Concept Sketch. A graphical representation of an idea that can quickly communicate design intent and details

Transcription

1 Concept Sketch A graphical representation of an idea that can quickly communicate design intent and details All content and images 2016 Project Lead The Way, Inc. unless noted otherwise.

2 Shading Step 2. Locate your light source and make a mental note. Areas closest to the light will be lighter Areas further from the light will be darker lightest darkest All content and images 2016 Project Lead The Way, Inc. unless noted otherwise.

3 What Is an Engineering Notebook? An engineering notebook is a book in which an engineer will formally document, in chronological order, all of his/her work that is associated with a specific design project. Clear and detailed description of your design process Someone unfamiliar with work could take over project without additional information istockphoto.com 2012 Project Lead The Way, Inc.

4 Why Keep an Engineering Notebook? An engineering notebook is recognized as a legal document that is used in patent activities to Prove the origin of an idea that led to a solution Prove when events or ideas occurred Prove diligence in turning the idea into a solution Prove when an idea became a working solution ( reduced to practice ) istockphoto.com 2012 Project Lead The Way, Inc.

5 Engineering Notebook Sections Title Page Table of Contents General Chronological Entries References Business/Expert Contacts 2012 Project Lead The Way, Inc.

6 Standard Page Layout Quad-ruled paper All pages are Numbered Dated Signed by the designer Signed by a witness Include a statement of the proprietary nature of notebook 2012 Project Lead The Way, Inc.

7 Standard Page Layout Quad-ruled paper All pages are Numbered Dated Signed by the designer Signed by a witness Include a statement of the proprietary nature of notebook 2012 Project Lead The Way, Inc.

8 Brainstorming A group technique for solving problems, generating ideas, stimulating creative thinking, etc. It involves collecting ideas without regard to feasibility Project Lead The Way, Inc.

9 Rules for Brainstorming No criticism allowed Work for quantity Welcome piling-on Allow free-for-all 2012 Project Lead The Way, Inc.

10 Brainstorming Documentation All ideas should be captured Have a notetaker Take photographs Compile ideas after the session Project Date Team Take good notes. Record all ideas Project Lead The Way, Inc.

11 Concept Generation Dysfunctions Utilizing a poor design brief Assuming there is only ONE right answer Getting hooked on the FIRST solution Considering the ideas from only one or two team members 2012 Project Lead The Way, Inc.

12 Concept Generation Dysfunctions Feeling too anxious to finish Becoming frustrated by the lack of success Getting hooked on a solution that almost works 2012 Project Lead The Way, Inc.

13 What Is Design? The word design is often used as a generic term that refers to anything that was made by a conscious human effort. Design is also a process that is used to systematically solve problems Project Lead The Way, Inc.

14 What Is a Design Process? A design process is a systematic problem-solving strategy, with criteria and constraints, used to develop many possible solutions to solve or satisfy human needs or wants and to narrow down the possible solutions to one final choice. ITEA Standards for Technological Literacy Images courtesy of NASA 2012 Project Lead The Way, Inc.

15 Design Process used in IED 1. Define the Problem 2. Generate Concepts 3. Develop a Solution 4. Construct and Test a Prototype 5. Evaluate the Solution 6. Present the Solution This design process was developed based on the University of Maryland - College Park - IRB Research Project 2012 Project Lead The Way, Inc.

16 Define the Problem Identify a problem Validate the problem Who says it is a problem? Needs and wants Prior solutions Justify the problem Is the problem worth solving? Create design requirements (specifications) Criteria and constraints Design Brief 2012 Project Lead The Way, Inc.

17 Define the Problem Design Brief A written plan that identifies a problem to be solved, its criteria, and its constraints. Used to encourage thinking of all aspects of a problem before attempting a solution Project Lead The Way, Inc.

18 Generate Concepts Research Brainstorm possible solutions Consider additional design goals Apply STEM principles Select an approach Decision Matrix 2012 Project Lead The Way, Inc.

19 Develop a Solution Create detailed design solution Justify the solution path Technical Drawings 2012 Project Lead The Way, Inc.

20 Construct and Test a Prototype Construct a testable prototype Plan prototype testing Performance Usability Durability Test prototype collect test data analyze test data Test Report 2012 Project Lead The Way, Inc.

21 Evaluate the Solution Evaluate solution effectiveness Reflect on design Recommend improvements Optimize / Redesign the solution [Return to prior design process steps, if necessary] Revise design documents Project Recommendations 2012 Project Lead The Way, Inc.

22 Present the Solution Document the project Project Portfolio Communicate the project Formal Presentation 2012 Project Lead The Way, Inc.

23 2012 Project Lead The Way, Inc. Design Process Iterative a process that repeats a series of steps over and over until the desired outcome is obtained

24 Question #4: What might the design brief look like? Client / End User / Target Consumer Problem Statement Design Statement Criteria / Constraints 2012 Project Lead The Way, Inc.

25 Engineering Engineering is the application of mathematics and scientific principles to better or improve life Project Lead The Way, Inc.

26 Fields of Engineering The big four fields of engineering include: Chemical Civil Electrical Mechanical Most other disciplines are a derivative, combination, or extension of one of these Project Lead The Way, Inc.

27 What Do Engineers Do? Research Develop Design Supervise Manage 2012 Project Lead The Way, Inc.

28 RESEARCH The purpose of research is to: Employ basic scientific principles in the discovery and application of new knowledge that will have commercial or economic value Develop existing or invent new products Discover truths about a subject 2012 Project Lead The Way, Inc.

29 DEVELOPMENT Can involve searches in library, manufacturing literature, and patents for existing ideas Is the actual construction, fabrication, assembly, layout, and testing of scale models, pilot models, and experimental models for pilot processes or procedures that will work Does not deal exclusively with new discoveries but involves using well-known principles and employing existing processes or machines to perform a new or unusual function 2012 Project Lead The Way, Inc.

30 DESIGN Anticipate all manner of problems that the user may create in the application of a machine or use of a structure Prevent user errors, accidents, and dissatisfaction Requires a mastery of basic engineeringprinciples and mathematics and an understanding of the capabilities of machines 2012 Project Lead The Way, Inc.

31 SUPERVISE Must take the design engineer s drawings and supervise the assembly of the object as it was conceived Works closely with the technicians, mechanics, and laborers Associated with the process of estimating and bidding for competitive jobs Employ knowledge of structural materials, fabricating processes, and general physical principles to estimate both time and cost to accomplish a task 2012 Project Lead The Way, Inc.

32 What Functions Do Engineers Perform? MANAGEMENT Recent surveys show that the trend today is for corporate leaders in the United States to have a background in engineering and science Leaders use the capabilities of the company to the best advantage to produce a desirable product in a competitive economy Make decisions involving: Equipment in the plant The labor force Financial assets 2012 Project Lead The Way, Inc.

33 Primary Research Original research Generates current information Includes methods such as observation, experiments, surveys, and interviews Analyzes, synthesizes, and evaluates all information and data 2012 Project Lead The Way, Inc.

34 Secondary Research Look to see what has been written/done before on a topic Includes: Published works: books, journals, magazines, newspapers Unpublished works: business reports, operating manuals, master s theses, doctoral dissertations, web pages Is the most commonly conducted type of research 2012 Project Lead The Way, Inc.

35 Pictorial Drawing 2D illustration of a 3D object Shows three faces of an object in one view Provides a realistic view of an object Three types Isometric Oblique Perspective Isometric Oblique (Cavalier) Oblique (Cabinet) Perspective

36 Oblique Pictorials An oblique pictorial starts with a straight-on view of one of the object s faces, which is often the front face. Angled, parallel lines are drawn to one side to represent the object s depth. Common oblique angles include 30, 45, and

37 Isometric Pictorial Isometric means equal measure. Three adjacent faces on a cube will share a single point Edges converge at one point will appear as 120 degree angles or 30 degrees from the horizon line

38 Orthographic View Selection No hidden edges Best shape Description Most natural position Longest Dimension

39 Perspective Drawings

40 One-Point Perspective The one-point perspective is relatively simple to make, but is somewhat awkward in appearance when compared to other types of pictorials. A horizontal line represents the horizon. One vanishing point is identified on the horizon line. A series of lines are drawn from distinctive points on the object to the vanishing point, outlining the object being constructed.

41 Two-Point Perspective The two-point perspective is the most common perspective drawing. A step-by-step procedure will be explained for the perspective.

42 Three-Point Perspective The three-point perspective gives the viewer either a worm s-eye, or bird s-eye view of an object.

43 Construction Line Very lightly drawn lines to guide drawing other lines and shapes

44 Construction Line Very lightly drawn lines to guide drawing other lines and shapes

45 Object Line Thick and dark Define the object

46 Hidden Line Show interior detail not visible from the outside of the part

47 Center Line Define the center of arcs, circles, or symmetrical parts Half as thick as an object line

48 Section Line Define where material is cut away

49 Short-Break Line Freehand drawn line Shows where part is broken to reveal detail behind the part or to shorten a long continuous part

50 Dimension Line Shows distance Arrows drawn on ends to show where dimension line starts and ends Actual distance is typically located in middle of this line to display distance

51 Extension Line Shows where a dimension starts and stops Used with dimension lines Line is 1/16 away from part to avoid confusion with object lines

52 Long-Break Line Shorten very long objects with uniform detail Typically represented as a jagged cut or break

53 Leader Line Show dimensions of arcs, circles, and detail

54 Precedence of Lines Complex object sketches may require different line types to overlap. Line precedence must be used. Rules that govern line precedence in sketches and technical drawings Object lines take precedence over hidden and center lines. Hidden lines take precedence over center lines. Cutting plane lines take precedence over all others.

55 Multiview Drawing Shows two or more two-dimensional views of a three-dimensional object. Provides the shape description of an object. When combined with dimensions, serves as the main form of communication between designers and manufacturers.

56 Multiview Drawing

57 Orthographic Projection A technique used to create multiview drawings. Any projection of the features of an object onto an imaginary plane of projection. The projection of the features of the object is made by lines of sight that are perpendicular to the plane of the feature.

58 The International System of Units (SI) The International System of Units (SI) is a system of units of measurement consisting of seven base units Unit Name Symbol Measurement meter m length kilogram* kg mass second s time ampere A electric current kelvin K thermodynamic temperature candela cd luminous intensity mole mol amount of substance Mostly widely used system of measurement The United States is the only industrialized nation that has not adopted the SI system

59 The International System of Units Often referred to as the metric scale Prefixes indicate an integer power of 10 Power of 10 Prefix Abbreviation Power of 10 Prefix Abbreviation 10 1 deca- da 10 2 hecto- h 10 3 kilo- k 10 6 Mega- M 10 9 Giga- G Tera- T 10-1 deci- d 10-2 centi- c 10-3 milli- m 10-6 micro- µ 10-9 nano- n pico- p

60 Recording Measurements A measurement always includes a value A measurement always includes units A measurement always involves uncertainty A measurement is the best estimate of a quantity

61 Significant Digits Scientists and engineers often use significant digits to indicate the uncertainty of a measurement Significant digits are digits in a decimal number that carry meaning indicating the certainty of the value All digits you record for a measurement are considered significant Include all certain digits in a measurement and one uncertain or estimated digit

62 The U S Customary System System of measurement used in the United States Similar to the British Imperial System of Measurement, but not identical Common U S Customary Units Measurement Symbol Unit length in. ft mi inch foot mile mass slug slug force lb pound time s second thermodynamic temperature F Fahrenheit degree

63 Precision and Accuracy Precision (repeatability) = The degree to which repeated measurements show the same result Accuracy = The degree of closeness of measurements of a quantity to the actual (or accepted) value High Accuracy Low Precision Low Accuracy High Precision High Accuracy High Precision

64 Unit Conversion Conversion factor Multiplied by a quantity to convert the quantity to alternate units A ratio (fraction) in which the quantity in the numerator is equivalent to the quantity in the denominator Contains desired units in the numerator and the given units in the denominator The value of the conversion factor is 1 Conversion Factor = 1 Given Units Given Units 1 Desired Units Given Units = Desired Units Desired Units 1

65 Section View Provides a view of an object as if it were cut by a saw Location is indicated by a cutting plane line on another view Cutting plane line

66 Section View Cutting plane line Indicates location of the cut Thick and broken line Arrows indicate direction of view Labeled with a letter for identification on drawing Cutting plane line

67 Dimensioning Dimensions should reflect actual size of the object, not the scaled size. Include overall dimension in the three principle directions width, height, and depth. Include all dimensions necessary to produce or inspect the part. Do not include unnecessary dimensions. Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned. A dimension should be attached to only one view; for example, extension lines should not connect two views. Whenever possible, locate dimensions between adjacent views. Avoid dimensioning to hidden lines.

68 Dimensioning Do not place dimensions on the object unless it is absolutely necessary. Do not cross a dimension line with another dimension line or with an extension line. Avoid crossing dimension or extension lines with leader lines. Leader lines point toward the center of the feature and should not occur horizontally or vertically. Dimension numbers should be centered between arrowheads, except when using stacked dimensions, and then the numbers should be staggered. In general, a circle is dimensioned by its diameter and an arc by its radius. Holes should be located and sized in the view that shows the feature as a circle. Holes are located by their centerlines, which may be extended and used as extension lines.

69 Statistics The collection, evaluation, and interpretation of data Statistical analysis of measurements can help verify the quality of a design or process

70 Summary Statistics Central Tendency Center of a distribution Mean, median, mode Variation Spread of values around the center Range, standard deviation, interquartile range Distribution Summary of the frequency of values Frequency tables, histograms, normal distribution

71 Mean Central Tendency The mean is the sum of the values of a set of data divided by the number of values in that data set. μ = N x i

72 A Note about Rounding in Statistics General Rule: Don t round until the final answer If you are writing intermediate results you may round values, but keep unrounded number in memory Mean round to one more decimal place than the original data Standard Deviation round to one more decimal place than the original data

73 Mode Central Tendency Measure of central tendency The most frequently occurring value in a set of data is the mode Symbol is M Data Set:

74 Median Central Tendency Measure of central tendency The median is the value that occurs in the middle of a set of data that has been arranged in numerical order Symbol is x, pronounced x-tilde ~

75 Range Variation Measure of data variation The range is the difference between the largest and smallest values that occur in a set of data Symbol is R Data Set: Range = R = maximum value minimum value R = 44 3 = 41

76 Standard Deviation Measure of data variation Variation The standard deviation is a measure of the spread of data values A larger standard deviation indicates a wider spread in data values

77 Standard Deviation Variation σ = x i μ 2 N σ = standard deviation x i = individual data value ( x 1, x 2, x 3, ) μ = mean N = size of population

78 Frequency Normal Distribution Distribution Bell shaped curve Data Elements

79 Modeling The act of representing designs or ideas in various forms in order to present or evaluate a design. Concept Modeling Graphical Modeling Mathematical Modeling Computer Modeling Physical Modeling

80 Concept Modeling Listing or mapping the concepts involved in a design or process under investigation. Example: Designing a Theme Park Perhaps the first step to designing a theme park would be to create a list of the rides, attractions, and facilities that would be included in the design. Easy access to major transportation system Circular pattern of attractions A theme (fairy tale, nations, sports) Access to Emergency Medical facilities Etc.

81 Graphical Modeling Representing information in the form of charts, graphs, maps, or geometric figures. Example: Mapping the Ocean Floor

82 Mathematical Modeling Using mathematical equations or geometric representations to predict or model a phenomenon or behavior. Example: Designing a Beverage Container Design a cylindrical beverage container to hold a given volume of liquid. V = π r 2 h

83 Computer Modeling Using a computer and software to create a representation of an object or concept. Can include 3D modeling of parts Modeling of structures for structural analysis Modeling of circuits for circuit analysis Modeling of chemical processes to check reactions and byproducts, etc.

84 Physical Modeling Using physical materials to create a representation of an object or concept. Mock-up: An appearance model used to present the general concept of a design Scale Model: A representation of a design that is either larger or smaller than the actual model Prototype: A working model of the actual design

85 Assembly Constraints Assembly constraints are parameters that define geometric relationships between components in a CAD assembly Constraints include Mate/Flush Angle Tangent Insert

86 Degrees of Freedom A component floating in space has six degrees of freedom 3 rotations around X, Y, and Z axes 3 translations along X, Y, and Z axes Degrees of freedom are systematically removed in an assembly until only the desired components are allowed to move

87 What Is a Portfolio? A collection of documents selected for a particular purpose. Record history or important events Document a design Display experience and skills Display best work Organize a collection of materials

88 Physical Aspects of a Portfolio Protective front and back covers Spiral binding so that portfolio opens fully to lie flat Personal logo Contact information

89 Personal Information Page Contains Your picture Brief autobiography Content related to your goals

90 Project Information Page Design project introduction Design brief Explains the problem, the challenge, and the project constraints

91 Research Examples of project research Key findings Validation Justification Information is straightforward and clear Brief

92 Sketches Show ideation process or result of brainstorming Include several types Evidence of concept selection process

93 Technical Drawings Document idea development work All dimensions Information to justify materials selected Mathematical calculations

94 Modeling Assembly explanations Images of prototypes

95 Testing and Evaluation Test procedure Test data Statistical information to support solution Suggested improvements or modifications

96 Reflection and Rubrics Reflect on process and outcome Include rubrics May include self-assessment May include team assessment

97 Solid Modeling Solid CAD models are the result of additive and/or subtractive processes. All CAD solid modeling programs utilize additive and subtractive modeling methods to create virtual 3D objects. They are also referred to as Boolean operations, named after the 18 th century English mathematician Charles Boole.

98 Additive Methods A three dimensional object can be viewed as the combination of two or more simple forms. In the creation of real world objects, this method is represented by construction processes such as welding, gluing, mechanical fastening, and joinery.

99 Subtractive Methods An object can be viewed as the remainder of a solid block that has had the geometry of one or more forms sequentially removed. In the creation of real world objects, this method is represented by milling, drilling, turning, grinding, and other manufacturing processes.

100 Ellipses To calculate the area of an ellipse, the lengths of the major and minor axis must be known. A = ab 2a = major axis 2b = minor axis = 3.14 A = area

101 Area of Triangle The area of a triangle can be calculated by A = 1 2 (bh) b b = base h h = height A = area

102 Parallelograms The area of a parallelogram can be calculated by A = bh h b = base h = height A = area

103 Multisided Polygons Area calculation of a multisided regular polygon: A = area s = side length n = number of sides

104 Density Density is a measure of the amount of matter per unit of volume High Density Low Density Objects more dense than water sink Objects less dense than water float

105 Matter: Mass vs. Weight Mass is the amount of matter in an object or the quantity of the inertia of the object. Weight is the force of gravity on mass. W = mg W = weight m = mass g = acceleration of gravity Many materials are purchased by weight

106 Density Density can be indicated in multiple ways Mass Density = mass per unit volume Weight Density = weight per unit volume Formula Sheet m = VD m Dm = m V W = VD w Dw = W V

107 Mass and Weight: Measurement Balance measures mass Uses objects of known mass to find the unknown mass of an object Measurement is unaffected by difference in gravity Scale measures weight Measures force caused by gravity Measurement is affected by difference in the acceleration of gravity May display a mass measurement reading by using an assumed acceleration of gravity to convert from weight to mass

108 Volume: Measurement Volume is the amount of three dimensional space enclosed by an object. Two methods to determine volume Calculate using geometry of object Measure indirectly using water displacement (or 3D scanner)

109 Properties of Solids Volume, mass, weight, density, and surface area are properties that all solids possess. These properties are used by engineers and manufacturers to determine material type, cost, and other factors associated with the design of objects.

110 Volume of Rectangular Prism The formula for calculating the volume (V) of a rectangular prism is: V = wdh V= wdh V= 4.00 in. x 5.25 in. x 2.50 in. V = 52.5 in. 3

111 Volume of a Cylinder To calculate the volume of a cylinder, its radius (r) and height (h) must be known. The formula for calculating the volume (V) of a cylinder is: V = r 2 h V= r 2 h V= 3.14 x (1.50 in.) 2 x 6.00 in. V = 42.4 in. 3

112 Volume of a Cone The formula for calculating the volume (V) of a cone is: V = πr2 h V = π(0.75 in.)2 (2.00 in.) 3 V = 1.18 in. 3

113 Center of Gravity A 3D point where the total weight of the body may be considered to be concentrated The average location of an object If an object rotates when thrown it rotates about its center of gravity. An object can be balanced on a sharp point placed directly beneath its center of gravity

114 Centroid A 3D point defining the geometric center of a solid Do not confuse centroid with the center of gravity. The two only exist at the same 3D point when the part has uniform geometry and density.

115 Principal Axes The lines of intersection created from three mutually perpendicular planes, with the three planes point of intersection at the centroid of the part The X-, Y-, and Z-axes show the principal axes of the ellipsoid.

116 Visual Design Elements Eight integral components used in the creation of a design: Point Line Color Value Shape Form Space Texture

117 Line Types Vertical - Represents dignity, formality, stability, and strength Horizontal - Represents calm, peace, and relaxation Diagonal - Represents action, activity, excitement, and movement Curved - Represents freedom, the natural, having the appearance of softness, and creates a soothing feeling or mood

118 Color Described by a number of qualities Hue: base color (e.g., red) Value: lightness or darkness Saturation: purity or intensity relative to gray

119 Principles of Design Many principles add to an interesting design Balance Emphasis Contrast Rhythm Proportion Unity Economy

120 Balance Visual and physical balance The distribution of elements within a design Types Symmetrical (formal) Asymmetrical (informal) Radial

121 Emphasis Used to draw attention to one area Focal Point feature in a design that attracts the eye Can be achieved through Size Placement Shape Contrast Use of lines Wikipedia.org Microsoft Office clipart

122 Contrast Microsoft Office clipart The degree of relative difference between elements istockphoto.com Image courtesy Autodesk, Inc.

123 Rhythm Repeated use of line, shape, color, texture or pattern A harmonious pattern or sequence Types Regular Random Gradated Graduated Microsoft Office clipart

124 Proportion Microsoft Office clipart Comparative relationship between elements in a design with respect to size Scale The proportion or size of an element in relation to the other elements Microsoft Office clipart Microsoft Office clipart

125 Unity The consistent use of design elements istockphoto.com Microsoft Office clipart istockphoto.com

126 Economy Use of the bare minimum of elements Can be achieved by removing extraneous elements In simplicity there is beauty Less is more Image courtesy Autodesk, Inc.

127 WHAT is Reverse Engineering? Reverse engineering (RE) is the process of taking something apart and analyzing its workings in detail, usually with the intention of understanding its structure, function, and operation. Microsoft Office clipart

128 WHY is Reverse Engineering Used? Documentation Discovery Investigation Product Improvement istockphoto.com

129 Stages of Reverse Engineering Visual Analysis Functional Analysis Structural Analysis

130 Functional Analysis After a product has been selected, a nondestructive functional analysis is performed. First, the product s purpose is identified. Next, observations are made to determine how the product functions. These observations are recorded in detail. Lastly, the system s inputs and outputs are listed.

131 Product Disassembly and Documentation Procedure 1. Disassemble the product 2. Create pictorial sketches to describe the operation 3. Carefully observe and measure each part 4. Record your finding on the Product Disassembly Chart 5. Create an annotated sketch of each part 6. Compare your hypothesis for operation to the actual operation of the part 7. Create 3D solid models for each part 8. Document your findings

132 Dimension Components Dimension Text Dimension Line Extension Lines Arrow Head

133 Dimensioning Methods Unidirectional Dimensions are placed so that they can be read from the bottom of the drawing sheet. This method is commonly used in mechanical drafting. Aligned Dimensions are placed so the horizontal dimensions can be read from the bottom of the drawing sheet and the vertical dimensions can be read from the right side of the drawing sheet. This method is commonly used in architectural and structural drafting.

134 Linear Dimensioning Chain Dimensioning Dimensioning from feature to feature Common dimensioning technique

135 Datum Dimensioning Datum Dimensioning Dimensioning from a single point of origin called a DATUM Reduces dimensional deviations in manufactured parts because each size/location dimension is referenced to a single point

136 Dimensioning Symbols

137 Dimensioning Arcs and Circles Arcs and circles are dimensioned in views that show the arc or circle. Arcs are dimensioned with a leader to identify the radius; in some cases, a center mark is included. Circles should have a center mark and are dimensioned with a leader to identify the diameter.

138 Hole Definitions Through/Thru Hole cuts through entire thickness Clearance Hole large enough to allow screw head (and driver) to pass through Blind Hole does not cut through entire thickness

139 Hole Definitions Countersink Conical-shaped recess around hole at surface Often used to accept tapered screw Counterbore Cylindrical recess around hole at surface Often used to receive a bolt head or nut Tapped Hole has internal threads

140 Hole Note Symbols

141 Unified National Thread Notes Thread per Inch Major Diameter Coarse or Fine threads. In this case C for course, F is for fine.

142 Tolerances A tolerance is an acceptable amount of dimensional variation that will still allow an object to function correctly.

143 Tolerances Three basic tolerances that occur most often on working drawings are: limit dimensions bilateral tolerance unilateral tolerance

144 Tolerances Identify the type of tolerance displayed in red Limit dimensions Bilateral Unilateral

145 Definitions Limits are the maximum and minimum sizes shown by the toleranced dimension Upper limit is the maximum allowable dimension Upper Lower Limit limit = Specified is the minimum Dimension allowable + positive dimension variance 1.55 = Lower Limit = Specified Dimension + negative variance 1.45 = ( 0.05)

146 Definitions Tolerance is the total variance in a dimension and is equal to the difference between the upper and lower limits. Tolerance = Upper Limit Lower Limit 0.10 =

147 General Tolerances General tolerances are tolerances that are assumed if no specific tolerance is given for a dimension Typically tolerances are specified based on the number of digits to the right of the decimal point in a dimension Shown on drawing Linear Dimensions Angles = ±.5 X.X = ±.020 X.XX = ±.010 X.XXX = ±.005

148 Types of Fit Clearance Fit limits the size of mating parts so that a clearance always results when mating parts are assembled Interference Fit limits the size of mating parts so that an interference always results when mating parts are assembled Transition fit occurs when two mating parts can sometimes have a clearance fit and sometimes have an interference fit

149 Definitions Allowance is the minimum clearance or maximum interference between parts Allowance = MMC internal feature MMC external feature

150 Design Criteria The explicit requirements that a product must meet in order to be successful Used to evaluate a product s potential to be successful Used to create testing procedures May address Performance Product Size and Shape Aesthetics Materials Safety and Legal Issues Ergonomics Environment Life Cycle Maintenance Customer Needs Others

151 Design Constraints The limits on the design and production of a product Resources (people, equipment, etc.) Budget Time Energy Materials Manufacturing Process Others