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Big Blue Saw Blog General Updates

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.

 

 

Load Holding Fixtures Using Waterjet Cutting

Fresh out of my e-mail inbox comes this fixture from a customer who wishes to remain anonymous. 

(Of course, at Big Blue Saw we keep your designs confidential. We also keep the fact that you're even a customer confidential as well. Many of the things we make end up in finished products, and our customers see Big Blue Saw's service as a competitive advantage. [Many are happy to provide testimonials, thankfully.] )

The structural pieces  were waterjet cut by Big Blue Saw from 1/4 inch thick aluminum 6061 and assembled by the customer using off the shelf hardware. The design uses tab-and-slot with the pieces held together with through bolts as in tensioned plate construction.

The customer says:


These are medium-load holding fixtures.  Using BBS for these type of fixtures saves us 50%+ on traditional tooling and also allows us to build instrument & medium load machines in a clean office!  (No welding, milling, sawing, etc - -just a few fasteners and counter-sinks.)  These fixtures are doing the job of machined 1/4" Al C-channel assemblies.


Got any parts you would like to show off or want to tell us how we are doing? Let us know!

Bitmaps Embedded in Vector Files

Our online quoting and ordering system works best with files in the DXF or DWG format. That's because these two file formats have nearly universal support in CAD software as well as in the waterjet and laser cutting world.

Significantly, these file formats are vector formats. As a quick recap: image files generally fall into one of two types -- vector files and raster (AKA bitmap) files.

Raster files consist of a regular grid of pixels, each of which has its own color. Think of a mosaic picture made using only square tiles of the same size. Or coloring in the squares on a sheet of graph paper.

Popular formats for raster files are JPG, GIF, and PNG. These files are typically created by digital cameras, scanners, and software like Windows Paint, Gimp and Photoshop.

 

A raster image is made up of pixels filled in with colors. In this image, the area in the red rectangle on the left has been zoomed in on the right so that you can see each pixel.

Vector files, on the other hand, create an image from a set of precisely defined lines and curves. Vector files are produced with CAD software like AutoCAD, DraftSight, etc. as well as by drawing programs like Inkscape and Adobe Illustrator.

A vector image is made of curves and straight lines. In this picture, you can see the end points of the lines as well as the control points that make up the curves.

One nice thing about vector files is that they can be zoomed or scaled and the lines look just as smooth. When you zoom in on a bitmap embedded within a vector file, this is not the case.

Unlike a raster image, a vector image can be resized or zoomed without losing any detail. The letters on the left look round even when made much bigger, as shown on the right.

When it comes time to make parts using waterjet cutting or laser cutting, we need a vector file because this gives the exact outline of the shape and a path for the cutting tool to follow. Astute users of our service will notice that uploaded GIF and PNG files are converted to DXF by a tracing process on our servers when the quoting process begins.

The Confusing Thing

Strangely, files can contain both bitmap AND vector data! This happens commonly when exporting to a vector format from a bitmap-oriented editor. When a vector file contains an embedded bitmap, the embedded bitmap does not have the exact outline of the shape and a path for the cutting tool. It's still a bitmap and shares the limitations of all bitmaps.

DXF, PDF, and SVG all support embedded bitmaps to coexist with vectors.

How to Tell If Your Vector File Has an Embedded Bitmap

Zooming In

One way to tell if a file has an embedded bitmap is by zooming in. You will be able to see the jagged edges of the pixels in the bitmap image once you zoom in far enough.

An overview of a CAD design in Inkscape. It looks just like a vector drawing at this zoom level.

Zoomed in, you can see the telltale jagged outline of an embedded bitmap.

Outline View

Another way to check for embedded bitmaps is to use the outline view mode of your editor. In Inkscape, that's done by choosing View > Display Mode > Outline from the menu. An embedded bitmap will then be shown as a plain rectangle with an X in the middle. In this view, true vectors will be shown with their original path, but with alll styling (colors, thickness, etc.) removed.

Outline view in Inkscape.

The same design as a vector, zoomed in.

If you need free or low cost software that will create vector files for your design, take a look at our list of recommended software. Then learn how to format your CAD files for our online quoting system to make custom parts from aluminum, steel, plastic, and more.

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Big Blue Saw
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Waterjet and Laser Cut Custom Parts.
Address for correspondence only:
3522 Ashford Dunwoody Rd NE #145
Atlanta, GA 30319
Phone: (678) WAY-SAW4 (678) 929-7294