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John@MPL
United Kingdom
3 Posts |
 Posted - 05 Jun 2014 : 15:20:20
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Ver. 17.0.3.
I have laid down 2 diodes side by side, one reversed. My PCB assembler has flagged an offset error on one diode.
It would appear that the X/Y component position generated in 'Component Positions CSV' uses the Top Silk Screen information as the component centre not the pads. If the 2 diodes are 'Side by Side' with pads aligned in X, then there is no error, if I reverse one diode with pads aligned I get an 0.51 mm error.
My diode top screen show a block at one end for assembly direction.
Does this mean that the top screen outer edges must be symetrical around the pads ?
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edrees
United Kingdom
779 Posts |
Posted - 05 Jun 2014 : 15:23:45
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Yes you are quite correct regarding the component centre generated from the s/screen outline and NOT from the pad centres.
I place the component origin (source) in the centre of the silk screen, that way you can place the components on the grid. |
Edited by - edrees on 05 Jun 2014 15:25:05 |
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Iain Wilkie
United Kingdom
1015 Posts |
Posted - 05 Jun 2014 : 16:57:32
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Correct, the silk screen is used to decide the x,y coordinates. However your pcb assembler should be able to correct any mis-alignment when setting up the pick and place.
Iain |
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John@MPL
United Kingdom
3 Posts |
Posted - 05 Jun 2014 : 17:04:38
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Thanks Edrees,
I have SM R/A Connectors that are not set with pads in the centre of the Silk Screen, can the reference be changed from the silk screen to Pad Centre Line, e.g. the EasyPCLib - Csm shows a 64ABPR-M connector but the pads that are not center of the Silk therefore would you need to manually measure the position of the pads and change the CSV file.
Thanks John.
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edrees
United Kingdom
779 Posts |
Posted - 05 Jun 2014 : 17:06:52
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| One of my CEMs doesn't even bother to use the PIcknPlace info. His machines optically scans the pcb to work out the component centres for themselves. |
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edrees
United Kingdom
779 Posts |
Posted - 05 Jun 2014 : 17:17:40
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John, I'm not aware of a method of changing how the software calculates the component centres. What you suggest is a rather fiddly way of doing it, - unless No1 can suggest an alternative method which doesn't involve growing the outline to fudge the component centre.
The easiest way is just to advise your Subbie of such "awkward" components and I'm sure he'll oblige. |
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John@MPL
United Kingdom
3 Posts |
Posted - 05 Jun 2014 : 17:48:26
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Thanks Edrees,
Now I understand how the X/Y file is generated, I can change the components in my Library or just get the CEM to jiggle the components.
Regards ... John.
Thanks for the feedback Iain ...
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Topic |
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X Y Component Position Error