CATIA 3D Modeler: SECTION 4: BUILDING A TOLERANCE MODEL

Manuals

This section defines the procedures used to create each individual entity type. The prompts shown in italics are generic prompts. The syntax for these prompts varies between CAD systems. For more information about the differences associated with your system, see Section 3: "CATIA-CATS Commands".

DEFINING DATUM REFERENCE FRAMES

Select datum type

Choose from the list of datum types:

• rectangular
• cylindrical
• spherical

Select center point

Choose a point from the geometry that will be used as the vertex of the datum.

Select axis direction

Choose a line in the geometry that has the same direction as an axis of the datum. Datum axes are significant since they correspond to the axes about which angular variations may occur due to a manufacturing process (non-kinematic rotation).

Specify angle tolerance

Enter the value of the symmetric tolerance that will be applied to the nominal angle about this axis. If there is no tolerance on the angle then enter "0".

Repeat for other axes

Enter up to three axes with tolerances for each datum.

Select solid

Choose from the geometry a solid that is defined by the datum.

Enter part name

Enter the name by which the part will be referenced.

DEFINING JOINTS

Select joint type

Choose from the list of datum types:

• Rigid
• Revolute
• Cylindrical
• Prismatic
• Parallel Cylinders
• Ball-and-Socket
• Sliding Planar
• Edge Slider
• Cylindrical Slider
• Point Slider
• Spherical Slider
• Crossed Cylinders

Select center point

Choose a point from the geometry that will be used as the vertex of the joint.

Select 1st axis direction

Choose a line in the geometry that has the same direction as the primary axis of the joint. The axis will be constructed parallel to the direction chosen, through the joint center point. This direction differs between joint types. The primary axis for each joint type is shown in Appendix B, labeled as "Axis 1."

Select 2nd axis direction

Choose a line in the geometry that has the same direction as the secondary axis of the joint. If the Appendix does not specify which direction "Axis 2" must lie, than any axis perpendicular to "Axis 1" should be selected.

Select 1st Solid

Choose one of the two mating solids from the geometry

Define datum path to DRF

Choose or create feature datums that lie in the path to the first selected solid's DRF. An existing feature datum may be used if it belongs to the same solid as the DRF, otherwise a new datum must be created. The DRF must be the end of the path.

Select 2nd Solid

Choose the other mating solid from the geometry

Define datum path to DRF

Choose or create feature datums that lie in the path to the second selected solid's DRF. An existing feature datum may be used if it belongs to the same solid as the DRF otherwise a new datum must be created. The DRF must be the end of the path.

DEFINING LOOPS

Vector loops are defined manually as a series of joints. The corresponding datum paths across each part are added automatically.

Closed Loops

Select starting joint

Choose the starting joint from the model.

Select all intermediate joints

Choose the next joint in the loop. The next joint must be on the same part as the previous joint. The loop then passes through the joint to the next mating part.

Select starting joint again to close loop

Choose the starting joint when the loop is complete to close the loop.

Open Loops

Select specification

Choose a tolerance specification from the CATS assembly model.

Select all intermediate joints

Choose the next joint in the loop. The next joint must be on the same part as the previous joint or specification.

Select the specification again to close loop

Choose the specification when the loop is complete to close the loop.

DEFINING FEATURE CONTROLS

Select feature control type

Choose from the list of feature control types:

• flatness circularity circular runout
• straightness cylindricity total runout
• perpendicularity line profile concentricity
• angularity surface profile true position
• parallelism

Select joint

Choose the joint to which the feature control applies.

Select solid

Choose the solid whose surface variation is controlled by the feature control.

Specify tolerance

Enter the tolerance value associated with the feature control.

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