Parent Category: Big Blue Saw Blog
Created: Monday, 09 August 2010 21:00
Written by Simon Arthur
As many of you know, our online quoting system accepts both vector (DXF format or Big Blue Saw Designer JPX format) and bitmap (AKA raster) format files (like PNG or GIF) for automatic online quoting. When customers ask, I tell them that DXF is really the better format, and a raster file is really only appropriate where close tolerances are not required, such as for decorative applications. Let's take a look at why that is so.
Here's a typical part designed in Inkscape. It is a simple 5x4 inch plate with some 1/8 inch diameter holes in it.
When you export this file as a DXF, the holes turn out pretty close to being circular. The image below shows how the laser cutter will make those 1/8 inch holes from a DXF file exported from Inkscape.
Inkscape can also export a bitmap file as well. When you export the same file as a PNG and zoom in on one of the holes, here's what you'll see. Notice, first of all, that the image contains anti-aliasing (grey pixels), which, as mentioned in the FAQ on raster files doesn't work so well with our online quoting system.
The edges aren't well defined, so when we go to make the part on the laser, the system has to "guess" as to where to cut the part. Here's a diagram showing how the hole will be cut.
Finally, the following photo shows a closeup of one of the holes laser cut into black acrylic. As you can see, the hole has an irregular shape to it.
For many applications, the irregularities caused by using a bitmap file aren't a significant problem, such as decorative pieces or parts where a close fit is not required. But for maximum precision, it's best to use a DXF or JPX file.
If you are file with the limitations of using a PNG or GIF file, please read our FAQ on raster files first and make sure that your file is formatted correctly. In particular please ensure that:
- The file is formatted so that the solid parts are in black, with the holes or negative space in white.
- The edges are not antialiased in the file.
This will help ensure that you get the best results for waterjet and laser cutting