Input data necessary for a proper drill data (auto)import are like below:
Two of listed data can be found in a Excellon file header. Thats are units and zero suppression type.
For example based on:
we have got only two of necessary informations:
So how FAB3000 (or similar tools featured with Autoload command) knows other data (Integer and Decimal digits and type (Absolute or Incremental) ?
I noticed that if drill file is loaded separately (using autoimport) then result of autoimport is broken:
Broken result (too small drill diameters, and too huge PCB area:
while during autoload of full package (drill + Gerbers) aotoload give us correct results:
Why it works this way? Is there any good explanation of why single drill file after autoload give us broken results, while everything is OK after if we use autoload on drill + Gerbers together?
Thank you very much for your feedback.
PS. As I see inside Excellon spec ( http://www.ieslosviveros.es/electronica/apuntes/asig14/formato%20excellon.pdf ) according this standard there is no space in a drill header:
to specify all necessary (for drill file import) data:
So finally... where are the type and zero suppression defined / located to make an autoimport possible? How can it works?
Thanks for the information regarding Drill Import. Drill data "almost always" is missing something in the header, which is why it's the most notorious format to import - in addition integer/decimal digits are never defined in drill data header. The biggest problem is the missing integer/decimal digits.
Thus all CAM tool must perform some type of automation to import the drill files. FAB 3000 uses the following:
1. If the user loads the drill manually (menu: File/Import/Drill...) FAB 3000 will use the settings you define unless it sees something in the header file to overwrite your settings. This is the most user reliant method, and recommend only if Autoload cannot correctly bring in a Drill file.
2. Autoload means "automatic loading" - so FAB 3000 will make adjustments when it sees fit to correctly import your Gerber, Drill, etc. When using AutoLoad, FAB 3000 will first load the Gerbers and then load the drills afterwards. Since it already knows the gerbers are imported and scaled "correctly" it will then check that the drill holes align with pads on the Gerber -- if not the drill is scaled up or down 10X until it can determine an alignment. This is not fool proof, because sometimes the PCB CAD tool will output drill files with a different origin from the Gerbers (so alignment will not work), if the "Zero Suppression" or "Type" is missing from the Drill header FAB 3000 will have to use the default Autoload settings (which may or may not be correct).
Thanks again, and please let me know if you have any other questions or suggestions.