Using Inkscape for laser cutting

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Draft

1 Introduction

Inkscape is a popular tool within creative commons/opensource communities, e.g. fab labs and for several reasons:

  • The drawing tool is decent enough
  • It supports the popular SVG format (and uses an extended version for itself). This allows publishing drawings directly on an HTML5 page. In addition, there are nice repositories for drawings, e.g. http://clipart.org or the https://thenounproject.com.
  • There are interesting extensions and probably, over time, there will be more.


Before you start: Make sure to install the latest version. We found that Inkscape 0.49 (that somehow survived in the program files (x86) directory) did not produce proper print files for cutting.

2 Using Inkscape with Trotec laser cutters

Trotec CO2 laser cutters seem to work like most other laser cutting machines:

  • Very thin lines (<= 0.01mm or < 0.25pt) are coded with a color and then cut according to settings for each color.
  • Geometry for engraving is also encoded with a color and then engraved according to settings for each color. Alternatively there is a "picture" mode that takes into account all objects for engraving, i.e. it will do grey-scale dithering.

Make sure to create files that include

  • fine (red) lines for cutting (if you need to cut)
  • standard (black) lines and fills for engraving

You may not be able to engrave fonts. In that case (only), once you are happy with a font, make a copy of the file and save it, then convert fonts to paths. Verify that both fills and lines are defined if you want both.

If your drawing is ready:

  • Resize the document to the size of the graphic + 1mm on each size. If it is resized you can place several files on a plate. If the drawing sits in a big sheet of paper (as opposed to resizing the document) then tell at least the laser to reduce (Jobcontrol of Trotec can do this)
  • Send it to the laser cutter.

There is some better information in french

3 Working with patterns

3.1 Generate from path extension

The first you do this, you may make mistakes and dammage some drawings. We therefore recommend saving the file into a new version, before each major operation.

  • Set all units to mm's, otherwise you may get dimensions wrong and pieces will not fit.
File->Document Properties
Page TAB: Set default units: mm and Units:mm
Grids Tab: Set Grid units: mm

Let's assume that you want add objects along a path and/or use a series of objects along a path for some subtractive () geometry:

Scatter an object along a path - principle

  • Make sure that object to be repeated is on top of the other drawings.
  • Select first the object you want to repeat, then the path (holding down the SHIFT key)
  • Select Extensions->Generate from Path-> Scatter
  • Use the preview to play with parameters. Distances seem to be in pixels
  • After applying, ungroup and adjust individual members.

Scatter and subtract

To subtract the pattern from another path, e.g. a dinosaur

  • Create a layer for the dinosaur: dino
  • Right-click on the dinosaur and move it to this new dino layer, lock it
  • Create a second layer for the pattern: pattern
  • Copy/paste the dinosaur to this new pattern layer
  • Splice out a path from the copy (read the Using Inkscape for web animation) and kill the rest
  • Draw a rectangle that will create the "cuts"
  • Remove the path from the rectangle or make it hairline (also make a copy of it since you may want to add one manually)
  • Proceed as above, i.e. create the scatter using the generate from path extension
  • Remove the path
  • Ungroup and fix individual elements if needed (clicking twice on an object allows to rotate)
  • Make a single path from the rectangles. Select all, ungroup all, then Path->Union.
  • Position if not already done so.
  • Unlock dino layer, Select the dinosaur
  • Select the new pattern
  • Path-> Difference
  • (Optional) With the extra rectangle make some "cuts" in the legs.

The three pictures below illustrate the most important steps of the procedure (creation of the path is not included)

1. Select both an object to replicate and a path
2. Result of the operation. This still needs to made into a single path (degroup all and union)
3. Final result (first trial). The red line then had be reduced to 0.01mm and some insets had to be adjusted a bit. However, better adjust the rectangles before union and subtraction !

Later, I changed the model a bit (longer/higher neck, 3mm insets)


The dinosaur was extended from this (the big red one in the back). I cut away the head and added a long neck (yes this a heavy genetic splice). Also made the tail somewhat prettier ;

4 Using fonts

In some "modes" you cannot directly print fonts. They have to be transformed to drawings (either strokes or fills). (I actually have to check this in more detail because I never had problems, my students did - Daniel K. Schneider (talk) 2 November 2016 ( oct 2017).

4.1 Fonts for cutting

  • Transform the fonts to path (once you are happy), then remove the fills or rather change it to a color that will not be engraved (e.g. light blue).

4.2 Fonts for engraving

Globally speaking, a font used for engraving:

  • should neither be too thin (details being lost) or too fat (too much materials to remove)
  • should not be too cramped (e.g. like TimesRoman). There should be some space between the letters.

It probably is best to convert fonts to paths and wind up with fills. There are two possibilities:

  • Hollow letters: add stroke and remove fill, then transform stroke to fill
  • Filled letters: add fill and remove stroke

Alternatively, install the Hershey text Inkscape extension. It includes fonts that are nice for engraving, i.e. so-called stroke-based fonts.

4.3 Advice for token lettering

E.g. tokens for simulations and games

  • Use a simple font like Tahoma or even good old Helvetica
  • Bold (also consider engraving twice or defocusing the lens a bit)
  • 14pt (smaller also can work, but it's more difficult to read)


4.4 Resources

There are commercial specialized websites that provide fonts suitable for cutting and engraving.

5 Image processing

I'd have to see the Trotec Control software which does have some built-in image processing facility.

Importing

  • Import the picture
  • Object->Transform->Scale

Greyscale and contrasts

  • Transform to Greyscale (the laser only has 1 color, i.e. depth): Filters -> Color -> GreyScale
  • Play with contrast and brightness to make the picture more "black and white" and still preserve details you want to engrave: Filters -> Color -> Lightness Contrast

Aggregate

  • Aggregate pixels to larger surfaces. You can use various filters for that (optional)
  • Raytrace the whole thing, i.e. translate pixels to vectors. (optional): Path -> Trace Bitmap
    • I suggest (for now) playing with brightness cutoff, e.g. select 0.2 to take away greys, also

6 List of extensions

First, learn how to install extensions. Basically, you have to find the extension directory and then copy all the files

Some extensions may not work, either because they were not tested on your operation system or because they are not compatible with your inkscape version.

6.1 JigSaw Extension

This extensions allows to generate puzzles. Tested in Inkscape 0.91, Ubuntu 16LTS in Sept 2016.

Read and Download

Test under Ubuntu 16 LTS

  • This works, under the condition to copy manually the contents of the *.py and *.inx files from Github. Click to open, then "raw", then copy/paste.
  • The puzzle may to too small to see when you try it first time, since the lines are very faint. Make it bigger.

6.2 Lasercut box

This extensions allows to create "saw tooth" boxes. Tested in Inkscape 0.91, Ubuntu 16LTS in Sept 2016.

6.3 EggBot extension

The eggbot is a open-source art robot that can draw on spherical or egg-shaped objects. The Inkscape eggboot extension eases the design process for writing and drawing on eggs. However, some of its functionality can be useful for laser cutting and engraving, in particular the Hershey fonts which generate drawings (glyphs as opposed to fonts).

6.4 Seamless Pattern extension

(not yet tested)

For engraving larger surfaces it is better to use a nice pattern (as opposed to "milling" off a whole area)

  • Download (click on the small download arrow).

However, this extension does not seem to be browser compatible, i.e. may produce some kind of raster format (to be tested).

Alternatively, Inkscape does have built-in "pattern" facility. Not so easy, search for tutorials.

7 Links

Official