LayerControl

Introduction

Since dxf2gcode does not save any kind of file itself all required input data for G-Code generation is taken from the .dxf File.

By naming Layers in the .dxf file in special ways you can easily influence how shapes in these layers are translated to G-Code.

Milling parameters

By using MILL: as a prefix to your layer name you can define milling parameters by using one of the following identifiers (taken from https://groups.google.com/forum/#!topic/dxf2gcode-users/q3hPQkN2OCo ):

    # mill options
    mill_depth_identifiers = MillDepth, Md, TiefeGesamt, Tg
    slice_depth_identifiers = SliceDepth, Sd, TiefeZustellung, Tz
    start_mill_depth_identifiers = StartMillDepth, SMd, StartTiefe, St
    retract_identifiers = RetractHeight, Rh, FreifahrHohe, FFh
    safe_margin_identifiers = SafeMargin, Sm, SicherheitsHoehe, Sh
    f_g1_plane_identifiers = FeedXY, Fxy, VorschubXY, Vxy, F
    f_g1_depth_identifiers = FeedZ, Fz, VorschubZ, Vz

    #Tool Options
    tool_nr_identifiers = ToolNr, Tn, T, WerkzeugNummer, Wn
    tool_diameter_identifiers = ToolDiameter, Td, WerkzeugDurchmesser, Wd
    spindle_speed_identifiers = SpindleSpeed, Drehzahl, RPM, UPM, S
    start_radius_identifiers = StartRadius, Sr

Example:

MILL: 1 Md: 2 Sd: 2 FeedXY: 400 FeedZ: 200

This will cut shapes on the layer 2 mm deep (in one pass, since Sd == Md) using 400 mm / minute speed for X/Y movement and 200 mm / minute for Z movement.

Tip: You can combine workpieces for different materials in one .dxf file, just put all the pieces that belong to one kind of material (e.g. thickness of plywood) onto one layer.

Ignored layers

If you start your layer name with IGNORE:, the shapes in it will be disabled by default (i.e. the checkboxes in the Entities/Layers tab will be deselected by default).

Example:

IGNORE: Helper

This defines a helper - layer that may contain orientation lines, etc.

Tip: You can use this prefix for layers that contain measurements, orientation lines or other content that is important for the .dxf drawing to understand but not required for milling

Making tabs with Breaking layers

It is common practice to not entirely mill out workpieces but leave small gaps in the milling path known as tabs (in German this is called "Frässtäge" or "Stützbrücken"). The reason behind this is that without tabs the workpiece may be kicked away or take damage in another way by the milling head.

It is of course totally feasible to produce tabs by simple drawing them in the .dxf file with the CAD software. This however has the disadvantage that the blueprint of your workpiece is now interspersed with tabs and shapes are no longer closed.

dxf2gcode allows to define tabs as intersection points between lines of shapes to mill and lines of shapes on a breaking layer. If a shape to mill is intersected exactly two times by a shape on a breaking layer, a tab will be introduced. This allows for tabs to be introduced as rectangles on the breaking layer. The image below has a magenta breaking layer and a white layer defining the workpiece.

Breaking layers are defined by the prefix BREAKS: in the layer name.

Note that some parameters from the 'Milling parameters' section above apply to the breaking layer as well: FeedZ (or Fz, VorschubZ, Vz) will define the speed the milling head is retracted at the beginning and reinserted at the end of the tab. FeedXY (Fxy, VorschubXY, Vxy, F) will define the speed the milling head is passing the tab MillDepth (Md, TiefeGesamt, Tg) will define the height the milling head will have while passing the tab. This allows to pass the workpiece completely (Md > 0) or just prevent from cutting all the way through (Md < 0 but bigger than Md from your milling layer).

Example:

• BREAKS: 1 Md: -1 FeedZ: 200 FeedXY: 400 will retract the milling head at 200 mm/minute until it is 1 mm below the surface, then go to the end point of the tab with a 400 mm/minute feed and finally lower the milling head to the original depth with 200 mm/minute.
• An example .dxf file can be found at https://docs.google.com/uc?export=download&id=0B2negA0eQERDek01WDNXSVc2T1U. It contains a single rectangle to be milled out of a 3 mm plywood sheet. It contains four tabs (one on each side) where the milling is reduced to only 1 mm, thus leaving 2 mm of plywood to keep the workpiece in place.

Drilling layers

Milling machines can also be used for drilling holes in the workpiece. To achieve this with dxf2gcode you have to draw points on a drilling layer.

Drilling layers are defined by the prefix DRILL: in the layer name.

Drilling layers can have all the parameters specified unter Milling parameters above, thus defining how deep (MillDepth) or how fast (FeedZ) the hole should be drilled. Also the given ToolDiameter will be used to visualize the hole.

[Anonymous]

Originally posted by: david.ne...@gmail.com

In English, the interruptions/gaps in the milling path are known as "tabs". They are to prevent the workpiece from separating from the blank (and possibly becoming airborne...). Tabs are not necessary if other clamping or securing mechanisms are in place. -- Pud Nelson

[Robert Lichtenberger]

I updated the text accordingly. Thank you.

[Mike McCauley]

If you export a dxf file from inkscape with layer names as suggested, they will not be recognised, since inkscape converts all spaces in layer names into underscores when exporting dxf files.

Instead leave the spaces out eg:

MILL:1Md:2Sd:2FeedXY:400FeedZ:300

and dxf2gcode will recognise the encoded layer name

[Andrey Zabolotnyi]

Unfortunately, in QCad, which is a excellent editor for creating DXF files, you can't even enter a colon in layer name. The only characters allowed are letters, numbers and ~!@#$%^&()_-+[].
So, I had to change the "Configuration -> Automatic tool config -> Separator between identifier and value" to ~ and now I use constructs like MILL~3~Md~2Sd~2 etc. Tried to use other separators (-, + etc), but they all are special regexp characters and lead to crash in some dxf2gcode module.

[Colin Durrans]

Andrey,

I'm new here and finding my way with QCAD and dxf2gcode...

I've used advice from else where, used ! instead of : then used my favorite text editor and replace all feature.

However, the editor isn't required - you simply need to go to the configuration, select Automatic Tool Config and change the separator identifier from : to !

Hope this helps.

regards,
Colin

EDIT: There's a better way!!

[spicer]

Where do I have to enter the prefixes?

[chrisko]

While creating the drawing use the layer name according this description. As an alternative you can also open the dxf with a CAD tool and edit / change the layer names according to your needs.
regards
Christian