Save and load files > Working with other CAD systems > Data accuracy
Data accuracy
Creo Elements/Direct Modeling represents the accuracy of a part as a single numerical value expressed in millimeters. The accuracy cannot vary within a part, but an assembly can have parts with different accuracy values. This value is also called model resolution.
Accuracy in Creo Elements/Direct Modeling is defined as
Any two points separated by a distance less than the accuracy value are considered identical.
A point less than the accuracy value away from an edge or face is considered to be contained in that edge or face.
Two edges are considered identical if one of the edges is contained in a tube of radius accuracy surrounding the other edge.
An edge along which each point is less than the accuracy value away from a face is considered to be contained in that face.
Any edge is valid if and only if its length is greater than the accuracy value.
While the first four items refer to the concept of gap size (distance), the last item is based on the concept of minimum extent (size of edges). However, there is only a single accuracy value for both concepts. These two concepts are opposed to each other: If you reduce the accuracy value for a given part in order to allow for small edges, you may introduce gaps. On the other hand, if you increase the accuracy value to accommodate gaps, you might lose small edges.
Another important aspect when you import data from other systems is the range of possible accuracy values in both the source and the destination system. For best results it is strongly recommended to make sure that the accuracy value of the model to be exchanged is within the common domain of the accuracy value ranges of both systems.
Guidelines from user organizations like VDA (VDA 4955) or ODETTE specify that geometric data must adhere to certain limits. The coarsest recommended distance accuracy is 1.0E-2 mm. The range of accuracy in Creo Elements/Direct Modeling is between 1.0E-1 mm and 1.0E-6 mm.
Data accuracy in other CAD formats
You can choose from two accuracy values:
Source accuracy is the accuracy value provided in the source file or by inquiry into the other CAD system.
Type any value from 1.0E-1to 1.0E-6.
The source accuracy is usually a good choice, but the result may be better if you provide a fixed value. Parisolid-based systems, for example, allow you to assign a different accuracy to an edge. A single value must be derived for Creo Elements/Direct Modeling.
Different types of curve and surface representations, and different demands on geometry such as smoothness, may cause changes in the model during import that introduce errors. Select the variable switch to allow the processor to change accuracy values.
IGES data accuracy
If you select Generic IGES for healing, then the maximum part resolution of all exported parts is used. You can make the resolution coarser by changing the Tolerance in the IGES export options dialog.
If you select a different option for healing in the IGES export options dialog, then Creo Elements/Direct Modeling will automatically use the best tolerance.
STEP data accuracy
When you save Creo Elements/Direct Modeling data in a STEP format, the accuracy value for each part is coded in the STEP file. This distance accuracy value is set
To the default by the system.
By the user in Creo Elements/Direct Modeling.