26 eccentric mechanism kho tài liệu bách khoa

ME-430 INTRODUCTION TO COMPUTER AIDED DESIGN ECCENTRIC MECHANISM OF FOUR-BAR LINKAGE Pro/ENGINEER Wildfire 2.0 Dr Herli Surjanhata A component can be placed as a connection within mechanism assembly The following six joint types are available: Pin Joint Cylinder Joint Planar Joint Slider Joint Ball Joint Bearing Joint PREPARE THE PARTS FOR MECHANISM Download the part files eccentric_mechanism.zip There are eleven parts that make up the mechanism: arm.prt base.prt bushing.prt clip-1.prt clip-2.prt link.prt 10 11 eccentric.prt post.prt shaft.prt washer-1.prt washer-2.prt arm.prt bushing.prt base.prt eccentric.prt post.prt clip-1.prt shaft.prt clip-2.prt washer-1.prt washer-2.prt link.prt CREATE AN SUB-ASSEMBLY eccentric_asm.asm Sub-assembly called eccentric_asm.asm will be consisted of six component parts – eccentric, shaft, clip-1, clip-2, washer-1, and washer-2 Create a new assembly called ECCENTRIC_ASM Bring in eccentric.prt and constrain it at default location by picking , then Open Pick eccentric.prt The assembly is shown below Next, place shaft.prt to the assembly Pick , then Open shaft.prt Pick the axis of the shaft, then select the axis of the center hole of the eccentric Pick the surfaces as shown below Mate both surfaces Be sure to enter when prompted with offset distance to flip the If necessary, click orientation of the shaft The resulted assembly is shown below 10 Change the Specification to Velocity Uncheck the Current box under Initial Condition Be sure Constant is selected under Magnitude Enter the following value for A = 100 deg/sec Uncheck Velocity box and select the Position check box to see a Click the Graph button graph of the servo motor function over 10 seconds 53 From Format pull down menu, select Graph Select X Axis tab, make sure the range of time to Maximum 10 Click the OK button, then File -> Exit to close the graph window Then click OK button of Servo Motor Definition Click the Close button on the Servo Motors dialog box Specify the Zero Reference 54 Select Mechanism -> Jt Axis Settings The Joint Axis Settings dialog box appears Pick the joint axis with the servo motor Connection_1.axis_1 Under the Zero Refs tab, check Specify References Select ASM_TOP datum plane of eccentric_mechanism as the Green Body Reference Select ASM_RIGHT datum plane of eccentric_asm subassembly as the Orange Body Reference 55 On the Regen Value tab, select Specify Regeneration Values, and enter for Regeneration Value Click Preview, then pick OK button Run the Connection Analysis Select Mechanism -> Connect Click Run There is no need to lock any of the bodies or connectors Mechanism design uses the regeneration value previously entered to assemble the mechanism 56 Click Yes CREATING AND RUNNING A KINEMATIC ANALYSIS From MECHANISM menu, select Analyses or Click Click the New button 57 Click Motors tab, and make sure ServoMotor1 is selected Click the OK button Pick the Run button Pick the Close button in the Analyses window 58 Click analysis to replay the result of The Playback dialog box appears 59 Select the Global Interference option, then click the Play button Note: If there is any interference, it will be highlighted in red There is no interference in this mechanism Use options on the Animate dialog box to run the results of motion study Click Click to begin the animation to stop 60 Pick the Capture button to create the movie file Type in the name of movie mpg file e.g eccentric_mechanism.mpg Click the OK button, the motion of mechanism will be recorded, and saved in the working directory This file can be inserted in the PowerPoint slide for presentation When finish with capturing, click Close on the Animate dialog box 61 to save the results as a Click pbk file In the Save dialog box, accept the default name or change to another name The AnalysisDefinitionq.pbk file can be opened int the on future by clicking the Playbacks dialog box and selecting the playback file Click in the Playbacks dialog box 62 CREATING AND GRAPHING MEASURES Click Click Change the Type from Position to Velocity 63 Change the name to Velocity_Connector Pick the joint between link and arm Pick this joint Click OK Select the measure Velocity_Connector and AnalysisDefinition1 From above, we notice that the velocity at the end of 10 seconds is 18.229 deg/sec Click 64 Exit from the GraphTool Creating a Trace Curve A trace curve graphically represents the motion of a point or vertex relative to a part in your mechanism 65 Mechanism -> Trace Curve Select base.prt as the Paper Part, then pick a point near the lower hole as the trace point Note: Paper Part—Select a body on your assembly or subassembly to serve as the reference on which to trace the curve If you visualize a pen tracing on paper, you can think of this part as the paper The trace curve you generate will be a feature of the part you select as the paper part You can access trace curves and cam synthesis curves from the model tree To trace the motion of a body relative to ground, select a body that is in ground for the paper part The point must be on a different body from the one you selected for the paper part Mechanism Design uses the trajectory of this point to define the trace curve If you visualize a pen tracing on paper, this location is like the tip of the pen Highlight AnalysisDefinition1 as the Result Set 66 Pick a point here as trace point Click OK to close the dialog box The trace curve appears on your model Close out the Mechanism option and save the assembly 67 ... washer-1.prt washer-2.prt arm.prt bushing.prt base.prt eccentric. prt post.prt clip-1.prt shaft.prt clip-2.prt washer-1.prt washer-2.prt link.prt CREATE AN SUB-ASSEMBLY eccentric_ asm.asm Sub-assembly... Sub-assembly called eccentric_ asm.asm will be consisted of six component parts – eccentric, shaft, clip-1, clip-2, washer-1, and washer-2 Create a new assembly called ECCENTRIC_ ASM Bring in eccentric. prt... PARTS FOR MECHANISM Download the part files eccentric_ mechanism. zip There are eleven parts that make up the mechanism: arm.prt base.prt bushing.prt clip-1.prt clip-2.prt link.prt 10 11 eccentric. prt