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Re: 3d-viewer: via diameter calculation off?


> On Jul 8, 2020, at 2:47 PM, Joshua Redstone <redstone@xxxxxxxxx> wrote:
> Hi,
> I'm a bit new to pcbs and Kicad, but I thought that the effective diameter of a through-hole is the drill diameter minus copper plating thickness (since plating is done after drilling).
> In the 3d-viewer code, it looks like it's increasing the drill diameter to account for the plating so the plated hole is the drill diameter rather than the unplated hole, which seems odd.
> I was thinking of doing a diff to fix that, but wanted to check if I'm reading the code correctly.
> Specifically, in 3d-viewer/3d_canvas/create_layer_items.cpp
> the calculation of a hole's inner diameter is (hole_inner_radius) rather than (hole_inner_radius - [plating_]thickness).  And there's a corresponding offset in the calc of the outer diameter.
> An example: https://gitlab.com/kicad/code/kicad/-/blob/master/3d-viewer/3d_canvas/create_layer_items.cpp#L306 <https://gitlab.com/kicad/code/kicad/-/blob/master/3d-viewer/3d_canvas/create_layer_items.cpp#L306>
> I played around with rendering some test circuits and confirmed that the rendering seems to be producing holes that are too big.
> Am I reading this right?

Most board houses these days specify hole sizes as “finished hole size,” that is, with plating.

That’s because they rarely use drill bits in favor of water jet or whatever.

And it’s a lot easier to specify finished hole size rather than the manufacturer and the customer guessing.