JGCGen is a preprocessor and code generator for NC files used to control CNC milling machines. It is built around Apache Velocity template engine. JGCGen aims to be an easy to use program which stays out of the way when not needed, but still have enough advanced features to make your work easier.

The code generated by jgcgen is relatively human readable, parametrized and makes use of looping constructs for conciseness.

What can JGCgen do for you? It will

• Keep track of O word numbers
• Expand macros
• Composite code from multiple files
• Generate toolpaths for geometric shapes like rectangles, circles, etc.
• Manipulate tool paths
• Render text (Hershey fonts)
• Convert heightmap images to g-code
• Split a single source file into multiple output files
• And more! See the user manual and example files for details

The code generation functions are currently optimized for 3 axis mills, but jgcgen can be used to code for any type of machine.

Jgcgen can be compiled using Eclipse or from the command line with ant. The following dependencies are needed:

• Velocity engine + dependencies (http://velocity.apache.org/)
• Commons-cli (http://commons.apache.org/cli/)
• JEP (http://sourceforge.net/projects/jep/)

Place the required libraries in the jars/ subdirectory, then run ant or export a runnable jar with Eclipse.

You can have EMC automatically call jgcgen when opening a .jgc file. Simply add these lines to your machine configuration ini file:

PROGRAM_EXTENSION = .jgc JGCGen script
jgc = java -jar /path/to/your/jgcgen.jar -o -

Jgcgen takes the drudgery out of O words.

#o("sub", "cut_square")
	#3 = -0.5
	g00 x[#1-10] y[#2+10] z#<_safe>
	#o("repeat", "10")
		g01 z#3
			x[#1+10]
			y[#2-10]
			x[#1-10]
			y[#2+10]
		#3 = [#3 - 0.5]
	#end
	g00 z#<_safe>
#end

#ocall("cut_square", "0", "0")

The above subroutine cuts a little square centered around the given X and Y coordinates.

#o("sub", "cut_square")
	#g($Shapes.outline.rectangle.corners("[#1-10]", "[#2-10]", "20", "20"), "-5") 
#end

The above subroutine cuts a little square centered around the given X and Y coordinates. Note that you can use g-code variables when defining the rectangle coordinates! The number of cutting passes made depends on the g-code variable #<_passdepth>.

If a built-in method can't generate a suitable path for you, you can write it yourself.

#capture($path)
g00 x-10 y0
g01 x10
g02 x-10 i-10
#end

#g($path.offset("x10 y10"), "-5")

The above code cuts a little D shape 5 millimeters deep. (Top of the workpiece is assumed to be at Z0) No Z coordinates need to be given. Safe Z (#<_zsafe>) is automatically added to rapids and the cut will be made in passes #<_passdepth> deep until the offset (-5) is reached.

You can split jgcgen output into multiple files by running it with the -s parameter. This is useful if you want the program separated into multiple independent parts, e.g. for manual tool changes.

This part goes to all files.

#split(0)
This part is omitted if splitting is enabled.
#end

#split(1)
This part goes to file_1.ngc
If splitting is to be used, split block 1 must be present!
#end

#split(100)
The blocks don't need to be consecutive. 
#end

#split(2)
This part goes to file_2.ngc
#end

Jgcgen comes bundled with a set of engraving fonts (Hershey fonts) The sample below engraves the text "Hello World" with 2 mm letter spacing using a times roman font.

#set($font = $Fonts.get("timesr.jhf"))
$font.setOption("lspace", 2.0)

#g3($font.getString("Hello world!", "-1")