Aug 09

Burning Rubber


There’s a fine line between being a Maker and a Crafter (if indeed there really is any line at all). Personally I got into this hobby with the firm intention to stay on the side of the line that is occupied by computer-controlled lasers and Tesla coils, but lately have found myself spending an inordinate amount of time playing with construction paper. I feel like somehow I should be more enlightened and not care about such trivialities, but the fact remains that when one sets out to find their inner Edison it’s a bit of a shock to discover that really it’s Martha Stewart in there. I take some comfort in the fact that I’m not the only one who struggles with this. Let’s face it, the only reason to crochet a hand grenade is to prevent your idle hands from turning out a tea cozy.

I gave up toeing the line and jumped right over it with this weekend’s project – rubber stamps. My kid said something about wanting some new stamps and the part of me that is constantly looking for any excuse to pop over to TechShop for a few hours sprang into action. I knew that it was possible to etch custom rubber stamps with a laser cutter, but not much more than that. Less than 24 hours later I’d made a bunch of mistakes but ended up with some pretty good stamps.

Raw Materials

I had a goal and no plan, but I didn’t let that prevent me from getting started. I wandered around a local art supply store looking for things I could etch with a laser. It turns out they actually sell plain rubber sheets for hand-engraving and through some random bit of luck I walked right up to them in the store. They are exactly the color and texture of newborn hamster – pink and squishy and somehow unsettling. Then all I needed was some wood to use as a handle for the stamp. I had some scraps in the garage that I cut down to size. That plus some hot glue and I was ready to go.

RawMaterials Gun

For artwork I grabbed some pictures of our cat and some Super Mario characters. Stamping with ink has the same constraint as some of my previous art projects – there is no way to modulate the intensity of the ink so you need to modulate the density of placement to get gradations of color. I should rename this to the halftone blog, since I end up using halftoning techniques for everything I do. In CorelPaint I converted the images to monochrome and used a variety of halftone methods to see what worked best. In the images below the Shine Sprite uses a dot halftone whereas the cat is using a 45-degree line halftone.

shine pea_lines

Frickin’ Laser Beams

Armed with something to burn and some suitable images I headed over bright and early (the only way to get time on a laser on short notice is to get there at 9AM) to use the 45 watt Epilog laser cutter. Inking paper with a stamp means we want to place ink where the images are dark. This is the reverse of how the laser usually works, which is to burn the material where the image is dark. For our rubber stamps we want to burn away the bits that shouldn’t pick up ink which is the white parts of the image.

The Epilog print driver has a specific setting in the Advanced tab called “Stamp Mode” which reverses this logic so white areas turn the laser on rather than black. This was just what I needed so I picked that and then went to start my etching/cutting job. Since my piece of rubber material was fairly large (around 100mm x 75mm) my job consisted of several stamps I would etch into and cut from the rubber. I added hairline vector outlines around the raster images which would cut partially through the rubber making it easy to separate the stamps.

But when I ran my job it only etched one of the stamp images and skipped all the others. Additionally it didn’t do any of the vector cutting at all. I’ve had issues like this before – setting the wrong line weight or fill/clipping options can cause a part of your document to get skipped. After wasting half an hour I was completely stumped. In desperation I turned off “Stamp Mode” in the driver and voila everything started working again. So rather than continue reverse-engineering the inscrutable logic of Stamp Mode, I just inverted my colors manually and started my job up. The vectors cut and the images etched and all was well.

Vector Cutting2

The job was about 98% done and I was admiring how nice the text stamps (Happy Birthday) were coming out when it occurred to me that there’s at least one other thing that Stamp Mode must be doing. Clearly it is also flipping the images horizontally, since what you get on the paper is a mirror image of what you see on the bottom of the stamp. So my text stamps were only useful for stamping birthday wishes on the front of cars so they could be read from another vehicle’s rear-view mirror. Another hard-won piece of knowledge gained.

The Verdict

FinishedStampsI had other stamps I wanted to etch, but at this point nearly 2 hours had gone by and as intoxicating as the fumes of burning rubber were it was time to call it a day. I cut the stamps out and affixed them to the wood blocks and did a few test runs to see how they came out.

CatFace-Stamp All told I’m pretty satisfied with the results. There linear halftones have the lines a bit too close together so the lines aren’t as distinct. In the future I’ll probably go with fewer lines-per-inch for the halftone. Additionally, I only ended up etching out about 1/16th of an inch or so which isn’t enough to get a really clean stamp. I had to run the laser fairly slow (~15% speed) to get that so next time I’ll probably do 2 passes to burn away a bit more material. You don’t want to go any slower than I did, because at slower speeds rather than etch deeper the rubber simply gets overly hot and starts to melt.

Although the next logical step in the progression is probably something like laser-cut doilies, I’m not sure what I’ll be doing next. I was inspired by the #awesomeaugust trend on Twitter, which is a challenge to finish 4 projects in the month of August. I made a list of projects either already partially started or band-new and I’ve got a few days of vacation, so we’ll see where inspiration strikes next.


PS: I mentioned the crocheted hand grenade guy earlier. You’ve got to check out his site at http://woowork.blogspot.com/ – everything he does is pure effin’ gold.

Jul 09

The Accidental Buddhist

I should probably start by saying I’m not an expert in Buddhist practices or those of just about any other religion. The sum total of my knowledge in this area was picked up from Chinese restaurants, re-runs of Kung Fu and the occasional PBS documentary. Somehow amidst the Honey Walnut Prawns and pledge drives I’ve become aware of an exercise practiced by Buddhist monks that I find fascinating.

sand-painting Tibetan Sand Painting is an ancient art where monks creating beautiful and exquisitely detailed pieces of artwork with colored sand. It’s a labor-intensive process that can take days to complete, and the results are amazing. But when the art is completed they simply brush the sand away destroying the image. It’s a metaphor for the fleeting nature of life. That’s always seemed intriguing to me – creating something just to destroy it. Now I’m not sure if this next part is true or not, but I recall hearing that they destroy the artwork the instant it is completed. There’s no sitting around gazing upon their work in awe and high-fiving each other. The point of the creation is the destruction and nothing else. So the logical thing to do upon its completion is to immediately trash it. It’s religious meditation as punk rock. Maybe that’s why this idea is appealing to me.

This practice is appealing to me in theory, that is. There are a lot of things I like conceptually but really it’s the idea I like and not the doing. Flying in an F-16, for example, is an incredibly attractive thing that I hope I’m never rich enough to actually do because apparently every non-pilot who has done it has hated the experience. I can appreciate things that others do without actually doing them myself. I don’t actually need to be destitute and living on a diet of White Russians and bowling alley nachos, because The Dude is out there takin’ ‘er easy for all of us. Similarly, I don’t need to destroy my handiwork because The Monks are out there reminding us all of how fragile our existence is while I watch them on my flat-screen TV from the comfort of my couch.

45 Watts of Enlightenment

These thoughts were far from my mind as I started my cutting job on the Epilog Laser at Techshop. It was my first test of my laser-cut paper halftoning technique and I was cutting out a photograph from some cardstock. I created a linear halftone that consisted of a bunch of parallel lines where the thickness of the line varied according to the darkness of the image. Here is a close-up of the vector image I was cutting – if you squint or back up across the room you can see that it’s a pretty good effect.


It’s quite an intricate design that needs to be cut, but fortunately the laser cutter is doing all the work. Several minutes later the Epilog beeped indicating the job was finished and I pulled out the finished work.

Have you figured out where the story is going yet?

I picked up the piece of cut cardstock and for a brief fraction of a second the image of the photograph hung in mid-air before collapsing into a pile of confetti. I immediately recognized my error – each diagonal line was completely separate and thus had nothing to hold them together. I had turned the Epilog into a $30,000 paper shredder. As the pieces of paper fluttered to the floor I was reminded of the impermanence of existence and felt an overwhelming craving for Mongolian Beef. But lunch and enlightenment would have to wait, because I needed to finish my project.

I decided to try a fairly simple fix. In CorelDraw I created a rectangle that was as tall as my image and .02 inches wide. I then duplicated it several times so I had a series of vertical bars and then used the Weld command to join these bars to my image. Finally I trimmed the edges so there weren’t any bars poking out past the edge of the photo. The result looked something like this:


The results came out far better than I expected. The vertical lines were thin enough to not distract overly from the image, but were substantial enough to hold the paper together very well.


Lesson Re-Learned

It’s not like you need an advanced degree in topology to avoid a mistake like this. Most of us learned these principles in Kindergarten while cutting shapes from construction paper. It’s obvious in hindsight that the laws of physics apply to a laser cutter just as much as they apply to blunt scissors. But making the mistake is the best way I know to assure you never make it again.

Jul 09

Pictures From Paper

One of my favorite toys at Techshop is the Epilog laser cutter. It can cut and etch at resolutions up to 1200dpi. It can cut through things like paper, cardboard, acrylic and thin wood as well as etching into those materials, metal and even food.

Lately I’ve been experimenting with creating pictures by cutting pieces out of colored card stock and stacking them up. The way to think about it is that each layer of paper gives you a single color – it’s like a 1-bit monochrome bitmap that’s either the color of the paper or transparent showing what’s behind it. Newspaper printers figured out ages ago how to deal with a similar set of constraints – a single ink color, but high resolution of ink placement – and approximate multiple shades of color using a technique called half-toning. Here’s how I adapted this technique for paper-cut images.


My first test was to see how I could approximate a gradient fill. I started by creating a jpeg image containing a simple black-to-white radial fill (left). Then in my paint program I converted the grayscale image to a monochrome black-and-white image. When you do this in CorelPaint it gives a variety of options on how to do the conversion. One of them is creating a half-tone image, which is what I used. I created a halftone using squares (dots are the ones you see in newspapers) at a 45 degree angle and a very low resolution of 7 lines per inch. The result is the picture on the right.

Now I needed to turn this image into vector outlines so the laser cutter can deal with it. I imported the bitmap into CorelDraw and used the bitmap tracing feature to trace it in line-art mode. Corel’s tracing is fairly flexible and can attempt to trace multi-colored images by creating vector shapes in different colors. Sometimes even if you feed it a simple picture, things like anti-aliasing artifacts can trick it into using a bunch of colors which I didn’t want. Using line art tracing settings gave me a shape containing about 1500 little vector polygons that approximated the half-tone bitmap. I gave the shape an empty fill and hairline outline which tells the laser cutter to perform a cut of the outline rather than a raster-scan etch. The result looks like the image below.

It turns out the hardest part of the project was getting time on the laser cutter. My schedule has been very busy and between travel and working evenings and weekends I’ve only had a few chances to get to Techshop recently. The two laser cutters are very popular so it was almost 2 weeks before I had a chance to try it out. I cut at 600dpi, 100% speed and medium-low power which gave good speed and minimal charring. They call it a cutter, but what it’s doing is burning the paper, so too high a power or too slow a speed will end up with visible burn marks on the paper. A fire in the machine is a possibility as well and before they let you use the cutter you have to take a safety class where they force you to deal with a fire, which is not nearly as exciting as it sounds but still awesome.

I cut it out of dark brown card stock and then placed it on top of a background of red construction paper . The result is a radial ramp from red to brown that looks pretty good. I could have made the squares a lot smaller, but wanted them to be fairly big and obvious. Also, the file took 10 minutes to cut as it is. With a lot more polygons it would have increased the cutting time significantly.

You’ll notice that in the middle the halftone squares got so close they ended up touching and it cut the entire middle out. I didn’t worry about it because this was going to be the background for a picture and the middle would end up being covered. The full finished picture was a picture of a tea drink my daughter likes which you can see below. The additional layers are glued on top of plastic and acrylic spacers to give the whole image depth and the upper layers actually cast shadows on the lower ones.