Running slow: eliminating wobbles

There is a trade off between speed and quality with x-y laser cutting. This 80# cardstock test shows a slow run on the left and a fast run on the right. To get the best results I run the laser at a slow speed; it ensures very smooth curves and a close representation of the original art.

At a fast speed the laser beam carriage runs with some wobbles. If this loss in accuracy is acceptable for your project please let me know. Depending on the circumstances it may lower the cutting cost 10-50%.

Cutting OSBP’s logo: behind the scenes

http://www.youtube.com/watch?v=8V3Qbh3C32w?rel=0

I was delighted to have Carina of Crow & Canary swing by the workshop last week to take some photos for a guest post on Oh So Beautiful Paper. Here’s what it took to prepare the OSBP logo, with calligraphy by Bryn Chernoff, to be cut.

Here is the original logo:

Original version of OSBP logo

and here is the laser-ready version:

The OSBP logo prepared for the laser

The original logo would cut as several separate pieces (“O” “H” “S” “O” “Beautiful” “P” “aper” and the dot of the “i”), so the first thing I did was tie everything together. I start with a frame that the words will be bridged to:

OSBP logo with a simple frame

The straightforward solution to bridge the text is to add a rectangle that intersects each text baseline. Tall portions of the design might flop over when the paper is held upright, so those need to be secured as well.

OSBP with lines added to bridge to the frame

Unfortunately, this doesn’t fit with the aesthetic of the logo and the long start to the “P” is likely to sag. Instead, I decided to pull everything together with some well placed curves.

OBSP tied to the border with curves

Next, all of the black portions of the image are unioned together. The correct line width and color are selected for compatibility with the laser, the path is offset to adjust for the kerf, and a test cut is made.

The test cut revealed a few weak spots so the paths were tweaked and it was ready to go. The video took several takes; I’m a video novice so it took a while to get reasonable depth of field with the low light in the workshop.

Please let me know what topics you’d like to hear more about. I’ve been working on an FAQ for the site that touches on several areas that could be addressed in more detail. Thanks for reading!

How to improve laser raster images with tuning

Adjusting the “tuning” in the Universal Control Panel (UCP) can make a dramatic difference in the clarity of raster images. For GCC/LaserPro machines this feature is also called tuning. On Epilog it is called “Laser Match.”

Last autumn I added a second laser to my shop. One day I saw a live auction listing and the next I was the slightly nervous and very excited owner of a machine that I’d never seen powered on. The first text tests were barely legible. One of the many steps to refine the output was to adjust the tuning.

The following diagram demonstrates the result we would like to achieve.

When a raster image is sent to the laser the driver splits it into horizontal slices. Each slice represents a pass that the laser head will make in the X direction of travel.

Tuning changes the distance that the X belt moves before the laser begins to pulse in each row. Poor tuning will cause a misalignment of an etched line in the right-to-left direction versus the left-to-right direction.

The fix is fairly straightforward. First, draw a solid, long thin rectangle. Change the raster settings to use the lowest image density (lines per inch). Etch on a material that has very high contrast. Anodized aluminum is fantastic; since I didn’t have any on hand I used a dark black paper that shows a nice mark.

The desired result is for the left and right edges of each line to be flush. The following image shows an example of running this test. The first column shows the original ragged line. Next, I moved the line over, adjusted the tuning, and ran the job again. This is the value I chose; the next two tests use different tuning values and are slightly ragged again.

After fixing the tuning my sample text was still slightly blurry compared to the results from my other laser. The accelerating/decelleration curve didn’t seem as good on the older model. That is; it wasn’t slowing down enough to give a really clean etch. By lowering the speed I finally saw the crisp text that I demand.

If the tuning value you need to use seems unusually high or low you should check the laser’s X belt; it may be too loose.

Common bridge problems

One of the critical pieces of making a design work in the physical work is paying attention to bridges — paths that cross gaps in your design to hold it together. A potential client is working on a gatefold envelopment for an invitation. She’d like to have some text cut out of the gatefold; that is, the text is negative space. We start our design by just typing in the text:

Without any changes, we’d end up with something like this:

Now it’s obvious that some bridges need to be added to the design. We’ll start by adding bridges (or rather, removing part of the design) to connect every island, like so:

Now the design looks like we intended when cut:

However, there is still a problem. Imagine taking your finger and pushing on different parts of the cut piece, for example, the middle of the “o”. This piece is quite floppy, making it likely to shift around, get pushed in and out and ultimately tear off. We could make the bridges really wide, but we risk throwing off the balance of the design or ruin the legibility. To reinforce the islands, we instead add more bridges:

Finally we have a design that looks good and is structurally sound:

I am of course happy to take your money in exchange for doing this work for you. I’ll make the needed changes, cut a physical prototype, photograph it for your approval, and send back the modified file.

Freshly Cut – Business cards for Mod My LLC

Laser cut business cards

Cut from Mohawk Beckett Cambric in Blazer Blue/White. Stitch-effect edge and rounded corners.

ModMyi is an Apple news site with community forums and downloads. Kyle contacted me about creating cards to bring to the upcoming Apple developer conference in San Francisco.

Custom box for laser cut business cardsOpened custom box for laser cut business cardsLaser cut business card showing detail of etching and linen texture

Using a vector file of their logo I created five design choices and tested a couple of duplex blue papers. The thicker 130lb paper with its delicate linen texture was a clear winner. Why duplex? For my own cards I’ve used a wide range of papers. I found that the dark papers were frustrating because I had nowhere to write. With a dark/light duplex the problem is solved by having the back of the card to write on.

After a lot of testing I found the precise setting so that the laser would burn away just the blue layer of the paper, leaving the white to give high contrast for the text. Unfortunately this paper is relatively smokey; I had to clean the lens of the laser between each sheet to maintain the optimal power.

The duplex engraving isn’t as legible as printed text but it’s a very unique look. Additionally, there are no plates to make, no ink to use, and no nasty chemicals to clean up the ink.

To complete the project I designed a custom box to match the cards. (I’m eyeing a copy of The Packaging and Design Templates Sourcebook to make this process faster.)

Additional photos are over in my flickr photostream. You too can own a swanky set of laser-cut business cards if you just email to get the ball rolling.

Kerf widths, inside cuts and Illustrator

Cutting art with fine details requires accounting for the kerf of the laser beam. The laser beam’s center follows the center of the vector path. Some material will be burned away; the width of the removed material is called the kerf.

The kerf depends on a few factors, including the size of the lens, the type of the material, and the speed of the cut. For example, when cutting cardstock with a 1.5” lens a ULS 4.60 there is a 0.003” kerf on straight cuts and a 0.007” kerf on round cuts. Since the beam is centered, we only need to account for half of the kerf. In practice I’ve found that a 0.003” addition to the art allows for a good approximation of the original art.

Normally in Illustrator CS4 I use the appearance palette to add a Path->Offset Path… to account for the kerf. However, this doesn’t work correctly with inside cuts.

For example, from this art:

we would like to end up with a frame.

However, the kerf (purple) will cut from the exterior and interior, leaving a frame with a narrower width than intended.

Original art (two nested squares)

Desired cut (inner square cut from the outer, leaving a frame)

Frame narrower than intended

With Offset Path… only, both paths become larger.

The final frame is bigger all around.

Squares shown scaled up

Narrow scaled up frame

One easy change is to set the outer square to a positive offset, and the inner square to a negative offset. However, with complex artwork it is tedious to select every inner and outer cut separately.

Instead, select the cuts and use Object->Compound Path->Make. Then with the compound path selected apply the Offset Path.

Now the kerf is correctly accounted for and the desired frame is achieved.

Outer square has outer outline, inner square has inner outline

Final correct frame

Candyspotting specializes in laser-cut paper. Contact me for a free estimate.

I’m lucky to have a friend who’s incredibly passionate about energy consumption. It makes me think about how my business and my family can reduce our draw. Since we have a baby in cloth diapers we start out pretty poorly — the washer, dryer, and dishwasher are run every day. We’ve made three recent changes to help our impact.

1. Replace the thermostat with an ecobee. I love our programmable thermostat. It makes it dead simple to keep the heat off or low when we don’t need it. Best of all, there’s an iPhone application so that when we’re out of the house we can remotely turn off the heat. It feels like the future when I can check the temperature of the house when I’m not inside it.

2. Go car-free. We were living “car light” for several years; we both used alternate forms of transportation to get to work. Portland’s public transportation is generally good and there are three Zipcars in walking distance from our house. We decided to sell the car and budget the money we would be spending on insurance for car rentals. Three months later, our son is much happier on the bus than strapped in his car seat, we don’t have the hassles of car ownership, and we get more fresh air! We’ve also successfully used Zipcar for a middle-of-the-night urgent care visit.

3. Sign up for energy offsets. Portland’s energy company, PGE, has a great program where you pay a bit extra to have your electricity offset with renewable energy. I like this program since it’s clear where the money is going. Most of the renewable source comes from wind. Who doesn’t love that? My laser was the motivator for signing up for this program. It doesn’t consume a huge amount of power, but it’s enough to make me conscious of it. I did some tests with a Kill A Watt with these results:

ULS 4.60 50W laser cutter

17W plugged in (“vampire” cost). The laser has a dedicated power outlet controlled by a switch, so I try to remember to turn it off.

86W turned on but not running

115W – 880W running – since it’s unusual for me to cut anything other than paper my actual usage is at the bottom of this scale. The few times I’ve cut acrylic or thick matboard I’ve had to crank up the power.

Quatro SPH-426 exhaust

107W – 128W. Again, this is normally at the lower end of the scale since I don’t need to run the exhaust at 100% when I’m just cutting paper. Since the exhaust is partway across the room I always turn it on and off via the dedicated wall switch, so I didn’t measure the vampire draw.

Up next? Insulating the garage and having a “blow test” done on the house.

The bridges of Geogrotesque Stencil

2010 CalendarGeogrotesque Stencil is the first font I’ve found that has different bridge widths for the same font size. I highly recommend this font for physical applications such as laser cutting. The bridge is the line that connects islands (typographic closed counters), for example the middle of the “o” or “a” that would fall out if they weren’t bridged. Most stencil fonts play it safe with fat bridges. Once the font gets to a certain size the bridge stands out and is wider than necessary to physically hold the island in place. With a choice you can get a nice balance between the bridge width and the font size.

Ideally the bridges would be parameterized so that I could adjust them the same way I can adjust leading or other type properties.

After some experimenting these are my recommendations:

Geogrotesque Stencil A for 60pt+

Geogrotesque Stencil B for 24pt – 60pt

Geogrotesque Stencil C for 14pt – 24pt

Below 14pt the islands fall out (65# paper).

Geogrotesque Stencil A Regular Geogrotesque Stencil B Regular Geogrotesque Stencil C Regular

2010 calendars featuring Geogrotesque Stencil are available in the shop. Convo me on Etsy if I don’t have any listed and you’d like one :).

It’s only fitting that my first video upload is shaky, poorly lit, and has a mystery time gap, but there you have it.