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Big Blue Saw Blog General Updates

Multi Part Layered Sign: The Great Seal

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".

Thanks to Wikipedia we have a nice vector version of this design. Here's what it looks like when you open it in Inkscape.

 

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.

 

Custom laser cut acrylic lighting diffuser

At Big Blue Saw galactic headquarters, we have a number of recessed ceiling lights that have sprouted high efficiency CFL bulbs. They produce plenty of bright light, helpful in the dark winter months. The downside is that they look kind of ugly. See for yourself in the photo below.

I had the idea to make these a bit prettier by making a cover.  But why make a plain lighting diffuser when I could use the laser cutter to make them Big Blue Saw themed! I designed a 10 inch diameter diffuser with a series of 5 mounting holes the at the same diameter as the recessed lighting fixture ring.

 

 

For the material, I chose our stock P95 acrylic, which is ideal for a lighting fixture as it transmits 95% of light and diffuses light in a soft pattern. After laser cutting and removing the protective paper coating, we had the piece shown below.

To install these, I used some clips made from copper wire. The diffusers were installed frosted side up. Here are the results.

Much better. I especially like the way the edges catch the light. What do you think? Let us know in the comments.

 

 

Sale February 9-10 on Custom Waterjet Cut Parts

Big Blue Saw is having a sale on custom waterjet cut parts! On Tuesday, February 9, and Wednesday, February 10, all orders of waterjet cut aluminum 6061 in 1/4 inch thickness will automatically receive a quantity discount. When ordering as few as 1 part, you're getting the same price as if you ordered 10.

Let's see a couple examples of how this works.

Our 36x22 inch salon sign from our list of examples, waterjet cut from 1/4 inch thick aluminum 6061 normally costs $248.70 in quantity 1. But during the sale, you'll be able to get it for just $211. That's a savings of 15%.

Here's another piece from our example page: the gearbox side plate at 4.7x4.4 inches. When cut from 1/4 inch aluminum 6061, this piece would normally cost you $92.10 in quantity 1. During the sale, you'll save $79.50 on this, or 86%!

Get started by uploading your design to our online quoting and ordering system.

 

Jewlery and Other Small Parts with Waterjet Cutting

Big Blue Saw has done quite a bit of waterjet cutting of small parts. Small parts are often jewelry made with special materials like silver and bronze.

Let's take a look at how this can work out for a simple trefoil design cut from 1/8" thick aluminum plate. As you can see below, we made the design in several different sizes, from about 2 inches (50 mm) across down to 1/4 inch (6.4 mm) across.

The parts all had a rectangle at the top 0.125 inches wide. On the smallest two pieces, the lobes were 0.262 (6.7 mm) and 0.131 inches (3.3 mm) in diameter.

You can see how they turned out in the closeup photo below. Note that our limiting factor here is the cutting stream size (kerf width) of the waterjet: about 0.04 inches or 1 mm in diameter. That's slightly thinner than a CD or DVD. You will notice that the sharp inside corners of the original design become visibly rounded off at this scale. Designs at this scale and smaller are quite limited in the amount of detail they can have.

Below is an even closer look at the smallest piece. The top lobe is slightly asymmetrical, possibly due to the waterjet cutting path or vibration during cutting.

Small parts are typically tabbed to the sheet from which they're cut to prevent them from falling into the water catch tank. Here we can see that the tab is about 1/64 inch (0.4 mm) wide. This is almost too small for this particular design and material.  The larger pieces actually broke loose from their tabs during the simple handling needed to take these photos. The tab is designed to be thin enough that we can remove the part from the sheet easily. (Thin areas tend to break.) Thinner and weaker materials (remember that we're using 1/8" aluminum here) will likely require a wider tab, which could interfere with a small part's design.

 

Thin features on waterjet cut parts

It's true that waterjet cutting doesn't put much stress on the sides of the material that it's cutting compared to, say, milling. But vibrations from the cutting process can cause problems, especially near thin features. We created a couple sample pieces from aluminum 6061 to show just how thin you can make waterjet cut features. The photo above shows on the left a piece made from 1/4 inch (6.35 mm) thick material, and on the right you can see the same design cut from 1/16 inch (1.6 mm) stock.

You'll notice that the thinner material has one fewer bar. That's because the beefier material can hold thin features better than its skinnier counterpart. Thinner material is weaker for a given area and so it's more likely to vibrate when cut. You can see in the closeup below where the bar broke off. This bar was drawn to be 0.018 inches (0.46 mm) thick.

Even the thicker material had some trouble with a bar this thin. You can see that on the top face (the side where the waterjet stream first enters the material), the bar is missing some of its thickness and is just barely attached.

Below is a CAD drawing with the thinnest 3 bars. They are 0.0566, 0.0372 and 0.018 inches thick, respectively.


 

Keep in mind that these bars are only suspended from one side to the main body of the part. Connecting them to a bigger piece on both ends would help keep them stable when cutting. Also, different materials will behave differently when waterjet cut.

To summarize: narrow areas in  your design under 0.018 inches (0.046 mm) will probably not work out. Keep feature thickness to 0.037 inches (0.95 mm) and above. If absolutely must have thin features, use thicker material.

 

 

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