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Generating Gerber RS274X In 2:3 Format & Gerber File Syntax Issue.

excellon1

Hi, I have a couple of issues with exporting gerber data from Orcad/Allegro PCB Editor (16.6) & (17.2)

My first issue pertains to exporting the gerber files in a standard 2:3 Format. I work in mils and trying many combinations of database accuracy I have found no
way to export in 2:3 positional format. I am wondering if it is even possible ?

Looking in the help file 2:3 does appear to be supported.

I keep getting a dialog box popping up saying. ( For Raster Artwork Formats Accuracy must be at least one greater than the database accuracy)

If my database accuracy is set to 0,1,2 etc I can export without issue using a 2:5 Format but not 2:3

My second issue pertains to the actual syntax of the generated Gerber file. I have a commercial CNC mill that I use for quick RF Proto type boards. Basically
the software used with the mill converts the Gerber data to G-Code. That mill software works without issue with many different cad packages that create
Gerber files including Altiumn, P-Cad, Mentor etc. It also works with Gerber editors such as cam350 etc. Using the native RS274X data exported from Orcad
PCB editor results in un-usable data.

In checking the Gerber export syntax from Orcad/Allegro I have isolated the issue. Here are the details.
Opening the Gerber file in a text editor shows the following after the GO4 statements in the Header of the file.

G04 ================== end FILE IDENTIFICATION RECORD ====================*
%FSLAX25Y25*MOIN*%    <<<<<<< Issue I with this line

The first line ( %FSLAX25Y25*MOIN*% ) indicates that the format of the Gerber file is 2:5 and that the units are in inch.

In looking at the Gerber specification and other Gerber output from various cad packages It looks like Cadence has combined this line into one. Normally it should read like this.
Or should I say the other tools I have put the info out like this.

%FSLAX25Y25*%
%MOIN*%

As you can see there are two separate lines. One indicating the Format & one indicating the Units. If I edit the cadence gerber file to look like this then my CNC package has
no issues reading the data.

My question. Is there a template fle available that I can edit so that cadence puts out RS274X gerber in the above syntax ? just like other cad tools.

Thanks Paul.

Parents

  • The correct setting for outputting artwork will need to be 3:4 if your design parameters are set to Mils accuracy 0. Not 2:3.  My explanation--- 

    1mil =.001

    10Mils =.010in

    100Mils =.100in

    1000mils = 1.000in

    10000mils=10.000in

    Please note the how many numbers are before and after the decimal for 10.000 in. There are 2 leading and 3 trailing. Thus, the artwork output needs 3:4 to cover all graphics in your design up to 99 inches. And down to 1mil.

    If you set your accuracy down to 1. Then you need 3:5 to cover .0001 in.

    I hope this makes sense to you.  

  • in reply to Dale Peterson

    Hi Dale,

    Thanks for the reply.

    In my case, for RS274X 2.4 format (99.9999"), I assumed I would need to make:

    Integer places = 2 (before the decimal point)

    Decimal places = 4 (after the decimal point)

    Are these fields defined some other way?

    Thanks,

    Emmett

Reply
  • in reply to Dale Peterson

    Hi Dale,

    Thanks for the reply.

    In my case, for RS274X 2.4 format (99.9999"), I assumed I would need to make:

    Integer places = 2 (before the decimal point)

    Decimal places = 4 (after the decimal point)

    Are these fields defined some other way?

    Thanks,

    Emmett

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