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Tutorial 2: Mechanism of a Fourbar Linkage

Dept. of Mechanical Engineering 22.321 Mechanical Design IWritten By: Xiang Li

Revised by: Nick Cleveland 9/7/11

Objectives:

After completing the first tutorial and creating all of the required parts for a fourbar linkage

we can now create an assembly. For a fourbar linkage you should have part files for a baseplate, crank, coupler, and output link. The movable assembly allows us to configure a

motion analysis and to observe the linkage in action.

After completing this tutorial, you will be able to: Build mechanisms with connections

Convert unmovable assemblies into movable assemblies

Simulate assembly movement using the drag functionality

Describe the purpose of servo motors

Create servo motors

Configure motion analysis with one servo motors

Create static images and movies of your motion runs

Create trace curves

Measure and display plots

Task 1: Creating a fourbar linkage.

The first step in mechanism design is to simulate assembly motion. By assembling the

movable components using connections, you can create a movable system instead of one

rigid body.

1. Start Pro/E Wildfire 5.0 Start -> All Programs -> Pro Engineer -> Pro

Engineer

ClickOKif any errors pop up to continue.2. Set working directory where you save the partsFile -> Set Working Directory

3. ClickFile->New->Assembly, enter Linkage as the name and clickOK

4. Click Insert->Component->Assembleor , and select the base part file that

you created earlier and open it.5. A toolbar will popup at the top of the window. The first pull down menu should say

User Defined. Change the second pull down menu to Default and click the

green arrow. Change the orientation of the plate to get a better view of the hole

locations for assembly (Figure 1).

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Figure1 Base part

6. Click Insert->Component->Assembleor , and select the crank part file andopen it. (shown in Figure 2)

Figure 2 Base and crank

7. Change the first pull down menu toPin . Make sure the connection isConnection_1. To check this, click on thePlacementtab. To change the name of theconnection, click the Placement tab and select the name of the connection. When

selected, a small renaming box will appear to the right of the name.8. Zoom in and select the two surfaces as shown in Figure 3.

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Figure 3 Selecting surfaces to make a connection

9. Spin the model and select the other two surfaces, as shown in Figure 4.

Figure 4 Selecting surfaces to complete the definition of the connection

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10. If your result look similar to Figure 5, click the green arrow. If not clickCancelandrepeat step 6-10. If the part is upside down, click the Flipbutton in thePlacementtab next toConstrainttype.

Figure 5 Completed base and crank connection

11. Click Insert->Component->Assembleor , and select the coupler part file andopen it.

12. Make connections by following the same steps as 7-10 to connect the crank to the

coupler. Check that the connection name is updated for each new connection. At thispoint, it should beconnection_2. If it is not, click the name to edit it. The connection

TYPE should bePin.

13. ClickOKwhen you are satisfied with the connection, orCancelto start over.

14. Click Insert->Component->Assembleor , and select the output rocker part

file and open it.

15. Make connections by following the same steps as 7-10 to connect the output

rocker to the coupler and base plate. This will require two connections, the first is

connection_3. The connection TYPE should be Pin.16. When the 3

rdconnection is defined clickNew Setat the bottom of the Placement

window to startconnection_4. The connection TYPE should be Pin.17. The result looks similar to Figure 6.

Figure 6 Assembled fourbar linkage

18. ClickOK

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Task 2: Drag the mechanism

1. Select Applications->Mechanism

2. Click from the top toolbar, and click anywhere on the crank.

3. Move the mouse to check out the motion of this fourbar linkage.4. Click Closeto finish.

Task 3: Defining Servo Motor

As part of your mechanism analysis, you can use a servo motor to study the kinematic

behavior.

1. Click from the right toolbar.

Selectthis axis

Figure 7 Axis selection for servo motor

2. Select the axis shown in Figure 7.

3. Click theProfiletab [1], selectVelocity[2] from the pull down menu, and set the

velocity to360 deg/sec[3], as shown in Figure 8.

In theType tab,you have to selectgeometrythen change motion type to

Rotationfromtranslationtab to change units from in/sec.

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Figure 8 Servo motor definition entries

4. ClickApplyand OK.

Task 4: Run the motion analysis

1. Click from the right toolbar.

2. Set the values as shown in Figure 9.

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Figure 9 Analysis definition entries

3. ClickRun. As you can see, the linkage is moving.

4. ClickOK.

Task 5: Playback of Motion Analysis Results

1. In the model tree, expandPlaybacks, right click AnalysisDefinition1, you can save

or play it.2. ClickPlay.As seen in Figure 10, you can view the animation or save the animation

as a movie by clicking the button.

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Figure 10 Animation options

Task 6: Trace Curve of Motion Analysis Results

To provide a plot of the displacement of a point on the coupler, we must first add a point to

the coupler part file.

1. Open the coupler part file.

2. Click the arrow on theDatum Point Tool.

button in the right tool box and select the Sketch

3. The Sketch Datum Point dialog box appears. Click on a line on the couplerand clickOk.

4. Click theCreate geometric pointsbutton in the right tool box (inside the tab).5. Click on somewhere along the center of the link, as shown in Figure 11.

Figure 11 Point located along center of link

6. Click the middle button to exit the Create points command. Double click on the

dimension from the hole (as seen in Figure 11) and edit it to locate the point at thecenter of the coupler link.

7. Savethe sketch, exit the sketch and Savethe file.

8. Return to the Linkage assembly and regenerate the assembly by clicking thebutton on the top tool box menu.

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9. Click to show the points. The point you created on the coupler should appear.10. From the top menu, select Insert ->Trace curves.11. Refer to Figure 12. On the Trace Curve menu, select the base as the Paper Part [1]

and then pick the point you created [2], open and select AnalysisDefinition1[3] and

then click Preview[4]. ClickOK[5] to finish.

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2

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5Figure 12 Trace Curve menu selections

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Task 7: Measure of Motion Analysis Results

1. Click from the right toolbar.

Figure 13 Measure results

2. Click to add a measure definition. Follow the steps in Figure 14.

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4

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Figure 14 Selections for measure definition

3. SelectX component of your point and AnalysisDefinition1and click .

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Figure 15 Measure results

4. The plot shown should look similar to Figure 16.

Figure 16 Example results for motion analysis

5. In the Graphtool window, by clickingFile->Export Excel, you can save the data to

open in Microsoft Excel and plot in Excel to take the displacement bias off.6. In the similar way, you can plot the velocity and acceleration.