1. CAD/CAM
Unit 79

2. Objectives Define CAD and CAM Explain the purposes of solid modeling
Know the differences between Cadworthy and Camworthy
Describe process chaining and list the steps in the process
State the purposes of pocket, contour, drill, and surface toolpaths

3. CAD/CAM
Marriage of computerized forms of drafting/design and manufacturing
Computer graphics is CAD part
NC is CAM part
Covers creation of part from initial design to finish-machines part produced on numerically controlled machine tool
Progressed quickly in past 10 years
Amount of math increasingly exponential

4. CAD Development Primarily centered around
Modeling techniques to present conventional drawings
Production for solid models
Should provide means for designer to do job faster and more accurately
Should be closely integrated with techniques for modeling shape and structure of design

5. Systems Presently In Use
No longer consist of only 2D or 3D wireframe units and simple toolpaths
Software
enables manufacturers to produce parts faster, more economically and more consistent quality
Manufacturers continually revising modeling technology, improving machining capabilities and automated processes

6. Solid Modeling Rapidly becoming industry-modeling standard
Solids provide more accurate picture of where material lies
Wireframe data is less easy to understand
Geometric model outlining edges
Lines in back of object show through from front

7. Solid Modeling and CAD/CAM
PC-based solid modeling make it available to smaller machine shops
Increases adaptability
Gives shop capability to use data it wants
Wireframe taken from solid
Surfaces taken from solid
Solid itself
Gives shop more choices for programming

8. How CAD/CAM Works "Art to Part"
Step one: Inputting the geometry
Creating geometry in CAD
Imported via translators from another CAD system
IGES, DXF, ASCII, STL, VDA, SAT, Parosol
System imported in 2D, 3D wirefrace, 3D surfaces or solids
Import geometry in form of XYZ coordinates
Points converted to splines

9. Cadworthy Geometry Created from a drafting point of view
All details and edges of part represented
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. Camworthy Drawing Purpose strictly for CNC machine use
Contains fewer lines – only lines needed to create toolpath included
Make toolpath creation easier and less confusing
Sometimes geometry modified to control toolpath
Applies to 2D, wireframe, surfaces
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. Camworthy Drawing
To make camworthy drawing from cadworthy drawing, geometry edited so all endpoints are connected and no gap remains
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12. Defining Where the Cut Takes Place
After geometry, next step is selecting order in which geometry to be machined
Process chaining (where cuts are to take place)
Geometry evaluated as to appropriate toolpath
Many different toolpath types in various CAD/CAM softwares

13. How the Cut Takes Place Next step after toolpath assigned to geometry
Parameters used to identify
What tool to use
Size of tool
Speeds, feeds and depth of cuts (up and down)
Width of cut (side to side)
Cutter compensation

14. Backplotting
Process of displaying toolpath once the parameters have been set
Displayed
Showing centerlines
Solid model with material removed or being removed
Onscreen visualization helps to catch errors prior to actual cutting of part

15. Converting the Toolpath to G- and M-Codes
Next step
Called post processing
Converts toolpath to NC file customized for a particular machine control
Possible to process one toolpath through several different post processors
Run on several different brands of controls

16. Downloading Program to Machine
Next step in process
Download G- and M-codes into NC controller
Via direct cable connection if networked
Via floppy disk
Usually programs too big

17. Setting Up the Machine
Once loaded, part must be securely held in holding fixture and machine set up
Set home position on machine at same point as program home position or origin
Standard for location of point is with X and Y zero positions at part's lower left corner and Z zero on top surface
If circular part, X and Y zero is center an Z is top
Tip of tools or tool zero position must be set
Set size and tool number of all tools used

18. Final Step: Running the Part
After machine setup, time to press cycle start button
Begin machining process
When finished machining, CAD/CAM process completed
"art to part"

19. Toolpaths Pocket toolpath Contour toolpath Drill toolpath
Purpose to remove material from cavity in stock
Material left standing in pocket called islands
Contour toolpath
Purpose to cut along line/surface to form shape
Drill toolpath
Purpose to create holes and/or enlarge them
Surface toolpath
Purpose to remove material from part designed as surface or solid

20. Functions Constant Volume Removal Optimize Entire Shop Smart Cornering
Feedrate optimization carries feedrate based on volume of material being removed
Can set upper and lower limits to match machine
Optimize Entire Shop
Feedrate optimization helps find each machine tool's maximum efficiency zone
Smart Cornering
Adjusts feedrate around corners and small radii