MIL-D-28000
Class II - Engineering Drawings

3.2.2. Class II subset - engineering drawings. This engineering drawing subset of ASME Y14.26M shall be used to encode product data being acquired in accordance with MIL-T-31000 for delivery in digital form. The data exchange shall preserve the requirements of style and content as set forth by DOD-STD-100 and MIL-T-31000. Exchange emphasis is on completeness, visual equivalency for human interpretation, and functionality of the received drawing.

3.2.2.1. Information requirements and data functionality. Currently, engineering drawings form the mainstay of product definition and form the accepted medium for viewing computer generated data. Geometry and text annotation form the majority of data items. Extensive use is made of dimensions, sectioned areas, text notes, and feature control symbols. Non-geometric information in the form of color, line weight, line font, and level is needed as well. Finally, relationships among the data help to structure the large quantities of data. Information requirements for this application subset include (but are not limited to):

  1. Simple geometry in the form of points, lines, circular arcs, conic arcs, and spline curves.
  2. Non-geometric attributes of color, line weight, and line font.
  3. Data relationships, including the concept of subfigures.
  4. Data organization methods such as level.
  5. Part name, drawing number, formal identification, and drawing revision.
  6. Annotation represented by the corresponding ASME Y14.26M entity type thus retaining its intended functionality.

3.2.2.2. ASME Y14.26M entity subset specification. Table II lists the entities of this subset. Only ASME Y14.26M entities which are enumerated in this table shall be used for representing engineering drawing product definition data. Other valid ASME Y14.26M entity types may be present in the file as described by 3.1.1. Additional requirements are placed on the global section of a file, and certain field value restrictions are placed on the range of parameter values in both the directory entry(DE) and the parameter data(PD) sections of a valid ASME Y14.26M file.


TABLE II. - ASME Y14.26M entity content of engineering drawing subset

When the form column in Table II is blank for an entity which has multiple form numbers, all forms of that entity are included in the subset.


100 Series

TYPE FORM ENTITY NAME X-FILE
0 0 Null entity F000X
100 0 Circular arc F100X
102 0 Composite curve F102X
104 1 Conic arc - ellipse F104X
104 2 Conic arc - hyperbola
104 3 Conic arc - parabola
106 1 Copious data - coordinate pairs
106 2 Copious data - coordinate triples
106 11 Copious data - Piecewise planar, linear string (2D linear path)
106 12 Copious data - Piecewise linear string (3D linear path)
106 20 Centerline F10620X
106 21 Centerline through circle centers
106 31 Section lines - General use, iron, brick, stone masonry
106 32 Section lines - Steel
106 33 Section lines - Bronze, brass, copper
106 34 Section lines - Plastic, rubber
106 35 Section lines - fire brick, refractory material
106 36 Section lines - Marble, slate, glass
106 37 Section lines - Lead, zinc, magnesium, insulation
106 38 Section lines - Aluminum
106 40 Witness line F10640X
106 63 Simple closed planar curve
108 0 Plane, Unbounded
108 1 Plane, Bounded
110 0 Line F110X
112 0 Parametric spline curve F112X
114 0 Parametric spline surface
116 0 Point
118 0 Ruled surface (Equal relative arc length)
118 1 Ruled surface (Equal relative parametric values)
120 0 Surface of Revolution
122 0 Tabulated cylinder
124 0 Transformation matrix
124 1 Orthonormal mirror
126 0 Rational B-spline curve F126X
126 1 Rational B-spline curve - Line
126 2 Rational B-spline curve - Circular arc
126 3 Rational B-spline curve - Elliptical arc
126 4 Rational B-spline curve - Parabolic arc
126 5 Rational B-spline curve - Hyperbolic arc
128 0 Rational B-spline surface
128 1 Rational B-spline surface - Plane
128 2 Rational B-spline surface - Right circular cylinder
128 3 Rational B-spline surface - Cone
128 4 Rational B-spline surface - Sphere
128 5 Rational B-spline surface - Torus
128 6 Rational B-spline surface - Surface of Revolution
128 7 Rational B-spline surface - Tabulated cylinder
128 8 Rational B-spline surface - Ruled surface
128 9 Rational B-spline surface - General quadric surface
130 0 Offset curve
140 0 Offset surface
142 0 Curve on a parametric surface
144 0 Trimmed surface

200 Series

TYPE FORM ENTITY NAME X-FILE
202 0 Angular dimension F202X
206 0 Diameter dimension F206X
210 0 General Label F210X
212 0 General note F212X
212 1 General note - dual-stack dimension
212 2 General note - imbedded font change dimension
212 3 General note - superscripted dimension
212 4 General note - subscripted dimension
212 5 General note - superscripted/subscripted dimension
212 6 General note - multiple stack - left justified
212 7 General note - multiple stack - center justified
212 8 General note - multiple stack - right justified
212 100 General note - simple fractional dimension
212 101 General note - dual stack fractional dimension
212 102 General note - imbedded font change/double fractional dimension
212 105 General note - super-/sub-scripted fractional dimension
214 1 Leader arrow - Wedge F214X
214 2 Leader arrow - Triangle
214 3 Leader arrow - Filled triangle
214 4 Leader arrow - No arrowhead
214 5 Leader arrow - Circle
214 6 Leader arrow - Filled circle
214 7 Leader arrow - Rectangle
214 8 Leader arrow - Filled rectangle
214 9 Leader arrow - Slash
214 10 Leader arrow - Integral sign
214 11 Leader arrow - Open triangle
214 12 Leader arrow - Dimension origin
216 0 Linear dimension F216X
216 1 Linear dimension (Diameter) F216X01
216 2 Linear dimension (Radius) F216X01
218 0 Ordinate dimension F218X
218 1 Ordinate dimension with datum F218X01
220 0 Point dimension
222 0 Radius dimension F222X
222 1 Radius dimension/multiple leader F22201X
228 0 General symbol
228 1 Datum feature symbol
228 2 Datum target symbol
228 3 Feature control frame
230 0 Sectioned area (Standard Crosshatching) F230X
230 1 Sectioned area (Inverted Crosshatching) F23001AX

300 Series

TYPE FORM ENTITY NAME X-FILE
304 1 Line font definition - subfigure
304 2 Line font definition - repeating pattern F30402X
308 0 Subfigure definition F408X
314 0 Color definition

400 Series

TYPE FORM ENTITY NAME X-FILE
402 3 Views visible instance
402 4 Views visible, Color, Line weight instance
402 7 Unordered group without back-pointers instance
404 0 Drawing
406 1 Property - Definition levels
406 3 Property - Level function
406 15 Property - Name
406 16 Property - Drawing size
406 17 Property - Drawing units
406 18 Property - Intercharacter spacing F40618X
408 0 Single Subfigure Instance F408X
410 0 View - Orthographic parallel
410 1 View - Perspective
412 0 Rectangular Array Subfigure Instance
414 0 Circular Array Subfigure Instance

3.2.2.3. Entity construction. The following entities (in entity number order) have particular meanings when used for engineering drawings. The requirements in this section shall be met in all conforming data files and by all translator implementations of the Class II subset of ASME Y14.26M.
102 Composite Curve. Composite curves are intended for showing connectivity and continuity. They shall contain a minimum of two entities one of which shall be a curve the line entity included.
124 Transformation Matrix. Defining matrices are used to position an entity into model space from its definition space. When entities share the same plane of definition, they shall use the same transformation matrix to avoid multiple identical matrices being included in the file. If an entity contains translation information in its PD section, a transformation matrix shall not be used to translate the entity.
202 Angular Dimension. This entity shall have two leaders, and a vertex point. The Z displacement of the vertex point can be attained from any of the subordinates.
206 Diameter Dimension. This entity shall specify its arc center (may not be defaulted). The Z displacement of the arc center can be obtained from the subordinates. The arc center shall be valid. If multiple leaders occur, the first segment of each leader shall be collinear and opposite in direction.
212 General Note. General notes shall use a font code to minimize the number of text strings in the note. At least one string is required, but the number of different strings shall be minimized. Form numbers plus position information on each string shall be used. The Rotation Angle field shall contain the string angle. Transformation matrices shall not be used for string angles. Null strings are allowed and may be used to pattern a note into one of the standard forms.
216 Linear Dimension. When there are two witness lines, they shall be parallel to each other.
218 Ordinate Dimension. This entity shall not be used in place of the general label. The leader shall contain only one segment.
222 Radius Dimension. This entity shall specify its arc center (may not be defaulted). Z displacement of the arc center can be attained from any of its subordinates. Arc center shall be valid. If multiple leaders occur, the first segment of each shall be collinear. If two leaders are used, one and only one shall be of Form 4.
228 General Symbol. This entity shall be used for annotation. Flags in the subordinate entities (even geometry) shall be set to annotation. This entity shall not be used in place of a subfigure or group. All subordinate entities to the general symbol entity shall be coplanar.
230 Sectioned Area. This entity is used to provide for area fills. The normal distance between lines is constant and shall not be zero. Wider spaces between lines are to be considered blank lines with regard to normal distances. Boundary curve and islands are closed and not self- intersecting. Island interiors are mutually disjoint. Islands lie in the interior of the boundary curve. Boundary curve and islands can be logically dependent and do not need to be marked as annotation if they are not annotation.
404 Drawing. The drawing entity defines the basic engineering drawing format for each sheet. One drawing entity shall exist in the file for each sheet, or collection of sheets, of an engineering drawing. An example of a collection of sheets would be several B size sheets placed in an H size engineering drawing. All entities pointed to by the drawing entity shall be physically dependent and shall be flagged as annotation.
406 Form 5 Line Widening. The only allowed use of the line widening property is the case when physical model space width is important. It shall not be used to indicate plotter width or line weight.
406 Form 15 Name. This entity is used to convey the drawing name. A Drawing Name using Entity 406, Form 15 is required. If there is no name available in the architecture of the system, the preprocessor shall insert one, a reasonable default being global parameter 3.
406 Form 16 Drawing Size. A drawing size property shall be included for each drawing entity in the file. If drawing size is not in the architecture of the system, the preprocessor shall insert one and the drawing size for each sheet shall match the drawing size letter defined in the start section (see 3.2.2.4.1).
406 Form 17 Drawing Units. A drawing units property shall be included for each drawing entity in the file. If drawing units is not in the architecture of the system, the preprocessor shall use the defaults given in global parameters 14 and 15.

The simplest entity type shall be used to represent each piece of geometry, and zero size entities shall not be used. For instance, a B-Spline curve shall not be used to represent a circular arc. A zero length line entity or a zero diameter circle shall not occur in the file.

All 200 series entities shall be flagged as annotation and shall be parallel to the viewing plane, except for crosshatching. All dependent entities with parent 200 entities shall be flagged as annotation and shall be coplanar with their parent. The only exception is for geometry entities associated with the Sectioned Area (230 and 106 Forms 31-38). Any annotation entity which points to multiple leaders and multiple witness lines shall order those leaders and witness lines so that leader-1 corresponds logically to witness-1 and leader-2 to witness-2.

See also: Class2 (NENTITY)


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