog box, select Valve_Position in the Measures list and click measure) (Copy selected Select copy_of_Valve_Position, and (Edit selected measure) The click Measure Definition dialog box opens Change the Name entry to Valve_Acceleration, and select Acceleration for the Type Click OK to accept the definition Click (Create new measure) On the Measure Definition dialog box, enter Spring_Load under Name, and select Net Load under Type Use the arrow button to select the spring on your mechanism, and accept Each Time Step as the Evaluation Method Click OK to accept the definition and return to the Measure Results dialog box 41 Click (Create new measure) On the Measure Definition dialog box, enter Servo_Load under Name, and select Net Load under Type Use the arrow button to select the servo motor on your mechanism, and accept Each Time Step as the Evaluation Method Click OK to accept the definition and return to the Measure Results dialog box Note: Servo motor is located at pin joint between camshaft.prt and shaft_mount.prt 42 On the Measure Results dialog box, select Valve_Position, Valve_Velocity, and Valve_Acceleration under Measures Select Dynamic Oscillation under Result Set (Graph) to see a graph that Click compares the three measures 43 Close the Graph Click the Close button of Measure Results dialog box Plot Valve_Position, Valve_Velocity, and Valve_Acceleration separately 44 Check Graph measures separately 45 This is a NOT good design!!!! Why? SAVING AND REVIEWING RESULTS 46 For the future sessions of Mechanism Design, the dynamic analysis results should be saved as playback file that can be reviewed later Click The Playbacks dialog box appears When you play back your analysis results, you can display three-dimensional arrows that represent the magnitude and direction of the measures, forces, torques, gravity, and force motors associated with your analysis Use these arrows to see the relative effect of loads on your mechanism Single-headed arrows are used for force, linear velocity, and linear acceleration vectors Double-headed arrows are used for moment, angular velocity and angular acceleration vectors The color of the arrow depends on the type of measure or load You must have a Mechanism Dynamics option license to use arrows in analysis results As you play back your analysis results, the size of the arrow reflects the calculated value of the measure, force, or torque The direction of the arrow changes as the calculated vector direction changes If you select several measures or input loads, the selection is displayed with the largest value within each type as the largest arrow In addition, model size affects the initial arrow size The default arrow size, which is the size of the largest arrow within a type at 100% scale, is proportional to the characteristic length of the model Tip: The default size of an arrow is based on the value of the measure or input load at the beginning of the analysis If your measure or input load covers a large range of values during an analysis, the arrows can become unacceptably large or disappear You may, therefore, need to readjust the scale and rerun the analysis to get a more useful animation If you are preparing an animation for a presentation, you may want to use the Movie Schedule tab to remove those parts of the analysis in which the arrows become too big or too small Pick on button The Collision Detection Settings appears 47 Keep default setting or choose the setting you wish to investigate OK Select Display Arrows tab Under Measures box, check Spring_Load Also check Name and Value in the Annotation area Click on The Animate dialog box appears 48 Click to play the animation Click to stop 49 Experiment with other measures To capture the animation in MPEG movie file: Click button, then OK button Click Close to close the Animate dialog box On the Playbacks dialog box, click set) (Save result 50 Accept the default name, which is based on the analysis name, or change it The default directory is the current working directory You can accept it, or browse to find another directory to save the file When you click Save, Mechanism Design saves the file with the extension pbk You can retrieve this file in future sessions by clicking (Restore) on the Playbacks or Measure Results dialog box Close the Playbacks dialog box Save the valve_cam mechanism 51 ASSIGNMENT Run the dynamic analysis for 1000 rpm or 6000 deg/sec Submit the following information with your report Snapshot of mechanism with joints, spring, cam-follower and driver are clearly shown – turn off ALL the datum planes, axes, and points Graph of the servo motor function over 10 seconds (position in degrees vs time) Graph of the position, velocity and acceleration of valve at point PNT1 over 0.06 second for a complete revolution – use Graph measure separately Graph of spring load and servo load over time separately 52