More on kinematics and IK.
Some concepts from dynamics.
This time: Manufacturing & Materials
Manufacturing is undergoing a revolution:
Casting, molding, fusing, slumping
Milling, lathing (non CNC-versions)
Shape is “write-once” (not programmable) in
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.
CNC milling example
(Deskproto web site)
Finish is quite smooth
ballnose cutting tool.
Lots of waste, but can
Created with CAD tools.
• Low cost in volume.
• High complexity possible.
Multi-step process, BUT:
Web-based services have 24-hour turnaround,
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.
Laser Cutter Capabilities
Precision is good enough to make smooth
sliding surfaces (gears).
Layering can be used to make
3D surfaces (very popular for
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
Plasma cutters use an
jet to cut
Sweeps away material.
Thin shapes in a variety of metals.
Torchmate 3 machine
is $10,000 for 4x8’
Similar idea to plasma but based on high-
Cleaner method: water plus metal can be
A variety of 3D printing techniques have
appeared in the last few years.
SLA: Stereolithography: laser curing of
SLS: Selective Laser Sintering: similar, laser
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.
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 thermo-
Requires X-Y-X motion (like
a CNC machine).
Stratasys machines start at
Roll-your-own 3D Printers
Material feeding heads are
Microfab makes heads for
solvent-based and thermo-
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 electro-
Two prototype printers
3D Printer Disadvantages
Slow! Adding material is much slower than
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.