3dPrinting: Embedding parts

[last updated: 2021-11-14]
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• Suppose you have a part (EP = Embedded Part) that you want to embed inside the body of a model you are printing.
  For example it may be a hex nut, a rod or wire for support, bb's or washers to give weight, or anything else.

  
  Further recognize and be mindful of the orientation you desire for your EP.

  With the shape and orientation of your EP defined, the process for embedding the part into your print is broadly as follows:

• Embedding parts into a print:
  • Draw a model with a cavity that is shaped to accommodate the part you want to embed.
    The cavity must be deep enough that, when the part is inserted, no portion of the EP extends above the top of the cavity.
  • Model and print any spacers you need.
  • Start your print, and pause it at the required time.
  • Insert your EP and any spacers required.
  • Resume and complete your print.

  This process will encapsulate your embedded part with printed filament inside the printed model.
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  In detail, the steps are:

• Draw a model with a cavity:
  • The top surface of the EP must not extend above the top of the cavity,
    or else the print head will hit the EP as it prints the next layers.

  • The bottom surface of the cavity should conform to the shape of the EP.
    If it does not, due for example to having holes in the EP that are at an angle to the build plane,
    then you must make a decision as to whether you can tolerate empty spaces inside the model,
    or whether you should print separate plug pieces to fill any holes or gaps.

  • If it happens conveniently that inserting your EP into its cavity, in its desired orientation, results in a completely filled cavity, with a flat top surface, then you're done.
    But if, when the EP is inserted, the cavity is Not filled, and the top surface is Not flat and horizontal to the build plate,
    then you must model and print a spacer to add on top of your EP to bring the resulting top surface to be horizontal
    and at the same height as the top of the already printed model.

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• Pause print:
  • This can be done manually, but it's way more convenient to edit your gcode so that your printer will pause automatically
    where required to allow inserting your EP.
    Using PrusaSlicer (PS):
    • With your stl loaded into PS, switch to layer view (icon in lower left of screen that looks like a stack of flat sheets)
    • Scroll down (drag pointer on the vertical scroll bar that is at the right side of the main view screen)
      to find the layer number where you want your printer to pause. You'll be pausing After this layer is printed,
      so you'll want to find the last layer before your printer puts down material on top of your EP.
    • Then, in PS: Printer Settings, Custom G-code
      insert this code in the "After layer change G-code" section.
      (replace the "60" in the below code with the layer number where you want to pause.)
      ; pause at specified layer:
      {if layer_num == 60}
      ; do long beep
      M300 S1500 P3000 ; tone 1500Hz, 3 sec
      M601 ; pause print
      {endif}

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• Insert the EP and any spacers needed:
  • Remember the goal is that, after your parts are inserted,
    the cavity will be completely filled, and the top surface will be horizontal
    and at the same height as (ie. not protruding above) the height of the rest of the model that has been printed so far.

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• Resume and complete the print:
  • Prusa MkIII LCD screen bottom line will show: Print Paused
  • Go into menu and select: Resume Print

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