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Big Blue Saw Blog General Updates

Vector vs. Raster Files for Waterjet and Laser Cutting

As many of you know, our online quoting system accepts both vector (DXF format or Big Blue Saw Designer JPX format) and bitmap (AKA raster) format files (like PNG or GIF) for automatic online quoting. When customers ask, I tell them that DXF is really the better format, and a raster file is really only appropriate where close tolerances are not required, such as for decorative applications. Let's take a look at why that is so.

Here's a typical part designed in Inkscape. It is a simple 5x4 inch plate with some 1/8 inch diameter holes in it.

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When you export this file as a DXF, the holes turn out pretty close to being circular. The image below shows how the laser cutter will make those 1/8 inch holes from a DXF file exported from Inkscape.

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Inkscape can also export a bitmap file as well. When you export the same file as a PNG and zoom in on one of the holes, here's what you'll see. Notice, first of all, that the image contains anti-aliasing (grey pixels), which, as mentioned in the FAQ on raster files doesn't work so well with our online quoting system.

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The edges aren't well defined, so when we go to make the part on the laser, the system has to "guess" as to where to cut the part. Here's a diagram showing how the hole will be cut.

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Finally, the following photo shows a closeup of one of the holes laser cut into black acrylic. As you can see, the hole has an irregular shape to it.

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For many applications, the irregularities caused by using a bitmap file aren't a significant problem, such as decorative pieces or parts where a close fit is not required. But for maximum precision, it's best to use a DXF or JPX file.

If you are file with the limitations of using a PNG or GIF file, please read our FAQ on raster files first and make sure that your file is formatted correctly. In particular please ensure that:

  1. The file is formatted so that the solid parts are in black, with the holes or negative space in white.
  2. The edges are not antialiased in the file.

This will help ensure that you get the best results for waterjet and laser cutting

The Best Tip for Saving Money On Custom Waterjet Cut and Laser Cut Parts with Big Blue Saw

There's something really easy you can do to save money when you're ordering online from Big Blue Saw. I've mentioned it to many customers over the years. Here it is in one sentence:

If you have two or more parts that are made from the same material, combine all of your parts into a single file before uploading.

Let's take a look at how this might work. Suppose you have designed the two parts shown below, and want to purchase one of each. They're both going to be made from 0.25 inch thick 6061 alloy aluminum.

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If each of the two parts is stored in a separate DXF file, you'll have to upload them separately. When you do this, your total cost will be $86.10 for the first part, and $81.10 for the second part, for a total of $167.20.

But take a look what happens when you combine both parts into a single DXF file, using your favorite CAD or design software as shown here.

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The price comes down to $89.60 for both parts. That's a savings of $77.60, or over 46%!

Get an immediate quote and order now by uploading your CAD files!


Save Even More by Getting the Latest Discounts, Sales, and Design Tips on Big Blue Saw's Mailing List

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New RSS & Podcast Feed Location

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Big Blue Saw now has a new RSS feed, courtesy of Google Feedburner. Everyone using the old RSS feed is encouraged to switch to the new feed URL:

http://feeds.feedburner.com/BigBlueSawBlog

The new location will automatically function as a podcast feed, so you can easily download audio and video from Big Blue Saw.

Our old feed URLs are eventually going away, so it's probably best to just switch now.

Why I Created Big Blue Saw

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I've told this story many times to customers, friends, and business associates, but I've never posted the full story here on the Big Blue Saw website itself.

The story really begins in the mid 1990's. Marc Thorpe was a a guest at the Dragon*Con science fiction convention. He was showing videos of an event he had produced in San Francisco called Robot Wars. It featured robotic gladiators with names like The Master and Thor fighting to the death in a hazard filled arena. Robot Wars was a game of destruction and brawn, true, but it also featured elegance and beauty as well, and required brains to win. As a bonus, Dragon*Con had been running a fighting robot of its own for several years: Robot Battles. In summary, my mind was blown and I was hooked on making fighting robots.

Being a computer programmer, the closest I had ever come to building my own robot was making a mutant R2D2 with the Star Wars Droid Factory when I was a kid. Eventually I became interested not only in the robots themselves, but in the tools and techniques I needed to make them.

I eventually learned that many of the things I wanted to create were well beyond the capabilities of my simple home workshop. Often, I found myself reaching out to fabrication and machine shops to create the designs I had envisioned. Dealing with these types of business was incredibly unsatisfactory. Their sales teams, such as they were, usually consisted of one surly fellow who seemed like he desperately wanted to be anywhere but his rusty office chair. I would find myself calling repeatedly to check on the status of an order or even just to get a quote. E-mail communication was non-existent. Most commonly, I found that they simply did not want to deal with a hobbyist ordering just a handful of parts.

One incident in particular sticks out in my mind. I contacted one of the largest machine shops in Georgia to weld a robot frame for me from my pre-cut parts. The finished piece 3 weeks late and the welding work was shoddy. To add insult to injury, I later learned that I was charged 4 times the going rate. When I picked up the part, the man who wrote up my receipt had to ask for my help spelling the name of the city where the shop is located.

I knew there had to be a better way to get custom machined parts, but I couldn't find it.

In 2005, I was facing a life-changing prospect: becoming a father for the first time. I had been making a living as a freelance computer consultant for the past 5 years, taking on clients as it suited me and making enough to earn a good living. I loved the variety of the work and the ability to take long chunks of the year off if I chose to. But I knew, in order to create a stable future for my family, I had to do something that was independent of both the labor market for freelance software engineers and my ability to work billable hours. I'm not really cut out for corporate jobs; I get bored just thinking about it. I know, I thought, there's nothing more secure and stable than starting a new business; that'll bring in the steady cash! (No, it didn't work out that way, but more on that in a moment.)

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Graphic from an early version of the Big Blue Saw website

Based upon my experience building robots and my background developing software for the web, I decided I could make a website that made it easy for people to order high-quality parts online, custom made to their specifications. There would be as little friction as possible in the ordering process, making it as easy to order 1 simple part as it is to order 1000 complex ones. My eventual goal was, and still is, to allow engineers, artists, hobbyists, crafters, designers, and makers of all kinds to turn a concept or idea into a real thing.

There were (and still are) a few websites out there that attempt to make the whole process of ordering custom machined parts easier. For example, the first one I looked at in 2005 required you to download and install a Microsoft Windows-only client program just to get a quote. The prices they gave for waterjet cutting when I started Big Blue Saw were 2-3 times higher than what I charged (and still are, the last time I checked).

After having created the great way to order waterjet and laser cut parts online, I was thoroughly shocked that I didn't get an immediate flood of grateful customers. Instead, it's been a slow and deliberate process of regularly improving the website, making buying from Big Blue Saw more pleasant, and building relationships with customers. I still take on consulting work from time to time to make ends meet. But sales keep going up, and this year is on track to be the most profitable ever. My wife has been very understanding, even when I need to work long hours or when the sales have been slow. We now have two little rugrats.

Big Blue Saw continues to grow because of you, our customers. Without your visions for what we can do with raw material, Big Blue Saw wouldn't exist. Thank you.

Using Inkscape to Design Parts for Big Blue Saw

Duck Stand

Update 2010-08-24: There is a new extension which does a better job of exporting to DXF from Inkscape: Big Blue Saw's DXF Export for Inkscape.

I often recommend Inkscape to people who are new to Big Blue Saw and CAD design. Inkscape is a a zero-cost, open source drawing tool that's simple to use, but also quite powerful. If you need very precise lines and curves in a design, you need to use software like Inkscape, which can create and manipulate vector graphics.

Inkscape Logo

Our own Big Blue Saw Designer is useful for creating many kinds of parts, but it doesn't have the file import/export capabilities or sophisticated curve and shape tools that Inkscape has.

The example below created using Inkscape version 0.47. Follow along with it to see how you can design a simple part using Inkscape.

Here is the part we will be making. Two of these parts can be slotted together to form a small square stand, perfect for elevating your rubber duck to protect it from passing predators, among other things.

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Here is what Inkscape looks like when it first starts up. What a wonderful selection of buttons and controls! The main area depicts a piece of letter-sized paper to help you have some idea of the scale of the drawing.

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We will start by drawing a square for the outline of our part. Click on the rectangle drawing button, then drag in the document area.

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Next, you want to resize the rectangle so that it is a precise 2 inch square. On the toolbar, there is a drop down list which shows the measurement units for your new rectangle. By default, this is set to "px" (pixels). Change the units to "in" (inches). Then enter "2" for both the width ("W") and height ("H") and press the Enter key on your keyboard.

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Now you are ready to create the slot in the edge of the square. Using the rectangle tool as before, draw a thin rectangle near the right size and location.

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This creates a another black shape, which is hard to see against our existing black outline. Change its color to white by clicking on the palette just underneath the drawing area.

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Now switch to selection mode by clicking on the selection tool on the tool palette on the left-hand side of the window.

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We want the slot to extend halfway down the square and be just wide enough to accommodate a 0.236 inch thick piece of acrylic. So on the geometry toolbar, after making sure that the units are set to "in", enter "0.236" for the rectangle's width and "1" for its height. Then press Enter.

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The slot needs to extend from the top-center of the outer square to the middle of the square. We can get the slot in the exact position by using Inkscape's alignment tools. Click on the slot rectangle, hold down the Shift key, and click on the square. This will cause both objects to be selected. Open the Alignment panel by choosing Object | Align and Distribute from the menu or by or using the keyboard shortcut Ctrl-Shift-A.

Click the "Center objects horizontally" button to place the slot in the middle of the square.

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Then click the "Align top edges" button to move the slot to the top edge of the square.

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To get a better idea of how Inkscape will export the file when you are ready to send it to Big Blue Saw, switch to outline mode by choosing View | Display Mode | Outline from the menu. This will hide the fill colors of the shapes and show all lines with the same width.

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If you take a look at Big Blue Saw's FAQ on vector file formatting, you'll notice that we need to make sure that the lines in our file trace the outline of the part and do not cross. The drawing is not quite right at this point; the top of the slot is still closed off. At this point, we can make the smaller rectangle a cut out from the larger square.

You will need to make sure that the slot crosses over the outline of the square. This will ensure that the square's edge follows the contour of the slot. Make the slot slightly taller by clicking on it and dragging the center resize handle at the top.

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Now add the square to the selection by holding down the Shift key and clicking on it. Choose Path | Difference from the menu cut the slot from the square.

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The new object is a square with a slot cut in it. It's a little hard to see because Inkscape displays a dotted line around the currently selected objects. Click on the background to remove that outline and see the just the outline of your part.

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At this point, the file is ready to be exported for use with Big Blue Saw. Choose File | Save from the menu and pick "AutoCAD DXF R12 (*.dxf)" for the file format.

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After you click the "Save" button, you will be prompted for several "PostScript". Just leave these at the default.

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At this point, you have a DXF file suitable for use with Big Blue Saw. You can upload the file to our online quotation system. From the online quotation system, you can choose your material, and order your part online.

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Big Blue Saw
5.0 stars - based on 17 reviews
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