Laser Classes for July

More sessions of the basic operation and safety training course for the Sol Diego laser cutter/engraver at Colab have been scheduled:

Tuesday, July 23, 1pm to 6pm (CLASS IS FULL)

or

Thursday, July 25, 6pm to 10pm (CLASS IS FULL)

or

Sunday, July 28, 1pm to 6pm (CLASS IS FULL)

or (UPDATE!)

Wednesday, July 31, 6pm to 10pm

To sign up, email class@colaser.org and let me know which session you prefer. The class is free, and once you’ve completed the class you’ll be able to schedule time to use the Colaser, which is also free for art and personal projects. You don’t need to bring anything special to class. Be prepared for about 90 minutes of classroom instruction, followed by hands-on exercises with the laser.

UPDATE: This will be the last class scheduled before Burning Man.

Raster Engraving Trick

One of the characteristics of our laser is that when raster engraving, vertical edges tend to be emphasized. As the head travels across the image, whenever it encounters a transition from laser-off to laser-on, an extra pulse of power is generated as the laser starts firing. This extra pulse of power adds to the laser’s effect on the material at that edge. Here’s an example, taken from the front cover of the first volume of our log book.

Engraving on logbook cover

The original image artwork was filled-in black letters, with no outline features. All the outlining you see is due to the extra power pulse effect. (There’s some doubling of the lines because I bumped the notebook slightly before trying a second pass.) The effect is especially noticeable in this case, because we’re engraving on paper with a colored glossy coating, which is very easy to cut and reveals differences in cutting power. If you examine the B in that image, you can see that true horizontal edges are not emphasized, but all the edges that have a vertical component have an extra outline. It doesn’t matter whether the vertical edge is on the left or right side of the filled area, because the laser fires in both directions when rastering.

Full Spectrum Laser told me this was an unavoidable property of CO2 lasers. I have my doubts about that. I suspect that smarter controller electronics could compensate for any such tendency and reduce or eliminate the problem. I’ve seen work from other brands of laser that don’t show this effect. Be that as it may, we are stuck with the problem.

Today I was calibrating laser speed and power on some scraps of light-colored leather I picked up at Artist & Craftsman Supply. For my raster test image, I just used some plain Arial text. Here’s one of my first results.

Leather inline

As you can see, the horizontals are pretty much invisible. The square geometry of Arial text makes the effect very noticeable. (If you look closely you can also see some evidence that the explanation I gave above isn’t the whole story.)

My usual workaround for the problem is to use more power. Most materials change color quickly from their original color to their laser-burned color, and additional power just cuts deeper into the material. If we use enough laser power to fully change the color of non-vertical features, then the vertical features won’t be darker than the other engraved areas. They’ll just be deeper, which is not nearly as obvious to the eye. That workaround won’t work with this leather, any more than it worked with the logbook cover above, because the leather has a thin top layer that we don’t really want to penetrate.

Today’s invention is a new workaround. I rotated the image of the text by 45 degrees in the drawing program, and also rotated the leather 45 degrees on the laser bed. In effect, this rotates the raster scan 45 degrees with respect to the artwork, without otherwise changing the design. Here’s the result.

Leather diagonal

As you can see, this is like magic on the small Arial text. The dominant horizontal and vertical lines are all rendered rather nicely. As it happens, this sample doesn’t contain any significant edges at a -45 degree angle, so all the edges are emphasized equally. The sample also doesn’t contain any wide areas to be engraved, so effectively it’s all edges. If the text were larger, you’d probably see that each stroke of the letterforms had two strong edges around a weaker middle, but that’s invisible at this scale. It would still be a nicer effect than losing the horizontal lines.

There isn’t anything magic about 45 degrees, except that it theoretically balances the effect between horizontal and vertical edges. You can use whatever rotation you need in order to minimize the visual importance of lines and edges that are parallel to the raster scan. If your artwork was a geometric design with lots of lines at 45 degree angles, you’d definitely want to use some other angle.

This isn’t a complete solution, of course, but it’s a useful trick to know about when it’s applicable.

You Must Stay In The Room

I’ve heard that some users have been leaving the room unattended while the laser is running. This is NOT PERMITTED. No matter how safe you think the job is, Colaser safety policy requires you to remain in the room whenever the laser is running. If you are forced to leave the room for any reason, you must pause or cancel the job before you do.

If you feel unable to comply with this safety policy, please don’t use the laser.

Log Books Scanned

You may have noticed that Volume 2 of the paper log book has been losing its pages. My mistake for buying a notebook with tear-out pages! I’ve gathered up all the loose pages and sorted them into chronological order as best I could, and scanned both volumes into PDF files. Those files are now available for reference here in the Download section of the web site.

There is a third paper volume (hardcover, with pages that don’t tear out) in the laser room now. Please continue to log your work in the paper log book.

Laser Classes April 22 and May 26

More sessions of the basic operation and safety training course for the Sol Diego laser cutter/engraver at Colab have been scheduled:

Sunday, April 22, 1pm to 5pm [ALREADY FULL]
or
Saturday, May 26, 1pm to 5pm
To sign up, go to the schedule page and find the class you want on the calendar. In the Details for that event you will find a link to click on to add yourself to the class.
If that doesn’t work for you, here is a direct link to the signup form:
The class is free, and once you’ve completed the class you’ll be able to schedule time to use the Colaser, which is also free for art and personal projects. You don’t need to bring anything special to class. Be prepared for about 90 minutes of classroom instruction, followed by hands-on exercises with the laser.

Laser Classes Feb 19 and Mar 4

More sessions of the basic operation and safety training course for the Sol Diego laser cutter/engraver at Colab have been scheduled:

Monday, February 19 (President’s Day), 1pm to 5pm
or
Sunday, March 4, 1pm to 5pm
To sign up, go to the schedule page and find the class you want on the calendar. In the Details for that event you will find a link to click on to add yourself to the class.
If that doesn’t work for you, here is a direct link to the signup form:
The class is free, and once you’ve completed the class you’ll be able to schedule time to use the Colaser, which is also free for art and personal projects. You don’t need to bring anything special to class. Be prepared for about 90 minutes of classroom instruction, followed by hands-on exercises with the laser.

Laser Class Jan 14

A session of the basic operation and safety training course for the Sol Diego laser cutter/engraver at Colab has been scheduled:

Sunday, January 14, 1pm to 5pm
This time we are experimenting with a different way of taking sign-ups for the class. Please visit the Colab web site at http://sdcolab.org and click on Colab Laser. You’ll find a calendar there. Open up the scheduled class event for the above date and go into the Details. There you will find a link to click on to add yourself to the class.
If that doesn’t work for you, here is a direct link to the signup form:
The class is free, and once you’ve completed the class you’ll be able to schedule time to use the Colaser, which is also free for art and personal projects. You don’t need to bring anything special to class. Be prepared for about 90 minutes of classroom instruction, followed by hands-on exercises with the laser.

Raster-Preventing Bug in RE3D

Lately we’ve observed a strange behavior in the print driver settings for the “Full Spectrum Engineering Driver” printer created by Retina Engrave 3D. The paper size shows as “Letter” by default, but is actually set to 36×48 inches. Since the program can’t handle rasters that big, it means that rasters just don’t show up. Trying to print excessively large rasters also seems to cause other parts of the program to misbehave in random ways.

There’s probably a setting somewhere that will fix this. Until we find it, the workaround is to go into the “Advanced” settings and change the paper size to something else, and then back to the size you actually want (Letter is good if your art fits, otherwise use the smallest paper size your art will fit on). This resets the paper size setting and the driver behaves as expected.

Engraving a Bamboo Bowl

I found an inexpensive bamboo bowl at Daiso and decided to try it on the laser.

Here’s the label on the bottom of the bowl:

First I tried vector engraving. My guess was that it would take very little power to mark the soft wood, and that turned out to be correct. Here’s the result with vector speed at 100, vector power at 1, and vector current at 30%. Nice crisp letters, very black, quite shallow. Pretty good result.

Next test was raster engraving. Here’s what my file looked like:

And here’s my first attempt. I tried a very low power setting again, based on the fine results from vector engraving. However, it wasn’t enough for raster engraving. You can see how the fine lines tend to fade out. Note how the fat lines have been broken into two lines, on the left and right edges where the laser turns on during rastering, and the horizontal fat line is missing entirely because it doesn’t get the turn-on pulse.

So, I turned the power up until the fat lines filled in. Here’s the result. The fine lines are nicely fleshed out and the fat lines are filled in, and everything is nice and dark. Very promising looking!

But then I wiped the bowl with a damp paper towel, and most of the black came right off, revealing an ugly core material that resembles cheap cardboard. This is not the effect I was hoping to get.

Even after wiping, there was some darkening in the places where the laser had the most effect, so I decided to see if I could get consistent dark engraving by simply turning up the power. I interrupted the test after it had engraved just the top of the pentagon. It was cutting quite deep into the bowl, and generating a lot of black debris on the surface.

The debris wiped off easily, but so did a lot of the black material, even deep down into the cut.

I have to conclude that this material is not suitable for raster engraving, unless you really like that ugly cardboard finish. For vector engraving, it seems OK, but you probably need to make sure to use a very low setting, so as not to penetrate the thin outer layer of the material.