CAD/CAM Unit 79

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

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

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

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

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

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

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

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.

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.

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.

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

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

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

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

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

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

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"

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

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