Design Realization lecture 9 John Canny 9/23/03

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)  Stamping  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 surface.  Not new, but now inexpensive, PC-based.  Plastics, wood, metal, glass. Flashcut 2000, XYZ-axes, 9x7x6.5”, $2895

Milling  Milling involves a moving XYZ head that cuts into the workpiece:  Bits can achieve different finishes.

Lathing  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 easily  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’ workspace.

Water Cutters  Similar idea to plasma but based on high- pressure waterjet.  Cleaner method: water plus metal can be collected.  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 thermo- plastics.  Requires X-Y-X motion (like a CNC machine).  Stratasys machines start at $30,000

Roll-your-own 3D Printers  Material feeding heads are commercial modules.  Microfab makes heads for solvent-based and thermo- plastics.  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- mechanical 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 materials.

3D Printing Data  The standard 3D printing format is “STL”.  Available as an output option for most CAD tools, as a 3 rd -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.

Summary  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.