Mechanical Engineering Drawing MECH 211/M Lecture #11; Chapter 14 Dr. John Cheung

Concurrent Design DESIGN PROCESS Identification of design problem Problem-solving concepts and ideas Compromise solutions Models or prototypes Production or working drawings

3D Models

Technical Documentation Developed for each new product Maintained over the product's life cycle Includes Working drawings (Assembly & Component) Calculations Technology details Assembly scheme Regulatory Compliance Much more

Working Drawings Made for each non-standard component Component Working Drawings Used for manufacturing Assembly Working Drawings Shows how components are assembled Shows how many and what components are needed Recommendation Use reference material when creating a working drawing Adhere to standards

Working Drawing

Working Drawing

Working Drawing

Working Drawing Detail Drawing A working drawings of an individual part Single or multiple sheets Neatly made Checked and signed by drafter and Senior Engineer Assembly drawings are done on a separate sheet

Part Name and Number Located in the drawing area

Drawing Form Drawing format is standardized within an organization The scale is selected to make sure that the component would fit the format A preliminary evaluation should be performed before the drawing is completed Take into consideration the space for dimensions

Drawing Form Refer front inside cover of the book for details

Drawing Form John Peach

Title Blocks Used to record important information and keep track of the parts Name and address of the company Title of the drawing Drawing number Names of the designers Completion date Design approval Additional approval Scale Supply code for manufacturers Weight of the item Standards vary with paper size and organization

Drawing Numbers All drawings are numbered Serial numbers lower right or upper left corner of sheet Serial numbers Codified information Indicating functionality Model No. Paper size Revision Number

Bill of Materials Consists of itemized list of parts Two possible locations Above title block Top right corner Numbering Largest parts first Standard parts last If above title block, it is numbered upwards If in the top right corner, it is numbered downwards Contains Part numbers and title Quantity Other relevant info

Revisions Revisions are required due to changes in design Revisions are numbered and documented The track of modifications is kept on the drawing CAD allows additional information to be tracked New drawing are made to replace large changes OBSOLETE stamped on old

Simplifying the Design Process Use text description to eliminate the need for a: Drawing Projected views Detailed drawing of standard parts (threads, gears etc.) Use descriptions like e.g. HEX, SQ, DIA, R Show partial views of symmetrical objects Avoid elaborate, pictorial or repetitive detail.

Simplifying the Design Process When necessary to detail threads, do not show them over the whole length. Eliminate detail of nuts, bolt heads, and other standard parts. Show outlines and position only. Reduce detail of parts on assembly drawing Avoid unnecessary hidden lines that add no clarification Use sectioning only when it is necessary for the clarity

Simplifying the Design Process For holes and tapped holes use symbols Omit views with no dimensional or written instructions A smaller drawing is usually easier and quicker to make than a large one When two parts are slightly different, a complete graphical representation of both parts is not required. Use the note: SAME AS EXCEPT … OTHERWISE SAME AS …

Simplifying the Design Process Drawings made to modify stock parts should be as plain as possible. Avoid detail. Use standard abbreviations whenever possible. Whenever necessary, enlarge small details on larger parts for clarity. Draw small parts large enough to avoid crowding so they may be easy to read

Simplifying the Design Process Use standard symbols to represent common objects Eliminate repetitive data by use of notes Do as much free-hand drawing as possible Use geometric symbols instead of notes

Assembly Drawing Assembly drawing shows how each component is positioned with respect to the others General assembly gives a general graphic description of the shape Sectioned assembly shows the hidden features and their interdependence Installation or outline assembly indicates how the parts, shown separated, are assembled Pictorial assembly usually isometric, indicates how the parts, shown separated, are assembled

General Assembly Drawing Detail drawing of a automobile connecting rod

Sub-assembly Drawing Assembly drawing of a automobile connecting rod Shows the relationship between parts in an assembly Minimum number of views used Here one view is enough to show the relationship This is also called a sub-assembly because this forms a part of the bigger assembly

Sectional Assembly Drawing To avoid hidden lines, sectioning is done to improve clarity Assembly drawing of a Grinder The purpose is relation ship between parts in assembly than individual shape. Minimum number of views must be used. Only two views are needed to show the relationship

Sectional Assembly Drawing To distinguish parts, section lines are drawn in different directions Change of angle (not 45°) may be done if needed Thin materials like gaskets are shown as thick lines in section Standard practice is not to section bolts, shafts, even though section lines pass through them

Outline Assembly Drawing Made specifically to show how to install a machine This is also called an installation assembly It outline the relationships of exterior surfaces

Outline Assembly Drawing In aircraft drafting, installation assembly gives complete information for placing details of sub-assemblies in their final positions

Pictorial Assembly Drawing Shows how to install a machine Isometric views show separated parts

Pictorial Assembly Drawing

Pictorial Assembly Drawing

Pictorial Assembly Drawing

Tabular Drawings One drawing serves for a range of sizes Dimensions are replaced by letters and an accompany table lists the corresponding dimensions for a series of sizes One drawing serves for a range of sizes There is a risk that the table will be misread

Standardized Drawing Drawing is made without dimensions To avoid misreading of tables as in tabular drawing yet simplify drawing process Drawing is made without dimensions Copied by any method Dimensions filled accordingly Drawing is not to scale (NTS)

Checklist for a Good Design Is the drawing easy to read? Are the part outlines distinct from dimension lines? Is the lettering neat and clear? Is all of the information on the drawing? Will the drawing make a good print? Have all the rules of standard drafting practices been followed?

Checklist for a Good Design Is the nomenclature correct? Will everyone understand it the same way? Is the drawing title truly descriptive? Are all the necessary views given? Are all the dimensions shown? Is there double dimensioning? Are all the notes properly located? Could any of the notes be misunderstood?

Checklist for a Good Design Do the parts agree with the part list? Are the standard parts specified correctly? Is the scale designated? Are the finishes specified in the drawing? Is a heat treatment recommended? Have standard manufacturing processes been followed? Can the part be produced simpler and more economically?

Checklist for a Good Design Are the materials specified? Are the standard parts used as much as possible? Are the suppliers for the standard parts indicated? The design is yours. Are you ready to approve it?

Technical Data Presentation Technical communication requires enhanced ways to convey data and numerical information

Encoding Data and Markers

Plots 2 D - scatter plot 2 D – connected line plot

Plots Regression line graph Mean and standard deviation Mean and standard error

Plots Bar graph (horizontal) Composite bar graph

Plots

Plots Histogram (distribution of image) 3D – scatter plot

Case Study - Introduction

Design a Catapult You are an engineer (that is good to know and even better to start imagining being one) Your kid brother or sister is asking you to make a catapult for them for playing during the winter season What are the things that you should know to design and manufacture this catapult

Needs and Functionality What you are going to throw? How fast you want to throw a particular object? The range of the catapult? What will be the working mechanism? How are you going to design that? How are you going to produce it?

Preliminary Design Constraints The part you are going to throw with your design is “assumed to be the eraser that you use in drawing class” It has to be thrown a minimum distance of 10-meters Since you are designing this for your kid brother or sister, you cannot use unsafe mechanisms like Nothing that give out lot of energy No explosive materials etc No petroleum based fuels No heat to power the device

Design Requirements Use a minimum number of parts in the assembly (<15) Use power sources like Spring Air cylinder Rubber band Use as many standard parts in your design as possible

What You Have to Do? Come to the next class with a piece of paper outlining the design including the following The components and their sizes and specs What were your considerations to choose those particular dimensions and sizes 2 or 3 lines about the mechanism of operation An OHT or JPEG of the design We will discuss those designs

Best Designs! First place – 10% Second place – 7% Third place - 5%