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Methodology for 3D-Printed Part Design

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What is 3-D printing?

1) Is there an existing demand for the part or product?

  If No, determine why the part should be created.
  If yes, is there improved viability, feasibility, desirability or sustainability with 3-D printing? 

2) Is there an existing offering/part made by traditional manufacturing processes?

  If No, determine why there is not an existing offering.
  If Yes, is there a benefit to 3-D printing the part? (e.g. geometry complexity, customization, density, rapid prototyping, reduce lead times, or unique 3D printing material)?

3) Is it feasible to 3D print part?

  Is the the volume of part less than the build envelope? 
  Is the maximum operating temperature range for part less than glass transition temperature for printing filament?
Property ABS PLA HDPE
Glass Transition Temperature 100C 50-60C 80-110C
Extrusion Temperature 210-230C 160-220C 130-190C
Melting Temperature 200-230C 120-190C 190C
[1]

4) Is there an existing CAD Model or STL file for part?

  Search CAD or 3D printing repositories.
  Existing models can be used to influence design considerations.
  If there are no existing files, a new model must be created.

5) Determine and quantify necessary mechanical properties, standards, and loads for part.

  Determine applicable mechanical properties (e.g. Tensile Strength, Compression Strength, Flexural Strength, Impact Strength, Fatigue Limit, Wear Resistance, and Stiffness). 
  Reference industry standards for the part (e.g. ASTM International, ANSI, or ASME).

6) Prioritize necessary mechanical properties, standards, and loads for part.

  Based on requirements for part, prioritize Tensile Strength, Compression Strength, Flexural Strength, Impact Strength, Fatigue Limit, Wear Resistance, and Stiffness.
  Use prioritized list of mechanical properties to influence design considerations and FEA simulation.

7) Model existing part or prototype.

  Use Comparison of CAD Modeling  softwares to determine the most suitable package.
  OpenSCAD, FeeCAD, and Blender are the most commonly used Open source engineering software packages.
  Save an IGES file or a Parasolid for Finite Element Analysis.
  Save a STL file for the slicing software.

8) Conduct Finite Element Analysis (FEA).

  Select from List of FEA Software Packages
  Review basics for Finite element analysis: MOST
  ANSYS and Abaqus are two commonly used FEA software packages.
  Determine type of analysis. (e.g. structural, thermal, computational fluid dynamics (CFD), or electrical)
  Select element type.
  Define loads, constants, and boundary limits.
  Input Young's Modulus and Poisson's Ratio, and stress-strain data for material.
  Create a mesh.
  Refine mesh using iterative process of FEA theory.
  Run simulation. 
  Output data points graphically or numerically.
  Finite element analysis requires an in-depth knowledge of FEA theory and significant practice using Software Packages.
  It is likely necessary to take courses and consult experts in the field to become proficient. 
  

9) Determine if part should be 3D printed based on (FEA).

  Does the part fail as anticipated?
  Does the upper-limit of failure meet the required mechanical properties, standards, and loads?
  Should the part be redesigned before printing?

10) Select the most appropriate 3D printing filament.

  PLA, Nylon, and Polycarbonate are recommended. 
  Determine Mechanical properties of components printed with PLA and ABS.
(Make table with parameters and references for PLA, Nylon, Polycarbonate).

11) Import CAD file into slicing software.

  Cura is the most commonly used slicing software.     
  slic3r is an alternative.  Useful documentation for getting started with Slic3r. 
  RepRap printing protocol: MOST contains information on preparing your file for printing.

12) Determine optimal printing build parameters in slicing software with regard to necessary mechanical properties, standards, and loads.

(e.g. orientation, fill density, fill pattern, layer thickness, bead width, deposition temperature, deposition speed, raster angle, etc.)

    How Does Build Orientation Affect a 3D Printed Part?
    Cura - Fill Density 
   
    Cura User Manual contains information on settings for layer height, shell thickness, enable retraction, bottom/top thickness, fill density, print spreed, print temperature, support type, platform adhesion type, filament diameter, and filament flow].
    Silc3r Print Settings contains information on settings for Layer Height, Perimeters, Fill Density, Fill Pattern, Support Material, Speed, Brim, Sequential Printing, Filament Settings, & Printer Settings

13) Export G-Code from slicing software and import G-Code file into 3D printing software.

   G-Code is the file type (.gcode) needed to print.

14) Select printing software.

   Repetier-Host and Pronterface are recommended.
   Repetier-Host Documentation
   Pronterface Basics
   

15) Ensure printer is calibrated.

   Calibration will depend on the type of 3D printer used. 
   Calibration Tutorial
   MOST Delta Auto Bed Leveling

16) Print part.

   RepRap printing protocol: MOST
   3D_Printing_Basics:MOST
   MOST_Reprap_Printing_Lessons
   Tips for Designing 3D Printed Parts

17) Test printed part to failure.

   Determine appropriate failure analysis method (e.g. Tensile, compression test, Torsion Test, or Rockwell Hardness.
   Tensile test protocol: MOST

18) Does part fail as expected in FEA simulation?

   If No, reassess printing build parameters.
   If Yes, continue to next step.

19) Does part meet necessary mechanical properties, standards, and loads for part?

   If No, reassess CAD design and printing parameters.
   If Yes, compare 3D printed part to existing offerings.

20) Cost Analysis

       The equation below can be used to determine the cost of printing a part:
      (Op) = (E)(Ce) + 1/1000(mf)(Cf) [2]
      
      Op: Operating costs for the RepRap-produced products
      E:  Energy use (kW-hr)
      Ce: Cost of energy (US$/kw-hr)
      mf: mass consumed (g)   
      Cf: Cost of filament (US$/kg)

21) Quantify why 3D-Printed product is better than existing offerings.

   Compare manufacturing cost, time, energy, and mechanical properties.

22) Qualify why 3D-Printed product is better than existing offerings.

   What are the social considerations?
   Are there other parameters that can be used to qualify 3D printed part?

23) Continue iterative design process to optimize part for end user.


See also[edit]


References[edit]

  1. http://theseus32-kk.lib.helsinki.fi/bitstream/handle/10024/86198/Thesis%20final.pdf?sequence=1
  2. http://www.academia.edu/4067796/Life-Cycle_Economic_Analysis_of_Distributed_Manufacturing_with_Open-Source_3-D_Printers