Assembly constraints overview

May 2024 · 43 minute read

Assembly constraints determine how components in the assembly fit together. As you apply constraints, you remove degrees of freedom, restricting the ways components can move. You can assign maximum, minimum, and resting position values to specify the allowable range of motion for a constraint.

What types of assembly constraints are available?

The Place Constraints dialog box creates constraints to control position and animation. Motion constraints do not affect position constraints.

The Assembly tab has the following constraints to control position:

The Assembly tab also supports user-defined constraint limits. You can define a minimum, maximum, and resting position for constraints in the assembly tab.

The Motion tab has the following constraints to specify intended motion ratios between assembly components:

How are constraints created?

Constraints are created using either the Constrain command or the Assemble command.

Constrain command

You select a constraint type to update the Place Constraint dialog box then select the objects to constrain. In addition to creating the constraint, you can change the browser name and apply limits.

To help you position components correctly, you can preview the effects of a constraint before it is applied. After you select the constraint type, the two components, and set the angle or offset, the components move into the constrained position. You can adjust settings as needed, and then apply them.

Assemble command

You select the objects to constrain, and then select the type of constraint to apply. A mini toolbar displays in the graphics window instead of a dialog box. Assemble automatically selects valid constraint types based on your geometry selections. For example, if you select planar faces only the Mate-Mate, Mate-Flush, and Angle-Directed constraint types are displayed in the list. If your first selection is a circular edge, only the Insert-Opposed and Insert-Aligned constraints are listed, and your second selection is limited to a circular edge.

The Assemble command always moves the first selected component to the second selection. If necessary, existing constraints or grounded status are relaxed to allow the first component to move. When you exit the Assemble command, all new and existing constraints are calculated. If there is a conflict, the Assemble Constraint Management dialog displays so you can suppress or delete the constraints. Use this workflow to change the location of a component when you are unsure how it was constrained. You can reposition the component and then resolve any constraint conflicts.

Some constraint types (Motion, Translation, Angle-Undirected, and Angle-Explicit Reference Vector) are not supported in the Assemble command. Also, you cannot change the constraint name or apply limits. You can edit the constraint after it is created to change those settings.

Grip Snap command

Grip Snap moves a component relative to another component or reference geometry. It does not create constraints, but you can ground the component when you have positioned it. You can change several Grip Snap settings in the Application Options. For example, you can select whether it ignores the grounded status while moving components.

What are constraint limits?

Constraint limits use specified values to define the allowable range of motion for components that move or rotate. You can specify a Maximum, a Minimum, and a Resting Position for a constraint in the Assembly tab. The Resting Position uses the value specified in the Offset box. A constraint with limits is identified in the browser by a +/- symbol.

Contact sets require physical contact with other components to determine the limits. Constraint limits use assigned values to limit movement and do not require physical contact. Use constraint limits to evaluate a design based on known maximum, minimum, and resting values.

TipAs with contact sets, consider assembly performance when you use constraint limits. For best performance, use constraint limits to evaluate your design and then edit the constraint and clear the check boxes. The limit values are stored with the constraint and remain available when you reactivate the limits.

Should I use constraint limits, contact sets, or dynamic simulation for moving parts?

If you are designing a mechanism with moving parts, simulating the motion is a key component of the digital prototyping process. Before deciding on the appropriate method, consider the following:

What is a Layout constraint?

Layout constraints are created when you execute Make Components. Layout constraints define the relationship between the layout and parts push derived from the layout. The Layout constraint comprises flush constraints between the three primary planes of the layout and derived parts, and a zero degree angle constraint between the Z axes of the layout and derived parts.

Layout constraints provide certain behaviors that are useful in skeletal modeling:

The default behaviors for layout constraints are initialized based on your sketch constraint relationships and options you select during Make Components. To changes behaviors for a component, right-click the component instance in the browser, select Layout Constraint in the context menu, and choose the appropriate position options.

You can modify layout constraints to achieve the target behavior. However, you cannot place new layout constraints except by the Make Components workflow.

How do constraints position components?

How do drive constraints and motion constraints differ?

Drive constraints do not control motion between components, but simulate mechanical motion by driving a constraint through a sequence of steps for a single component. You can, however, animate two components by using Equation to create algebraic relationships between components. A drive constraint operation is a temporary animation.

Motion constraints specify motion ratios between components, either by rotation or by rotation and translation. Such constraints are useful for specifying motion of gears and pulleys, a rack and pinion. They can also specify motion between third-party components, such as a gearbox, and input and output shafts. Use work geometry and assembly constraints to limit the range of motion.

Can constraint names be modified?

After you place constraints, they are shown in the assembly browser. You can rename constraints to indicate which can be driven, for example. Constraints can be renamed in the browser or the Place Constraint dialog box.

Can constraints be retained on replaced components?

There are two ways to retain constraints for replaced components:

iMates are constraint pairs in parts that define how a part fits together with other components each time it is placed in an assembly.

Convert existing assembly constraints to iMate definitions by right-clicking the component in the browser, and then selecting Infer iMates. You can also create iMates as you edit or modify a component.

What is a good strategy for creating constraints in complex assemblies?

To simplify constraining the members of a complex assembly, create several small assemblies; apply constraints as needed, then save each one as a separate file. This approach allows the subassembly to be constrained in upstream assemblies as a single unit.

Grouping parts in subassemblies also simplifies the process of using the parts in more than one assembly.

Procedures

Place Mate or Flush constraints in assemblies

A Mate constraint positions selected components face to face or with the faces flush. The geometry you select is usually a component face, but you can also select curves, planes, edges, or points.

You can place a Mate constraint three ways:

To begin, place the components to constrain in an assembly file.

To use Constrain to place Mate or Flush constraints

 
  • On the ribbon, click .
  •  
  • On the Assembly tab, the Type is set to Mate by default. If necessary, click Mate.
  • Select the Predict Offset and Orientation check box if the components are close to the desired position.
    • The offset is the distance between the selected components. The current distance is automatically entered into the Offset field.
    • The orientation sets the Mate or Flush solution. If the components are parallel, and the surface normals are opposite (indicated by arrows), the constraint solution is set to Mate. Otherwise, the constraint solution is set to Flush.
  • Select the first point, curve, face, or work feature. If necessary, click First Selection to enable the selection. Use Select Other to cycle through geometry.
  • Select the geometry to mate to the first. If necessary, click Second Selection to enable the selection. Use Select Other to cycle through geometry.
  • In the Solutions box, select one:
    • Click Mate to constrain geometry face to face (or to make curves, planes, edges, or points coincident).
    • Click Flush to constrain faces or planes to be flush.
  • Enter a different Offset value, as needed.
  • To change the name of the constraint or set limits, click the More button.
    • In the Name box, enter a constraint name, or leave blank and a default name is automatically created.
    • Check Maximum and enter a value to specify the maximum limit position.
    • Check Minimum and enter a value to specify the minimum limit position.
    • Check Use Offset As Resting Position and enter the required value in the Offset value box to specify the resting position.

    Clear the check box to remove limits. Values are retained in an inactive state.

  • If Show Preview is selected, observe the effects of the applied constraint. If either component is adaptive, constraints are not previewed.
  • Do one of the following:
    • Click Apply to continue to place constraints.
    • Click OK to create the constraint and close the dialog box.

    Show Me how to create a mate constraint

  • To use Assemble to place Mate or Flush constraints

     
  • On the ribbon, click .
  •  
  • Select a point, curve, face, or work feature on the component that changes position.
  • Select a point, curve, face, or work feature on the component that remains in position.
  • Enter an offset value, if applicable.
  • Change the solution from Mate to Flush to reverse the direction of the first component.
  • Do one of the following:
    • Click Apply and continue to define constraints.
    • Click OK to create the constraints and exit the Assemble command.
    • Click Undo to delete the selections and continue to define constraints.
  • To drag a component into position and place a Mate constraint

    You can drag a component into position and automatically place a Mate constraint with no offset.

    When you drag a cylindrical part over another cylindrical part or hole, the inferred Mate constraint is along the axes. If you position the dragged part over a component face, the system infers a mate between planar faces.

  • Hold down ALT, and then click the component to drag.
  • Drag the component into position. As the dragged component nears the target component, the constraint is previewed.
  • When the component is in the appropriate position, release the mouse to place the mate constraint.
  • Kinematics mode for translated constraints

    If the selected constraint was created with Make Components, you sometimes have the option to select between 2D and 3D Kinematics. See Set kinematics mode in the Make components procedure for more information.

    NoteIf other components obscure selection, do one of the following:

    Place Angle constraints in assemblies

    Use the Constrain command or Assemble command to place an Angle constraint between two assembly components. An Angle constraint controls the angle between edges or planar faces.

    To begin, place the components to constrain in an assembly file.

    Use Constrain to place Angle constraints

     
  • On the ribbon, click .
  •  
  • On the Assembly tab, in the Type box, click Angle.
  • Select the Predict Offset and Orientation check box if the components are close to the desired position. The current angle between the selections is automatically entered in the Angle field.
  • Select the first face or edge. If necessary, click First Selection to enable the selection.
  • Click the second face or edge to constrain to the first selection. If necessary, click Second Selection to enable the selection.
  • When using the Explicit Reference Vector option, a third selection command is available. Select a face, linear edge, work plane, or work axis. The selection indicates the direction of the cross product (Z axis) of the vectors from the first two selections. If necessary, click Third Selection to enable the selection.

    NoteFor best results, make the third selection on a stationary component.

  • In the Solutions box, select the appropriate solution:
    • Click Directed Angle to apply the right-hand rule in all cases. Some cases, such as zero or 180°, can flip in the opposite direction. Infers the Z axis or vector product.
    • Click Undirected Angle to apply either. If the solved position more closely resembles the last-calculated position, the default behavior is to apply the left-hand rule. Infers the Z axis or vector product.
    • Click Explicit Reference Vector to define by selection the Z axis or cross product of the first two selections.
  • In the Angle field, enter a different angle value, as needed.
  •  
  • To change the name of the constraint or set limits, click the More button.
    • In the Name box, enter a constraint name, or leave blank and a default name is automatically created.
    • Check Maximum and enter a value to specify the maximum limit position.
    • Check Minimum and enter a value to specify the minimum limit position.
    • Check Use Offset As Resting Position and enter the required value in the Offset value box to specify the resting position.

    Clear the check box to remove limits. Values are retained in an inactive state.

    NoteThe following rules apply to limits:
    • Limits are not available for Directed Angle.
    • if the combined total does not to exceed 180 degrees, undirected Angle limits of -180 to 180 degrees is supported.
    • If the combined total does not exceed 360 degrees. explicit Reference Vector limits of -360 to 360 degrees is supported.
  • If Show Preview is selected, observe the effects of the applied constraint. If either component is adaptive, constraints are not previewed.
  • Click Apply to continue to place constraints or click OK to create the constraint and close the dialog box.
  • Show Me how to create an angle constraint

     

    Use Assemble to place Directed Angle constraints

  • On the ribbon, click .
  • Select a face or an edge on the component that changes position.
  • Select a face or an edge on the component that remains in position.
  • Select Angle-Directed from the Solution Type list.
  • Enter an angle value, if applicable.
  • Do one of the following:
    • Click Apply and continue to define constraints.
    • Click OK to create the constraints and exit the Assemble command.
    • Click Undo to delete the selections and continue to define constraints.
  • NoteIf other components obscure selection, do one of the following:

    Place Tangent constraints in assemblies

    Use the Constrain command or Assemble command to place a Tangent constraint between assembly components. A Tangent constraint positions faces, planes, cylinders, spheres, cones, and ruled splines tangent to one another.

    To begin, place the components to constrain in an assembly file.

    Use Constrain to place Tangent constraints

     
  • On the ribbon, click .
  •  
  • In the dialog box, under Type, click Tangent.
  • Select the first face, curve, or work plane. If necessary, click First Selection to enable the selection. Use Select Other to cycle through geometry.
  • Select the second face, curve, or work plane. If necessary, click Second Selection to enable the selection. Use Select Other to cycle through geometry.
  • Enter an offset value, if applicable.
  • Click Inside or Outside to specify the tangency position.
  • Click the More button to change the name the constraint or set limits.
    • In the Name box, enter a constraint name, or leave blank and a default name is automatically created.
    • Check Maximum and enter a value to specify the maximum limit position.
    • Check Minimum and enter a value to specify the minimum limit position.
    • Check Use Offset As Resting Position and enter the required value in the Offset value box to specify the resting position.

    Clear the check box to remove limits. Values are retained in an inactive state.

  • If Show Preview is selected, observe the effects of the applied constraint. If either component is adaptive, constraints are not previewed.
  • Click Apply to continue to place constraints or click OK to create the constraint and close the dialog box.

    Show Me how to create a tangent constraint

  • Use Assemble to place Tangent constraints

     
  • On the ribbon, click .
  •  
  • Select a face, curve, or work plane on the component that changes position.
  • Select a face, curve, or work plane on the component remains in position.
  • Enter an offset value, if applicable.
  • Change the solution from Outside to Inside to specify the tangency position.
  • Do one of the following:
    • Click Apply and continue to define constraints.
    • Click OK to create the constraint and exit the Assemble command.
    • Click Undo to delete the selections and continue to define constraints.
  • NoteIf other components obscure selection, do one of the following:

    Place Insert constraints in assemblies

    Use the Constrain command or Assemble command to place an Insert constraint. An Insert constraint places a planar and axial mate as a single constraint between selected cylindrical faces or edges. For example, use an Insert constraint to position a bolt in a hole. The bolt is free to rotate, but is constrained plane to plane and axis to axis.

    To begin, place the components to constrain in an assembly file.

    Use Constrain to place Insert constraints

     
  • On the ribbon, click .
  •  
  • In the dialog box, under Type, click Insert constraint.
  • Select the first arc or circle edge. If necessary, click First Selection to enable the selection. Use Select Other to cycle through geometry.
  • Select the second arc or circle edge to constrain to the first selection. If necessary, click Second Selection to enable the selection. Use Select Other to cycle through geometry.
  • Enter an offset value, if applicable.
  • Click Opposed or Aligned to reverse the direction of the constraint.
  • Click the More button to change the name the constraint or set limits.
    • In the Name box, enter a constraint name, or leave blank and a default name is automatically created.
    • Check Maximum and enter a value to specify the maximum limit position.
    • Check Minimum and enter a value to specify the minimum limit position.
    • Check Use Offset As Resting Position and enter the required value in the Offset value box to specify the resting position.

    Clear the check box to remove limits. Values are retained in an inactive state.

  • If Show Preview is selected, observe the effects of the applied constraint. If either component is adaptive, constraints are not previewed.
  • Do one of the following:
    • Click OK to create the constraint and close the dialog box.
    • Click Apply and continue to place constraints.

    Show Me how to insert a constraint

  • To use Assemble to place Insert constraints

     
  • On the ribbon, click .
  •  
  • Select an arc or circle edge on the component that changes position.
  • Select an arc or circle edge on the component that remains in position.
  • Enter an offset value, if applicable.
  • Change the solution from Insert-Opposed to Insert-Aligned to reverse the direction of the constraint.
  • Do one of the following:
    • Click Apply and continue to define constraints.
    • Click OK to create the constraint and exit the Assemble command.
    • Click Undo to delete the selections and continue to define constraints.
  • NoteIf other components obscure selection, do one of the following:

    Create assembly constraints using the Assemble command

    Assembly constraints maintain positions of components relative to one another in an assembly. Use the Assemble command to create constraints by selecting geometry first and then the constraint type. The geometry you select determines the available constraint type.

    You can constrain only one component at a time with Assemble. When you finish defining constraints for a component, select OK to create the constraints and exit the command. Repeat Assemble to constrain the next component.

    New constraints are not compared to existing constraints until you finish the Assemble command. If any constraint conflicts are found, the Assemble Constraint Management dialog box displays. Use this dialog box to diagnose and resolve the conflicts.

    General workflow

     
  • On the ribbon, click .
  •  
  • Select geometry on the component that changes position.
  • Select geometry on the component that remains in position.
  • Enter an offset or angle value, if applicable.
  • Change the solution type, if necessary.
  • Do one of the following:
    • Click Apply and continue to define constraints.
    • Click OK to create the constraints and exit the Assemble command.
    • Click Undo to delete the selections and continue to define constraints.
  • Specific workflows by constraint type

    Place assembly constraints using ALT-drag

    Assembly constraints maintain positions of components relative to one another in an assembly. Optionally, use the ALT-drag shortcut instead of using the Place Constraint dialog box or Assemble command.

  • The selected geometry determines the type of constraint to apply:
    • Click a planar face, linear edge, or axis to place a mate or flush constraint.
    • Click a cylindrical face to place a tangent constraint.
    • Click a circular edge to place an insert constraint.
  • Hold down ALT, then select and drag the component into position. As you drag over features on other parts, the preview shows the constraint type.
  • Optionally, press the spacebar to cycle through options for the constraint type:
    • Select a mate or flush constraint.
    • Select a tangent constraint inside or outside the selected cylindrical face.
    • Select the direction of an insert constraint.
  • Optionally, drag the component to a new position and cycle through constraint options.
  • When the parts are positioned as needed, release the mouse button to create the constraint. A snap sound indicates that the components are in a constrained position.

    If the face you must constrain to is hidden, pause long enough to display the Select Other command. Cycle through the available selectable options, then click the center dot to confirm the selection and place the constraint.

  • A constraint symbol is displayed with both components in the browser.

    Tips, Shortcut Keys

    Use the ALT-drag shortcut to infer constraints. Press ALT, and then drag a component into the appropriate position. The inferred constraints are previewed in the graphics window as you drag over the affected components.

    When constraining components using the ALT-drag shortcut, you can change the constraint type after you start dragging the first part.

    Release ALT, and enter a shortcut key:

    M or 1

    Changes to a mate constraint. Press the space bar to flip to a flush constraint.

    A or 2

    Changes to an angle constraint. Press the space bar to flip angle direction on the selected component.

    T or 3

    Changes to a tangent constraint. Press the space bar to flip between an inside and outside tangent constraint.

    I or 4

    Changes to an insert constraint. Press the space bar to flip insert direction.

    R or 5

    Changes to a rotation motion constraint. Press the space bar to flip rotation direction.

    S or 6

    Changes to a translation (slide) constraint. Press the space bar to flip slide direction.

    X or 8

    Changes to a transitional constraint.

    NoteIf you create constraint and forget which components are constrained to each other, click a constraint to highlight the constrained components.

    Apply assembly constraints to sketch geometry

     

    You can create assembly constraints between sketch geometry and geometry on other components.

    Lines, circles, points, and their vectors can be incorporated into constraint schemes. Sketch behavior is like any other component used in an assembly: it can be adaptive, is previewed before a constraint is placed, and can be edited in the assembly.

    To begin, do one of the following in an assembly file:

     

    To constrain a component to sketch geometry:

  • On the ribbon, click .
  • In the dialog box, click the button for the type of constraint you want to add.
  • Click First Selection, and then select the first face, curve, plane, or point.
  • Click Second Selection, and then select the geometry to constrain to the first selection.
  • Select the Solution for the constraint.
  • Enter an offset, if applicable.
  • Observe the previewed constraint. If either the component or sketch are adaptive, a constraint is not previewed.
  • Click Apply to continue placing constraints or OK to create the constraint and close the dialog box.
  • Find constraints in an assembly

    Changes to assemblies during the design process can affect existing constraints causing them to conflict with others or become unsolvable. Designers must then locate the constraints in question to resolve the errors or to collect additional information.

    You can locate all constraints in the assembly or locate the other half of a single assembly constraint.

    Locate all constraints in an assembly

  • Select the Modeling View option from the browser view menu to gather constraints into a folder at the top of the browser hierarchy.
  • Expand the folder to view the constraints.
  • Highlight a constraint or a constraint error to see the constrained parts highlight and zoom to the selected constraint in the graphics window.
  • Locate the other half of a single constraint

    There are two halves to every assembly constraint. When multiple constraints of one type exist, such as several Mate or Flush constraints, it can be difficult to locate the other half. To make constraints easier to locate, the browser automatically expands to show the other half of the selected constraint and highlights it.

  • Select the Position View from the browser view menu.
  • Expand the components to view a needed constraint.
  • Highlight a single constraint or a constraint with errors, right-click, and select Other Half.
  • Use Find to locate constraints

  • Click the binoculars icon on the browser toolbar.
  • In the Find dialog box, set the search criteria or click Open Search to search on previously specified criteria.
  • Select Constraints from the Look For list.
  • In the Define more criteria box, you can make your search more specific. Optionally, enter one or more:
    • Using the And/Or operators, select And to accumulate criteria or select Or to satisfy the search if either criteria is met.
    • Specify Property. The Find command recognizes the active environment and offers search criteria based on the environment.
    • Select a Condition.
    • Specify a Value to complete the Property, Condition, Value statement.
  • Click Add to List to add the refined criteria to the search box.
  • Specify the current path file.
  • Click Find Now to initiate the search. You can save the search results to a text file and view them using a text editor.
  • Delete assembly constraints

    If your constraint strategy or design requirements change, you can delete an assembly constraint.

    In the browser, do the following:

  • Click the plus sign (+) to expand components.
  • Pause the cursor over the constraint to delete. The constrained parts are highlighted.
  • Right-click the constraint, and then select Delete. The constraint is outlined with a red box and constrained features are highlighted.
  • TipAn alternate method for deleting a constraint is to select the constraint in the browser, and then press the Delete key.

    In a complicated assembly, components can obscure the features or components whose constraints you want to delete. If you prefer, click the component in the graphics window to highlight it in the browser. Or in the browser, select the component, right-click, and then select Find in Window.

    NoteIf you chose to display the contents of the browser using the Modeling View, constraints are listed under Constraints at the top of the browser. If you have difficulty determining which constraint applies to a component, display the browser contents using the Position View before you delete constraints.

    Edit assembly constraints

    You can edit the constraint type, offset, angle, selected components, and direction. If possible, constraints are retained through editing operations. Some constraints do not survive and must be reapplied.

    NoteThis procedure presumes that the Position View is active. If you activated the Modeling View, all constraints for each assembly are collected below the assembly origin folder (although each part displays its features when expanded).

  • To identify components constrained together, click a constraint in the browser to highlight the affected components in the graphics window.
  • In the browser, click to expand the component whose constraint you want to edit.
  • Pause the cursor over the constraint, right-click, and then select Edit to open the Edit Constraint dialog box.
  • Change values as needed, and then click OK.
  • To edit only the offset or angle, highlight the constraint in the browser. Then click to open the edit box at the bottom of the browser. Enter the new value for the constraint, and then press Enter.

    NotePredict Offset or Angle is only available when creating constraints.

    Tips for editing constraints

    Drive Constraints in assemblies

    Use Drive Constraint on the context menu to simulate mechanical motion by driving a constraint through a sequence of steps. The Drive Constraint command is limited to one constraint, but you can drive additional constraints by using Equations to create algebraic relationships between constraints.

    To begin, constrain two components together.

  • In the browser, right-click the constraint, and then select Drive Constraint. The Drive Constraint dialog box opens.
  • In Start, enter the beginning value. The default value is the angle or offset defined for the constraint.
  • In End, enter the ending value. The default is the Start value plus ten.
  • In Pause Delay, set the time in seconds between steps. Adjust the default value to speed up or slow down motion.
  • Click More to set options, as follows:
    • Select the Drive Adaptivity check box to adapt components while maintaining the constraint relationship, if needed.
    • Select the Collision Detection check box to check for interference.
    • Set the Increment between steps by specifying either the value or the total number of steps. Enter a value or click the arrow to select Measure or a recently used value.
    • Set the Repetition or Cycles of the sequence: Start/End runs once and returns to the beginning; Start/End/Start runs once forward, then once backward depending on the number of cycles set. Each motion is considered one cycle. For example, for a component to move out, set one cycle. To move out, in, and out again requires three cycles. Optionally, enter a value to run the sequence more than once.
  • Click Forward to start the sequence or click Step Forward to advance the sequence one step at a time.

    After the sequence begins, click Stop, click Forward or Reverse, Step Forward or Step Reverse, or Go to Beginning or Go to End.

  • Show Me how to drive a constraint

    TipTo record the driven constraint sequence, click More and set the AVI rate. Then click Record. Enter the file name with extension and click Save in the Save As dialog box. For an .asf or .wmv file, set the export options in the ASF Export Properties dialog box. After you close the ASF Export Properties dialog box, click Play in the Drive Constraint dialog box to create the recording.

    Place Motion constraints between assembly components

    Use the Constrain command to specify intended motion ratios between assembly components.

    A Motion constraint maintains rotational or rotational-translational movement between components. You can specify the ratio or determine the ratio by picking geometry.

    To specify the ratio for rotational components, select a circular face or edge on each component. To calculate the ratio based on relative size, select a cylindrical face on each component.

    To specify the distance for rotational-translational components, select a circular face or edge on the rotational component and a linear edge on the translational component. You can calculate the distance based on circumference and length. Select a cylindrical face on the rotational component and a linear edge or sketched line on the translational component.

    To begin, place the components to constrain in an assembly file.

    Place Transitional surface constraints

     

    Use the Constrain command to place a Transitional constraint between assembly components.

    A Transitional constraint maintains tangency between a (typically) cylindrical face and a contiguous set of faces on another part, such as a cam in a slot. You can slide the component along open degrees of freedom.

    Place Constraint Set (constrain UCS to UCS)

    References

    Assembly constraints

    Assembly constraints remove degrees of freedom between two selected components, positioning them relative to one another.

    Constrain

    The Place Constraint dialog displays and you select a constraint type. The dialog updates and you make the selections for that type of constraint.

    Assemble

    A mini toolbar displays in the graphics window instead of a dialog. As you select geometry, the list of constraint types updates based on those selections.

    The first component always moves to the second component, even if the first component is fully constrained. If this causes constraint errors, the Assembly Constraint Management dialog lists the conflicting constraints so you can suppress or delete them.

    You can only add constraints to one component at a time with Assemble. When you finish defining constraints for a component, select OK to create the constraints and exit the command. When you restart Assemble you select the next component you want to constrain.

     

    The Constraint Type list updates as you select geometry to list only valid constraints. You can select a constraint type at any time to limit the type of geometry you can select. For example, if you select Insert- Opposed, you can only select circular edges.

     

    Enter the offset or angle value.

     

    The OK button creates the constraint and exits Assemble.

     

    The Apply button creates the constraint and leaves Assemble active.

     

    The Undo button clears any selections.

    ESCPress ESC to create any applied constraints and exit the Assemble command.

    Assembly constraints - Assembly tab

    Assembly constraints remove degrees of freedom between selected components. Adaptive components can resize or change shape when constraints are applied.

    Access:

    , and then click the Assembly tab.

    Type and Solutions

    Specifies the type of constraint and illustrates the solution used to position components before you apply the constraint. Change constraint type and place constraints when the dialog box is open. When you select a face, curve, or point (including midpoint), an arrow shows the default direction of the solution. Click constraint icons on the dialog box to change solution. Use constraint limits to define the range of allowable movement or rotation. You can specify a maximum, minimum, and resting position value for constraints in the Assembly tab.

     

    A Mate constraint positions components face to face or next to one another with faces flush. Removes one degree of linear translation and two degrees of angular rotation between planar surfaces.

     

    A Mate constraint positions selected faces normal to one another, with faces coincident.

    Supports user specified limits and resting position.
     

    A Flush constraint aligns components next to one another with faces flush. Positions selected faces, curves, or points so that they are aligned with surface normals pointing in the same direction.

    Supports user specified limits and resting position.
     

    An Angle constraint positions edges or planar faces on two components at a specified angle to define a pivot point. Removes one degree of freedom in rotation or two degrees of angular rotation between planar surfaces.

     

    Directed Angle solution always applies the right-hand rule.

    Does not support user specified limits and resting position.
     

    Undirected Angle allows either orientation, thus resolving situations where component orientation flips during a constraint drive or drag.

    Supports user specified limits and resting position.
      

    Explicit Reference Vector Explicitly defines direction of Z axis vector (Cross Product) by adding a third pick to the selection process. Reduces tendency of angle constraint to switch to an alternate solution during a constraint drive or drag. This solution is the default.

    Supports user specified limits and resting position.
     

    A Tangent constraint causes faces, planes, cylinders, spheres, and cones to contact at the point of tangency. Tangency can be inside or outside a curve, depending on the direction of the selected surface normal. A tangent constraint removes one degree of linear translation. Between a cylinder and a plane, it removes one degree of linear freedom and one degree of rotational freedom.

     

    Inside Positions the first selected part inside the second selected part at the tangent point.

    Supports user specified limits and resting position.
     

    Outside Positions the first selected part outside the second selected part at the tangent point. Outside tangency is the default solution.

    Supports user specified limits and resting position.
     

    An Insert constraint is a combination of a face-to-face mate constraint between planar faces and a mate constraint between the axes of the two components. The Insert constraint positions a bolt shank in a hole. The shank aligns with the hole and the bottom of the bolt head mates with the planar face. A rotational degree of freedom remains open.

     

    Opposed reverses the mate direction of the first selected component.

    Supports user specified limits and resting position.
     

    Aligned reverses the mate direction of the second selected component.

    Supports user specified limits and resting position.

    Show me how to set constraint limits

    Selection

    Selects geometry on two components to constrain together. You can specify one or more curves, planes, or points to define how features fit together.

    You can see the geometry to which a constraint is applied. A color bar on each selection button corresponds to the color of the selected geometry.

    If you make a mistake and want to select different geometry, click the appropriate selection command and reselect.
     

    First Selection Selects curves, planes or points on the first component. To end the first selection, click Second Selection or the second face in the graphics window. The first selection is previewed in the same color as the select button color bar in the graphics window.

     

    Second Selection Selects curves, planes, or points on the second component. The second selection is previewed in the same color as the select button color bar in the graphics window

     

    Third Selection Available for Explicit Reference Vector angle constraint. Selects a face, linear edge, work plane, or work axis. The third selection is previewed in the same color as the select button color bar in the graphics window.

     

    Pick Part First Limits the selectable geometry to a single component. Use when components are close to or partially obscure one another. Clear the check box to restore selection mode.

    Offset or Angle

    Specifies distance by which constrained components are offset from one another.

    Use to enter a value equal to a distance or angle that exists in the assembly, but when you do not know the offset or angle. Click the down arrow to measure the angle or distance between components, show dimensions of selected component, or enter a recently used value.

    Specify positive or negative values. Default setting is zero. The first picked component determines the positive direction. Enter a negative number to reverse the offset or angle direction.

    Show Preview

     

    Shows effect of the constraint on the selected geometry. After both selections are made, underconstrained objects automatically move into constrained positions. Default setting is on. Clear the check box to turn preview off.

    If either component is adaptive, constraints are not previewed.

    Predict Offset and Orientation

     

    If the Offset box is empty, inserts the offset and orientation for mate, flush, and angle constraints. The default setting is On. Clear the check box to set orientation and offset manually.

    • If the selected component normals (indicated by direction arrows) point in the same direction, a flush constraint is inferred. The offset between them is measured.
    • If the selected component normals are opposite, a mate constraint is inferred.

    For an angle constraint, with an empty Offset box, the angle is measured and automatically applied.

    More

    Sets the constraint name and options for assembly constraint limits.
    Name

    Creates a unique name for the constraint in the browser. You can enter a name or leave blank and a default name is automatically created.

    Limits

    Use Offset As Resting Position Sets the offset value as the default position of a constraint with limits. For example, a constraint with a Maximum value of 50-mm, a Minimum of 0-mm and an Offset of 25-mm assumes the 25-mm position after a drag.

    Check the box to activate. Clear the check box to deactivate.

     

    Maximum Sets the maximum extent of constraint movement. Check the box to activate. Clear the check box to deactivate. The assigned value is retained when the check box is cleared.

     

    Minimum Sets the minimum extent of constraint movement. Check the box to activate. Clear the check box to deactivate. The assigned value is retained when the check box is cleared.

    Assembly constraints - Motion tab

    Motion constraints specify the intended motion between assembly components. Because they operate only on open degrees of freedom, they do not conflict with positional constraints, resize adaptive parts, or move grounded components.

    Motion constraints are shown in the browser. When clicked or the cursor hovers over the browser entry, constrained components are highlighted in the graphics window.

    The Drive Constraint command is not available for motion constraints. However, parts constrained by motion constraints can be indirectly driven according to the specified direction and ratio.

    Access:

    , and then click the Motion tab.

    Type and Solutions

    Specifies the constraint type and illustrates the solution that shows the intended motion between selected components. May be applied between linear, planar, cylindrical, and conical elements.

    You can change constraint type when the dialog box is open during constraint placement or editing. When the cursor pauses over a component, an arrow shows the direction of the constraint. In the Solution box, click Forward or Reverse to change direction.

     

    Rotation constraint specifies that the first selected part rotates in relation to another part using a specified ratio. Typically used for bearings, gears and pulleys.

     

    Rotation-Translation constraint specifies that the first selected part rotates in relation to translation of another part using a specified distance. Typically used to show planar motion, such as a rack and pinion.

    Selection

    Selects geometry on two components to constrain together.

     

    First Selection Selects the first component. Select a planar face to specify the ratio or distance. Select a cylindrical face to calculate the ratio or distance. The selection is previewed in red in the graphics screen. To end the first selection, click Second Selection.

     

    Second Selection Selects the second component. Select a cylindrical face on a rotational component or a linear edge on a translational component to calculate the ratio or distance. The selection is previewed in green in the graphics screen. To select different geometry on the first component, click First Selection and reselect.

     

    Pick Part First Limits the selectable geometry to a single component. Use when components are close to or partially obscure one another. Clear the check box to restore selection mode.

    Ratio or Distance

    Specifies the movement of the first selected component relative to the second selected component.

    Ratio

    For Rotation constraints, the ratio specifies how much the second selection rotates when the first selection rotates. For example, a value of 4.0 (4:1) rotates the second selection four units for every unit the first selection rotates. A value of 0.25 (1:4) rotates the second selection one unit for every four units the first selection rotates. The default value is 1.0 (1:1). If two cylindrical surfaces are selected, Autodesk Inventor computes and displays a default ratio that is relative to the radii of the two selections.

    Distance

    For Rotation-Translation constraints, the distance specifies how much the second selection moves relative to one rotation of the first selection. For example, a value of 4.0 mm moves the second selection 4.0 mm for every complete rotation of the first selection. If the first selection is a cylindrical surface, Autodesk Inventor computes and displays a default distance that is the circumference of the first selection.

    NoteAlthough The ratio and distance parameters are used to specify the amount of movement for the second selection with respect to the first selection. However, the constraint is bidirectional. If the second selection is moved, the first selection moves by an inverse amount of either the ratio or distance, as appropriate to the constraint type.

    More

    Sets the constraint name.
    Name

    Creates a unique name for the constraint in the browser. You can enter a name or leave blank and a default name is automatically created.

    Assembly constraints - Transitional tab

     

    A transitional constraint specifies the intended relationship between (typically) a cylindrical part face and a contiguous set of faces on another part, such as a cam in a slot. A transitional constraint maintains contact between the faces as you slide the component along open degrees of freedom.

    Access:

    , and then click the Transitional tab.

    Selections

    Selects geometry on two components to constrain together.

     

    First Selection (Moving Face) Selects the first component. 

     

    Second Selection (Transitional Face) Selects the second component. To select different geometry on the first component, click First Selection, and then reselect.

     

    Pick Part First Limits the selectable geometry to a single component. Use when components are close to or partially obscure one another. Clear the check box to restore feature priority selection mode.

    Show Preview

    Select the check box to preview the constraint to apply.

    More

    Sets the constraint name.
    Name

    Creates a unique name for the constraint in the browser. You can enter a name or leave blank and a default name is automatically created.

    Assembly constraints - Constraint Set tab

    Constraint Set enables you to constrain two UCSs together. You can select UCS in part or assembly file.

    Access:

    , and then click the Constraint Set tab.

    Selections

    Selects two UCSs to constrain together.

     

    First UCS Selects the first UCS.

     

    Second UCS Selects the second UCS. To select different first UCS, click First UCS, and then reselect.

     

    Pick Part First Limits the selectable UCS to a single component. Use when UCSs are close to or partially obscure one another. Clear the check box to restore feature priority selection mode.

    Show Preview

    Select the check box to preview the constraint to apply. Constraint set UCS to UCS results in three Mate constraints, created between the corresponding pairs of YZ, XZ, and XY planes.

    More

    Sets the constraint name.
    Name

    Creates a unique name for the constraint in the browser. You can enter a name or leave blank and a default name is automatically created.

    Drive assembly constraints

    Simulates mechanical motion by driving a constraint through a sequence of steps. The component repositions sequentially by specified increments and a distance.

    Access:

    In the browser, right-click the assembly constraint and select Drive Constraint.

    Drive sequence settings

    Set a precise amount of motion along a vector or about an axis. Use to simulate motion or test a range of motion for a constrained component. Click More to override default values for Increment and Repetitions.

    Start

    Sets start position of the offset or angle. Value can be entered, measured, or set to dimensioned value. Default value is the defined offset or angle.

    End

    Sets end position of the offset or angle. Value can be entered, measured, or set to dimensioned value. Default is start value plus 10.

    Pause Delay

    Sets delay between steps in seconds. Default is 0.0.

    Drive Adaptivity

    Adapts components while maintaining the constraint relationship.

    Collision Detection

    Drives the constrained assembly until a collision is detected. When an interference is detected, it is displayed and its constraint value shown.

    Increment

    Amount of Value specifies that the increment is the value specified in the edit box. Default is 1.0.

    Total # of Steps divides the drive sequence into a specified number of equal steps.

    Edit box sets the value of each increment or the number of steps. Value can be measured, entered, or as dimensioned.

    Repetitions

    Start/End drives the constraint from the start value to the end value and resets at the start value.

    Start/End/Start drives the constraint from the start value to the end value and then in reverse to the start value. Number of cycles completed within one repetition is dependent on the Edit Box value.

    Edit box sets the number of repetitions for Start/End and the number of cycles for Start/End/Start. Each movement is considered one cycle.

    Avi rate

    Specifies the increments at which a "snapshot" is taken for inclusion as a frame in a recorded animation.

    Control buttons

    Advance and reverse the drive sequence. The dialog box remains open while the drive sequence plays. Values can be changed any time the sequence is paused or stopped.

     

    Forward drives the constraint forward. Not available unless both Start and End boxes have values. May resume forward play after a Stop.

     

    Reverse drives the constraint in reverse. Not available unless both Start and End boxes have values. May resume reverse play after a Stop.

     

    Stop temporarily stops the constraint drive sequence. Allows values to be edited and forward or reverse play to be resumed, advanced a step at a time, or advanced to beginning or end.

     

    Go to Start returns the constraint to the starting value and resets the constraint driver. Not available unless the constraint driver has been run.

     

    Single Step Reverse reverses the constraint driver one step in the sequence. Not available unless the drive sequence has been stopped.

     

    Single Step Forward advances the constraint driver one step in the sequence. Not available unless the drive sequence has been stopped.

     

    Go to End advances the constraint sequence to the end value.

     

    Start recording begins capturing frames at the specified rate for inclusion in an animation.

    ASF Export Properties

    Sets properties for saving the simulated mechanical motion of a driven constraint to an .asf, .wmv, or .avi file.

    TipAfter you set export properties and close the ASF Export Properties dialog box, click Play in the Drive Constraint dialog box to create the recording.

    Access:

    In the browser, right-click an assembly constraint and select Drive Constraint. Then click Record in the Drive Constraint dialog box. Enter the file name in the Save As dialog box, and click Save.

    Profile

    Displays a list of export profiles from which to select. See the information about the selected profile in the Profile Description field. If you select Custom Profile, you can set the Network Bandwidth and Image Size.

    Add Markers

    Saves markers to the recorded file.

    Network Bandwidth

    Specifies the network bandwidth. Select the bandwidth corresponding to your network connection. This option controls size of the output file and quality of the recording.

    Image Size

    Specifies the size of the recorded window.

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