A Brief Introduction to Engineering Graphics This set of slides is designed to be read as a graphics resource. Can take excerpts for presentations. Bring: fastener/tools examples,, big real engineering drawing, an object to spin, LEGOs for tolerance section, collection of shafts and holes for tolerancing, See Notes pages 10/2011 Add: Get sample of a real engg dwg from Toro, Tennant. Along with photos of the part. 10/2009 Add: Types of drawings (detail, assembly, exploded view assembly, BOM; see Meyer et al., Technical Graphics, Chapter 9). For required text, consider Technical Graphics, Meyer et al. See lecture notes for OSU course http://www.feh.osu.edu/materials/autumn_2008.htm 10/2007 Add: tolerance stackup; show a part w/ pin mating with a hole…and all the things that could go wrong; offset section. Add features sections. Add material on hole and threading types. Intro: Eng graphics important for meche students to know…but not intellectually demanding. Basics here, details in any eng graphics text. Will Durfee & Tim Kowalewski Department of Mechanical Engineering University of Minnesota

Opening comments Engineering graphics is the method for documenting a design Mechanical engineering students must be familiar with standards of engineering graphics as it is expected in industry This set of slides introduces some of the basics, but is not comprehensive For more, see Engineering Graphics section on the Resources page of the course ME2011 website Any engineering graphics textbook

Documenting a part requires... 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE 5. FINISH To fully document a part requires all of these What are examples?

Engineering drawings Universal language Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy CAD packages make formal drawing easy…if you follow the conventions The machinist will laugh at you behind your back if you show up with a non-standard drawing Graphics is all about how to transmit this info using the conventional language. Buck these conventions at your peril…The machinist will laugh at you and your boss will relegate you to fetching coffee CAD packages automate this. Nobody uses a T-square and pencil any more

Multiview drawings Top Right Front TOP RIGHT SIDE FRONT Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details. RIGHT SIDE FRONT “3rd angle projection”

Multiview drawings Top Right Front TOP RIGHT SIDE FRONT Views MUST align Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details. RIGHT SIDE FRONT “3rd angle projection”

Multiview drawings Top Right Front TOP RIGHT SIDE FRONT Views MUST align Views must line up Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”. Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”. See Betroline for details. RIGHT SIDE FRONT Rotate the part to the right (Europe) “3rd angle projection” You walk around part to the right (US)

The Glass Box: Bertoline, Engineering Graphics

Alignment & Orientation are preserved… Bertoline, Engineering Graphics

Six Principle views: obey layout Great way to get relegated to making coffee.

Basic lines (the “alphabet of lines”) Object line Hidden line Center line The “alphabet of lines” ANSI standards for these Dimension line

HIDDEN LINES Show internal features or holes

CENTER LINES Long-short dashed lines showing lines of symmetry and axes of cylinders and holes

Interpreting Center Lines Long-short dashed lines showing lines of symmetry and axes of cylinders and holes Enough Info? Enough Info?

COULD BE THIS... Be careful when interpreting center lines. Do not assume axial symmetry

Centerlines imply symmetry, OR THIS Centerlines imply symmetry, NOT revolution per se

HERE, ONLY 2 VIEWS NEEDED (Correct drawing) If circularly symmetric, drawing should tell you. If it is circularly symmetric, only need 2 views.

Find The Mistakes! AT least 8 mistakes

Find The Mistakes! Top view not on top; inside circle in top view not solid Bottom view not on bottom Hidden line used instead of center line Centerline in right view does not extend beyond part; Right view not aligned correctly More views than necessary No additional info like dimensions, materials, etc.

FRONT Here’s a 3-D object that has to be represented in a set of 2-D drawings. One must be careful about the conversion.

FRONT 5 mistakes CORRECT DRAWING FIND THE MISTAKES!

CORRECT DRAWING

SECTIONS A Use sections for showing complex internal shapes where hidden lines would be confusing Slice through the object (the cutting plane) Hatch cut material (exposed surfaces) <…add offset sections…> YES NO

Working with person sitting next to you copy this and Now draw this, How many disagree? Working with person sitting next to you copy this and draw the TOP VIEW

Working with person sitting next to you copy this and Possible Geometries Now draw this, How many disagree? Working with person sitting next to you copy this and draw the TOP VIEW

Working with person sitting next to you, sketch the Section View How many disagree? Bring samples up to front Working with person sitting next to you, sketch the Section View

OK OK Correct Section Views How many disagree? Bring samples up to front Correct Section Views

Working with person sitting next to you, Find the MISTAKES Wrong Wrong How many disagree? Bring samples up to front Working with person sitting next to you, Find the MISTAKES

Working with person sitting next to you, sketch the Section View How many disagree? Bring samples up to front Working with person sitting next to you, sketch the Section View

REVOLVED SECTION Preferred “True” section For revolved sections, hole pattern symmetric (convention) Preferred “True” section

DIMENSIONING 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE AND FINISH Reference: Bertoline, Chapter 4

Dimensioning Conventions exist for choice and placement Not too many and not too few Never should measure off drawing with a ruler 5 5 3 Adds *size* to object W/ CAD, natural part of part creation. W/ traditional drafting, added later Conventions for CHOICE, PLACEMENT Leave nothing to chance. Machinist should not be taking dimensions off your dwg with a ruler 3

Under/Over Dimensioning 3 5 3 5 2 Leave nothing to chance. Do not over dimension, do not under dimension

Dimensioning rules: …find the mistakes. 3 5 3 5 2 Leave nothing to chance. Do not over dimension, do not under dimension

Dimensioning guidelines 3 5 1. Don’t overdefine or underdefine the object. [MOST IMPORTANT] 2. Dimension to the visible contour or shape of the feature / Don’t dimension to hidden lines. 4. Don’t dimension to object lines (model edges), use extension lines. 5. Don’t overlap a dimension and the model. Place dimensions away from the model’s surface. 6. Don’t cross extension lines if possible. 7. Group dimensions when possible unless it become difficult to read. 8. Place dimensions on the side of the view were adjacent views exist (for easy referencing). Leave nothing to chance. Do not over dimension, do not under dimension 3 5 2

Design Detail ½” thick aluminum block Which is more expensive: A or B and why? 6.0 A 6.0 B B is not standard stock, way more expensive. In same vein, use standard fasteners 4.0 4.1

www.mcmaster.com Browse to materials > metals > aluminum > bar/sheet stock > 6061 > .50” thick > 6” long.

Dimensioning Choices & Design Intent If change width of block to 8, what happens to the hole location? A B 6 2 6 4 2 If change width to 8 inches, does hole move? Think *carefully* about design intent before picking a dimensioning scheme. With CAD, wrong dimensioning scheme is a major pain to correct.

Placement conventions Extension and dimension lines thinner than object lines Dimensions legible but not dominate See Leuptow pp. 52-55 for conventions

Lettering: 1 or 2 directions only OK OK NO

Extension Lines No gaps when crossing object lines to dimension internal features OK to cross extension lines Pro/E automates this

All on one side YES NO

Dimensioning Rounds Place dimension on view that shows the circle 0.25 0.75 R 0.125 Put dimension on view that shows the circle. Show diameter, unless other considerations dictate radius Place dimension on view that shows the circle Show diameter rather than radius

Highlight holes and notes

TOLERANCES Reference: Bertoline, Chapter 4. Strongly suggest reading this chapter. Tolerances matter because it is rare that you can sit there and custom fit parts. For modern assembly, every instance of Part A must fit into every instance of Part B or else you will have a problem assembling. It is impossible to make things to an exact dimension. All mfg processes will give you a range about the nominal dimension. The more you pay, the tighter the range. For example, the outside dimensions of a block may not matter so much (tol = 0.1), but the diameter of the hole in that block matters a lot because it receives a press fit bearing (tol = tenths) A ½ inch hole made on an ordinary drill press gives you a hole in the range 0.496 to 0.504 (+/- 0.004). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate. Moral: Go with the loosest tolerance you can. www.efunda.com/processes/machining/drill.cfm www.efunda.com/processes/machining/drill_press.cfm

Tolerances Matter because parts cannot be made to an exact dimension Must specify dimension tolerance so that every part A fits every part B Higher tolerance = higher cost A ½ inch hole made on an ordinary drill press gives you a hole in the range 0.496 to 0.504 (+/- 0.004). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate.

½ inch drill bit: +/- .0040 ½ inch reamer: +.0003, -.0000 For low tolerance, drill undersize and follow with reamer ½ inch reamer: +.0003, -.0000

LEGOS ! ABS plastic You can combine six 8-stud bricks of the same color 102,981,500 different ways 91% of all households with children in Denmark own LEGO products During the period 1949-1990, 110,000,000,000 (110 billion) LEGO elements were molded Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group. Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. Dimension tolerance of mold is 0.005 mm (0.0002 inch)! Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group. LEGO bricks are one of the most demanding ABS applications Mold tolerance is five thousandths of a millimeter (0.005 mm) or two tenths (0.0002 in.) in English units Most molds are held to 0.001 in. (one thou) in. Lego dimensions are five times more accurate. Molds for LEGO pieces are made in a factory in Germany and two factories in Switzerland Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. ABS resin not only offers (1) tight dimensional stability required for molding to narrow tolerances, (2) flow rate, (3) impact resistance, (4) surface appearance, (5) anti-static properties, (6) no long-term creep, (7) nonflammable, (8) non-toxic. 9.6 1.7 8 D 5

Representing tolerances

Tolerance stack-up ? 14.75 15.25 3.0 ± .05 5 high stack What is min and max height of stack? 14.75 15.25 ? 3.0 ± .05 5 high stack

Tolerance Stacking What’s the tolerance (+/-) on dimension x? Microphone hot-potato What’s the tolerance (+/-) on dimension x? Ans: +/- 0.3

Chain or Baseline Dimensioning? … You decide Choice of dimensions from “Design Intent” Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum. Watch out for tolerance stackup

Chain or Baseline Dimensioning Choice of dimensions from “Design Intent” Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum. Watch out for tolerance stackup

.623 .626 .622 .625 Holes and shafts hole shaft Will all shafts fit into all holes? What is maximum clearance? hole shaft .626 .625 .623 .622 Will this shaft always fit in this hole? What is max/min clearance? .623 .622 .626 .625

ANSI standards for shaft & holes Clearance Shaft smaller than hole for all shafts and holes Interference Shaft larger than hole for all shafts and holes Transition Smallest shaft fits in largest hole Running/Sliding RC1 (fit together, no play) to RC9 (fit loosely) Force/shrink FN1 (light drive and pressure) to FN5 (high stresses and pressures) …and others Like Locational, etc. “How loose should it be?” Much has been worked out in past. Use it. Consult machinery handbook or drafting handbook for details Basic hole Use nominal size of hole as starting point Basic shaft Use nominal size of shaft as starting point

Preferred Fit Example…

“Basic Hole” Tolerancing Example 1.0000 + .0012 - .0000 - .0008 - .0016 Smallest hole & largest shaft: 1.0000 – 0.9992 = 0.0008 clearance Largest hole, smallest shaft 1.0012 – 0.9984 = 0.0028 clearance Drawing shows 1 in. nominal, ANSI RC4 clearance fit “Basic Hole” means smallest possible hole = nominal, then size shaft for clearance RC4 clearance = [0.0008, 0.0028] = [smallest hole-largest shaft, largest hole - smallest shaft]

Title block information for tolerance ALL DIMENSIONS IN INCHES HOLD ALL DIMENSIONS TO ± 0.010 UNLESS SPECIFIED 4.250 = good to +/- .001 4.25 = good to +/- .01 4.3 = good to +/- .1 Dimension Tolerance X.X ± 0.1 X.XX ± 0.05 X.XXX ± 0.001

{ Design Detail Bent aluminum sheet, 1/16” thick A or B: Which is more expensive and why? A B 4.0 + - 0.003 0.030 { A. Punch shape & holes, then bend ===> cheap Press = $100/hr, 200 parts/hr B. Bend then drill ==> expensive $0.50 per hole Work with mfg (even for prototype) to reduce cost

Tolerance vs. Cost $ $$ $$$$ 1.00 ±.075 1.00 ±.05 1.000 ±.005 1.0000 ±.00005

Manufacturing Tolerances

Geometric Dimensioning and Tolerancing (GD&T)

Traditional tolerancing is ambiguous 3.000 ±.005 1.000 ±.005 ? ? Can left side be .995 and right side be 1.005? Can part be .995 at edges and 1.005 in middle and thus not sit flat on a table?

Ambiguity… + + Square deviation Circular deviation .25 ± .01 Hole location defines an error *square*, but we really want to allow a *circular* deviation Solved by the “Geometric Dimensioning and Tolerancing System” that allows you to specify design intent. Based on showing nominal dimensions augmented with a notation system for showing design intent for tolerances. More?: See Chapter 6 in Lueptow + + Square deviation Circular deviation

Geometric Dimensioning and Tolerancing .125 +/- .002 .01 .25 Ideal position of hole is marked with box; the “true-position dimension”; no +/- notation. Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01 Ideal position of hole. .25, is marked with box and no +/- notation. Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01

Geometric Dimensioning and Tolerancing .25

GD&T Resources https://sites.google.com/a/u mn.edu/me2011/resources ME2011 website: https://sites.google.com/a/u mn.edu/me2011/resources Efunda tutorial: http://www.efunda.com/de signstandards/gdt

What they are and how to indicate on a drawing Threaded Fasteners What they are and how to indicate on a drawing

Threaded Fasteners Holes Threads Threaded fasteners Bertoline references: Holes: Fig. 4.55, Sec. 8.3, Fig. 8.32, 8.37 Threads: Sect. 9.3, Fig. 9.33, 9.34 Threaded fasteners: Sect. 9.3-9.4 Fillets, rounds, chamfers: Sect. 9.6, Fig. 9.52 Bearings: Sect 9.7.4 Gears: Sect 9.7.1, Fig. 9.58-9.60

Holes 19 DRILL – 0.75 DEEP or O .166 . 75 DEPTH 0.75 REF Pix from www.mcmaster.com unless noted

Thru holes 19 DRILL – THRU or O .166

Threads http://www.machinist.org/harvard_cotreau/mshop6.html http://www.americanfastener.com/technical/thread_terminology.asp

Threaded Fasteners (screws, bolts) Specify diameter, thread, length, head 1/4" DIA 1/4-20 x 1, RHMS 20 THREADS PER INCH 1" LONG ROUND HEAD MACHINE SCREW

Common screw thread sizes Unified Thread Standard 2-56 4-40 6-32 8-32 10-24 1/4-20 3/8-16 1/2-13 5/8-11 3/4-10 DIA. = (N*.013) + .060 (inches)

Alternate Thread Callout

Head shapes Cap screw Pan Socket head cap screw (SHCS) Set screw Flat Round

Driving a fastener Slotted Phillips Torx Hex cap Hex head (Allen head)

McMaster-Carr www.mcmaster.com

Name the Fastener: Socket Head Cap Screws

Name the Fastener: Socket Head Cap Screw Socket Head Cap Screw with counterbore Socket Head Cap Screws

Socket Head Cap Screw with counterbore Phillips Flat Head Screw with countersink

Set Screw Countersunk, Phillips Flat head

Convention for screws “SCHEMATIC” “SIMPLIFIED”

Convention for threaded holes 6-32 THRU TOP FRONT FRONT SECTION

Blind threaded holes 1/2 – 13 x 1.325 DEEP .4219 1.50 1/2 – 13 1.325 .4219 1.50 1/2 – 13 1.325 THREAD DEPTH DRILL DEPTH

Countersunk holes .562 – 82O CSK, 1.125 .562 1.125 x 82O

Counterbored holes 19 DRILL – 29 CBORE, 14 DEEP 19 29 14 C-BORE DEPTH

Other Items for Drawings

Leaders & notes To annotate dwg with notes useful to machinist NOTE B Can also refer to a notes section at bottom of page NOTE B

TITLE BLOCKS Basic Optional Follow your company standards Title Name Date Units Optional Company name, sheet number, scale, tolerances, material, finish.... Follow your company standards

ALL DIMENSIONS IN INCHES Basic Title Name Date Optional Company name, sheet number, scale, tolerances, material, finish.... Follow ANSI or company standards For Pro/E, what are your units? A basic title block MY PART W. DURFEE 10/2/2014 ALL DIMENSIONS IN INCHES

A title block with more information

A title block using a company template www.classic-components.co.uk

Production Drawings Many types of drawings can be produced from the CAD database ASSEMBLY SKETCHES MODEL SKETCHES SKETCHES DETAIL DETAIL DETAIL DETAIL DETAIL BOM MANUALS MFG PROCESS