Norms to be Observed for Assembly Drawings
As per the code of BIS-SP-46-1988, accepted norms for assembly drawings must be observed. Few of them are as follows:
1. Selection of views
A assembly drawing or detailed drawing should only contain those views needed for a clear and complete shape description of the object. Views are selected that show the best essential contours or shapes and contain the least humber of hidden lines. Detail drawings and assembly drawings can utilize any number of necessary views including sectional views, auxiliary views and partial views.
2. Section views
Sectioning is used in assembly drawings to eliminate the need to draw hidden parts. Any kind of sectional views such as full sections, half sections, aligned sections offset sections may be used.
3. Hidden lines
Hidden lines in assembly drawings are generally not needed as a result of extensive use of sectional views. These should be used wherever necessary for clearness. Dotted lines are omitted from the assembly drawing when they are not needed for clearness.
4. Dimensions
Dimensions are given in detailed working drawings. Dimensioning can be either unidirectional or aligned but not both in the same set of drawings. Dimensions are not generally given on assembly drawings.
5. Part Identification
Parts are identified in assembly drawings by a leader line with an arrow that points to the part. The other end of the leader has a circle or balloon showing the part detail number. Bill of materials
A bill of materials i.e. BOM is a comprehensive list of the raw materials, assemblies, subassemblies, parts and components as well as the quantities of each needed to manufacture a product. In other words it is the complete list of all the items that are required to build a product. A bill of materials on assembly drawing consists of following information.
1. Part Name
2. Part Number
3. Material of the part
4.Quantity per unit
5. Part description
The bill of material is included on all assembly drawings. A bill of materials is also known as part list which is a tabular list of the items used to make an assembly. When placed on the assembly drawing, generally part list can be located in the upper right corner above the title block.
