Dimension Tolerances

	The following task explains the methodology for managing V5 Dimension Tolerance standards for V4 to V5 migration. You will learn: how the migration of Dimension Tolerances is carried out, and what you need to pre-define concerning the V5 standard parameters before starting the migration process. One has to distinguish between single tolerances and multi-tolerances.
	Single Tolerances Migration mechanism The migration engine tries to map the name of the V4 Tolerance used by the dimension to migrate to the name of a V5 Tolerance Format: If a V5 Tolerance Format bearing the same name as the V4 Tolerance is found, then this Tolerance will be applied to the new dimension in V5. If not, all existing V5 Tolerance Formats will be scanned and the closest description will be used. However, the result will not be exactly the same. Pre-definition There are two possibilities: If you used a standard PRJ (delivered by DS), you do not have to customize anything in particular before migrating the V4 2D Models. If you created a specific Tolerance in V4, you need to re-create it in V5. If you do not then, dimensions which use this Tolerance will not be mapped during the migration and the result will be different than in V4. In V4, the Tolerance (including all its parameters and values) is defined in the DRWSTD function, under `Annotations > Description > Visualization > Tolerance`. In V5, the Tolerance Format is defined in the Standards Editor, under `Standard > name_of_standard > ToleranceFormats`.
	Most of the pre-defined Single Tolerance formats which are provided by default in V5 cannot be modified: for example, TOL_NUM2, ISONUM, etc. Since they cannot be edited, these formats do not appear in the Standards Editor. The detailed mapping between V4 and V5 Tolerance parameters is explained in 2D Standard Mapping for V4 to V5 migration.
	Multi-Tolerances In V4 as well as in V5, two default Multi- Tolerances are available: MTL_A1N2 and ISOCOMB. However, whereas it is possible to create user-defined tolerances in V4, this is not the case in V5. Migration mechanism If a dimension has been created in V4 using one of the 2 default Multi-Tolerances, its specifications will be migrated and the V5 definitions will be used. If a dimension has been created in V4 using a user-defined Multi-Tolerance, it is not migrated and can only be seen in graphic mode. Pre-definition In V4, user-defined multi-tolerances are defined in the DRWSTD function, under `Annotations > Description > Create > Multi-Tolerancing`. In V5, by default, the numerical definition of a multi-tolerance is associative to the dimension value (in which case it is automatically updated when the dimension value is changed). This was not the case in V4. As a result, if you want multi-tolerances to be migrated to V5 with the same value as in V4, you need to make the numerical definition of a multi-tolerance not associative to the dimension value. To do this, in the Standards Editor, under `Standard > name_of_standard > Dimensions`, set the `DIMTolMultiAuto` parameter to `No`. In V5, it is not possible to create user-defined multi-tolerances. As for the two default Multi-Tolerances (MTL_A1N2 and ISOCOMB), since they cannot be edited, these formats do not appear in the Standards Editor.

	For detailed information regarding the mapping of V4 and V5 Dimension Tolerance parameters, refer to the "Dimensions: Tolerancing" section in `V4V5_Standards_Mapping_V07.pdf`. This document is available on the Program Directories CD-ROM shipped with CATIA documentation, selecting `Solutions and Products > General and Open Issues > CATIA Mechanical Design > Interactive Drafting`.