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Rapid Prototyping Methods (Subtractive (CNC/NC (Computer Numerical…

- - - - Components in an SLA machine
        
        Mirror
        
        Laser
        
        Work table (elevating table)
        
        Resin (liquid polymer)
      - CAD to SLA
        
        CAD output SLA
        
        Geometry is sliced into layer
        
        Generate support
        
        Start layer by layer processing
        
        Part is built bottom up
        
        When done, the part is raised out of the vat
        
        Support is removed and part is cleaned
        
        proceed to the Post Curing Apparatus for the final cure
  - - - What is SLS?
        
        A process which uses a laser selectively to trace the surface of powder ad sinters the
        material together
        
        Amourphous materials
        
        Rough surface finishes and porous
      - SLS Machine
        
        Computer/control
        
        PC with Windows OS
        
        Prepare the .STL files
        
        Slice the part
        
        Monitors and control the entire building process
        
        Astmostphere control
        
        Houses the equipment to filter gas recirculated from the process chamber
        
        Maintains a set temperature on the air flowing into the process chamber
        
        Regulates the nitrogen atmosphere used in the unit
        
        Process chamber
        
        Optics and scanning mirrors are used to focus a CO2 laser beam onto the part cylinder
      - Advantages
        
        Ability to provide self support during building
        
        Un-sintered powder surrounding the part in the build cylinder acts as a natural support for the next layer
        
        No elaborate supports need to be built such as in some photopolymer systems
        
        Excess powder materials can be returned to the powder feed cartridges for reuse
        
        Part building speed is quite fast
        
        Accuracy is quite good
        
        Almost any material that softens and decreases in viscosity upon heating can theoretically be selectively sintered
        
        Powdered metals, ceramics, and advanced composite powders with suitable binders
        
        New materials such as stainless steel for SLS are being developed
- - - - Remove material from a solid workpiece until the desired shape
      - The process is programmable textControl by NC program
      - Manual programming (Text File)
      - Can be generated from a Computer Aided Manufacturing (CAM) system
    - - a manufacturing process in which pre programmed computer software dictates the movement of the tools/cutters while it removes material from a raw workpiece/material
    - - The process is programmable
      - It can cut on hard metallic material
      - Smooth surface finish
    - - Decide how to hold the part on the machine table
      - Workpiece need to be "clamped"
      - Only the top part can be machined
      - Workpiece is held by a rotating chuck
      - Decide the depth of the cut, the tool-bit size
      - Limitation of tool-bit (cutter diameter) size to produce small details
    - - What is CAM ?
        
        Design done in a Cad System can Output to STL format
        
        The machining path can be programmed in a CAM System (Computer Aided Manufacturing)
      - Work Flow
        
        CAD -> CAM -> CNC
        
        .STL file (layers/slices) -> generate tool-path in a CAM system -> output is NC part program for 3 axis CNC router
      - Parameter setting for toolpath
        
        Step depth
        
        Step over
        
        Feed rate
        
        Spindle speed
        
        Roughing and finishing toolpath
        
        Finishing