Creating the Aperture List

In order to run the dxf2gbr engine and create a Gerber file the calling application must first create an aperture list. Because there are many different approaches to drawing circuits in AutoCAD, there is no single best way of deciding how to convert a DXF file into Gerber. This document is not intended to describe the various approaches but rather to document what is in a valid aperture list.

The following apt file directives define the Gerber format:

APTUNITS inch               units (inch or mm are the only two choices)

FORMAT 2.4                  data format (max 9 i.e. 4.5 is ok but 5.5 is out of range)
   
SUPPRESS LEADING            coordinates in the Gerber file have leading zeros suppressed

CIRANG 360                  circular interpolation uses 360 degrees

ABSOLUTE on                 data coordinates are absolute. Only absolute coordinates 
                            are supported in the dxf to gerber direction.

Aperture Definitions

There are two different types of entries depending on whether the aperture is used as a draw or a flash. Ifl used as both, use the flash entry.

If a Draw

D10 0.00100000 d Round 0.00100000 0.00100000

column 1 = d-code (valid entry ranges from d10 through d999)

column 2 = diameter or side of square (only round and square types may be used for draws)

column 3 = d

column 4 = value of the diameter or side of square

column 5 = doesn’t matter as round and square only read a single value.

If a Flash

D11 BLOCK11 f Rect 0.03000000 0.02000000

column 1= d-code (valid range from D11 through D999)

column 2= block name for AutoCAD (characters/numbers, no spaces, max length=31 must begin with character)

column 3= f

column 4= aperture type (round, square, donut, rectangle, oblong, thermal, octagon)

column 5= first dimension

column 6= second dimension

column 7= third dimension (if needed) only the thermal relief has three dimensions