2 Chap 16: Engineering Drawing Drawing StandardsProjection SystemsAuxiliary and Section ViewsDimensioningTolerancingFitsTolerances for 100% InterchaneabilitySurface Finish SymbolsReview Questions
3 IntroductionStandards are necessary in CAD design since designs are typically complex.Designers create drawings for others to make..Engineering and Manufacturing needs common symbols, fonts, dimensions, call outs, section views to reduce cost of reading drawings and producing parts from them.AmericanANSI standardASME standardEuropeanISO standard
4 Introduction History Little coordination between ASA, SAE and Military Design standards are thought to have been used in ancient Egypt for the pyramids.Drafting Standards started in England in the 1940sStanley ParkerEnglish worker in a torpedo factory in Scotland, devised a method of specifying cylindrical tolerance zones surrounding an absolute location from what was previously specified as rectangular plus/minus tolerances. This became true position.1935: American Standards Association (ASA) published first standard for engineering drawings.Only 20 pages in length with 5 pages devoted to dimensioning.1940: SAE Draftsman handbookChevrolet division at GM detailed standards for automotive draftsmen.1945: US Army publication of ordinance manual specified dimensioning and tolerance for the US Army.1949: Military Standard 8 was published to specify dimensioning and tolerancing standards for US Army.Little coordination between ASA, SAE and Military
5 Introduction History 1957: American Standards Association Approved first American standard devoted to dimensioning and tolerancing.Britain and Canada cooperated.1966: First unified standard published by American National Standards Institute (ANSI)Standard ANSI 14.1 to 14.5Updated in 1973 and 19821994 and 1995 updated and published by the ASME95% in agreement with ISO global standards.ISO is the European standards (metric)
6 ANSI Y14 Design Drafting Standards Establishes a series of recommended drawing sizes and basic format for engineering drawing in the United States.Provides common standards to aid in the interchange of drawings between companies, government, and other users.Started in 1975 in Detroit, MI, and revised every 5 years or so.1994 and 1995 updated and published by the ASMEANSI Y14.1 Drawing Sheet Size and FormatANSI Y14.2 Line Conventions and LetteringANSI Y14.3 Multi and Sectional View DrawingsANSI Y14.4 American Drafting Standards ManualANSI Y14.5 Dimensioning and TolerancingANSI Y14.6 Screw Thread RepresentationANSI Y14.7 Gear Drawing StandardANSI Y14.8 CastingsANSI Y14.9 ForgingsANSI Y14.1 Metal StampingsANSI Y14.13 to Section 36 Springs, electrical, Title and Notes, …
7 ANSI Y StandardsDrawing Sheet Size and Format Standards (ASME and SAE)Renamed ASME YScopeDefinitionsDrawing sizeStandard Drawing sheet sizesBasic FormatsTitle BlocksRevision BlockParts List or Bill of Materials (BOM)Supplementary BocksDrawing Numbers
8 ANSI Y14.1-1980 Standards Scope Definitions Defines standard sheet sizes and formats for engineering drawingsDefinitionsDrawing refers to original sheet on which information is suppliedStandard Drawing sheet sizesLetter size designations are listed below.Fig 1 Flat size Formats A through F. Note: Roll sizes are not used at GMOnly flat sizesMostly 8.5” x 11”Basic FormatsBasic Arrangement Fig 1Size of BlocksTitle Block Fig 4 and Continuation sheet Fig 5Lettering- ANSI 14.2LinesThick (0.030 in) for Borderline, outline, and main division of blocks.Thin (0.015 in) for division of parts list and revision blocks, minor subdivision of title blocks and zone markers.
9 ANSI Y StandardsTitle Blocks- Fig 4 & 5 (MFGT124 drawings must follow this!)Location- lower right cornerContentsBlock A: Name and address of the company or design activityBlock B: Drawing TitleBlock C: Drawing numberBlock D: Drafts-person, checker with datesBlock E: Approval with DateBlock F: Approval from other sources with Date (optional)Block G: Predominate Scale of DrawingBlock H: Drawing number or filename numberBlock J: Drawing size letter designationBlock K: Actual or estimated weight of itemBlock L: Sheet number for multiple sheet drawings.
10 ANSI Y14.1-1980 Standards Revision Block Location: Located in upper right hand corner of the drawingContents: Provides space for revision number or symbol, description or identification of change authorization, date, and approvals.Parts List or Bill of Materials (BOM)Location: Located on lower right corner near title block, Additional lists may be located at the left of and adjacent to original block.For large assemblies, BOM is located in a specified layer of the model.Example,Layer 1 is title page with revisions, title block, revision list, and exploded view of assemblyLayer 2 is assembly 1 with detailed dimensions.Layer 99 is Bill of Material. Layer number of BOM can be standardized on all documents to a layer that is never used for design.BOM is the order list that the purchase order is written to.BOM will list those items that are purchased and those items that are manufactured in house.
11 ANSI Y14.1-1980 Standards Supplementary Bocks Drawing Numbers Information covering GD&T notes, material treatment, finish, general notes.Drawing NumbersLocation: Lower right corner of the title block and in at least one other location.Fig 1, 2, and 3Fig 9: block descriptionsRevision symbol blockNumbering multiple sheetsSecond and subsequent sheets of drawings consisting of more than one sheet are identified by same basic drawing number ant the applicable sheet number.Example, Sheet 1 of 4, sheet 2 of 4, sheet 4 of 4, etc…
12 ANSI Y14.2-1980 Standards Line Conventions and Lettering Renamed ASME YScopeLine ConventionsLine WidthsVisible lines, hidden lines, section lines, center lines, break lines, etc.ArrowheadsSection Lining for cut surfaces of sectional views. Figure 9Lettering in Table 1One style of lettering should be used throughout a drawing.Upper case letters on drawings unless lower case is needed with approved equipment or special characters.Lettering should not be underlined except when special emphasis is required
13 ANSI/ASME Y14.2-1995Standards Line Conventions and LetteringRenamed ASME YScopeLine ConventionsLine WidthsVisible lines, hidden lines, section lines, center lines, break lines, etc.ArrowheadsSection Lining for cut surfaces of sectional views. Figure 9Lettering in Table 1One style of lettering should be used throughout a drawing.Upper case letters on drawings unless lower case is needed with approved equipment or special characters.Lettering should not be underlined except when special emphasis is required
14 ASME Y14.2-1995 Standards Line Conventions and Lettering Developed from ANSI ScopeTypes of LinesV
15 ANSI/ASME Y14.3-1995 Standards TopFrontUS StandardANSI/ASME Y Standards1st2nd3rd4thQuadrantsMulti and Sectional View DrawingsFrom ANSI YMultiview System of Orthographic DrawingsEstablishes orthographic views for shape descriptionsRefers to the trigonometric quadrants relative to front and top viewing planes of the part. (See Figure)6 principal orthographic views have third angle projection in USFront view is under the top view (Figure Handout)Most common views are right, top, front, (plus isometric)Others are left, bottom, rear.6 principal orthographic views have first angle projection in EuropeTop view is under the front viewMultiview Drawing AppliedNumber of views required to describe a part.For complex parts, three or four views are required with one being orthographic.Standard layout includes Front, top, side, and isometric views.European StandardTopFront
16 ANSI/ASME Y14.3-1995 Standards Multi and Sectional View DrawingsAuxiliary ViewsUsed to show the true size & shape of features not parallel to principal views.Projected from a principal view.Sectional ViewsShows interior details that are clearer than exterior views due to hidden lines.Location of sectional view is indicated by a cutting plane line and arrows.Used to show the solid materials with thin lines at 45°. Figure 16-6More than one line may occupy the same position in a view. Fig 16-7Line Order of PreferenceObject lines take preference over hidden lines and centerlines.Hidden lines take preference over centerlines.Cutting planes take preference over centerlines when showing path of sectional view.Notice in the right-side-view that when ever a hidden line has precedence over a centerline, the centerline is still drawn in the view by leaving a space and then extending it beyond the edge.
17 ANSI/ASME Y14.5-1994 Standards Dimensioning StandardsDimensions describe the details of a part so it can be constructed to the proper size.Dimensions options in SolidWorksDetermine the display and position of text and extension linesReference dimensions require parenthesesParentheses can be added to a dimension at anytime through Property option.Guidelines for dimension spacingSpace between the first dimension line and the part outline should not be less than 10mm.Space between subsequent parallel dimension lines should not be less than 6 mm.Spacing may be different depending upon drawing size and scale.Set the offset distance from last dimension to 6 mm.Set offset distance from model to 10 mm.Specify that unless otherwise stated, dimensions are in millimeters of inchesArrowheads is recommended to be solid filled arrow
18 ANSI/ASME Y14.5-1994 Standards Dimensions and TolerancesAll dimensions are subject to tolerancing (amount of permissible variability)Guidelines for dimensionsBasic dimensions are identified by an enclosing frame symbol. Is exact size and shape of object which will resize the object if changedReference dimensions are identified by a parentheses (40)Is intended size and for information only. Won’t resize object if changed.DimensioningChain dimension: Used when tolerances between adjacent features is more important than the overall tolerance of the feature.Baseline dimension :used when the location of features must be controlled from a common reference point or plane.Direct Dimensioning: Applied to control specific featuresDimension largest dimension to the outside of the inner dimensions.Crossing dimension lines with arrow should be avoided.Guidelines for Witness LinesWitness lines are extension linesVisible gap exists between the Extension line and the visible line.Extension line extends 1.5 mm beyond the Dimension line .
19 ANSI/ASME Y14.5-1994 Standards TolerancingParts typically are made in part of an assembly that has to fit together.Parts are not made to exact dimensions but are made to plus/minus.Exact dimensions would be expensive to make.Higher precision = higher costsGage blocks are made to very precise dimensions but are used to check parts.Parts are made to varying degrees of accuracy depending on part requirements.Some parts are required to be built with low precision (+/ in)Some parts are required to be built with medium precision (+/ in)Some parts are required to be built with high precision (+/ in)Major termsNominal size is designation for general ID, e.g. 9/32 drill or 2 by 4Basic size is size from which limits of size are derived by application of allowances and tolerances. Basic size of 9/32 drill is in.Limits are the extreme allowable sizes for a feature. +/- dim Fig 16-11Tolerance is permissible variation in dimension. (Big – Small) Fig 16-12
20 ANSI/ASME Y14.5-1994 Standards TolerancingMajor termsAllowance is minimum clearance between mating parts. (Big – Small) Fig 16-12Maximum material condition (MMC) is condition of a part when it contains the MOST amount of material. MMC of an external feature of size (e.g., shaft) is the upper limit. MMC of an internal feature of size (e.g., hole) is the lower limit.Least Material Condition (LMC) is the condition of a part when it contains the LEAST amount of material. LMC of an external feature of size (e.g., shaft) is lower limit. LMC of an internal feature of size (e.g., hole) is the upper limit.Limit dimensioning is the maximum and minimum sizes of a feature are specified as shown in FigUnilateral tolerances is a basic size followed by plus/minus that variaion is allowed only toward one side, usually from the smaller size. E.g., /Bilateral tolerances is a basic size followed by plus/minus tolerance that is directed toward both directions from nominal size. 1.88Criteria to determine tolerance for dimensionTolerance should be chosen to permit the assembly of randomly selected partsTolerance should be as large as possible1.8851.875+ .001- .001
21 American National Standard Holes and Fits Fit signifies type of clearance that exists between mating parts.Clearance Fits provide some gap between mating parts.Interference Fits have no clearance between mating parts.Transition fits are listed to result in either a clearance or interferenceAmerican National Standard and metric sizes for holes and shaftsSet of classes of fits based on the basic hole system.Basic hole system used from reamers and drills to produce standard size holes.Types of fit coveredRC - running and sliding fitsLC - clearance locational fits.LT – transition locational fits.LN – interference locational fits.FN force and shrink fits.Tables and standards are organized on hole basis, thus basic shaft size and type of fit are needed to determine the dimension and tolerance for mating parts.Example, RC4 is close running fit and RC 9 is a loose running fitStandard tables are in Machinery’s Handbook
22 ANSI/ASME Y14.5-1994 Standards GD&T StandardsAccording to ANSI Y standards, the following rules should be observed:Each dimension must have a tolerance, either applied directly or indicated by a general note.Identified as reference, basic, or maximum dimensions are exceptions.Dimensions for size, form, and location of features should be complete to the extent that there is full understanding of the characteristics of each feature.Scaling (measuring from drawing) of the print is not allowed.Assumption of a distance or size is not allowed.Dimensions should be shown between points, lines, or surfaces having necessary and specific relationship to each other.Dimensions must be selected and arranged to avoid accumulation of tolerances and more than one interpretation.
23 ANSI/ASME Y14.5-1994 Standards GD&T StandardsAccording to ANSI Y standards, the following rules should be observed:Multiview display should define a part without specifying manufacturing methods (CAM).Thus, only the diameter of the hole is given and not whether it is reamed, punched, drilled, etc.Finish allowance and shrinkage allowance can be added.Dimensions should be selected for display to provide required information.Wires, cables, sheets, or rods, and other display items must be specified by linear dimension, indicating the diameter or thickness.Surfaces or centerlines shown on displays at right angles to each other are implied to be 90° apart.
24 ANSI Y14.3-1980 Standards Multi and Sectional View Drawings Renamed ASME YMultiview System of Orthographic DrawingsEstablishes orthographic views for shape descriptions6 principle orthographics views have thirds angle projection in USMultiview Drawing AppliedNumber of views required to describe a part.For complex parts, three or four views are required with one being orthographic.Standard layout includes Front, top, side, and isometric views.Sectional ViewsConventional RepresentationSpace GeometrySpace Analysis and Applications
25 Chap 17: GD&T GD&T Standards Feature Control Frame Five Classifications of ToleranceReview Questions
26 GD&T Standards GD&T Standards Geometric dimensioning and tolerancing is a method of defining parts based on how they functionCurrent standard: ASME Y14.5M-1994Major changes from AINSI Y14.5M-1982Universal ISO datum feature symbolSymmetry tolerance symbol is accepted as standardElimination of material symbol for regardless of feature size (RFS)RFS condition applies when the symbols MMC and LMC are not stated on feature.Major RulesRule 1 establishes the default conditions for features of sizeRule 2 establishes a default material condition for feature control frames
27 GD&T Standards GD&T Standards Rule 1- Set Default Conditions for Features of SizeWhere only a tolerance of size is specifiedThe limits of size for an individual feature prescribe the extent to which variations in its form,a s well as size, are allowed.Dimensioning rule used to ensure that features of size (FOS) will assemble with one another.Feature size can be a cylinder or spherical surface or a set of opposed elements or surfaces associated with a size dimension.Features are simply part surfaces.Results in the maximum boundary for an external FOS is its maximum material condition (MMC).Results in the minimum envelope for an internal FOS is its MMC.To determine if two features of size will assemble, the designer compares the MMCs of the features of size.
28 GD&T Standards GD&T Standards Rule 2- Set Default Material Condition for Feature Control Frames
29 ANSI/ASME Y14.5-1994 Standards GD&T StandardsDimensions options in SolidWorksDetermine the display and position of text and extension linesReference dimensions require parenthesesParentheses can be added to a dimension at anytime through Property option.Guidelines for dimension spacingSpace between the first dimension line and the part outline should not be less than 10mm.Space between subsequent parallel dimension lines should not be less than 6 mm.Spacing may be different depending upon drawing size and scale.Set the offset distance from last dimension to 6 mm.Set offset distance from model to 10 mm.Arrowheads is recommended to be solid filled arrow
30 ANSI/ASME Y14.5-1994 Standards GD&T StandardsGuidelines for dimensionsCrossing dimension lines with arrow should be avoided.When dimension line cross, close to an arrowhead, the extension line (Witness line) must be broken.Order of dimensionDimension largest dimension to the outside of the inner dimensions.Guidelines for Witness LinesWitness lines are extension linesVisible gap exists between the Extension line and the visible line.Extension line extends 1.5 mm beyond the Dimension line .
31 ANSI/ASME Y14.5-1994 Standards GD&T StandardsAccording to ANSI Y standards, the following rules should be observed:Each dimension must have a tolerance, either applied directly or indicated by a general note.Identified as reference, basic, or maximum dimensions are exceptions.Dimensions for size, form, and location of features should be complete to the extent that there is full understanding of the characteristics of each feature.Scaling (measuring from drawing) of the print is not allowed.Assumption of a distance or size is not allowed.Dimensions should be shown between points, lines, or surfaces having necessary and specific relationship to each other.Dimensions must be selected and arranged to avoid accumulation of tolerances and more than one interpretation.
32 ANSI/ASME Y14.5-1994 Standards GD&T StandardsAccording to ANSI Y standards, the following rules should be observed:Multiview display should define a part without specifying manufacturing methods (CAM).Thus, only the diameter of the hole is given and not whether it is reamed, punched, drilled, etc.Finish allowance and shrinkage allowance can be added.Dimensions should be selected for display to provide required information.Wires, cables, sheets, or rods, and other display items must be specified by linear dimension, indicating the diameter or thickness.Surfaces or centerlines shown on displays at right angles to each other are implied to be 90° apart.
33 ANSI/ASME Y14.5-1994 Standards GD&T StandardsGeometric Dimensioning and Tolerancing (GD&T) establishes the standard by which designers can communicate the intended function of the part to the machinist making the part and the inspector checking the part.This standard lets the designer inform the machinist, toolmaker or fabricator what are the important features of the design when they are making the part.The standard also lets the inspector know what are the important features to inspect form.GD&T uses symbols to communicate the information to those involved in making the part to eliminate any misunderstanding.Word explanations can be confusing especially with the global market and the translations of words into different languages.A simple layout of the symbols used in GD&T can be found as follows
34 ANSI/ASME Y14.5-1994 Standards GD&T StandardsFeature Control Frames Geometric ToleranceGeometric Characteristic SymbolThe feature control frame helps to organize the various symbols, see Appendix A or sections 3b-3h, into a sentence. This sentence communicates the information in an organized manner. Figure 3a-1 shows a simple sentence with the geometric symbol and the geometric tolerance that is applied to the intended feature.The simple sentences can be expanded to contain a greater amount of information. A couple notes about the feature control frames that are important in understanding they’re meaning. The first is the Geometric Tolerance is the total tolerance band for that feature. This means that it is not a +/- tolerance. An example of this is if we have a dimension of 1.00 and a Geometric tolerance of .005, we can interpret this as /[|.005]Geometric Characteristic SymbolGeometric Tolerance
38 Chap 18: Computer Aided Design Wireframe, Surface, and Solid ModelingCircuit Board LayoutRapid PrototypingReview Questions
39 Rapid Prototype Methods Rapid prototypying is a process of building objects during the design phase to have a 3-D object to check for fit, form, and functionThe rapid prototype will help you visualize the dimensions of the part and see if 3-D object is desired.The object is made from the solid model geometry in a stereolithography file.Stereolithography represents the 3-D object as a shell of the part that is broken into triangles.Rapid prototype process can bring a design on the computer to 3-D shape in a matter of minutes to hours.
40 Rapid Prototype Process Process involves CAD system to digitizer to rapid partComputer Aided Design(CAD)Rapid Prototyping Device3-D Object
41 Stereolithography 3D Systems of Valencia, CA (www.3dsystems.com) Founded in 1987 currently offersSLA® (stereolithography) systems ($799,000),ThermoJet® solid object printer ($49,995), andSLS® (selective laser sintering)SLA 7000, 5000, 3500, 250 series systemsUsed for Limited production runs, Rapid tooling, Prototyping, Master patterns for investment castingLicenses the complementary 3D Keltool®Method to produce steel mold inserts.
42 Stereolithography Process UV laser cure of epoxy resin in a vat of liquidLayer of resin above an elevator platform is illuminated with laser and adheres to top of platform.Platform moves down and next layer drawn onto surface, etc.Uncured resin is washed with solvent.Part is post cured.SpecsLaser: wavelengthBuild layer: mmVat volume: LSize: W2.1 x D1.55 x H2.36 mWeight 1455 kgNot for office use.
43 Solid Object Printer Process ThermoJet® solid object printer Builds material yields superior model quality and surface finish that's perfect for most models and investment casting and RTV molding patterns.ProcessMulti Jet Modeling (MJM)Printing of plastic resinSpecsResolution: 300 x 400 x 600 DPI (XYZ)Color: Neutral, gray, or blackSize: 250 x 190 x 200 mm (10 x 7.5 x 8 in) (XYZ)Ready for office use.
44 Selective Layer Sintering The SLS Vanguard ProcessCreate durable, metal, plastic, or rubber-like parts directly from any solid CAD model in one dayProcessFuses thermoplastic powderSpecsLaser: 25 or 100 Watt CO2Build layer: mmVat volume: LSize: W370 x D320 x H445 mm (W14.5 x D12.5 x H17.5”)Weight 1455 kgNot for office use.
45 Selective Layer Sintering (SLS) SLS System Process1. Start with an STL file of your 3-D CAD data.2. Enter the data into a Vanguard HS si2™ SLS® system.3. Spread a layer of powdered material. As the process begins, a precision roller mechanism automatically spreads a thin layer of powdered SLS material across the build platform.4. Sinter a cross-section of the CAD file. Using data from the STL file, a CO2 laser selectively draws a cross section of the object on the layer of powder. As the laser draws the cross section, it selectively "sinters" (heats and fuses) the powder creating a solid mass that represents one cross section of the part.5. Repeat. The system spreads and sinters layer after layer until the object is complete.6. Remove the part. Once the part is complete, remove it from the part build chamber and blow away any loose powder.7. Finish as desired. Use the part as is—or sand, anneal, coat, or paint it beforeusing it for its intended application.
46 Laminated Object Manufacturing LOM process laminates adhesive-backed part materials together to form prototypes.Created by Helisys CorporationSpecsLaser: 25 or 100 Watt CO2Build layer: mmVat volume: LSize: W370 x D320 x H445 mm (W14.5 x D12.5 x H17.5”)Weight 1455 kgNot for office use.
47 Laminated Object Manufacturing LOM process laminates adhesive-backed part materials together to form prototypes.Created by Helisys CorporationProcessPart material enters the machine as a roll of adhesive-coated sheet.Sheet is pulled through the machine and over build area.Heated platen rolls laminate the new layer over previous layers.Laser outlines the boundary of the desired cross section of the part.Material outside the boundary area of the part is crosshatched.Process continues as additional layers are added until part is done.Crosshatched part material serves as a support for undercut features on higher layers within the part.Manual “debugging”step is required to remove all of the small cubes of crosshatched .Polymer material is used
48 Z Corporation 3-D Printing Licensee of 3-D Printing process from MITProcessSmooth bed of starch and cellulose powder.Liquid binder (water based) is deposited over certain regions of the bed and bound together.Porous surface is closed with heat or withwax for office environment, orcyanocrylate resin for stronger part.
49 Z Corporation 3-D Printing Licensee of 3-D Printing process from MITSpecsBuild layer:Vat volume:Size:WeightNot for office use.
50 Fused Deposition Modeling Stratasys CorporationProcessExtrudes plastic bead through nozzle onto heated table.Builds layers of plastic part.Plastic can be ABS, PolyesterRemovable support structure is built under part for support.SpecsBuild layer:Vat volume:Size:WeightReady for office use.
51 Rapid Prototype at CSU Chico CSU Chico selected:Genisys XS 3-D PrinterPolyester material.$65K new; $45K reconditioned educational discount.Material cost is $6 per hour of build.Build rate size is 16g per hour.Maximum build size is 8” x 10” x 4”Number of parts built: 30 in 6 monthsMaintenance contract is $6,000 per year. (We declined)Genisys XS is smaller version of Stratasys FDM with ABS
52 Chap 19: Product Design Tools Product Development StrategiesConcurrent EngineeringDesign for ManufacturingDesign For AssemblyFailure Mode and Effects AnalysisQuality Function DeploymentGroup TechnologyReview Questions
53 Design for Manufacturing Reference: Design for Manufacturability Handbook, J. Bralla, McGraw Hill (1999)Cost for manufacturing item is dependent uponType of machining operation: use general purposeMaterial selection: use common materialsProduction quantities: higher quantities = lower costDesign changes: keep the number smallDimensional accuracy: keep tolerances generous where allowable
54 Design for Manufacturing CNC Factors versus manual methodsLead time is reducedComplex parts routinely producedOptimize process conditions for feed rates and speedsMath data taken right from computer to cutter
55 DFM Principles Use of standards Use of common components Design to specifications and tolerancesUse of manufacturing guidelines in the early stages of design that maximize quality of manufactured partMinimize the use of materialsMinimize the use of floor space in plantLocate all necessary components near functional operationUse of automated machining for minimal errors
56 DFM Design RulesSimplify the design & reduce the number of parts required.Design for low labor cost operations, e.g., punch hole rather than drill.Make specific notes on drawings and avoid generalized statements, e.g., polish this surface.Dimensions should be made from specific surfaces and not points in space. (Don’t dimension off a center of a circle)Minimize part weight whenever possible.Avoid sharp corners, use generous fillets and radii.Dimensions should be from one datum point rather than from a variety of points.Design part so that as many operations can be used without repositioning part
57 DFM Design RulesCast, molded, or stamped parts should be made with no stepped parting lines.Keep uniform wall thickness.Space holes so that they can be made in one operation without tooling weaknessFollow minimum draft requirements for cast or molded parts
58 DFM Quick References Surface finish from Various Processes Normal maximum surface roughness of common machined partsDimensional tolerances from machiningProcesses for flat surfacesProcesses for 2D contoured surfacesProcesses for hollow shapesCommonly used materials and metal working processesFormed metal parts
59 Material SelectionProper material selection is a major factor for a successful designed and manufactured product.Common engineering materialsCommon commercial forms of selected raw materialsUltimate tensile strength of selected materialsSpecific gravity (density) of selected materialsMelting point of selected materialsThermal conductivityCLTERelative Cost per unit weight and per unit volume
60 Ferrous Metals Hot-rolled steel Produced in a variety of cross sections and sizesRound bars from 6 to 250 mm in DSquare bars from 6 to 150mm per sideRounded corners squares 10 to 200 mm per sideFlat bars from 5 mm in thickness to 200 mm in widthAngles, channels, tees, zees and other sectionsOvals, half roundsSheets 1.5 mm (16guage) or thicker and platesCommon cross-sectional shapes for hot rolled steel
61 Hot-Rolled SteelProduced by passing a heated billet, bloom, or ingot of steel through a set of shaped rollers.Repeated passes, the rollers increase the length of the billet and change it to a cross section of specified shape and size.After rolling the shape is pickled (immersion in water, dilute sulfuric acid) to remove scale and then is oiledCharacteristicsProduced in a variety of cross sections and sizes, which the following are:Round bars from 6 (0.25in) to 250 mm in diameterSquare bars from 6 to 150 mm per sideRound-cornered squares, 10 to 200 mm per sideFlat bars from 5 mm in thickness and up to 200 mm in width (< 80 cm2 area)Angles, channels, tees with largest cross section dimension of 75 mmOvals, half rounds and other special cross sectionsSheets, 1.5 mm or thickerHot rolled steel is about 30% lower in price than cold-finish steel.HRS has more dimensional variation, rougher surface, mill scale, less straightness, less strength, and poorer machinability.
62 Design Recommendations Grade selection design criterion is to design for minimum strengthGrades with higher carbon content or low alloy content will provide lower cost parts than that can be made from plain low-carbon grades due to lighter sections can be used.Bending hot finished steel to help avoid fracturing material at bend:Bend line should be at right angles to grain direction from the rolling operation.Bend radius should be as generous as possible.To achieve a true surface from machining,Remove sufficient stock to get below the surface defects and irregularities.Include seams, scale, deviations from straightness or flatnessAISI (American Iron and Steel Institute)Machine allowance1.5mm per side for finished diameters or thicknesses from 40 to 75mm3.0mm per side for diameters or thicknesses over 75mm.
63 Grades For Further Processing MachiningImproved due to increased hardness from drawing operationSulfur, lead, and tellurium are added to improve machiningCold Finished Steel Bar Formulations with Good MachinabiltyStampingCold-rolled sheet steel is better for stamping than hot finishedAbsence of scale, greater uniformity of stock thickness, better formabilitySurface finish is superiorGrade of steel required depends upon the severity of stampingDeep drawn parts may require Al kiln or drawing qualityLower carbon content (<0.10% C) is better
64 Grades For Further Processing WeldingMaterial is fully weldable, especially low C, low-alloy steelDistortion is inherent to arc-welding, might be better with hot finish steelResistance weldament is great for cold-rolled steelPreferred material for arc and resistance welding is C < 0.35%BrazingBest accomplished with steels of lower C and alloy content.Ideal materials have C in range of 0.13 to 0.2% and Mn in 0.3 to 0.6%PlatingAll cold finish bars are suitable for platingAdditional polishing is required
65 Grades For Further Processing Heat TreatingCold working materials are heat treatable and widely used.Grades for heat treatment processesCarburizing: 8620, 4620, 1020, 1024, 9310Nitriding: 4140, 4340,8640Flame hardening: Medium carbon steels (0.35 – 0.70 %C)Cyaniding/carbonitriding: 1020, 1022, 1010Induction hardening: 1045,1038, 1144Other through-hardening: 4140, 4130PaintingAll cold finish bars are practical for paintingExtensive cleaning is not required
66 Design Recommendations Design approach is to specify a size and shape of material that minimize subsequent machiningUse as-drawn or as-rolled surfaces and dimensionsOther RulesUse simplest cross-sectional shape possible; avoid holes & groovesWith special shapes, undercuts and reentrant angles can be produced but $$Use standard rather than special shapes.Avoid sharp corners & use the largest filets & radii (min 0.08mm)Grooves width should be less deep than 1.5 times the width.Keep section thickness as constant as possible, avoid abrupt changes should be avoided to reduce local stress concentrationsSpecify the most easily formed materials and lowest costWith tubular sections, welded rather than seamless types are more economical, especially if drawing after welding without mandrel
67 Stainless Steel Definition and Applications Alloys that posses unusual resistance to attack by corrosive mediaApplications include aircraft, railway cars, trucks, trailers,...AISI developed a 3digit numbering system for stainless steels200 series: Austenitic- Iron-Cr-Ni-MnHardenable only by cold working and nonmagnetic300 series: Austenitic- Iron-Cr-NiGeneral purpose alloy is type 304 (S30400)400 series:Ferritic- Iron-Cr alloy are not hardenable by heat treatment or cold workingType 430 (S43000) is a general purpose alloyMartensitic- Iron-Cr alloys are hardenable by heat treatment and magneticType 410 (S41000) is a general purpose alloy
68 Stainless SteelCorrosion of steels can be slowed with addition of Cr and Ni.Stainless steels have chromium (up to 12%) and Ni (optional)ferritic stainless: 12% to 25% Cr and 0.1% to 0.35% Carbonferritic up to melting temp and thus can not form the hard martensitic steel.can be strengthened by work hardeningvery formable makes it good for jewelry, decorations, utensils, trimaustenitic stainless: 16% to 26% Cr, 6% to 23% Ni, <0.15% Carbonnonmagnetic and low strength % to 25% Cr and 0.1% to 0.35% Carbonmachinable and weldable, but not heat-treatableused for chemical processing equipment, food utensils, architectural itemsmartensitic stainless: 6% to 18% Cr, up to 2% Ni, and 0.1% to 1.5% Chardened by rapid cooling (quenching) from austenitic range.Corrosion resistance, low machinability/weldability used for knives, cutlery.Marging (high strength) steels: 18% to 25% Ni, 7% Co, with othersheated and air cooled cycle with cold rolledMachinable used for large structures, e.g., buildings, bridges, aircraft
69 Stainless Steel Cold forming 200 and 300 series: 400 series: Excellent bending characteristicsWithstand a free bend of 180° with a radius equal to ½ material thickness.As hardness increases, the bending becomes more restrictiveCan be stretched more than carbon steelExcellent stretch-forming characteristics, preferred 301 or 201 due to cold working induced high strength305 series exhibit excellent deep drawability400 series:Good bending characteristicsLess ductility than the 300 series with minimum radius equal to thickness.Cannot be stretched severely without thinning and fracturingCan be processed for deep drawability
70 Stainless Steel Design Recommendations Use least expensive stainlessUse rolled finishesUse thinnest gauge requiredUse thinner gauge continuously backedUse standard roll-formed sectionsUse simple sections for economy of formingUse concealed welds to eliminate refinishingUse stainless steel types that are especially suited to manufacturing processes, e.g., free machiningDimensional Factors Standard TolerancesProvided in the Steel Products Manual for Stainless SteelsComparable to to carbon and alloy steels
71 Chap 33: Lean Production Mass Production Toyota Production System Essential Components of Lean ProductionJust-in-timeReview Questions
72 Six SigmaA tool box of statistical tools used to reduce defects in a process down to 3.4 DPMO, % yield6 - a symbol used for standard deviationStandard deviation- measurement of variationTherefore by reducing variation you reduce value of 4321-18.104.22.168.22.214.171.124.28.1Standard DeviationsUnits of MeasureUSLProbability of a defect greater than USLZUSLLSLProbability of a defect less than LSLZLSLxƠ
73 Define Identify Project Customers & Stakeholders (internal/external) Critical to Quality (CTQ) parametersQuality Function Deployment (QFD)Process MappingFishbonePareto ChartFailure Modes and Effects Analysis (FMEA)Develop Team CharterBusiness CaseProposal of why the project should be doneExplanation of consequences from no actionDemonstration of possible financial or other business gainProblem StatementGoal StatementTeam Member ResponsibilitiesDefine The Process
74 DEFINE Customer Name: Problem Statement / Scope: Computer CompanyCustomer Stakeholders / roles:Tom Misage- Manager Product DevelopmentProject Owner:Jason LaroccoTeam members / roles:Darpan Parikh- Customer needs advisorSheri Zarkoob- Black Belt (Mentor)Jim Jones- Testing facilitatorNeil Gow- Technical advisorProblem Statement / Scope:Computer company is currently going through a material selection phase for up coming two-shot overmolding applications. They are experiencing low adhesion performance between a competitors PC and ABS. They would like to see the adhesion performance data between both PC-PC, and PC-PC/ABS.Project CTQ’sTo provide data demonstrating the adhesion properties in two-shot overmolding of PC-PC and PC-PC/ABS, in comparison to PC-ABS.Process MapBusiness Case / Benefits:This project will provide information needed to establish a material share shift. It will also show the advantages of using higher performance materials such as PC and PC/ABS, over ABS.CustomerOutputsProcessInputsSupplierComputer Comp.Part with good adhesion propertiesTwo-shot injection moldingMaterialMolding ConditionsDrying ConditionsGE PlasticsOur’s (New business, Core protection, etc.)Project is for a material share shift.PC- (500,000 lbs)($1/lb)(.55)= $275,000PC/ABS- (500,000 lbs)($1/lb)(.29)= $145,000Total IR= $420,000
75 Defining Specification Limits Stage: MeasureDefining Specification LimitsSet Spec. Limits Around MeasurementDefine what qualifies as a defect
76 Validating A Measurement System Stage: MeasureValidating A Measurement SystemGage R&R-Will show how much of your spec limit will be used up by the variation in your measurement systemIf measurement system is not valid you cannot correctly identify a defectTotal GR&R < 10% is desirable, < 30% acceptable30% Measurement Var.70% Process VariationTotal Spec LimitLSLUSL
77 Precision vs. Accuracy Stage: Measure Target Analogy Graphical View I. Precise, not accurate==True Value = Bull's EyeXbarGraphical ViewII. Accurate, not precise==True ValueXbar