CAD and Drafting Standards

Working Drawings

Gregory Mocko

2Introduction

The purpose of drawing or generating a CAD document is to communicate

Essentially, since communication is the goal, some standards must be used, otherwise misunderstandings occur.

There are several standards, namely ASME Y14.5 and other US standards and ISO norms. They provide guidelines on how to communicate unambiguously.

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3Overview

Working drawings are what the design is implemented fromA detail drawing is of a single part of detailSpecification are written instructions that go with the drawingsSpecifications may be written on the drawings or on a separate sheetTolerances, mating, contact surfaces, proper motion must be insured – this is completed by designer not drafterThey are legal documents

– Describe what will be made

They must be revised and modified under control ($)

4Basic Elements of Working Drawings

Dimension and units– Remain consistent across all components– Dual dimensions may appear – note not continuous

Layout of drawing– Identify required views– Use scale– Title block

NotesChecking a drawing

– A designer and drafter– Result in a better product

Assembly Drawings– All parts that are made must be fit together

5Title Blocks

Name & Address of companyTitle of DrawingDrawing NumberNames and dates of drafter, checker, issue date,…Approval BlockPredominant Drawing ScaleSheet Number

6Bill of Material

Name of partPart Material# of times the part is usedPart Number (company assigned)Located lower right corner (ANSI)

7Multi-view Working drawing

8Assembly drawing

All parts drawing in their operating positionPart list or Bill of MaterialLeader lines with balloonsMachining and assembly operation specification

9Assembly drawing

10Revision Block

Because design changes/correction occursContains date, names, description, change number and approval

11Scale

Placed in the title blockMore than one scale – then its mentioned near the detailed drawing

12Tolerance Specification

Placed in title blockGeneral tolerance note for dimensions that don’t have specified tolerance

13Working Assembly Drawing

Combined detail drawing and assembly drawingUsually Sectioned viewHave mainly standard/purchased parts

14Working Assembly Drawing

15Alphabet of Lines

Object Lines

Hidden object lines

Center lines, axes

Extension lines, arrows

Cutting planes for sectioned views

16Drawing Rules

Unless absolutely compelled to do otherwise, honor the conventional rules of orthographic projection with top front and side views arranged as shown in the second figure of this presentationUse appropriate line weights (see previous slide)Normally, try dimension cylinders in views where they appear as rectangles. Dimension and locate holes where they appear as circlesAlways indicate centerlines for cylinders and holesAlways locate circles (and cylindrical features) from their centers.Dimension Holes by specifying the DIAMETERDimension rounds by specifying the RADIUS

17Drawing Rules

Make sure tolerances are specified where needed and appropriatelyDo not over define the tolerances, cost will be prohibitiveMake sure someone else can understand your drawing and can produce a 3D rendition from your CAD dataDo not forget to specify materialsWrite who has done the design and is responsible for itPut date of design, file name and location to find it later onNumber pages if multiple pages are needed, put titles and refer to appropriate drawings for clarifications, additional information.

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WORKING DRAWINGS EXAMPLE

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Isometric ViewsFront View

20Exploded Assembly

21Part 1: Forward Arm

22Part 2: Yoke Brace

23Part 3: Support Link

24Part 4: Hex Bolt

25Part 5: Hex Bolt (160mm)

26Part 6: Hex Bolt (260mm)

27Part 7: Hex Bolt (360 mm)

28Layout Drawing

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