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.
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
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