Using the Enventive Concept Auto-Constrainer

Import the IGES file

In this part of the tutorial, we will import an IGES file—a model of a flat bracket—into Concept.

  1. If needed, start a new Concept file by clicking the New File icon in the main toolbar.
  2. From the File menu, select Import.... The STEP/IGES Import dialog opens.
  3. Use the browse button under File To import to select FlatBracketIGES.igs from the ../Doc directory under the Enventive Concept installation directory (by default, C:\Program Files\Enventive\Enventive Concept version\Doc). (This IGES file is also downloadable from

    The IGES file is shown in the Preview area.

    IGES Import dialog

  4. Under the Post Processing area, select None. Click OK to import the file.
  5. The file is imported, and line endpoints that are within the distance specified for the Coincident Geometry Distance setting (0.1 by default) are automatically merged. Right-click in the Sketch view and select Zoom All from the right-click menu to see the entire model in the Sketch view.

    The DOF is 18. Toggle on the "Show/hide DOF arrows" option in the DOF display area.

    The underconstrained geometry is highlighted in yellow, with arrows that show the direction that each underconstrained object is able to move.

    Underconstrained geometry

  6. Toggle off the DOF arrows for now. We'll turn them back on later, after applying some constraints using the wizard.
  7. In a location of your choice outside of the Enventive Concept program directory, save the file as FlatBracket.enb.

Run the Auto-Constrain wizard

In this lesson, we will run Concept's automatic constraining wizard to apply constraints to the newly imported flat bracket model.

  1. From the Constrain menu, select Auto-Constrain…

    The Auto-Constrain wizard opens as an independent, undocked window, so you can move it anywhere you like, including outside of the Concept workspace.

    The wizard steps you through applying constraints, and gives instructions at each step. As you go through the steps, the wizard lets you make selections in the sketch to identify geometry to be constrained.

  2. Step 1 of the wizard lets you add datums, as well as fixed point and line at angle constraints, line length dimensions, and perpendicular constraints that are needed to fix the datums.

    Use the Datum tool  to place a datum first on the lower horizontal line and then on the left vertical line of the flat bracket in the sketch.

    Select datum 1

  3. The Primary Datum and Secondary Datum selections in the wizard automatically accept the datums in the order you created them, so the Primary Datum should be A and the Secondary Datum should be B, as shown below.

    Accept datum 1

  4. In the wizard, click Apply to complete Step 1, which applies fixed point and line at angle constraints to the primary datum, adds a perpendicular constraint between the datum lines, and dimensions the lengths of the datum lines. As we progress, move the constraints and dimensions as desired so they are easier to see.

    Note that the DOF is now 12.

    Apply Step 1

  5. At Step 2, which adds connectivity constraints, click Apply. No connectivity constraints are needed for this model, so no constraints are applied and the DOF remains at 12.

  6. Step 3 of the wizard adds diameter dimensions to all circles or only to selected circles. Press Esc or click the Select tool  in the Sketch view toolbar, and select the leftmost circle to add a diameter dimension only to this circle, and click Apply to complete Step 3.

    Diameter dimension

    The diameter dimension is applied only to the selected circle, the DOF is reduced to 11, and the Auto-Constrain wizard proceeds to Step 4.

  7. Step 4 adds position constraints to all circles in the sketch or only to selected circles. With the left circle still selected, click Apply to add the position constraint only to this circle.

    Position constraint

    Note that the DOF is now 9.

  8. Click Skip Step for Steps 5 and 6, which add arc constraints, because there are no arcs in the model.
  9. Step 7 adds orientation constraints to parallel lines based on the Criteria Angle setting, which defaults to 0.1 degrees.

    This step lets you add parallel constraints between lines, as well as add Line-to-Line or Point-to-Line constraints between lines that are parallel relative to the primary and/or secondary datum.

    You can deselect the Add dimensions from lines to secondary datum checkbox, because there are no orientation constraints relevant to datum 2. However, leaving it checked will have no effect on the results.

    Click Apply to complete Step 7. A parallel constraint is created between both the left and right horizontal lines. Note: Right-click in the sketch and select Show all constraints to see both parallel constraints.

    Parallel constraint

    The Auto-Constrainer could not apply a Line-to-Line dimension between the left line and primary datum, because a point-to-point dimension was previously applied in Step 1. To use a line-to-line dimension to constrain the lines relative to the datums, we must first remove the point-to-point constraint.

  10. Click Back to return to step 7, choosing No at the prompt to undo the previous step, and then delete the 40-length dimension.

  11. Click Apply to redo Step 7. Observe that the Auto-Constrainer added a line-to-line dimension between the datum A line and the line parallel to it. The DOF is now 7.

    Line-to-line dimension
  12. For Step 8, which adds angle dimensions to all or selected geometry, select the lower angled line on the right and click Apply.

    Select line

    Observe that the angle is applied only to the selected line.
  13. Select the 135-degree angle.

    Select angle

    Toggle the angle to 45 degrees using the supplemental angle tool  in the Properties Explorer.

    Toggle angle

  14. For Step 9, click Skip Step. (This step, which applies point-to-line dimensions to corners, is generally skipped because most models do not require these dimensions.)

    A summary of the constraints added during Auto-Constrain is displayed. Scroll down or expand the size of the wizard to review all added constraints and dimensions.

    Auto Constraining Wizard summary

    Observe that there are 6 DOF remaining.

Re-run the wizard to create additional constraints

In this lesson, we will re-run some of the steps in the wizard to add more constraints to the flat bracket model.

  1. Select Step 1 from the Return To Step selection list. (Note: If you closed the Auto-Constrain wizard before proceeding with this lesson, you can re-open it and continue this lesson at step 2.)

    Return to Step 1

    You return to the first step in the wizard.

  2. Toggle on the DOF display again, so you can see exactly what is still underconstrained. We can see that the left side of the bracket is fully constrained, but the right side still has underconstrained geometry.

    Next, we'll add datums to the right side of the flat bracket model.

  3. Place a datum first on the lower angled line in the sketch and then on the rightmost line in the sketch.

    Datums C and D

  4. In the wizard's Choose Datums area, select C as the Primary Datum and D as the Secondary Datum.
  5. Click Apply at Step 1 to apply line lengths and a perpendicular constraint to the datums.

    Note: Fixed Point and LAA constraints are not applied because we normally apply these constraints only once, which we did during our first pass using the Auto-Constrainer. If you want to create additional Fixed Point and LAA constraints to datums, you must create them manually, outside of the Auto-Constrainer.

  6. Click Skip Step at Step 2, because there are no relevant objects to constrain.
  7. Click Apply at Steps 3 and 4. A diameter dimension and position constraint relative to datums C and D are placed on the rightmost circle. The DOF is now 0.  

  8. Click Skip Step for Steps 5 and 6, because there are no relevant objects to constrain.
  9. At Step 7, delete the 40-length dimension that was applied to the rightmost line (datum D) in Step 1.

    This will let us apply a line-to-line dimension between the lines relative to the primary datum (now datum C for this Auto-Constraining session).

  10. Click Apply to apply the line-to-line dimension. Your model should now look like the following, and the DOF should be 0.

    Flat bracket model constraints
  11. Click Close to exit the wizard.

Run tolerance analysis

Now that our flat bracket model is fully constrained, we will run tolerance analysis to see how the constraints are working and make any needed adjustments. (Running tolerance analysis on underconstrained models is not recommended; you cannot rely on accurate results unless the model is fully constrained.) First, we must add a derived dimension on which to run the tolerance analysis. Only derived dimensions can be analyzed.

  1. Create a point-to-point dimension between the two circles in the flat bracket model by selecting the Linear dimension tool  and then selecting both circles. The dimension is added to the last row in the parameter table.

    Point-to-point dimension
  2. Note that the dimension is derived, indicated by the arrow symbol preceding the dimension value in the sketch and in the Lock status column of the parameter table.

    Derived dimension

    Troubleshooting: If the point-to-point dimension between the two circles is not derived, your model is missing one or more constraints. To resolve this, find the missing constraint(s) by comparing your parameter table to the one shown above. Unlock the point-to-point dimension (click on the lock symbol), and add any missing constraint(s). When all constraints that drive the value of the point-to-point dimension have been added, the dimension status will be changed to derived in the parameter table. You should also confirm that the DOF=0.

  3. From the Edit menu, select Default Tolerances...

  4. In the Constraints tab, set the default tolerances to 0.2 for all constraints except Point On.

  5. In the Dimensions tab, set linear dimensions to 0.2; radius dimensions to .005; and angle dimensions to 1.0. Leave the other values at their defaults and click OK to close the dialog.

    Default tolerances

  6. Now, we'll run tolerance analysis on the derived dimension we just added: Right-click on the derived dimension in the sketch, and select Analyze tolerance from the shortcut menu.
  7. Scroll down in the spreadsheet to see the Contributor Info section of the analysis report. You will see that the two perpendicular constraints are shown in red as non-contributors. Because they are non-FCF orientation constraints and have no tolerance values (the default tolerances apply only to parallel and perpendicular constraints that have been converted to FCF), they are considered construction contributors and do not affect the tolerance analysis results.

  8. Select one of the perpendicular constraints and perturb it (using the Perturb section in the Properties Explorer) to observe its effect on the analyzed dimension. Perturb the other perpendicular constraint as well.

    We can see that both perpendicular constraints affect the analyzed dimension. To get accurate tolerance analysis results, we must convert the constraints to FCF callouts.
  9. Select one of the perpendicular contributors in the spreadsheet, and then click the FCF button in the Properties Explorer. The constraint is converted into an FCF callout. Repeat this step for the other perpendicular constraint.

  10. To update the analysis report, which has been disconnected from the model due to the changes we made, select Update Current Analysis  from the spreadsheet toolbar.
  11. If needed, scroll to see the Contributor Info section in the analysis report. We now see that the perpendicular callouts are shown as contributors in the upper section of the report, which indicates they are main contributors to the tolerance results.

    Updated tolerance analysis

Congratulations! You have completed the Auto-Constrain tutorial.

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