Question: Board setting vs Fiducial

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Andy PausB

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Sep 16, 2022, 3:26:23 PMSep 16
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Hello 
I have a question. In openPNP when you will do a job, you first set the Board position at the edges and then you import the Partlist with positions. 

Sometimes i get Partlists with Part positions with offsets, while  the x and y zero position lays somewehre in the Board and not at the edge.  I dont know why this happens, but sometimes i receive such datas.

So my question ist: Why are not the fiducials used to set the position of the Board ? 
Why do i have to set the Boards corner and then use fiducials. 
Why are not the fiducials the "Master" of position ? 

Idea: You learn the position of the fiducials and the part coordinates change to the Boards position.

Maybe it is a bad idea.#

Thanks a lot 


Jonathan Oxer

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Sep 16, 2022, 5:18:51 PMSep 16
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Setting the board position first is for 2 reasons that I can think of. Perhaps there are more:

1. To set the height (z-axis position). This can't be done with fiducials.

2. So that OpenPnP has a general location for where it will find the fiducials to perform optical alignment. When using fiducials the board position is only a starting point. It's updated once the fiducials have been found. But if OpenPnP doesn't have an approximate board position to begin with, it doesn't know where in your entire workspace that it should begin looking for the fiducials.

Jon

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Litterio Andrea Guainella

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Sep 16, 2022, 5:20:40 PMSep 16
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Hi Andy,
I hope not to misunderstand but the behavior you described is already exsist in openpnp.
In my case after setting up the new board and importing the partlist, I insert approximately the position of the board visible from the dro (after positioning the camera).
Then I have two possibilities to correctly determine the position of the board ie through the fuducials or from some references of parts.

As shown in the photo below
30.png
clicking on the fiducial icon openpnp correctly verifies the position of the fiducials and at the end is positioned on the edge of the board that you can save to keep it in memory (and if you mark check fids this operation will doing ever job).

Or from the next photo
31.png
you can see how when you click on the parts reference openpnp asks you which parts to take as a reference and to position the telecara exactly in the center (my suggestion is always to include at least one mcu an oscillator and resistances and capacities for each mounting direction. horizontal and vertical.)

Sounds good?
LAG

tonyl...@gmail.com

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Sep 16, 2022, 8:19:31 PMSep 16
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>Sometimes i get Partlists with Part positions with offsets, while  the x and y zero position lays somewehre in the Board and not at the edge.  I dont know why this happens, but sometimes i receive such datas.

You need to set the origin in your CAD program to be at the corner of your board before you export the placement data.  In KiCad, select the menu Place>Drill/Place File Origin to set the origin where you want it.  I'm sure other CAD packages have a similar option.
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