Big Blue Saw Blog
- Parent Category: Big Blue Saw Blog
- Created: Friday, 19 February 2016 17:03
- Written by Simon Arthur
Elsewhere on the website, I've shown how waterjet cutting and laser cutting make it easy to create simple signs. Most of the signs we do are in a single layer, with the figure being either positive space (solid material) or negative space (holes). Read more about the variations on this kind of sign.
Occasionally, a customer will need something a little more sophisticated. Their logo, symbol, or seal will have many distinct elements. I'm going to walk you through how you can create one of these types of signs using the reverse of the Great Seal of the United States as an example. You probably recognize this design from the back of the $1 bill. The design was created in the 1780's and is used on official US government documents. The Wikipedia article on the Great Seal has more information about the symbolism and meanings of the mottoes "Novus ordo seclorum" and "Annuit cœptis".
Note that in Inkscape's outline view, we can see something a little different. Many of the pieces that appear to be one thing in the design are in fact made of several elements. The eye is created by using clipping and in the outline view doesn't look much like the regular view at all. I scaled the design to 11.5 inches in diameter so that it could be cut from a 12 inch wide sheet of brass.
So this needed some cleaning up before it was ready to be waterjet cut. Changes include:
- Deleting the plants in the foreground
- Removing several entities that were only there to provide gradient colors.
- Redrawing the outer circle to be made as false bevels [link] and still look like the original design.
- Eliminating the shadow layer from the letters at the top. These will be 1/8" thick metal and will really cast shadows.
- Redrawing the burst around the eye so that it's practical to waterjet cut.
- Changing the eye in the triangle so that it can be cut as one piece. The fill tool was essential for this.
- Fattening up the lines in the pyramid bricks, and making bridges so that it could be cut as one piece. The bridges were placed at the bottom of each layer so that it looks like they should be there.
- Adding an extra layer behind the eye so that its details wouldn't be lost in front of the sunburst.
- Modifying the banner so that it is one continuous outline. Again, the fill tool was essential for this.
Here's the outline view:
Next, the parts were split up by material: most parts were to be made from aluminum, or from stainless steel. These two methods are a slightly different color and provide contrast for pieces that are directly adjacent. The border and sunburst were done in brass for maximum impact. The backing piece for the eye in the triangle was black acrylic. All parts are 1/8 inch thick.
After waterjet cutting, it turns out that some of the details were a little too fine on the banner and lettering that appears at the top. You can see that many of the solid areas between letters on the banner were simply wiped out. The narrow areas from the letters at the top on the "A" and "P" also proved to be too thin.
I bumped up the size of these about 10%. I also carefully widened the bridges and other narrow areas to make absolutely sure that these pieces could be cut on the waterjet.
After waterjet cutting, all the pieces needed to be sanded to clean up any handling marks, mill marks, or overspray from the waterjet. Some pieces were tabbed together. The parts needed to be removed from their tabs, and the residual tab filed off.
The pieces as cut needed to be cleaned up to remove any waterjet overspray, mill marks, and other handling marks. Here's a closeup of the parts before finishing:
The smaller pieces like the letters, had tabs attached. The pieces could be broken off of their tabs by hand, but needed some additional filing afterward to completely remove the tabs.
Here's what the letters loked like after being sanded, but before the tabs were filed off:
After filing off the tabs:
Finally the whole thing was assembled and the layers carefully glued together using a 2 part epoxy. If I make a sign like this again, I would use a clear epoxy or E6000 adhesive, rather than the opaque grey epoxy I did use. A clear adhesive is harder to see when it squishes out from the edges or accidentally goes where it's not supposed to. Here is the final assembled version:
What do you think of the results? Let us know in the comments.