Welcome to Launsby Consulting’s design of experiments ... on this Pareto Chart, Pull Back has the...

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Welcome to Launsby Consulting’s design of experiments internet training.........Using Minitab Software. This module will show how to use Minitab software to set-up and analyze your experiments. Click on the arrows above to begin your training session. In this module, we will use Minitab to set-up and analyze our Statapult experiment. We would like the Statapult to fire the ball a certain distance. We will adjust three factors. They are: Pull Back, hook and peg.

Transcript of Welcome to Launsby Consulting’s design of experiments ... on this Pareto Chart, Pull Back has the...

Welcome to Launsby Consulting’s design of experiments internet training.........Using Minitab Software. This module will show how to use Minitab software to set-up and analyze your experiments. Click on the arrows above to begin your training session.

In this module, we will use Minitab to set-up and analyze our Statapult experiment. We would like the Statapult to fire the ball a certain distance. We will adjust three factors. They are: Pull Back, hook and peg.

When Minitab is opened, the following screen appears. To start a new project, choose File and New. Click Minitab Project, then click OK. In our statapult experiment, we have three factors. Since we suspect interactions, we would like to run full-factorial design.

Choose Stat and DOE. Minitab supports four types of experimental objectives, Factorial, Response Surface, Mixture and Taguchi. Choose Factorial. In the Create Factorial Design Window, choose “Display Available Designs”. Since you have three factors, you have two design type options: a 4 run fractional factorial design and an 8 run full-factorial design. Click OK. You are now back in the main dialog box.

Choose 2-level factorial (default generators) In Number of factors, enter 3. Click on the Designs button. In the Designs box, select Full Factorial. In Number of Replicates, enter 3. Click OK. The design has now been selected and you are back to the main dialog box. Notice that all buttons are now enabled.

We need to define 3 factors for our experiment. Click on the Factors button. Our first factor is Pull Back angle. We are going to vary it from 440 degrees to 490 degrees. Type Pull Back in the Name column. Tab to the “low column” and type in 440. Tab to the “high column” and type in 490.The same procedure is used for the other factors. Click on the OK button. This brings you back to the main dialog box.

Click on the Options button. In “Base for random data generator, type 7. Entering a base for the random data generator allows you to control the randomization so that you obtain the same pattern every time. Make sure “Store design in Worksheet” is checked. Click on the OK button. You are now back in the main dialog box. Click on OK. A design will now be generated and stored in the worksheet.

TASK: Create a factorial design with 4 factors.

TASK: Display the available designs.

TASK: Select a full factorial design with 2 replicates.

TASK: Enter the following factors: Factor Name Low Level High Level rpm 1000 1500 Temp 250 350 Time 20 40 Pressure 2000 3000

TASK: Select the option to randomize runs. Enter 9 as the base for random data generator.

To open the data window, choose Window > Worksheet 1. Click on the Maximize button. The window should now appear as shown here.Notice that we have 24 runs instead of only 8. This is because we decided to do 3 replicates. 3 times 8 equals 24.The first two columns are labeled. StdOrder and Run Order. Standard order shows what the order of the runs in the experiment would be if it were done in standard or Yates order. Run Order shows what the order of the runs in the expeirment would be if the experiment was run in random order. If you do not randomize a design, the standard order and run order are the same. The next columns represent the Factor columns. The actual factor levels are shown for each run. This form shows the runs to be performed in the order we are to perform them.

We now would like to print a form that we can give to the operators for data entry. Our response for this experiment is Distance. In the data window, click on the name field of column C8 and type Distance.Choose File and Print Worksheet. Make sure Print Grid Lines is checked. Click OK. You now have a hard copy on which to record the experiment.

TASK: We have two responses in our experiment. Enter Thickness in C9 and Dimension in C10.

Now it is time to perform our experiment. For the first run, we will set the Pull Back angle to 440, the Hook Position to 1 and the Peg to 1. We then launch the ball and measure the distance it traveled. In this case, it traveled 32.5 inches. We record this distance on the worksheet.

The worksheet shows that the second setup should be as follows: Pull Back Angle 490 degrees, Hook 1, Peg 4 After setting the statapult to these settings, we now launch a ball and measure the distance. In this case, the ball traveled 128 inches. This is recorded on the worksheet.

All additional runs are completed as outlined on the worksheet. The final worksheet appears as shown here.

It is now time to enter our data. In the Data window, move the cursor to column C8 and enter the results in the appropriate rows. Select File and Save Project to save your data.

TASK: For run number 1, the thickness was 21 and the dimension was 4.7 Enter these values.

Now it is time to analyze our data. This is where the software saves us a huge amount of time and effort as trying to analyze the data by hand would take days.

Choose Stat > DOE > Factorial > Analyze Factorial Design. In Responses enter Distance. Click Graphs. To generate two effects plots, check Normal and Pareto. Use the default alpha level of 0.10. Click OK. You are now back at the main dialog box. To display the requested output in the session window, and each graph in a separate Graph window, click OK. You can use both the session window output and the two effects plots to help determine which factors are important.

This is the Pareto Chart for our experiment. Based on this Pareto Chart, Pull Back has the most effect on the distance the ball is thrown.

Minimze the Pareto Chart window. The Normal Probability Chart of the Standardized Effects now appears. If a normal probability plot is constructed for the data drawn from a single normal distribution, the data will fall approximately along a straight line. Departures from this straight line indicate factors that had an impact on your response value. In our example, Pull Back, Hook, Peg, the Pull Back/hook interaction and the Pull Back/Peg interaction are all significant. Minimize the probability chart window. The session window will appear.

Go to the Estimated Effects and Coefficients Table for Distance. Use the values in the P column (highlight the P column) to determine which of the effects are significant. Pull Back, Hook, Peg, the Pull Back/hook interaction and the Pull Back/Peg interaction are all significant. This agrees with the normal probability plot of the standardized effects.

Minitab offers another way to open these windows. Go to Window and then Click on the Effects Plot for Distance. The Effects plot will now appear. You can do the same thing to display the Pareto Chart.

TASK: Display the Pareto Chart for Dimension.

We now want to fit a new model using only the terms we identified as being important. Choose Stat > DOE> Factorial > Analyze Factorial Design. Click on Terms. We will now set up the model we want to fit. From Include terms in the model up through order, choose 3. We want to remove the BC and ABC terms from our model. To do this click on BC in the Selected Terms box and then click the < button. This will move the AC term to the Available Terms list box. Repeat these actions to move the ABC interaction to the Available Terms box. Click OK. You are now back in the main dialog box..

Click Graphs. Uncheck Normal and Pareto. Click OK to return to the main dialog box. Click OK in the Analyze Factorial Design dialog box. The output will display in the session window. We now want to look at our refined model. In the session window, go to the Estimated Effects and Coefficients for Distance for your refined model. The refined model appears as shown here.

TASK: Remove the insignificant terms from this model.

Minitab also allows you to review the residual plots. Choose Stat > DOE> Factorial > Analyze Factorial Design. Click on Graphs. Check Histogram, normal plot,residuals versus fitted, and residuals versus order. Click OK to return to the main dialog box. Click OK in the Analyze Factorial Design dialog box. The residual plots will now appear. After reviewing each of the residual plots, minimize them in Minitab.

Now let’s generate the main effects plots. Choose Stat > DOE > Factorial > and factorial plots. Check Main effects and setup. In Responses, type Distance. Next select the terms you want to plot. Click on A: Pull Back in the Available box. Click on the single arrow that points to the right. This will move the Pull Back variable to the select box. Repeat these steps to move Hook and Peg. Click on OK. Check Interaction and then click on the setup button. Select the terms you want to plot. Click on A: Pull Back in the available box. Click on the single arrow that points to the right. This will move the Pull Back variable to the select box. Repeat these steps to move Hook and Peg. Click on OK to return to the Factorial Plots box. Click OK in the main Factorial Plots dialog box. Each plot will now display in a separate Graph Window.

Review the Interaction Plot. Click on the minimize button to minimize this window. Review the Main Effects Plot. Click on the minimize button to minimize this window.

So far we have learned that Pull Back, Hook, Peg, the Pull Back/Hook interaction and the Pull Back/Peg interaction are all important terms in our model. We would like to hit a target value of 120 inches. Let’s use the contour plot to help us determine how to do this.

Choose Stat > DOE > Factorial > and Contour/Surface Plots. Check Contour Plot and click on the setup button. Our response is Distance.We would like Pull Back on the X axis. We want Hook on the Y Axis. Click on the Settings button.Our constant factor is Peg. Set it to 4. Click OK on all screens. The Contour Plot will now appear.

The red line represents a distance of 120 inches. Any settings along this line would hit the target value of 120. For example. We can set Pull Back at 469, Hook at 2 and Peg at 4.0 to hit a distance of 120. We could also hit that distance by setting Pull Back to 452, Hook at 4 and Peg at 4.

Minitab also allows you to generate response surface plots. Choose Stat > DOE > Factorial > and Contour/Surface Plots. Check Surface (Wireframe) Plot and click on the setup button. Our response is Distance. We would like Pull Back on the X axis. We want Hook on the Y Axis. Click on the Settings button. Our constant factor is Peg. Set it to 4. Click OK on all screens. The Response Plot will now appear.

This concludes the Minitab software module. In this lesson we have shown how to use Minitab software to set-up and analyze a designed experiment. The use of software is vital to the successful implementation of experimental design. For more information about this powerful software, go to www.minitab.com.