Sep 09

Paper Pixels

IMG_0050Who the hell came up with Pin The Tail on the Donkey? And furthermore, why on earth are people still playing this asinine game? The wisdom of taking a bunch of kids, spinning them around until they’re dizzy, then sending them careening around the room blindfolded with the instructions “stick this thumbtack into something” is questionable at best. It’s one of those games like the 3-legged race where the amusement is not so much for the participant as it is the spectators who hope to laugh at some minor tragedy. Both games are based on the premise of performing under constraints – not being able to see, not being able to move freely, etc.

Constraints show up in creative projects often. The choice of medium for an art project will impose constraints, and those constraints force you to think creatively about how to deal with them. Success can come from turning the constraints into an advantage, like the staples sculptures here. Or it can be less about the actual results and more about the Sisyphus-like effort involved in the creation.

I’ve written about making pictures from colored card stock in the past, which imposes some fairly specific constraints. It’s essentially like a variation on a monochrome computer display – you can make any spot either the color of the paper or, by cutting a piece out, transparent. I spent some time recently adapting these techniques for use with my Craft Robo computer controlled paper cutter.

Play To Your Strengths

For this project, I wanted to reproduce photographs using two colors of paper. The top layer of paper would be dark and the bottom layer would be light. The technique I planned to use was to divide up the paper into a grid of many small squares. Then, depending on the brightness of the photograph at any give spot I would cut some portion of the small square out. If I needed a bright spot, I would cut a large square out showing mostly the rear light-colored paper. If I needed a darker spot the square I cut would be smaller so less light would come through, and for the darkest spots I wouldn’t cut anything at all out of the dark paper.

IMG_0046This technique gives the ability to reproduce various shades of brightness, but at the cost of reduced detail. Knowing this, I decided to start with a photograph of a simple object without much detail. If someone tells you to make music with one hand tied behind your back, better to choose singing rather than playing the guitar. So I took a picture of a white ceramic espresso cup. This also had the benefit that there was no color, and thus it would translate well to a monochromatic reproduction.

I then wrote a program that applied a grid to the image and based on the average brightness in each grid cell produced an appropriately sized white square in the cell. Through experimentation I decided to use an 11×11 pixel cell size, which translates into each cell being about 0.15 inch square on the paper.

I had to play with the contrast and brightness a bit to get a good result, but ultimately I ended up with the following. The original image is on the left and the monochrome processed version is on the right:




From Bits to Atoms

Now I needed to turn the monochrome bitmap into vectors that the Craft Robo cutter can understand. It was a simple matter of importing the bitmap into Corel Draw and then using the Trace Outline command to generate a vector art file:

Vector Espresso

The Craft Robo continues to impress. It took a while to cut out the 835 squares – about 10 minutes or so. But the results were stellar. Each square had nice sharp corners and even the smallest squares, which were just over 1mm wide (about 4/100ths of an inch) cut cleanly. Not all of them cut completely out, so there was a bit of picking pieces out with my tweezers. But after that was done the picture looked pretty good. I trimmed the picture (cut from darker colored paper) and the back layer of bright colored paper and assembled them in a frame.

IMG_0056 IMG_0059


One More Thing

I had another frame on hand, so I cut a second copy from a different color of paper. The final pictures have an abstract pop-art look to them, so it actually looks cool to have two of them in different colors hanging on the wall.



Aug 09

CNC T-Shirts

T-Shirts I have many random memories from my childhood – one of them is the time my mom and I tie-dyed some T-Shirts together.

The sentence that you just read, while being completely true, is also potentially a shining jewel of disinformation. Having read it you may have imagined me and my hippie mom barefooted and doing our tie-dying, stopping only to flip over the Janis Joplin record that was playing. This couldn’t be farther from the truth.

I grew up in Orange County, California – known for growing produce and conservative presidents. My parents have a framed photograph of Ronald Reagan hanging on the wall. I was sporting a buzz-cut given to me by my father, who had done a stint as a barber a few decades earlier and hadn’t sharpened his scissors since. So when I say my mom and I were tie-dying, it was not because we were turning on, tuning in and dropping out. It was more likely that the Ladies Home Journal had run an article on it. LSD had long-since jumped the shark by the time tie-dying became commonplace in my hometown.

But it was a fun time and I remember it to this day. I got to make some new memories with my family this weekend as we made our own screen-printed T-Shirts. Of course, I refuse to use anything so crude as hand-twisted fabric and rubber-bands. Around here we like our folk-art at 1200dpi precision or better and that’s what we got.

Making A Stencil

There are a lot of great Instructables on screen-printing, so I won’t go into details on the process beyond saying it’s essentially applying ink to a T-Shirt through a stencil. So the core problem is creating the stencil you want for your pattern.

My plan was to use my newly-acquired CraftRobo to cut a stencil out of vinyl. It’s the home equivalent of the CNC vinyl cutter I’ve used at TechShop but at a smaller scale. The CraftRobo needs vector outlines to describe the shape to cut, which was going to be generated from a photograph.

I started out with a picture of our cat and converted it to a monochrome image using a straight threshold filter in my image editor. The logic simply says that any pixel with a brightness greater than 50% is white and the other pixels are black. I adjusted the brightness and contrast of the source image first so I would get the best results after thresholding – it was particularly important to get the eyes right with lots of white with slivers of black. I then did some editing of the resulting black-and-white image to clean up the edges and get rid of random detail.

IMG_0398 PFace

Next I imported the bitmap into CorelDraw and used the outline trace to generate a vector outline version of the bitmap. Because of all the tiny little white dots in the image, I ended up with a fairly complex set of vectors. So I spent a bit of time deleting these tiny little shapes which are essentially unnecessary detail. This speeds up the cut as there’s much less work for the cutter to do and less time with tweezers weeding out tiny pieces of vinyl. Finally I added some text and had completed vector art ready to cut.

Dont Mess With Sweet Pea

Once the stencil was cut it was time to weed out the pieces of vinyl that weren’t part of the stencil. I did this once and removed the completely wrong pieces. In my defense it’s a bit confusing, since you want to throw away the pieces where you want ink to appear so you end up with a reverse image in the stencil. I printed out the image as a cheat sheet and spent about 5 minutes pulling off pieces with a pair of tweezers and got a nice stencil.


Then I applied the stencil to some transfer paper and it was ready to stick on my printing screen. The image is flipped horizontally at this point because the sticky part of the vinyl sticker is facing up.



If I had more time I would have made my own printing screen, but instead I bought one at the local art supply store for about 5 times more than the couple bucks it should cost. The company that makes it decided to call themselves “Speedball” which makes me think they don’t do much international business – not exactly a name that guarantees a hassle-free trip through customs. I also picked up a couple colors of fabric ink. I wanted to use different colors for the text and the image, so you can see I’ve masked off the image separately as I’m getting ready to apply the ink. This was a total hassle and for subsequent prints I’m just making separate stencils for the different colors.


The first print came out OK, but the ink was pretty uneven on the text due to me not being aggressive enough with the squeegee. Also some ink bled through on the side due to some poor making tape around the stencil. But I knew the first one would be rough, so I made my shirt the guinea pig so we’d have the kinks worked out before we did the others.


We were flying blind a bit on colors, not really knowing how they would look on the shirts. But by the time we did my daughter’s shirt the combination of good technique and great color combination produced an excellent result. We’ll add some text in a different color later – I’m assuming registration should be simple enough but we’ll see.


There’s a ton of places that will print custom T-Shirts so there’s plenty of competition and as a result prices are pretty low. So this DIY project isn’t much of a money-saver, but it was a lot of fun and at least now I can brag about my CNC T-Shirt.

Aug 09

Deadly Robotic Razorblades


Names and branding matter. My instincts tell me to never drink something called Calpis, so that name is a pretty big hurdle to get over. Having said that, if it tasted really good I’m certain I could get past the problematic moniker.

If you had told me last month how excited I would be about a product with the word “craft” in the name I’d have said you were insane. But a few days ago my brand new CraftRobo arrived in the mail and it’s pretty much the coolest thing I’ve acquired in a long time. Fortunately it’s got “robo” right there immediately after “craft” – the spoonful of sugar to help the medicine go down. It may be a crafty automated 2D paper cutter – but really it’s a razor controlled by a robot and that’s pretty cool no matter what you call it.

Through twitter I stumbled onto some video by Bre Pettis and Jeff Rutzky at http://www.craftrobostore.com/ of the Craft Robo in action. I’ve been using an Epilog laser cutter to cut cardstock and a CNC Vinyl Cutter to make stickers at TechShop, and the Craft Robo looked like it could handle these materials as well. I found one for around $200 new on eBay, so I clearly wasn’t expecting it do anything as intricate as I was doing on machines that cost 10 to 100 times as much. But for the price it seemed like a no-brainer to get and try out.

I started out cutting some simple shapes from cardstock and vinyl just to test it out and I was impressed by how fast it was. It cut out text from vinyl as fast as the CNC cutter I had used before and the resolution was indistinguishable as well.

The tests were so successful that I decided to throw down the gauntlet. I tried cutting one of the more challenging shapes I’ve done on the laser cutter – a photograph cut from cardstock. I literally opened the exact same CorelDraw file I had previously cut on the Epilog and sent it to the Craft Robo. The first thing I noticed is that it took about the same time to cut on both – about 5 minutes. When the job was done cutting I was blown away by how faithfully the Craft Robo had reproduced the photograph. I wasn’t able to find any resolution claims in the specs posted online for the Craft Robo, but there are sections of the image where the cuts are only .02 inches wide and it had no trouble resolving these lines.

The biggest issue was that most of the pieces didn’t completely cut through. The entire job consists of thin strips to be cut out and since the Craft Robo uses a drag-cutting blade that has to rotate to cut it’s not great at cutting sharp acute-angled corners. So what I ended up with was a bunch of slivers that I had to manually weed out using tweezers, whereas on the laser cutter all the pieces except a couple fell out. But for $200 and about 20 minutes of weeding I got a result that is pretty comparable to the laser cut version.


The other major limitation of the Craft Robo is the size of material it can handle, which is limited to about 7” x 10”. I’ve out 5 foot long stickers at TechShop to stick on my walls, which I couldn’t do with the Robo. But these are totally reasonable constraints given the impressive price point.

This weekend I’ll be working on some software to do some more creative halftoning and color separation, which should allow colored photographs to be reproduced with multiple layers of cut cardstock. I haven’t come close to finding the limits of this machine yet and can’t recommend it highly enough.