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Big Blue Saw Blog General Updates

Clearing Inside Corners on Waterjet Cut Parts


You've just received your parts from Big Blue Saw. You've got some sharp inside corners, but the waterjet rounded them off! You could take a file to the parts to get rid of the excess, but who has time for that? Read on for hints on how to clear the corners so you never have to face this problem again.

When the waterjet cuts, it will come up just short of the inside corner. This is due to the cutting diameter (kerf) of the waterjet stream. Remember that the waterjet stream is round, and can't reach a sharp inside corner. Read more about that in our article on the limitations of waterjet cutting. The rectangle on the right in the image below shows rounding of the inside corners on 1/4 inch thick waterjet cut aluminum.

Many designers will remove some extra material to make sure that the inside corner gets removed. The most obvious way to do that is by putting an arc centered on the corner.


Taking a closer look, you'll notice that the arc has a diameter of just over 0.07 inches. This is so that the waterjet can enter the corner area through an opening that's 0.05 inches wide. We recommend at least an 0.05 inch opening to make sure that the waterjet controller software is able to identify an open area which the cutting stream can reach.

Here's the result of this type of corner clearance.

You'll notice with this that with this design we're cutting away a lot more material than is truly necessary. There are other ways that don't remove quite so much material.

If we simply extend the cut away from the long side, with an arc with a diameter of 0.05 inches, we get something like the shape shown below. (I've heard this referred to as "Finn ears" because it resembles the hat of one of the characters on the Adventure Time cartoon.)


Here the arc is 180 degrees and ends on the original corner.

Another way to go about the same thing: put the arc on the short side.





But we could still remove even less material and still snip away that annoying corner. If you create a 180 degree arc with an 0.05" diameter which passes through the original corner, and ends about 0.0354 inches from the corner. See the diagram below.

The result is a rectangle with much less excess material removed near the corner than with any of the other corner clearing methods.

The result is what's shown in the images below.


This corner cutting method gives the best lookng results and removes the least material. One potential disadvantage is that you might need one of the sides to be fully straight all the way into the corner for strength or stability.

To test these designs out, I waterjet cut a tab piece from 0.25 inch thick aluminum. It fits well into any of the slots cut with the corner removal techniques listed above.


Have a favorite corner clearing shape? Let us  know in the comments.

Heads Up: Sale Is Coming June 15-17

A quick note: the next sale is coming up on Wednesday, June 15 and will run through Friday, June 17. The material: aluminum 6061 1/8" thick. Orders placed online will automatically receive a quantity discount. Watch this space or our mailing list for more details.

The Secrets to Waterjet Cut Lettering


Words have power, doubly so after they've been blasted into quarter inch thick stainless steel.

Imagine you're making a waterjet cut sign out of metal and want to have lettering as negagive space (holes). (This is the 2nd type of sign shown in our article on turning logos into signs.) Or perhaps you're making machine parts and just want lettering to identify your company.

You've got to choose the right font for your lettering. Not every font works equally well with waterjet cutting. Consider this if you need us to match a particular font for your coroporate identity or design guidelines.

Serif Fonts

Here you can see a typical serif font, Liberation Serif, in a variety of sizes from 16 point (about 1/8 inch tall for the capital letters) to 72 point (capitals about 0.57 inches tall). As the name suggests, this font has serifs, those tiny little flags that hang off the end of every line.

Even at the 72 point size, the detail is just too fine to be cut by the waterjet stream, represented in this diagram by the tiny red dot. The waterjet cutting stream is about 0.04 inches (1 mm) in diameter. In this diagram, the white area represents solid material, while the black area is the negative space, or hole, where the waterjet will cut out.

At 100 points (0.8 inches), shown below, the waterjet stream can barely reach into the serifs.

Below, at 200 points (1.6 inches), we now have enough room for the waterjet stream to reach into the serifs and do a good job representing their shape. Again, the red dot represents the size of the waterjet cutting stream, which places a limit on the amount of detail that the waterjet can create.


Sans-Serif Fonts

Let's compare that with Liberation Sans, a sans-serif font in the same family. At 72 points, the waterjet stream can reach most of the areas of the letters, with the exception of a few narrow spots like the lower section of the "a". It might be possible to fix this type of area up manually. Also note that the square corners of the letters will have to be rounded off. This is seen in the next image.

At 100 points, the waterjet stream can now reach all points of the lettering except the sharp inside corners. This is less than half the size needed for the serif font.

The size at which it becomes practical to waterjet cut will depend on the exact geometry of the font used, but most serif fonts are not practical below about 1.5 inches tall and most sans serif fonts are not practical below 0.5 inches tall.


When you're designing lettering, please keep in mind that certain letters will require bridges in order to connect the center of the letters to the outer part, like the lowercase "a".  In typography, this area is known as a closed counter, but at Big Blue Saw we refer to this type of shape in any part as an island.

Bridges can often reduce the space available for the waterjet stream. In this example below, bridges have been added to the "b", "e", and "a". You'll notice that the ends of the top half of the "e" are quite narrow and will be rounded off. This is with Liberation Sans 100 point (about 0.8 inches tall). The bridges shown here are about 0.1 inches wide, near the minimum of what I'd recommend.

If the font is too small, the bridges can make the text harder to read. Here's the same bridging done on a 72 point font:

In general, bridges should flow with the natural strokes of the letter for the best appearance.

There are other ways to do it, though. You could do all horizontal bridges, and have them aligned as closely as is practical. Note here that the shape of the "a" does not allow the bridge to be aligned with the bridges on the "b" and "e".

A common variant on this is to add bridges through all the letters, even those without islands, to provide consistency.


Vertical bridges centered on the island area are another popular choice.

I do recommend at least 2 bridges. This allows for maximum stability when the parts are cut and during handling. As I mentioned, the minimum size you should consider are around 0.1 inches wide, but this will vary depending on the material and size of the island. Larger islands will need more bridges. Thinner material will require wider bridges to support the island.

Below you can see a few more ways that the letters could be bridged. Create your bridges to look good and hold the islands in place based on the type of material and the font you're using.

More on this topic




Zoolophone: Animals as Musical Instruments

Recently I heard about a pretty cool project from Disney Research, Harvard, Columbia University and MIT that used waterjet cut parts to make a zoolophone: a xylophone with animal shaped keys. James Tompkin, one of the zoolophone's creators, was kind enough to pass along the DXF outlines used to make their version of the zoolophone, as well as the material and thickness needed.

I ended up modifying the outlines to be cut slightly. Also, I had to substitute the more common 6063 T5 for the somewhat exotic 6063 T83 that was originally used. Neither of these things affected the sound much as far as I could tell.

zoolophone outlines

For the stands, I used some small chunks of EVA foam. I had tried using various materials like thumbtacks, wood, and felt, but found that the foam worked the best. I found that placing the supports near the center of the shape gave better sound than placing them at the edges as the original creators did. This may have been due to the fact that they were using a less dense foam.

Take a look at the video below to hear my version of the zoolophone in action. Thanks to Steve Sparks for the audio production assistance.

Sale On Aluminum May 9 through May 11

Ready to save on custom CNC waterjet cut parts?

Big Blue Saw's sale runs from Monday, May 9, through Wednesday, May 11, 2016. The sale features discounts on waterjet cut 1/8 inch thick aluminum 6061 alloy. (That's 0.125 inch or just over 3 mm thickness.) All orders placed online during the sale for this material will automatically receive a quantity discount.

Examples of Savings

This 21x21 inch robot baseplate is usually $114.40 in quantity 1. During the sale, it is only $56.05, a savings of 51%.

The nameplate you see above is typically $92.10 in quantity 1. During the sale,  you can pick it up for only $10.60, for a savings of $81.50.

This gearbox side plate shown above normally costs $92.10 in quantity 1. During the sale, you'll receive the quantity 10 price: just $9.93 for one piece. That's 89% off!

All the parts above are shown on our examples page.

Getting The Sale Price
You will need to order online during the sale to take advantage of the low prices.  Read about how to format your CAD files for use with Big Blue Saw. Or, for decorative pieces, you can use a properly formatted PNG or GIF file with our online quoting system as well.

When you've got the design ready, upload it to our online quoting and ordering system.

Wrapping Up

Big Blue Saw's sale is Monday, May 9, through Wednesday, May 11. Save as much as 89% off on waerjet cut custom parts from aluminum 6061 in 1/8" thickness.

Get your CAD or PNG/GIF files ready and place your order with our online quoting and ordering system.


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Waterjet and Laser Cut Custom Parts.
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Phone: (678) WAY-SAW4 (678) 929-7294