Lecture 9

Design Realization
lecture 9
John Canny
Last Time
 More on kinematics and IK.
 Some concepts from dynamics.
This time: Manufacturing & Materials
 Manufacturing is undergoing a revolution:
 Traditional methods:
Casting, molding, fusing, slumping
Milling, lathing (non CNC-versions)
Rolling, extrusion
 Shape is “write-once” (not programmable) in
these methods.
Next-wave Manufacturing
 Reprogramming shape:
 CNC machining:
A computer outputs a path for a
cutting tool to create a specified
 Not new, but now inexpensive,
 Plastics, wood, metal, glass.
Flashcut 2000, XYZ-axes, 9x7x6.5”, $2895
 Milling involves a moving XYZ head that cuts
into the workpiece:
 Bits can achieve different
 Lathes cut circularly symmetric parts.
 Shafts, furniture, fasteners,… lenses.
 Can also do grinding and polishing.
Milling Example
 CNC milling example
(Deskproto web site)
 Finish is quite smooth
 ballnose cutting tool.
 Lots of waste, but can
be recycled!
Next-wave Manufacturing
 PC-boards:
 Created with CAD tools.
 Photographic reproduction:
• Low cost in volume.
• High complexity possible.
 Multi-step process, BUT:
 Web-based services have 24-hour turnaround,
low cost.
Next-wave Manufacturing
 CNC Laser cutter:
X-Y axes control a powerful laser.
Fine line (0.007” or better).
Positioning to 1000 dpi,
Some control of depth:
• Engraving as
well as cutting.
 Moderate cost:
$10,000 Versalaser
16x12” workspace.
Laser Cutter Capabilities
 Precision is good enough to make smooth
sliding surfaces (gears).
 Layering can be used to make
3D surfaces (very popular for
architectural models).
 Can even make PCBs
by etching metal
from clear plastic!
Other 2D Cutting Technologies
 Lasers can cut metal, but not
 Power limits, need to deal with
material removal.
 Plasma cutters use an
electrically-generated plasma
jet to cut
 Sweeps away material.
Plasma Cutters
 Thin shapes in a variety of metals.
 Torchmate 3 machine
is $10,000 for 4x8’
Water Cutters
 Similar idea to plasma but based on highpressure waterjet.
 Cleaner method: water plus metal can be
 Cost??
3D printers
 A variety of 3D printing techniques have
appeared in the last few years.
 SLA: Stereolithography: laser curing of
liquid plastic.
 SLS: Selective Laser Sintering: similar, laser
fuses powder.
 LOM: Layered Object Modeling: laser cuts
paper one layer at a time.
 FDM: Fused Deposition Modeling: a thread
of plastic is melted through a moving head.
Stereolithography: SLA
 Earliest 3D method, based on UV-set polymers.
 Resolution quite good: 0.002” layers.
 Curing needed before
part can be used.
LOM: Laminated Object Modelling
FDM: Fused Deposition Modelling
 FDM is one of the most
versatile 3D methods
 Many materials can be used:
solvent-based or thermoplastics.
 Requires X-Y-X motion (like
a CNC machine).
 Stratasys machines start at
Roll-your-own 3D Printers
 Material feeding heads are
commercial modules.
 Microfab makes heads for
solvent-based and thermoplastics.
 Add a CNC XYZ-stage to
create your own printer.
Roll-your-own 3D Printers
 Polymer electronics is printable with microfab
heads, working on actuators.
 Potential for printing complete electromechanical systems.
 Two prototype printers
at Berkeley.
3D Printer Disadvantages
 Slow! Adding material is much slower than
removing it.
 Speed scales very poorly with resolution:
double resolution and decrease speed by 8x.
 Laser 3D methods faster (than other heads)
for equivalent resolution, but limited
3D Printing Data
 The standard 3D printing format is “STL”.
 Available as an output option for most CAD
tools, as a 3rd-party translator for Maya.
 Then process-specific CAM software
(Computer-Aided Manufacturing) creates a
tool control file:
 Tool path for milling and lathing.
 Slices and support structures for 3D printers.
 CNC machines provide shape programmability.
 Lathes and mills provide traditional shaping.
 Layered methods can create almost unlimited
shapes, but slowly.
 2D and 3D shaping methods generally based
on CNC motion of an active head.
 Architecture of shaping machines is open:
movement and heads are available separately.