Avoid Fast Z motion

Yesterday I took the laser partway apart, looking for reasons why the Z-axis table keeps getting out of alignment. I think I know more than I did before, but I still don’t fully understand what’s happening. The problem seems to be in the acme threaded nut that rides up and down on the right rear acme threaded rod. You can hear the mechanism going “clunk clunk clunk” when that corner is slipping out of alignment.

This mainly seems to happen when the table is going UP in the FAST Z mode. That makes sense, because that’s when the mechanism is working hardest to lift the weight on the table, the honeycomb mesh, and your workpiece.

So, I am asking all laser users to please avoid using FAST Z motion until I’m able to isolate and fix the problem. It may take you a few extra seconds to focus using SLOW Z only, but it will help keep the table aligned and the laser working well. Thanks for your cooperation.

Laser Classes Feb 16, Mar 1

We (finally!) have begun again to schedule basic operation and safety classes for the Sol Diego laser cutter/engraver at Colab. The first class will be Sunday, February 16, 2020, 1pm to 5pm. We will try to do the first and third Sunday afternoon of each month, at least until the demand has been satisfied. Inevitably, some of these dates will be canceled due to conflicts. If you want to take the laser class but are generally unable to attend on a Sunday afternoon, please let me know what timeslots work for you and I’ll try to schedule an extra class.

If you are on the Dinner with a Whale project, dedicated classes are being scheduled for you through Diane, starting Feb 23. Schedule through me if you can’t make the dedicated class; otherwise please sign up through Diane.

Laser class Sunday Feb 16, 2020, 1pm to 5pm: CLASS IS FULL


Laser class Sunday March 1, 2020, 1pm to 5pm: CLASS IS FULL

To sign up, email me at class@colaser.org and ask for the March 1 laser class. Class size is very limited and this one will likely fill up fast. Please wait for further announcements before requesting any other dates.

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 two hours of classroom instruction, followed by hands-on exercises with the laser.

You can always email class@colaser.org if you have any questions.

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.