1. Unit 16 Engineering Drawing

2. Engineering Drawing Objectives Interpret different assembly drawings.
Aims
Introduce assembly drawing practices.
Objectives
Interpret different assembly drawings.

3. DEFINITION Working drawing Detail drawing Assembly drawing
Working drawing is a set of drawing used
during the work of making a product.
Working drawing
Detail drawing
Assembly drawing

4. DEFINITION
Detail drawing is a multiview representation of a single part with dimensions and notes.
Assembly drawing is a drawing of various
parts of a machine or structure assembled in their relative working positions.

5. PURPOSE 1. completed shape of the product. 2. overall dimensions.
Detail drawing conveys the information and instructions for manufacturing the part.
Assembly drawing conveys
1. completed shape of the product.
2. overall dimensions.
3. relative position of each part.
4. functional relationship among various components.

6. TYPES OF ASSEMBLY DRAWING
1. Exploded assembly drawings
The parts are separately displayed, but they are aligned according to their assembly positions and sequences.
2. General assembly drawings.
All parts are drawn in their working position.
3. Detail assembly drawings
All parts are drawn in their working position with a
completed dimensions.

7. Pictorial representation
EXPLODED ASSEMBLY
Pictorial representation
Finished product

8. 2. GENERAL ASSEMBLY
Pictorial
Orthographic

9. 3. DETAILED ASSEMBLY

10. Features of an assembly drawing
Dimensions
Detailed dimensions required for manufacture are excluded from assembly drawings. But overall dimensions of the assembled object are usually indicated.
If the spatial relationship between parts is important for the product to function correctly then these should also be indicated on the drawing. For example indicating the maximum and minimum clearance between two parts.
Internal Parts
If there are internal assemblies, sectional views should be used.

11. EXAMPLE 1 : Assembly steps
3 PIN, Steel, 1 REQD.
2 ARM, Steel, 1 REQD.
1 CLEVIS, Steel, 1 REQD.

12. Parts List Item No. Description Qty Material Remarks
Each part is given a unique number, indicated on the drawing by a circle with the number in it and a leader line pointing to the part. The leader line terminates in an arrow if the line touches the edge of the component, or in a circle if the line terminates inside the part.
A table of parts should be added to the drawing to identify each part, an example of a parts list is shown below:
Item No.
Description
Qty
Material
Remarks

13. Item Number
A table of parts
Or BOM
Leader lines

14. REQUIRED INFORMATION IN GENERAL ASSEMBLY DRAWING
1. All parts, drawn in their operating position.
2. Part list (or bill of materials, BOM)
Item number
Descriptive name
Material, MATL.
Quantity required (per a unit of machine), QTY.
3. Leader lines with balloons around part numbers.
4. Machining and assembly operations and critical dimensions related to operation of the machine.

15. EXAMPLE : Hidden lines omit or not ?
Part A
Part B A B

16. GENERAL PRACTICE Section technique is usually need to clarify
mating of the parts.
Use different section line styles for adjacent parts.
Part A
Part B
Correct
Better

17. Task- draw these components individually and then assembled.
Supply your own dimensions.
3 PIN, Steel, 1 REQD.
2 ARM, Steel, 1 REQD.
1 CLEVIS, Steel, 1 REQD.