SketchUp, Inkscape, and Ponoko Laser Cutting

Step 9 Tolerances and Allowing for Error

So far we have approached laser cutting as if it were the holy grail of precise manufacturing and made no allowances for the imperfections in materials and the channel or kerf cut by the laser (picture 1). Have a look at the following Ponoko video to understand what I am talking about.

Notice how at the end of the video the pieces stay put while the operator lifts out the surplus material. This means that a 4x4x4cm cube will only be that exact size if you allow for material cut away by the laser.

One possible solution to this problem is to scale your pieces to allow for the cutting. For example we could use Inkscape to scale a 40x40mm piece to 40.5x40.5mm (this would allow for a 1mm cut assuming that the laser runs down the middle of each line).

If you're more concerned about the fitting of pieces rather than the actual dimensions, we can alter the layout in Inkscape to make pieces fit snugly. For example, we could reduce the gap size (and thus increase the tooth size) in our "tooth and interlock" design. This would ensure that the tooth squeezes into the gap (see picture 2).

Yet another design choice that we have is to use bumps (refer to the Ponoko manual) is a good way to allow for tolerances and make sure that parts fit snugly (see pictures 3 and 4).