QR Codes are all the rage and though their usefulness is debatable, they’re still fun to think about. This article shows how to cut a large QR code on a Full Spectrum laser cutter. You’ll amaze your friends and maybe even acquire a couple groupies (after all, that is why I’m doing this.) If you want to follow along up to the point of the laser-cutting, you’ll need to install Inkscape on your system.
Wrong Turns Learning Strategy
When you move to a new city, you can stay on the main roads and make your way around, but you don’t really learn the city until you make a wrong turn. Once you’re “off-road”, you’re forced to find your way around, really learn the streets, maybe even see some natives. Your awareness and anxiety is heightened, your brain is wide-open seeing landmarks, signs, avoiding peds. My goal is to help get you off-road and help you when you are off-road. I could write this tutorial like rote turn-by-turn navigation and you’d get the result, a mondo QR code, but you wouldn’t really learn anything.
The wrong turn learning strategy pays off in spades especially if you can get someone else to make the wrong turns for you – that’s my job.
First, The Lowly QR Code
There are hundreds of programs and sites out there to make a QR Code, so I googled and picked an arbitrary service: head over to qrstuff.com and make a QR Code. I used the Inhale 3D home for the content:
When you download it, you have your first QR Code in a PNG format and if you don’t already know, PNG is a bitmap format.
When in Rome, do as the Romans
The Full Sprectrum laser family is completely tied to an “e-paper” format in the Windows world called XPS which is both a bitmap and vector format. While it’s considered an “open” XML format, in practice there are very limited ways to get it to it. What’s the most common way to XPS? Easy, It looks like a printer on your Windows machine but writes to a file instead of a printer.
I’m a multi-platform guy – I use OS X, Windows, and Linux on a daily basis – so I learned to adapt my work-flow to the tools I like the best on each platform. I looked high and low for an XPS printer driver for the Mac so I could print to an XPS file natively from OS X, but alas, I don’t think it exists. There are XPS readers for the Mac, but haven’t found a driver for writing. This issue dictates that at least the last stage of the process has to be done on Windows.
PNG to XPS
The question is how to turn a PNG into an XPS file for laser cutting? While CorelDRAW is a very common commercial package used with laser cutters, I wanted to use the free and open source Inkscape.
Inkscape is a cross-platform, vector drawing package and you can think of it as an open source analog to Adobe Illustrator or even CorelDRAW. Since it’s not possible share an XPS printer on Windows to a Mac, I put Inkscape on my Windows VM.
You’ll need to install the Windows XPS print driver package available from Microsoft, but then Inkscape on Windows can print to the XPS printer driver once the graphic is ready. Full Spectrum’s software, RetinaEngrave 3D, can then read the XPS file and turn it into the code to send to the laser cutter. On Windows 7, Retina Engrave 3D itself is a print driver so if you print to it, you skip the intermediate step of printing to an XPS file then importing it into Retina Engrave. On Windows XP you have to print to XPS then import it into Retina Engrave 3D which is inconvenient but not a showstopper.
Scaling the QR Code
The QR Code you import into Inkscape must be scaled to the size of your stock. In my case I chose a 12″X12″ piece of clear acrylic and I wanted a small border around the QR Code.
To do this, change the Inkscape document size to be the two-dimensional size of your stock (File->Document Properties->Page->Custom Size and also Default Units as shown below) – you can set the units to whatever you’d like but I set mine to inches since I had the 12×12″ stock.
Next draw a hairline, unfilled rectangle around the perimeter of the document. Why? RE3D will crop the XPS image to the outer perimeter of the QR code itself, leaving no margin around the outside. In other words, it won’t respect the full document size you set in Inkscape without the outer rectangle for content. This is problematic because it makes it harder to exactly line up the QR Code corner on the stock. If you have an exact 12×12 document with the hairline rectangle, the outer perimeter is 12X12 and you can line up the laser directly on the corner of the stock and everything will come out right.
The other reason is if you had a piece of acrylic that wasn’t already 12X12 and you wanted to have the laser do the outside cut, then both the engraving operation and the cutting operation will be precisely lined up if you don’t remove the piece between operations.
After you have the hairline border rectangle, import and scale up the QR code PNG file and center it in the middle of the 12X12″ document. Make sure when you’re scaling it up, you use uniform scaling – click on the corner of the QR Code, then press control then drag. The other way is to use parameters in the scale field. Click the QR Code, the type in the dimensions of the QR Code you want – in the example case, the origin will be 0,0 and the extents will be 12 (W and H). Make sure the units match your intentions – in my case it was set to “in”.
At this point, you have a scaled QR Code that fills the stock.
Printing to an XPS File
The next simple but key step is to print the QR Code to an XPS File on Windows (or print direct to Full Spectrum Laser printer driver which is RE3D.) It’s the XPS file that RE3D needs to set up the cut.
XPS to Full Spectrum Laser Cutter
Bring up RetinaEngrave 3D and load the XPS file. It’s subtle but make sure you have the full 12X12″ border around the piece. The image below shows what it should look like. If you didn’t do the hairline rectangle earlier, the extent would not be 12X12″ but rather closer to the 11.5″ where it would crop to the outer black area of the QR Code.
Preparing the material
The trick to making a large QR Code is to create a black and white mask over clear acrylic. To start with, peel one side of protective adhesive layer away from the acrylic piece – this will be the side that gets painted prior to etching:
Next paint it black on the exposed side – this forms the base of the mask.
I use the Rust-oleum Ultra Cover product since it creates a very smooth finish and is also billed to work on plastic.
Make sure to let it thoroughly dry because this is the side that will be etched by the laser. Load the piece into the laser – the QR Code stock is shown below before loading it in. Be sure to square it up within the laser frame and also be sure if you have a 12″ cut height as I do with this laser, that you position the piece at the top of the cutting limit.
Etching the Reverse QR Code Image
Since the mask is black, we want to etch off the black wherever there should be a white or translucent surface. In order to do that, it’s critical to tell RE3D to etch the opposite of the black QR code. Fortunately, RE3D has an easy way to do this by both inverting and mirroring the image.
A single click on the mirror and invert and the QR Code will be reverse etched. The reason for inverting it like this is that once the black paint is etched off wherever the white paint will be, then we paint over the whole mask again with white paint. The mirroring allows us to etch the back-side of the piece so that when you look at it from the front, it’s correct and the paint will be on the backside of the sign.
The masking would work just as well had we painted the side white first instead of black, then etched where the black would be (no inversion or mirroring required), and finished it off with black paint instead of white.
After etching and before painting the exposed mask white, the QR Code will be translucent which looks kind of cool, but you have to set it up just right for most QR code readers to recognize it.
The final step is to fill in the mask with white paint – the paint will go on the same side as the black paint – this is the piece laying in my paint booth
And now painted (also with the Rust-oleum 2X ultra coverage.)
Once this dries, you have a mondo QR code suitable for hanging in a trade-show booth, or store window.
