In the beginning phases of product development, designers will create a digital blueprint detailing the design intent in what is called Product Manufacturing Information (PMI). PMI eliminates the need for drawings by conveying non-geometric attributes in 3D CAD models for product manufacturing. Information included within the 3D CAD models include Geometric Dimensioning & Tolerancing (GD&T), 3D annotation, surface finish, and material specifications.
When the design intent is delivered to the quality team, the quality engineer validates that the design is manufacturable by consuming the PMI using PC-DMIS to develop a measurement routine. PC-DMIS is equipped with tools to convert the GD&T notes within the PMI into measurement commands within the measurement routine. The process begins after the quality team imports the CAD model carrying GD&T notes into PC-DMIS software.
Note: Some CAD file formats don’t support any aspect of GD&T notes; that is, they don’t allow them to be created, while others support their creation and display but don’t support linking them to CAD entities. So that a GD&T note may be used by PC-DMIS the CAD file format must support both the creation/display as well as the CAD element associativity.
Setting Up Default Values
Once the CAD model has been successfully imported, the next step is to set up the default values needed to create the feature commands. The default parameters needed include number of hits, direction and depth for a circle. In addition, PC-DMIS stores parameter information for each feature type including mode (DCC or Manual) and sensor type (touch or analog). When feature commands are created during the GD&T Selection process, these values are used to populate the feature commands as they are created.
Easily Identify GD&T Notes
The 3D CAD model specifies the color of the GD&T notes. In some instances, the colors don’t show up well or the selectable notes are the same color as the unselectable notes, making it hard to identify what PC-DMIS views as selectable and unselectable.
Note: If GD&T notes can’t be displayed by PC-DMIS this typically means that the notes have not been properly associated with the CAD model or model views.
PC-DMIS can customize the GD&T notes for easy identification of what notes are important. If there is a note that should be selectable, this says that further investigation on this note is needed. GD&T notes that define dimensions that are not meant for PC-DMIS can also colored adifferent color for easier identification.
Verify the GD&T Notes
Once the GD&T notes have been identified, the quality department will need to verify that each GD&T note links to CAD elements. PC-DMIS checks for common CAD file errors such as ensuring:
- All GD&T notes point to surfaces
- All reference datums exist
- All distance call-outs reference two CAD elements
While PC-DMIS lists any errors found in performing the above three checks it also lists unselected GD&T to ensure that the user doesn’t miss selecting a required note. When the Invalid GD&T tab shows an empty report, the next step is to use of the GD&T Selection tools to create measurement routine commands.
Select GD&T Notes to Create Commands
PC-DMIS has several methods for selecting GD&T including Select All, Current View, Active Model View, Box Select and individual using the standard method or, for faster selection, Quick GD&T. The following GD&T selection methods will select, evaluate and create commands for specific notes, adding them to the measurement routine.
- Select All: All GD&T notes assigned to the CAD model are selected.
- Current View: Any GD&T note that is displayed in the Graphic Display Window, even if it is only partially displayed, will be selected.
- Active Model View: This method only applies if the CAD model includes defined model views. Any GD&T note that is associated with the active model view will be selected and evaluated.
- Box Select: This method allows the user to box select one or more GD&T notes in the Graphic Display Window. Any note inside the box, even if it is only partially inside the box, will be selected.
- Individually Using the Standard Method: Simply click on a GD&T note, review the previewed commands and the individual note will be selected.
- Individually Using Quick GD&T: If you do not need to edit and review the dimensions before selecting simply hold down the<Shift>-key before clicking on the GD&T note and the commands are created in the measurement routine.
To take it a step further, PC-DMIS’s Flexible Measurement Strategy Wizard allows the user to take advantageof Quick Feature selection and GD&T Selection while still maintaining control of the measurement strategy. By combining the various GD&T Selection tools with the FMS Widget means that measurement routines can be created quickly andwith the needed flexibility to have features measured to your requirements.