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!

Overriding the ULS interlock

Enclosed lasers such as ULS and Epilog have a safety feature where the beam won’t fire if the doors are open. On my system the front panel shows a blinking red light when the doors are open and a green light when they’re shut. Yesterday the red light kept blinking even when the doors were shut.

Now, this is a very big problem, since it rendered the laser inoperable.

Hamlin 59140 miniature flange mount sensor

The interlock on ULS systems uses flange mount sensors (Hamlin 59140), two on each door. The sensor is mounted to the cabinet and the actuator to the door. When they touch the circuit completes.

There are at least five possible failure points:

  1. Sensor plug
  2. Lead from the plug to the main system
  3. Sensor
  4. Connection between sensor and actuator
  5. Actuator

The easiest route would be to rule out the connection and actuator first, but I didn’t know how to properly use magnets to do this (more on that later). Instead, I started by unplugging the sensors, inspecting them, and plugging them back in. Still no green light.

Permanently defeating the interlock

The next step was to take the sensor out of the equation. With the machine powered down, I unplugged the sensor and wrapped a piece of tinfoil around the two wires of the plug, completing the circuit. I got lucky with the first sensor I tried, and the light was once again green when the laser was powered up. Now that I knew which sensor was acting up and that the lead to the main system was okay, I could temporarily leave the tinfoil in place and figure out how to test the connection to the actuator.

Overriding the interlock with magnets

The standard trick to temporarily override the interlock is to use magnets. Some laser operators use this technique to engrave items longer than their laser bed. The front door is opened and the item projects past it. Some systems have a front and rear door for full pass-through. Safety glasses must be worn if the doors are open!

To allow the laser to fire, position magnets over the two front sensors on the cabinet. The magnet should be placed on one half of the sensor only; it will not work if it covers the entire sensor (this was the mistake I made earlier).

Removing the tinfoil and using the magnet test, I got a green light again, so the sensor was okay.

Now that I knew the problem was either with the connection between the sensor and actuator or actuator itself, I took a closer look with the door closed. There did seem to be a decent gap between the sensor and actuator, but I wasn’t sure if that was the problem. Since this just started occurring I thought it would be strange that the distance was suddenly too great.

Testing the actuator

With a magnet on one sensor, I unscrewed the actuator for the other and placed it directly on top of the sensor. Green light. Pulled it away a bit, still green light, a bit more, flashing red. I screwed the actuator back in on one side only, so that I could push the other side out a bit, making it closer to the sensor. Success!

Now, why did this happen? This problem occurred on my new-to-me laser, which is not yet in production. It’s been moved around quite a lot lately. First for workshop electrical upgrades, then a hardwired exhaust, and most recently to test tubes and try to get the beams aligned. My theory is that all of this moving has caused the front door to shift slightly so that it is closer to one side than the other. The tiny extra distance is too much for the sensor to pick up. I have tried moving the door back to center but no luck.

Freshly Cut – Stencil for Behrens Group

Brian of Behrens Group was commissioned by Make Animals and Opus Solutions to make some ”road cases” as part of Intel’s Rock Legend program. He was on a deadline so there wasn’t time to shop for materials; we used some 1/8” acrylic I had on hand. The art cut out well and the stencil worked great. Unfortunately the spray paint would build up on the stencil after a few uses so he had to laboriously clean it several times. Next time we will cut several copies out of matboard so that the cleaning step can be eliminated.

Photos graciously provided by Behrens Group.

Freshly Cut – Little Floridas for cevd

Cut from Arturo in Grey

Christine’s studio cevd designs beautiful custom invitations.

These little Florida cut-outs will become part of an invite.

The cotton Arturo paper was a dream to cut. There was virtually no odor or surface discoloration from the heat of the beam.

I’ve recently added a set of cotton and bamboo papers from Legion to my swatch catalog. Let me know if you’d like to see a sample.

More photos are on flickr.

Determining what to bridge

Here are three quick ways to determine what portions of your design need bridging.

In Illustrator:

  1. Select All
  2. Object -> Compound Path -> Release

This converts all of the closed paths of your design into their own objects. Now we can clearly see which pieces will be left on the laser bed, like so:

In Acorn, Photoshop etc:

  1. Eyedropper the color from your image
  2. Flood fill the background

All of the white portions need bridges.

To see what will actually be cut out, as with the Illustrator version:

  1. Use the magic wand to select the background
  2. Select -> Inverse (note: menu items may differ in Photoshop)
  3. Edit -> Fill
  4. Clear the selection

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 – Amanda & Nate’s Wedding Invitations

Cut from Paper Source in White and Stardream in Rose Quartz with coordinating 5 3/4” square envelope. Ink-free etched text.

My brother-in-law Nate was recently married to his high school sweetheart Amanda and I was delighted to design their wedding invitations.

A vinyl aficionado, Nate brought up the idea of making a mock-record invitation. I photographed and emailed several choices of paper to match their pink and white theme and they went with my favorite, a pearlescent rose. Spending some time on record sleeve production websites I came up with a good template that just required two strips of adhesive.

Perfecting the etching took the longest amount of time. I ultimately developed a technique that first etches the text, then finely outlines it to increase the contrast.

Heartfelt congratulations to the newlyweds. It was a joyous wedding with many sweet details.

If I made this invitation again I would make a few improvements. First, I’d change the font for the date. Perhaps adding bridges to the font used for the monogram would be enough. Second, I’d reverse-cut the sleeve so that the slight yellowing of the paper around the cuts would be on the inside instead of the outside. When I first did the cut it looked great; it wasn’t until a week or so later that the discoloration showed. Last, the white paper etched great (I tested at least eight whites from several mills) but it didn’t feel quite solid enough. It was somewhere in the 80-100# range; 120-140# would be much more record-like.

More photos are on flickr. This design is available to be customized for your special event from $5 an invite. I’m happy to work with your design or a third party designer as well, just email for more information or a quote.

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.