CS 294-3: RAPID PROTOTYPING
Lecture #7 -- Oct. 13, 2000.

More on Advanced Modes of QuickSlice

• Review of your latest designs.
• The semantic model of SSL.
  -- Your insights on how the orientation, nesting, coloring of SSL contours affects the road-fill pattern.

Course overview

• 2 weeks of introduction to SFF and part design (using symmetry ...)
• 4 weeks of exposure to the FDM machine and QuickSlice (getting ever deeper into SSL ...)
  ==> You should now be able to make almost any conceivable feasible part on the FDM machine.
  - - Plan to do one really nifty part that will serve as a show-piece for you and for 294-3.
• 3-4 weeks of rapid prototyping by machining (3-axis milling, WebCAD, CyberCut ...)
• 2-3 weeks of hands-on experience with another SFF machine (3D printing, perhaps wax deposition ...)
  - - You will do a second sophisiticated "project" part.

NC Machining -- 3-Axis Milling

The Physical / Engineering View

• The sweep of the tool removes material from the stock.
• The sweep of the machine spindle and the tool assembly (i.e. cutting tool and tool holder) must not interfere with the current part geometry.
• The sweep of the tool and its holder must not interfere with the fixturing devices.
• The milling task should be accomplished with a minimum number of re-fixturing of the part and of tool changes.
• The tool must be guided along a geometrical path so that it removes material only with its cutting edges.
• The tool must be guided in time so that it removes material only at an acceptable rate per unit time.
• All this takes a considerable amount of planning !

"Macroplanning"

• Decompose volume to be removed into simpler geometrical entities;
• Determine a good sequencing of the operations that will minimize re-fixturing;
• Determine a good grouping of setups and tools that will minimize tool changes.

"Microplanning"

• Find a strategy to remove these simpler volumes with complicated sweeps of one or more different cutting tools;
• Avoid tool collisions between features (volumes to be removed) and fixtures;
• Select appropriate parameters for table motion speed (feeds) and spindle rotation speed (cutting speed).

"Tool-path Planning"

• Motion planning for the individual paths;
• Generates the actual code that will be fed to the machine tool.

Abstracted, Conceptual View of Milling

• Web Designer's Simplified View:
  - - Only one basic operation: removal of pockets of constant depth;
  - - (Drilling a cylindrical hole is a particularly simple pocket.)
• Limiting Factors:
  - - Sharpness of inside corner radii;
  - - Depth of holes -- as afunction of diameter;
  - - Depth of pockets -- as a function of smallest dimensions;
  - - Proximities of holes and pockets;
  - - Proximity of holes and pockets to stock boundaries.

Homework Assignment:

POSTPONED: Make a thin-walled part

• Test the emerging voronoi-based contour software by Jordan Smith by trying to make a thin-walled part.

A#7: Thinking about Part Designs:

• Start planning a part that that you would like to make next week with WebCAD and 3-axis milling.
• Start thinking about a "show-off" FDM that will demonstrate your mastery of the FDM machine.
  Some ideas that come to mind, stimulated by work that some of you have done recently:
  - - A complex regular polyhedral framework, possibly a projection of a 4-D regular polytope (Hairong).
  - - A large threaded bolt with matching nut or sleeve, both executed as thinwalled parts using booleans (Tien).
  - - A drinking mug or teapot in the topology of a Klein-bottle (Jane).
  Hopefully these examples will trigger further creative thoughts.