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.
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.
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