doc/dxfngc.xml (953033f) - dxfngc · BlinkenArea

dxfngc.xml

<?xml version="1.0" encoding="utf-8"?>

<title>DXF to NGC Converter: dxfncg</title>

<title>Introduction</title>

<para>

The DXF to NGC converter <emphasis>dxfngc</emphasis> provides a
      means to convert 2D technical drawings in DXF file format to G-code
      in NGC format used by CNC mills or routers (e.g. LinuxCNC).

</para>

<para>

Usually, the 2D drawings in DXF format do not contain enough information
      for G-code creation, e.g. about which lines describe the border of a part
      and which lines describe holes.  The diameter of the cutting tool and the
      depth of the cut are other examples.  Therefore, dxfngc relies on a
      script file to control the G-code generation.  This script is the input
      to the tool.  It sets all required parameters, reads the drawing,
      controls generation of the G-code and finally writes the output file.

</para>

</sect1>

<title>A First Example</title>

<para>

To illustrate the usage of dxfngc, suppose a stencil for the
      <emphasis>BlinkenArea</emphasis> logo shall be cut with a CNC mill.  The
      basic shape of the stencil is a circle.  The logo is formed by two holes
      with a specific shape (see <xref linkend="logo_stencil"/>).

</para>

<figure xml:id="logo_stencil">
      <title>Logo Stencil</title>
      <mediaobject>
        <imageobject>
          <imagedata fileref="logo_stencil.svg" format="SVG" width="30%"/>
        </imageobject>
      </mediaobject>
      <caption>The logo stencil to be cut on the CNC mill.</caption>
    </figure>

<sect2>

<title>Creating the Drawing</title>

<para>

First, the 2D drawing is created with a CAD program in DXF format.  The
        circular border is drawn on layer <parameter>border</parameter> and the
        two holes are drawn on layer <parameter>holes</parameter> (see <xref
        linkend="logo_drawing"/>).

</para>

<figure xml:id="logo_drawing">
        <title>Logo Drawing</title>
        <mediaobject>
          <imageobject>
            <imagedata fileref="logo_drawing.svg" format="SVG" width="42%"/>
          </imageobject>
        </mediaobject>
        <caption>The CAD drawing of the logo stencil on 10mm grid.
                 Border and holes are on separate layers.</caption>
      </figure>

</sect2>

<sect2>

<title>Writing the Script</title>

<para>

The next step is to write the dxfngc script.  Such a script is shown in
        <xref linkend="logo_script"/>.  All lines starting with a hash
        character (<code>#</code>) are comments.  They will be ignored by
        dxfngc.  During processing of the script, dxfngc manages three three
        data objects in memory: the current settings, the current drawing and
        the list of G-code commands.  Initially, the settings are set to some
        reasonable defaults.  The drawing and the G-code are empty.

</para>

<para>

The first section of the example script fills the G-code list with
        some setup commands to configure the CNC mill.  This is done using
        the <code>cmd</code> command.  All the text folloing <code>cmd</code>
        is treated as a G-code command and is appended as a new command to
        the G-code list in memory.  Afterwards, the settings for processing the
        drawing to G-code are configured.  This includes the Z coordinates
        and the feed rates for moving and cutting as well as the diameter of
        the cutting tool.  Please see !!!TODO!!! for a description of all
        settings.

</para>

<para>

The <code>read_dxf</code> reads a CAD drawing in DXF format.  In this
        example, the logo drawing shown in <xref linkend="logo_drawing"/> is
        read.  This loads all layers of the DXF file to memory.  The layers can
        then be processed with the cutting commands (see !!!TODO!!!) to produce
        G-code.  The <code>cut_inside</code> command is used here to cut the
        holes.  It will calculate the path of the cutting tool to be half its
        diameter further to the inside of the holes.  This makes sure the hole
        has the desired size and shape after cutting - or more precise as close
        to it as possible with the selected cutting tool.  The
        <code>cut_outside</code> command is used for cutting the border of the
        stencil.  It basically works the same way, but moves the path of the
        cutting tool further to the outside.

</para>

<para>

After all G-code for cutting has been created, the G-code commands
        for finishing (e.g. turning off the CNC-mill) are appended using
        <code>cmd</code> like for the setup.  Finally, the G-code accumulated
        in memory is written to an output file useg <code>write_ngc</code>.

</para>

<figure xml:id="logo_script">
        <title>Logo Script</title>
        <programlisting><![CDATA[# add setup G-code commands
cmd G21
cmd G90
cmd G64 P0.01
cmd G17
cmd G40
cmd G49

# configure settings
set_precision 0.01
set_tool_diameter 3
set_move_z 5
set_base_z 0
set_cut_z -3.2
set_cut_z_step 1.1
set_feed_drill 100
set_feed_mill 200
set_layer_mode path_by_path

# read drawing
read_dxf logo.dxf

# generate G-code for actual cutting
cut_inside holes
cut_outside border

# add finishing G-code commands
cmd M2

# write G-code to output file
write_ngc logo.ngc]]></programlisting>
      </figure>

</sect2>

<sect2>

<title>Running the Script</title>

<para>

Once drawing and script are ready, the script can be run using the
        <code>dxfngc</code> tool.  (It is assumed here it has already been
        compiled. See !!!TODO!!! for instruction for compiling.)  As the script
        contains the filenames of input and output files, it is sufficient to
        provide the filename of the script file to dxfngc:

</para>

<para>

If everything goes well, this will produce a G-code file.  Otherwise an
        error message will be printed that informs about what went wrong.
        (There might also be some output like <code>dimeModel::largestHandle:
        65535</code>, which is coming from inside the DXF library used
        internally.  This output can be ignored.)
        <xref linkend="logo_g-code"/> shows the produced G-code rendered by
        LinuxCNC.

</para>

<figure xml:id="logo_g-code">
        <title>G-code for Logo Stencil</title>
        <mediaobject>
          <imageobject>
            <imagedata fileref="logo_g-code.png" format="PNG" width="100%"/>
          </imageobject>
        </mediaobject>
        <caption>G-code for the logo stencil, rendered by LinuxCNC.</caption>
      </figure>
    </sect2>

</sect1>

</article>

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