CETOL 6S Version 7.1

CETOL 6s Version 7.1

Valve Train Demo

Setup

Task 1.  Set Analyzer preferences.

1.  Start up the CETOL 6 Sigma Analyzer.

2.  In the Analyzer, select Edit > Preferences. Set Analysis options as shown below.

3.  Click OK and exit the Analyzer.

Task 2.  Start up CETOL Modeler.

1.  Start up the CETOL 6 Sigma Modeler and Pro/E.

2.  Open VALVE_TRAIN.ASM and synchronize CETOL to Pro/E.

Task 3.  Set CETOL Modeler preferences.

1.  Select Edit > Preferences.

2.  Click on Edit Default Variation Rule… on the General tab and set as shown below.

a.  Select Tolerance Drives Distribution.

b.  Set the following default tolerances:

Linear tolerances: 0.2 mm

Angular tolerances: 0.5 mm

Geometric tolerances: 0.2 mm

c.  Distribution type: Normal. Enforce mean. Cp=1.0.

Task 4.  If running a Pro/E Wildfire, set the following options to improve performance.

1.  In Pro/E, set prehighlight = no (in config.pro).

Demo

Task 1.  Add a measurement.

1.  Set view to 1-VALVE/SEAT.

2.  Click on to add a measurement.

3.  Select datum curve representing the valve seat on the cylinder head and the conical surface of the intake valve.

4.  Rename the measurement Gap(Closed).

5.  Click on the References tab. Click on next to the Direction field and select the shaft of the valve (the same one as in Step 3).

6.  On the Tolerance tab, set the target and tolerance values to 0.0±0.3.

Task 2.  Add an assembly joint between the Rocker and the Shaft_Rocker.

1.  Set view to 2-CAM/ROLLER.

2.  Click on and select the hole in the Rocker and the OD of the Shaft_Rocker.

3.  On the DOF tab, select Tangent.

4.  On the References tab, click on next to the Orient field. Toggle datum plane visibility on, and select DTM4. Toggle datum visibility off.

5.  Click on the DOF tab of the new joint and toggle the TZ DOF to the constrained state.

Task 3.  Add an assembly joint between the rocker insert and the intake valve.

1.  Set view to 3-VALVE/ROCKER.

2.  Click on and select the rounded tip of the rocker insert and the flat end of the intake valve stem.

Task 4.  Add a configuration joint to define the clocking angle of the cam shaft.

1.  Set view to 2-CAM/ROLLER.

2.  Click on in the CETOL Modeling toolbar.

3.  Turn on the display of datum planes and datum axes.

4.  Select the DTM7 in the CAMSHAFT and axis A9 of the ROLLER.

5.  Click on the DOF tab of the new joint and select Point Contact from the DOF state menu.

6.  Turn off the display of datum planes and datum axes.

Task 5.  Add a configuration joint to define contact between the roller and the cam.

1.  Click on in the CETOL Modeling toolbar.

2.  Select the surface of the roller and the large diameter of the cam.

3.  Click on the DOF tab of the new joint and select Point Contact from the DOF state menu.

Task 6.  Visualize the assembly constraints.

1.  Change the view to “Front”.

2.  Click on to and then Move to New Locations to visualize the model in the state in which it is constrained in CETOL.

Task 7.  Describe the CETOL interface.

1.  Expand the model tree.

Notice that as we define the CETOL model, the CETOL objects are listed in the CETOL Model Tree. All of the CETOL model data is stored directly in the PRO/E part and assembly files. This makes data management and reuse very simple. It also ensures that the CETOL data is always up-to-date because it will update automatically when changes are made to the PRO/E models.

2.  Click on several CETOL objects in the specification tree and note how they are highlighted in the PRO/E model.

Task 8.  The model graph is a schematic representation of the CETOL

This view of the model is a very efficient way of quickly understanding the content and state of a model.

1.  Explore the model graph, explain the meaning of the various objects, and show interaction with PRO/E model.

Task 9.  Define dimensioning scheme for the rocker.

1.  In Pro/E, right-click on the rocker and select Open from the context menu. Shrink window size so that it does not overlap the CETOL window.

2.  Click on to synchronize to the part.

3.  Rename the features:

Feature1 ® B

Feature2 ® A

Feature3 ® Insert Depth

Feature4 ® Insert Hole

4.  Click on to add a feature. Select the two planar surfaces shown below:

5.  Rename the new feature C.

6.  Reorder the features in the following order: A, B, C, Insert Hole, Insert Depth.

7.  Create the following geometric tolerances:

B: ⊕| ⊘ 0.2 | A

Insert Hole: ⊕|⊘ 0.2 | A | B | C

Insert Depth: ⌓| 0.2 | A | B | C

8.  Close the ROCKER.PRT window, activate the VALVETRAIN_SOHC.ASM window, and synchronize.

Task 10.  Explore second configuration.

1.  Right-click on Open in the specification and select Set as Active.

2.  Click on the joints of the configuration to see how the assembly constraints are defined for this configuration.

3.  Change the view to FRONT_ZOOMED.

4.  Click on to visualize the model in the state in which it is constrained in CETOL.

Task 11.  Run analysis.

1.  Select Model > Generate Analysis Results… and then OK to start the sensitivity calculations.

CETOL calculates the sensitivity of the design specification to each dimension included in the analysis. It then calculates the variation of the design specification based on these sensitivities and the tolerances on each of the dimensions.

Task 12.  Review results.

Once the analysis is complete, the results are displayed in the CETOL Analyzer window.

1.  Expand the tree. Click on Gap (Closed).

The plot represents the distribution for the measurement. The vertical lines represent the tolerance limits that we have defined for this measurement. The green area of the plot represents the percentage of assemblies that would fall between the limits and are considered acceptable. The red area represents the percentage of unacceptable measurements.

The quality for the measurements is also shown numerically in the top part of the analyzer window. The quality is lower than we would like. We will have to make some design changes in order to improve the quality of our assembly. CETOL provides a number of tools for helping to make design decisions.

Task 13.  Review sensitivities and contributions.

1.  Click on the Sensitivities tab.

This plot shows the relative sensitivity of the specification to each of the variables in the analysis. The highest sensitivities indicate the “Critical to Quality” dimensions. Conversely, those dimensions that have very low sensitivity values have very little influence on the specification, and indicate non-critical features where low-cost manufacturing processes may be adequate.

2.  Click on the Contributions tab.

The contribution plot shows the relative contribution of each variable to the variation of the specification. One way to improve this design is to manually tighten up the tolerances of the highest contributors.

Task 14.  Make changes to tolerances and manufacturing variation.

Note that the distribution is not centered between the design limits. One easy way to improve the quality of this design is to simply adjust the nominal dimensions so that this distribution is centered.

1.  Click one the Sensitivities tab.

The mean value of the distribution is --.155 mm. It would be best if the mean value for this measurement were 0.00 mm. We could adjust any of the dimensions in order to center the distribution. The sensitivity plot can be used to determine how much a dimension should be adjusted in order to get the desired effect on the measurement.

2.  Select the following dimension: VALVE_IN: VALVE_INTAKE:Valve Bottom: to Valve Top: Offset.

3.  Unselect Apply Rule and change the mean value of the dimension to 99.655.

Changing the mean value of this dimension changes the mean value of the measurement to be centered between its limits.

The quality is still not sufficiently high. We will need to make changes to reduce the variation of the measurement.

4.  Select the following dimension: Head:Shaft Axis: to C: Offset.

5.  Change the tolerance from 0.10 to 0.05.

We can also apply actual manufacturing process data to the dimensions in the model.

6.  Checkmark the Process box.

7.  Select Display All Processes and Run Query.

8.  Assign the Metal; Mach. Center, Face Mill manufacturing process.

Task 15.  Review worst-case results

Since we ran a derivative-based analysis, we can toggle between statistical analysis and worst-case analysis instantly.

1.  Select Analysis > Worst Case.

Note that the worst-case condition for this design violates our measurement limits by a large margin, while the statistical quality is not too far from being acceptable. This illustrates the benefit of using a statistical design approach.

Task 16.  Generate report.

Documentation is a critical part of the analysis process. CETOL provides a means to automatically generate reports based on customizable report templates. Your company can define a report template so that every tolerance analysis report is clear, concise, complete, and easily understood.

1.  Select File > Generate Report…

2.  Click on in the User Images section and select 2ModelGraph.png and 1Model.png.

3.  For the Style Sheet, select detailed_modular_wStyles.xsl.

4.  Click OK to generate the report.

5.  Scroll through report.

The report is in HTML format, so it can be reviewed in any HTML browser and edited with any HTML editor (like MS Word).

Task 17.  Save changes to Model

Any changes made in the analyzer window will have no effect on the Pro/E models until the user tells it to. Changes can be made to the Pro/E model with a simple menu pick.

1.  Select Analysis / Save to Model.

CETOL 6s Version 7.1