Working Drawings

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