Limitations
Introduction
GD&T Advisor is an application to be used in conjunction with Creo to correctly define the dimensioning and tolerancing on a part. Intelligent GD&T filtering has been developed to guide and advise the user based on the selected tolerancing standard.
This document describes the most significant limitations of this release of GD&T Advisor. In some cases, the limitation may be due to limitations in the capabilities of Creo. Keep in mind that GD&T is a very broad topic, so there may be additional limitations beyond those described here.
By understanding the limitations of the application, you can avoid trying to make it do things that it is not designed to support. However, it is important to understand that GD&T Advisor is a tool that is used to make GD&T annotation creation in Creo fast, easy, and correct (per the selected tolerancing standard). For some parts, you may be able to use GD&T Advisor to create most, but not all, of the necessary annotations. The remaining annotations can often be created using native Creo functionality.
The picture below shows a part in which all of the dimensions and geometric tolerances have been fully defined. The annotations in black were defined in GD&T Advisor. However due to some limitations in GD&T Advisor (as described in this document) there are some features and dimensions that are not fully supported yet. However, those remaining annotations have been created using native Creo functionality (shown in yellow). The only limitation in using additional Creo annotations is that those annotations cannot be evaluated for correctness and are not considered when determining the constraint state of the surfaces.
Keep in mind that many of these limitations will be addressed in upcoming versions of the software.
Assembly-Level Geometric Tolerances
GD&T Advisor works only with individual parts. It does not support dimensioning and tolerancing of assemblies.
Associating to CAD Dimensions
GD&T Advisor helps you properly define GD&T and associate dimensions for each part feature, and then automatically creates native Creo annotations. GD&T Advisor provides tools for visualizing the completeness of the dimensioning and tolerancing. It also evaluates the conformance with the rules of the selected tolerancing standard and best practices, providing feedback in the form of informational, warning, and error messages.
In all cases, dimensions must be created in Creo. In some cases, those dimensions can be associated with the GD&T Advisor features, in which case they will be considered in the visualization and evaluation of the scheme. In other cases, such as offset angular dimensions, they cannot be associated with the GD&T Advisor feature but can still be shown as part of the completed dimensioning scheme.
Size Dimensions
All size dimensions must be defined in the CAD model (either as parametric or annotation dimensions). GD&T Advisor supports the ability to associate the size dimensions of a feature to the related feature of size. In some cases, the size dimensions are inherent to the feature (e.g., hole, tapered slab, etc.). However, there may also be a size dimension between opposing elements on separate features. The table below shows the possible combinations of features for defining a size dimension. The values in each cell in the table indicate whether GD&T Advisor supports applying a size dimension between that pair of features.
Reference
Source
Plane
Cylinder
Sphere
Plane
Yes
No
No
Cylinder
No
No*
No
Sphere
No
No
No
In the previous table, for the Plane and Cylinder sources, the Plane and Cylinder references denote common conditions.
*Note: Length of slotted hole supported
The following examples show size dimensions that cannot be associated to features in GD&T Advisor.
Example: Planar Surface to an opposing element on a Hole
Example: Spherical Surface to an opposing Planar Surface
As mentioned previously, all dimensions are defined in the CAD system, so the limitation is only that GD&T Advisor cannot associate the feature with the dimensions pictured in these examples. The dimension can still be part of the completed dimension scheme for the part, but those dimensions cannot be evaluated by GD&T Advisor.
* 
Caution: Unvalidated annotations may not be compliant with specified tolerancing standard or may conflict with dimensions or geometric tolerances that have been defined within GD&T Advisor.
Offset Dimensions
The table below show the possible combinations of features for defining an offset dimension. The values in each cell in the table indicates whether GD&T Advisor supports applying an offset dimension between that pair of features.
Reference
Source
Plane
Cylinder Axis
Sphere Center
Plane
Yes
No
No
Cylinder Axis
No
No
No
Sphere Center
No
No
No
In the previous table, for the Plane source, the Plane reference denotes a common condition.
Keep in mind that the tolerancing standards generally discourage using offset dimensions for locating critical features.
Counterbore Depth
It is common practice to define the depth of a counterbore as shown in the picture below. However, this scheme is not supported in GD&T Advisor.
Dimensions to Intersections
The dimension scheme shown here can be defined in Creo, but is not supported in GD&T Advisor.
Angular Dimensions
Angular dimensions such as those shown below may be included in the completed dimension scheme, but those dimensions cannot be evaluated by GD&T Advisor.
Size Dimensions to Construction Circles
GD&T Advisor does not support dimensions to construction geometry, such as the diameter dimension shown here.
Topological Constraints
Tapered Shaft Size Driven by Shaft Diameter
You cannot define a tapered shaft whose gage diameter is driven by the diameter of an adjacent shaft feature in GD&T Advisor.
Tangent Surfaces
The size and location of spherical or cylindrical surfaces is sometimes implied by the feature topology, but these conditions are not supported in GD&T Advisor.
Example: Cylindrical Surface tangent to slab or slot
Example: Spherical Surface tangent to shaft
Unsupported Feature Types
The following feature types are not supported in GD&T Advisor:
Toroidal Surface — May be represented by a Revolve Surface feature, but there are limitations for the supported dimensions schemes (no diameter or radius dimensions supported).
Tube (or pipe) — This feature type is required in order to represent the wall thickness dimension between coaxial cylindrical surfaces.
Round
Chamfer
You can use native Creo functionality to define the dimensions and tolerances for these feature types, but those constraints cannot be evaluated in GD&T Advisor.
Geometric Tolerance Limitations
Directional Geometric Tolerances
GD&T Advisor does not support geometric tolerances that require a direction specification, for example straightness on a planar surface, because there is no practical way to specify the direction.
Bidirectional Positional Tolerances
GD&T Advisor does not support bidirectional positional tolerances on a hole or shaft feature.
Form Tolerances per Unit
GD&T Advisor does not support:
Flatness/area
Straightness/length
However, these can be defined using native Creo functionality.
Basic Dimensions
According to ASME Y14.41 and ISO 16792, the basic dimensions of the model may be obtained by querying the model. Therefore, displaying basic dimensions is generally not required.
GD&T Advisor only supports 'required’ basic dimensions (e.g., offset dimension related to a gage size on a tapered feature).
GD&T Advisor does not support 'optional’ basic dimensions (e.g., locating dimensions of a feature), although those can be shown using native Creo functionality.
Datums
GD&T Advisor does not support:
PNT datum features (e.g., ball or socket).
Co-datums referencing three datum features (e.g., A-B-C).
Also not supported
Controlled radius
Arc length dimension
Average diameter
Runout applied to a limited area of a surface.
Miscellaneous
Patterns of Multi-Surface Features
GD&T Advisor does not support a method to effectively define the scheme for an irregular feature of size such as a hex feature or a pattern of hex features.
Family Table Parts
GD&T Advisor does not support annotating multiple instances of a family table part. In order to avoid data corruption problems, GD&T Advisor will only operate on a single instance of a family table part.