Update (2010-09-01): I've fixed a bug based upon a report from commenter blackfox. Download the new version of Big Blue Saw's DXF Export For Inkscape Here.

After the last article on using Inkscape, I received some feedback in the comments section that let me know that DXF export wasn't available for all versions of Inkscape. After a little research, I came across a the free third party Inkscape extensions for DXF export Better DXF Export and Better Better DXF Export.

But I found that these two solutions lacked a few important features:

• There was a Python version incompatibility that caused the export to crash on Linux.
• They only supported metric output as the measurement units.
• When converting curves to line segments, the line segments were quite large, giving the curves a rough appearance.
• Color output was unsupported.
• They would produce layer names which were incompatible with many CAD packages.

With these problems in mind, I made a few modifications to Better Better DXF Output to create Big Blue Saw's DXF Export For Inkscape. It features everything from its predecessor, plus the following features:

• It has been tested on Fedora Linux, as well as Windows Vista.
• The units are now output as inches by default.
• It creates finer line segments, which is important for achieving the highest accuracy possible.
• The lines in the output file will be given the closest matching color in the DXF color palette.
• Spaces in layer names will be replaced with the underscore character.

To install:

1. Close down Inkscape.
2. Download the ZIP file containing Big Blue Saw's DXF Export For Inkscape.
3. Unpack the ZIP file into your Inkscape extensions directory: typically C:\Program Files\Inkscape\share\extensions on Windows or /usr/share/inkscape/extensions on Linux. (Mac users, help me out here.) You will need to overwrite the file simpletransformations.py with the version included in the ZIP archive.
4. Restart Inkscape.

To use after you've installed Blue Saw's DXF Export For Inkscape:

1. Create your drawing as normal.
2. Ungroup all items by selecting everything (Ctrl-A or Edit | Select All from the menu) and then ungrouping repeatedly (Shift-Ctrl-G or Object | Ungroup) until all groups are broken apart.
3. Convert all objects to paths. You can do this items by selecting everything (Ctrl-A or Edit | Select All from the menu) and then pressing Shift-Ctrl-C or choosing Path | Object to Path from the menu.
4. Choose File | Save As from the menu. In the dialog box that appears, choose "Big Blue Saw DXF Output" and click the Save button.

   

One more thing, for those reading this far. Most of the time when I, personally, want to get a DXF from a file loaded in Inkscape, I save it as an EPS, and convert to DXF using the pstoedit package. This preserves splines and curves, which is nice, but requires the use of a command-line tool, which isn't for everyone.

Download Big Blue Saw's DXF Export For Inkscape Here

The data center where Big Blue Saw's main web server is hosted is soon to be no more. I'm in the process of moving everything to a new and better server at a new location. The final cutover is scheduled for this weekend, August 21.

I'm in the process of bringing up the new server:

http://chainsaw.bigbluesaw.com/

Please let me know if you find any problems on the new machine. Please note that anything you do on the new server is likely to be wiped out when the changeover happens: comments, user accounts, uploaded files, and the like will all be deleted.

I recently conducted an interview with Ray Russell, founder of RoPro Design, a robotics engineering firm. Ray talked about his robotics and prototyping work with RoPro, as well as the tools and techniques he uses to turn his customers' ideas into reality.

In this interview, Ray talks about how his production schedule doesn't match with a traditional machine shop's ordering process. This eventually led him to order from Big Blue Saw.

The typical waterjet companies around here have the traditional quoting system. where you send them a paper drawing, you wait 3 weeks, the guy contacts you with a formal quote and it's just way too slow. In 3 weeks we usually have robots designed and built.

He mentions some of the advantages to making parts using waterjet cutting.

With waterjetting, you can get arcs and things that you can't get in a billet piece.

Ray is a big fan of rapid manufacturing techniques and believes that it will help US manufacturing competitiveness.

The only we're going to compete with foreign manufacturing is through this high tech arena. There's no way we're going to be able to do it on the old style of intensive labor.

Download the whole interview in MP3 format.

Here's the interview with some images of RoPro Design's and Ray's work.

Skip ahead to 8:15 in the video to see video of the hexapod robot he built in conjunction with Carnegie Mellon University.

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.

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.

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.

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.

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.

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

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.

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.

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

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.