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2.008 Design & Manufacturing

II

Spring 2004

Process PlanningCAD/CAM

Ref 1: CAD/CAM/CAE systems, by K.W. Lee, Addison-Wesley, 1999Ref. 2: Computer Aided Manufacturing, 2nd ed. by T.C. Chang, R. A. Wysk, and H-P Wang, Prentice Hall 1998Ref.3: Manufacturing: Design, Production, Automation and Integration, by B. Benhabib, Marcel Dekker, New York, 2003

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- Lab starts today.- Monday 2/16, President’s day, a Holiday- Tuesday 2/17, Monday’s lecture & lab group A- HW#1 due 2/11 (W)

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2D drafting v.s. digital Playdo

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Product Cycle

Analysis CAE

Synthesis CAD

Functional Requirements

Design Paramete

Design

Process Planning

CAM

Production

Quality control Packaging Shipping

Manufacturing

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3 day prototyping byCAD/CAM/CAE

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-Catia, Euclid, AutoCAD, ProEngineer Solidworks- MasterCAM, PowerMill- Moldflow, C-Flow, ANSYS, I-DEAS

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Geometric Modeling – HistoricalDevelopment

• 1960-1962: The first Graphical User Interface (GUI), Sketchpad, developed at MIT.• 1964-1965: DAC-1 by GM and CADAM by Lockheed.• 1970-1980: Various systems that ran on proprietary hardware – only a handful survived beyond the 1990s.• 1990-2000: Pro/Engineer, Solid Works and I-DEAS run on PC platforms.

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3D object geometric modeling

Wireframe Surface modeling

Solid modeling ?2.008 MIT-S. Kim

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Wire frame

■ List of ■ Curve equations ■ Coordinates of points■ Connectivity■ Easy method■ Ambiguity■ No mass, no surface

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Wireframe

Conversion to surface

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Surface Modeler

MIT Stata Center

Guggenheim, Bilbao2.008 MIT-S. Kim

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Surface Modeler

■ Wireframe data +■ Surfaces ■ Connectivity, Adjacency ■ Interpolation of points, curve nets ■ Translation or sweeping of curves■ Fits to complex free formed surfaces ■ Visual, aesthetic design ■ NC code generation

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Solid Modeler

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Solid modeler

■ Has a closed volume. ■ Knows “in” or “out”■ Has a mass and inertia.■ Huge input data, maths.■ User friendliness is a must. ■ Primitives ■ +/- by Boolean operations ■ Sweeping, rounding, lifting■ Hybrid (solid + Surface, CSG + BREP, Parametric + explicit)

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Primitives

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Block Cylinder

Wedge Sphere

Cone TorusTranslation sweep Rotation sweep

Tool

Then■ Add/subtract■ Move■ Modify

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Boolean operations

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Acceptable Operation?

union

intersection

difference

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By sweeping, skinning surfaces

translational

rotational

skinning

Director curve

Swept solid

Axis of revolution

Swept solid

Section 2

Trajectory

Generator surface

Generator surface

Section 1

Section 3

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By modifying existing shapes

Edge rounding Filleting

Lifting

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Constructive Solid Geometry

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• CSG modelers allow designers to combine a set of primitives through Boolean operations:

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Boundary Representation

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Polyhedron

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Feature-based Design

Open slotThrough hole

Chamfering Hole

Pocket fillet

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Machining Features

Blind hole Through hole Pocket

Blind slot Through slot Radius

Open slot Shoulder Angle

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Counterbore

Through tap

Counterbore

Blind tap

Countersink Countersink

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Parametric modeling

■ Feature-based■ Dimension data■ Geometric constraints

■ Assembly modeling■ No standard of data exchange■ IGES (Initial Graphic Exchnage Standards)

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Geometric Modeling - Curves

Least-square fit

spline fit

Bezier Curve

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Geometric Modeling - Curves

B-spline : more flexibility than Bezier

NURB (non-uniform rational B-spline): Combine all

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Geometric Modeling – Free form Surface

NURB (non-uniform rational B-spline): Combine all

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Process Planning (CAPP)

■ “Act of preparing detailed work instructions to machine or assemble a part or parts” –Chang, Wysk, Wang■ Sequence of manufacturing processes and/or assembly operations■ Operation sheet

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■ Have customers eat well■ Customers serviced well ■ speed ■ customization■ Affordable tab■ $$$ - Profit

Restaurant Owner

What’s the difference between McDonald v.s. Maison Robert?

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Super bowl 2004

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Play bookPlay number

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Image removed due to copyright considerations.

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Process Planning

■ Manual Approach

■ Comupter Aided Process Planning (CAPP) ■ Variant Approach: Group Technology

■ Generative Approach: features, tolerances

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Example 1 by manual approach

Setup 1Chuck the workpieceTurn S3 to a 100mm diameterFace S1Core drill S2Counter bore S4, S5

Setup 2Chuck the workpiece on S3Turn S6 to 50 mm diameterUndercut the neckThread S6Face S7

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Group Technology

Zip code: 02139Product Classification

Injection molding

Aluminum diecasting

Sheet metal fabrication

Inflammable plastic Regular

plastic

With ribs

Without ribs

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Vuoso-Praha coding system

4 digit system-Kind-Class-Group-Material

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Coding system (continued)

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3 3 7 2

Alloy steel

Threaded, hole not in axis

Max.φ40-80

Rotational through hole

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Feature-based CAPP

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Open slotThrough hole

Chamfering Hole

Pocket fillet

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Numerical Control

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Spindle speed selector

Feed change gear box

Compound rest and

slide (swivels)

Apron BedLead screw

Feed rod

Headstock

Spindle

Ways

Tool postCross slide

Cartridge (saddle)Center

Tailstock quill

TailstocklTool

Worktable

5-axis millingLathe - conventional

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Motion Control

■ Point to point, Continuous■ Interpolation■ Encoders, tachometers and interferometers provide high-precision displacement and velocity feedback:

Controller Amplifier Actuator Worktable

Displacement sensor

⊕⊕Input from interpolator

Velocity Sensor

+- -

+

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Adaptable Control

- sense cutting force, torque, temperature, etc.- tool wear, tool breakage

CNC controller

Adaptive controller

Machine tool

Sensors

Signal processing

Programmed dimensional data

feed rate , spindle speed

Updated spindle speed,

feed rate

Constraints

Strategy

Performance index

Displacement/velocity feedback

Displacement commands

Spindle-speed command

Torque

Vibration

Temperature

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NC milling machine

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Code function Explanation

g00 Point to point, positioning Use with combination point-to-point/contouring systems for in-

dicating positioning operation.

g01 Linear interpolation

(normal dimensions)

A mode of contouring control used of generating a slope or

Straight cut, where the incremental dimensions are normal (i.e.,

Input resolution is as specified).

g02 Circular interpolation are CW(normal dimensions)

A mode of contouring control that produces an arc of a circle by

The coordinated motion of two axes. The curvature of the path

(clockwise=g02, or counterclockwise=g03) is determined

when viewing the plane of motion in the negative direction of

The perpendicular axis. The distances to the arc center (I, j, k) are

“normal dimensions.”

g03 Circular interpolation are CCW

(normal dimensions)

g04 Dwell A programmed (or established) time delay, during which there is

No machine motion. Its duration is adjusted elsewhere, usually by

The f word. In this case dimension words should be set at zero.

g05 Hold Machine motion stopped until terminated by an operator or inter-

Lock action.

g06 Parabolic interpolation

(normal dimensions)

A mode of contouring control that uses the information contained

In successive blocks to produce a segment of a parabola.

g08 Acceleration The feed rate (axes’ velocity) increases smoothly (usually expo-

nentially) to the programmed rate, which is noted later in the

Same block.

g09 Deceleration The feed rate decreases (usually exponentially) to a fixed percent

Of the programmed feed rate in the deceleration block.

g10 Linear interpolation

Long dimensions = LD)

Similar to g01, except that all dimensions are multiplied by 10.

For example, a programmed dimension of 9874 will produce a

travel of 98740 basic lenth-units. (used only with incremental

Programming.)

g11 Linear interpolation

(short dimensions = SD)

As g01, but dividing all dimensions by 10 (e.g., 987 units for the

Example above).

Source : Y.Korenl, Computer Control of Manufacturing Systems, McGraw-Hill, 1983.

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Analogy: Word document ←→ Part

Embodiment Plan execution Translate plan Execute plan

Rough draft

User input

Formatting Pdf

Post script

Machine (i.e.

printer)

Word processor

Print set up

File exchange

Generate tangible

Sketch/idea

User input

Blueprint/ CAD

Feature generation

CAM

Process planning

G Code

File exchange

Machine (i.e. mill)

Generate tangible

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Tool path generation

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g-code

■ N0027 G01 X175.25 Y325.00 Z136.50 F125 S800T1712 M03 M08

Statement Number 27 (N0027) a linear-interpolation motion(G01) to a position defined by (X175.25 Y325.00 Z136.50),with a feed rate of 125 mm/min (F125), and a spindle speed of800 rpm (S800), using a tool Number 1712 (T1712), performinga c/w turn of the spindle (M03), and having the coolant on(M08).

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N001 G91N002 G71N003 G00 X0.0 Y0.0 Z40.0 T01, M06

N004 G01 X75.0 Y0.0 Z-40.0 F950 S717 M03N005 G01 Z10.0 F350 M08

N006 G01 X110.0N007 G01 Y70.0

N008 G01 X-40.86N009 G02 X-28.28 Y0.0 I14.14 J5.0

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Manual Programming

Start point

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Cutter Location, P4

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APT –Automatic Programming Tool

■ APT developed at MIT in 1956.

■ APT II, APT III

■ Identification statement ■ Geometric Statements ■ Motion statement ■ Post-processor statement ■ Auxiliary statement

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Geometry statements

Points

P1 = POINT/X,Y,Z

P2 = POINT/L1,L1 ; intersection of two lines already defined

P3 = POINT/CENTER,C1 ; center of a circle

P4 = POINT/YLARGE, INTOF, L1, C1

; intersection of a line and a circle, one with a

larger y coordinate

P5 = POINT/XLARGE, INTOF, L1, CI

; intersection of a line and a circle, one with a

larger x coordinate

P6 = POINT/YLARGE, INTOF, C1, C2

; intersection of two circles, one with a larger y

coordinate

P7 = POINT/XLARGE, INTOF, C1, C2

; intersection of two circles, one with a larger x

coordinate

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APT statements (cont.)

Lines Circles

degree

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Motion statement

• P to P-motion: GOTO/Point_Name; Go to Point Point_Name. GODLTA/ΔX, ΔY, ΔZ; Move incrementally.• CP-motion:

/ Drive_Surface,, Part Surface Check_

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Ending locations

TO ON PAST

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Example

FROM/SP

GO/TO, L1, TO, PS, ON L4

GORGT/L1, PAST, L2

GOLFT/L2, PAST, L3

GOLFT/L3, PAST , C1

GOLFT/C1, PAST, L3

GOLFT/L3, PAST, L4

GOLFT/L4, PAST, L1

GOTO/SP

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Tool path interval and Cusp

ContourNon-lace

LaceParallel

Cusp

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Contour

Non-lace

Parallel paths

Path interval

Cusp height

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Machined Surface

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Machined SurfaceW = “Waviness”

R = “Roughness”

Waviness Height

Flaw

Roughness Height

Lay direction

R. widthW. width R. Width cutoff

W. height

R. Height (arithmetical

average)

Lay

R. width

W. width

R. Width cutoff

Rough 1000

Medium 500

Avg. 125

Better than Avg. 63

Fine 32

Very fine 16

Extremely fine 8

µ inch

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Cutter Contact, Gouge

Contact Point

Gouging

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CC-point

CL-point

Location of gouging

Neighboring surface

Part surface