1. Working Drawings
Chapter 12

2. Objectives Define top down, bottom up, and middle out design
Discuss methods of constraining assemblies made using solid modeling and parametric modeling
Identify the elements of a detail drawing
List the parts of an assembly drawing

3. Objectives (cont.) List six types of assembly drawings
List the role of the record strip and title block in the approval process
Describe the process for revising drawings
Describe the special requirements of a patent drawing

4. Top Down Vs. Bottom Up Design
Top down refers to starting the process of design by:
Considering the function of the entire system
Breaking it down into subassemblies or components based on major functions
Each part is manufactured and assembled

5. Top Down Vs. Bottom Up Design
Bottom up design is helpful when the components are standardized parts:
The design process starts at the part level
Individual components are sized and designed
Final assembly is built around the design of the parts

6. Top Down Vs. Bottom Up Design
Middle out refers to a combination of top down and bottom up design:
Some parts are standardized
Other parts are designed within the context of fitting into the design of the assembly

7. Constraining 3D Assemblies
With constraint based modeling software, assembly constraints create relationships between modeled parts
The first part added to the assembly becomes the parent part
Other parts are mated to the parent part to build up the assembly

8. Constraining 3D Assemblies

9. Constraining 3D Assemblies
Subassemblies are groups of components of a larger machine
Breaking products into subassemblies can make it easier to coordinate when different designers are working on portions of the same device

10. 3D Layouts and Skeleton Assemblies
An assembly layout or skeleton assembly can be used to define locations of individual parts in an assembly
Parts are designed so they link to a skeleton framework in the assembly
The skeleton is a 3D drawing that defines major relationships in the assembly

11. Working Drawings or Construction Drawings
Working drawings are a set of assembly and detail drawing
These drawings are given to contractors to perform work or manufacture individual parts
These drawings are legal documents

12. Assembly Drawings Different type of assembly drawings include:
Design assemblies, or layouts
General assemblies
Detail assemblies
Working drawing assemblies
Outline or installation assemblies
Inseparable assemblies (weldments, etc.)

13. Assembly Drawings
Views should show how the parts fit together and suggest function of the unit
Hidden lines are typically not needed
Assembly drawings are usually not dimensioned

14. Detail Drawings
Detail drawings contain all of the necessary information to manufacture a part
Detail drawings are also called:
Piece part drawings
Part drawings

15. Identification

16. Multidetail Drawings
When multiple detail drawings are shown on one sheet, identify each part
Place the circles containing the part numbers adjacent to the parts

17. Parts Lists
A parts list or bill of materials (BOM) typically contains:
Part identification number (PIN)
Description of each part
Quantity required in the assembly
Abbreviations can be used to indicate quantities that are not known such as AR (as required) and EST (estimated quantity)

18. Parts List

19. Assembly Sections
In assembly sections it is necessary to show cut surfaces and distinguish between adjacent parts
To accomplish this, section lines are drawn in opposing directions
In relatively thin parts, section lines should be left out or shown solid black
Bolts, nuts, keys, etc. are left unsectioned

20. Assembly Sections

21. Working Drawing Formats
Number of details per sheet:
Showing one detailed part per sheet is typically preferred
Machines or structures composed of few parts sometimes show all the details on one large sheet

22. Working Drawing Formats
Electronic file formats such as Portable Document Format (PDF) allow the originator to send a document that can be commented on without allowing the original document to be changed
Using electronic files also saves trees and makes distribution quicker

23. Working Drawing Formats
Title and record strips show all necessary information not given directly on the drawing with its dimensions and notes
The type of title used depends on the filing system, manufacturing processes, and requirements of the product

24. Working Drawing Formats
The title form typically includes:
Name of the object shown
Name and address of manufacturer
Name and address of purchasing company
Signature of person who made the drawing and date of completion
Signature of the checker and date of completion

25. Working Drawing Formats
Title form information (cont.)
Signature of the chief drafter, chief engineer, or other official, and the date of approval
Scale of the drawing
Number of the drawing

26. Checking Drawings
The final checker should review the drawing with particular attention to:
Soundness of design
Choice of views
Dimensions
Standard parts
Notes
Clearances
Title form information

27. Drawing Revisions
An accurate record of changes made to released drawings is tracked via a revision block
The record of revisions should show:
What change was made
By whom the change was made
When the change was made
Why the change was made

28. Simplifying Drawings To simplify drawings:
Use word descriptions when practical
Do not show unnecessary views
Use standard symbols and abbreviations
Avoid elaborate, pictorial, or repetitive details
List rather than draw standard parts

29. Simplifying Drawings Cont. Omit unnecessary hidden lines
Use outline section lining in large areas
Omit unnecessary duplication of notes and lettering
Use symbolic representation for piping and thread
Use CAD libraries and standard parts when feasible

30. Patent Drawings Patent applications must include line drawings
All patent drawings must be mechanically correct and constitute complete illustrations of every feature of the invention claimed
The U.S. Patent office has strict requirements for patent drawings