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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, 9 x 7 x 6. 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 16 x 12” workspace.
Laser Cutter Capabilities § Precision is good enough to make smooth sliding surfaces (gears). § Layering can be used to make 3 D surfaces (very popular for architectural models). § Can even make PCBs by etching metal from clear plastic!
Other 2 D 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 4 x 8’ workspace.
Water Cutters § Similar idea to plasma but based on highpressure waterjet. § Cleaner method: water plus metal can be collected. § Cost? ?
3 D printers § A variety of 3 D 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 3 D 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 3 D methods § Many materials can be used: solvent-based or thermoplastics. § Requires X-Y-X motion (like a CNC machine). § Stratasys machines start at $30, 000
Roll-your-own 3 D 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 3 D Printers § Polymer electronics is printable with microfab heads, working on actuators. § Potential for printing complete electromechanical systems. § Two prototype printers at Berkeley.
3 D Printer Disadvantages § Slow! Adding material is much slower than removing it. § Speed scales very poorly with resolution: double resolution and decrease speed by 8 x. § Laser 3 D methods faster (than other heads) for equivalent resolution, but limited materials.
3 D Printing Data § The standard 3 D 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 3 D printers.
Summary § CNC machines provide shape programmability. § Lathes and mills provide traditional shaping. § Layered methods can create almost unlimited shapes, but slowly. § 2 D and 3 D shaping methods generally based on CNC motion of an active head. § Architecture of shaping machines is open: movement and heads are available separately.