Tutorial > Charts > Advanced Charts

Advanced Charts

AT Sigma SPC features comprehensive and advanced charting. Here is a quick guide to some of these features:

Contents:

Viewing a Pareto Chart View a Screen Cam demo.

The Pareto chart shows a sorted list in decreasing frequency. It is applied to showing the most common causes of defects or common causes of out-of-control conditions.

  1. Open samples\charts\pareto.SPC.
  2. Checkmark the first four variables and click OK.
  3. Select Pareto from the charts menu.
  4. A pareto chart including a Pareto Analysis summary window appears. You can maximize the window for a better view.


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Setting up moving average charts View a Screen Cam demo.
  1. Select Setup | SPC Edit from the main menu.
  2. Select the file samples\charts\moveavr.SPC.
  3. From the Fields to Analyze group box, select the field Width. Click on the Edit button.
  4. Click the Set … button to the immediate right of the Sample Size edit box. The Sample Size dialog box will appear.
  5. From within the Sample Size dialog box, check the Apply Moving Average check box. Enter 5 in the Length edit box.
  6. Click OK on all dialog boxes until you return to the main AT-Sigma SPC.
  7. Open the file, samples\charts\moveavr.SPC.
  8. Click Width in the Status Grid dialog box and click OK.
  9. The chart displayed is a moving average chart.
  10. Open samples\charts\nomove.SPC to see the same chart, but without Moving Average applied.

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Setting up median charts View a Screen Cam demo.
  1. Select Setup | SPC Edit from the main menu.
  2. Select the file samples\charts\median.SPC.
  3. Select Width. Then, click on the Edit button.
  4. From within the SPC Detail Setup, click on the Chart Type drop down box, and select Median, Range.
  5. Click OK on all dialog boxes until you are in the main AT-Sigma SPC window.
  6. Open ERIC.SPC again.
  7. From the Status Grid, check Width. Click OK.
  8. The charts that appear are for median charts for Width

Other SPC charts like for instance P, C, U, NP, Group, and Moving Range charts are selected in the same way, from the drop down menu in SPC Detail Setup (below).


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Setting up and using group charts View a Screen Cam demo.
  1. Select Setup | SPC Edit from the main menu.
  2. Select the file samples\charts\group.SPC.
  3. Click the Add button. You will see the New SPC Field dialog box.
  4. Type GroupField in the FieldName edit box. Click OK.
  5. From within the SPC Detail Setup, click on the Chart Type drop down box, and select Group Field.
  6. A button will appear captioned Select …. Click on this button.
  7. From within the Select Group Charts dialog box, move .0635 Diameter, 0317 Diameter and .210 Distance to the Destination Chart List.
  8. Click OK on all dialog boxes until you are in the main AT-Sigma SPC window.
  9. File > Open > samples\charts\group.SPC.
  10. From the Status Grid, check GroupField. Click OK.
  11. The charts that appear are for the newly added field, GroupField.

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Target Charts

Target charts are used for short production runs or where lots/batches change rapidly so that control charts cannot be populated with like values. In order to accommodate the changing product, you can use a Target control chart where a Target or Nominal value is subtracted from the measurement and the delta (left over) is plotted. AT-Sigma SPC uses a lookup method to automatically remove the nominal values as appropriate based on the content of one of the fields in the data record. For example, if the ‘operator’ is a field in the record, we can lookup the target based on the product field contents, for instance 'John' or 'Bill'.

  1. Select Setup | SPC Edit and open samples\chart\target.spc for the following example.
  2. From the SPC Setup select a variable name to assign a target chart to. Click on Height.
  3. Click Edit, to go to SPC Detail Setup. Check the Target Chart box. Click on Set.…

    The target mechanism needs all the fields entered properly. You also need to construct a lookup table where AT-Sigma SPC will search for nominal values. We have provided a lookup table (ericlu.db) that looks something like this:
    Operator Target
    Sven 1
    John 2
    Bill 0.5
    ...etc...  
  4. Enter the field name that AT-Sigma SPC will use to determine changes in target (in this case Operator.
  5. Set directory to c:\sigwin\samples\charts\ (or wherever you installed your copy of sigma)
  6. Set table name to ericlu.db.
  7. Finally, enter the field name in the lookup table that AT-Sigma SPC will use as the target value for this field. In this case type Target.

    Once set up, everything is automatic. Collect data and charts come out with Target transformations.

    The data in the original table is not altered, only the values as plotted. If a search field value does not provide a match in the lookup table, the measured value is left unaltered (Target=0).
  8. Click OK all the way back to Sigma SPC main screen.
  9. Select Setup > Options and click on the General tab.
  10. Make sure "Warn if Target Lookup not found" is not selected.
  11. Press OK to return to Sigma main window.
  12. Open target.spc, select Height in the status grid and notice the difference. If you want to compare this chart with the one without target values, then open target0.spc, which is identical except for that target values are turned off. Once again, select Height in the status grid. You can tile the windows (Windows>Tile) to get a better view.
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