Most CNC-type machines, including laser cutters, read a special language called G-code which describes toolpath positions. These toolpath positions also include the speed at which the toolhead should move as well as other complex data such as storing current position, probing, and equations. However, users who submit files to laser cutting services would never supply G-code as each machine is different, and therefore up to the operater to produce. Instead, engineers would provide a design file that contains their part to be manufactured, and then the operator would use a converter to convert the model into G-code to be executed by the laser cutter. Of all the files that an engineer can provide, DXF is one of the most common and popular choices as it is used to represent 2D shapes in a vector format which preserves distances as well as layers. In the case of Ponoko, DXF files should contain up to three different colors that represent either a cut, a line engraving, or an area engraving.
One fantastic gift as a result of the internet has been open-source hardware; free hardware resources that anyone can download, modify, and produce all without needing to pay for royalties or licenses. This open-source community includes just about every industry and application one can think of, and there are thousands of sites online that host CAD files. Ponoko also has a range of free designs to choose from created either by Ponoko or other customers who have used Ponoko services and want to share their ideas. Almost any image can be turned into a laser-cut part. The only requirement is that the final design file is in a vector format (such as DXF), meaning that pixel based image files need to be converted to vector paths first. There are many converters available both online and offline to do this, however caution must be exercised when converting images as there may be copyright protection over the original image.
Files used for laser cutters are nothing special and do not describe anything about the laser cutter itself; this is done with a dedicated toolpath converter that targets a specific laser cutter and creates G-code for that machine. However, what is important is that the right CAD software is chosen from the start before any work is started. Of all file formats, DXF is one of the best to use as it is vectorized, and so it is important that any CAD suite chosen is able to output DXF. Ponoko also accepts EPS, SVG and Ai files.
Generally speaking, there is no file format that is the best for producing laser-cut parts as the quality of the cut comes down to the G-code fed into the laser cutter as well as the quality of the laser cutter itself. However, file formats used by Ponoko need to be vectors and not raster images as raster images do not preserve outlines, areas, or layer differences that can be easily distinguished from each other. A vector file can describe different lines on different layers that can overlap each other. Furthermore, these individual lines can be colored separately to represent the type of line it is. In the case of Ponoko, three separate colors are used to indicate either cutting lines, engraving lines, or engraved areas. As previously stated, DXF is a file format that supports vectorized designs, preserves units and measurements, and supports multiple layers with different colors. When it comes to using Ponoko services, DXF is the preferred choice. Ponoko also accepts EPS, SVG and Ai files.
When creating laser-cut part design files, the first (and most important) step is to ensure that the CAD program being used is designed for 2D part development. Artistic programs can be used, but programs such as Alibre Atom and FreeCAD not only provide the ability to produce DXF, but also provide measurement capabilities (i.e., measuring size of parts in mm), and can be used in later 3D projects. The second step is to ensure that only three colors are ever used on a design, and that these colors are clearly defined. Using three similarly colored lines is possible, but it is highly ill-advised as confusion between what is a cut and what is an engraving can quickly form. An example of an appropriate color scheme would be red, green, and blue as all three colors are easily distinguishable. If CAD isn’t to be used, then it’s important that the program being used to draw parts not only works with vectored images, but also has export options that are vector files. While Ponoko does not support postscript, there are converters that can convert such designs to DXF suitable for Ponoko. Ponoko also accepts EPS, SVG and Ai files.
When downloading files from the internet you should always be careful to check that the site you are downloading from is trustworthy. When downloading files for creating parts, the next most important task is to check the licensing requirements of the file. Creative commons licenses almost always allow for commercial use provided attribution is given, but images may be protected under copyright. Other parts may be free to download but could have a royalty requirement where every part produced requires a royalty payment. Another concern that engineers should consider is that files freely available online with no licensing or royalty could potentially be stolen. Therefore, it is important that free files are downloaded from the original source and not from third-party hosts. Such files run the risk of having been stolen from other companies which would put whoever downloads them at legal risk. In short, it is best to download files from popular websites that are reputable and well known amongst engineering communities.