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Using FreeCad's TechDraw Feature to Indicate Threads

In order to manufacture the CNC case, the locations which need thread holes tapped needs to be communicated in a technical drawing.

I designed the parametric keyboard case in OpenScad. But, OpenScad isn't well suited to dealing with dimensioned drawings. (Although I do prefer the text-based / "as-code" nature of OpenScad).

To come up with technical drawings, it's easier to use FreeCad.

There's a TechDraw tutorial, but this use case is even simpler than what that covers.

Note, FreeCad Wiki Links:

Here's how:

  1. From OpenScad, render the case to CSG.
make ./cnc-pykey40-mx.csg
  1. Open the CSG file in FreeCad.

  1. Ensure the view is the top of the case, since this is the view we want of the case when communicating where we want threads.

    • I closed the report view.
    • I used the menu options:
      • "View -> Standard Views -> Fit All",
      • and "View -> Standard Views -> Top"

  1. Change the view to TechDraw.

    • "View -> Workbench -> TechDraw"
      • If TechDraw isn't there, go "Edit -> Preferences -> Workbenches" to enable it.

  1. Select the case.

    • Just click on it with the mouse.

  1. Insert Default Page.

    • Find the "Insert Default Page" icon on the toolbar, or otherwise use the menu option "TechDraw -> Page -> Insert Default Page".

  1. Insert View.

    • With the case selected,
    • Find the "Insert View" icon on the toolbar, or otherwise use the menu option "TechDraw -> TechDraw Views -> Insert View"

- I scale this view down.
  - With the View selected,
  - In the "Combo View" on the left, in the "Data" tab,
    - Change Scale type to "Custom".
    - Change Scale to an appropriate value.

Now you've got a FreeCad document set up which can suitably communicate the appropriate technical details.

TechDraw Features I Used

In this use case, the technical information I want to communicate is very simple.

  • Horizontal/Vertical Dimensions:

    • Select the two lines for the dimension to describe.

- Under "Combo View", "View" tab, I adjust the Arrowsize and Fontsize.
- The location of the dimension can be changed by:
  - Dragging the dimension with the mouse,
  - or by setting the X, Y values in the "Data" tab.

  • Circle Centerlines

  • Cosmetic Line through 2 Points

I have 5 threads of the same diameter and depth, so I just describe that in an annotation.