About Part Sizes

To understand how individual part sizes relate to the definition files of a part, it is important to understand how the part data is defined in the XML file. Part data stored in the XML definition file consists of 2 types of properties: common parameters and size parameters.

Common parameters remain constant for all part sizes. They are defined once in a part family and are shared by all part sizes. If you change a common parameter, it is updated for all part sizes. Common parameters include domain, type, and subtype. The following examples show common parameters for a mechanical, electrical, and plumbing part size.

Size parameters include a set of parameter attributes such as name, description, and units; and parameter values such as size dimensions and material type. A size parameter can define one or more part sizes depending on how the size parameter is stored in the part family. Different storage methods enable multiple part sizes to be defined by various combinations of size parameters.

Viewing part sizes in Catalog Editor and in the part size table of the Add dialog box

Size Parameter Attributes

Parameter attributes are defined by both fixed and extensible lists of values. Attribute values are specified by AutoCAD MEP 2022 toolset and cannot be changed; however, attribute values must be specified for custom data parameters that are added. Fixed data values cannot be edited. Extensible data values can be changed based on a list of predefined values, or extended to accommodate user-defined values. The following table shows the parameter attributes used to define size parameters.

Attribute Type of Data Examples
Name Extensible D1, A2, user-defined
Description Extensible Diameter D1, Angle A2, user-defined
Context Fixed Connection Port Diameter, Path Angle
Index Fixed 0, 1, 2, 3
Data Type Fixed Double, Integer, Boolean, String
Visible Fixed True, False
Units Extensible in, ft, mm, m, deg

Size Parameter Storage Types

Size parameters are separated into 4 types of data, referred to as “storage types.” Each storage type has unique characteristics that determine how the size parameters are used to define the part.