Last time we talked about the TOTEM S laser engraver from TwoTrees, we looked at controlling it using LightBurn. Today we’ll be looking at LaserGRBL, the other software package recommended by TwoTrees for the Totem S. LaserGRBL isn’t as feature-rich as LightBurn, but it’s free and open source.
Start by downloading and installing LaserGRBL from their website. It’s only available on Windows, but there are many ways to run Windows software on Mac and Linux.
LaserGRBL is relatively simple when compared to other laser control software. There’s no need to create a new device to connect your laser. After connecting your laser via USB, select the proper COM port from the drop-down menu and set the Baud rate to 115200.
These are the settings needed to connect to the TOTEM S. You may need to choose a different COM port.
Click “Grbl” in the toolbar across the top, then click “Connect” to connect your device. Alternatively, you can press F12 to connect or disconnect your device, or use the icon to the right of the baud rate. After connecting, you should see some gcode appear in the terminal.
The gcode that appears lists some settings received from the laser controller
If your device does not connect, you probably need to install some drivers. In the toolbar across the top click “Tools” then “Install CH340 Driver”.
If needed, installing the drivers only takes a few clicks.
With the drivers installed and device connected, the laser status in the lower right corner may say “Alarm”. Since the TOTEM S does not have homing switches, LaserGRBL does not know where the head is located in the build area. This can cause an Alarm state. Click the padlock icon in the toolbar at the bottom of the window to resolve the error. I did not experience this with my laser, but did read reports of it occurring to other TOTEM S users.
With everything connected and ready to run, we can bring in our file. LaserGRBL supports a range of raster files, but only supports .svg vectors. We’ll look at vectors first. The file I am using is the laser accuracy test from LaserGRBL’s site. We’ll start by clicking “File” then “Append File”. Navigate to the location of your .svg and select it.
You’ll be presented with a window that allows you to set cut parameters. The options are pretty limited. “Border Speed” is the cut speed for all vectors in your file. This is measured in mm/min. There’re two options for “Laser Mode”. “Dynamic Power” reduces power on some parts of the cut to account for variations in speed due to the laser’s acceleration. “Constant power” does not make these corrections. While the TOTEM S supports dynamic power, it’s usually unnecessary for cutting. Finally, we have “S-MIN” and “S-MAX”. These are minimum and maximum power settings. I had good results leaving “S-MIN” at 0 and setting “S-MAX” to 100 for cutting.
These are the settings I used for cutting. LaserGRBL does not offer as many options as LightBurn.
Unlike LightBurn, you don’t have the ability to separate processes by color. You’d have to use separate files if you want to run multiple processes at different settings. LaserGRBL does not support vector engraving, only vector cutting.
With all the settings in place, click “Create!”. To increase the number of passes, use the box next to the progress under the connection settings. I found I needed 13-14 passes to cut through 3mm plywood. You’re now ready to cut your vector file.
With everything set up to cut a vector file, your window should look like this.
Before we talk about starting the laser, we’re going to look at engraving a raster file. This is really the bread and butter of LaserGRBL, and we have many more options to choose from. First, we need to choose a photo. I decided to use this photo I took in Vancouver:
The photo has a simple background and good contrast between the sculpture and background. I have found these are key features for a successful photo engraving.
Once again, we’ll click “File”, “Append File”, then select the photo we want to engrave. This time we’ll have a lot more options to choose from.
Starting from the top, we can choose between smooth or sharp resizing. Smooth will have less aliasing than sharp.
Smooth (left side) vs. Sharp (right side) resizing
Next, we get to choose which method is used to convert our color photo to a grayscale photo. I found very little difference between the three presets. Custom allows you to manually mix each color channel to lighten or darken certain areas. The next 3 sliders allow you to alter the brightness, contrast, and white level of the photo. Finally, the “B&W” check box will turn your grayscale image into a two-tone image.
Next, we can choose our engraving process in the “Conversion Tool” block. For images, I like dithering. Line To Line Tracing also works well, but the results aren’t as smooth as dithering. Vectorize will convert your raster image to a vector, which is especially useful for two tone images. If you choose to vectorize an image, make sure you enable filling unless you just want an outline. Centerline is a vectorization process too, but it draws a single line down the middle of a shape rather than outlining a shape. There’s no fill option with centerline. Finally, we have “Passthrough”. This option is similar to line by line, but removes the options to resize the file. More information on each option is available in the LaserGRBL documentation. I chose Floyd Steinburg dithering with horizontal lines at 15 lines/mm for my sample image.
Click “Next”. In this window we can choose our engraving settings. I started at 2000mm/min and 100% dynamic power. I set my width to 50mm, which is about 2”. After entering your parameters, click “Create!”
These settings produced the engraving below.
Once your image is created, your window should look like this:
Regardless of the type of file you started with, the next steps will be the same. First, we’ll home the laser. Move the head of the laser to the lower left corner of your material. Next, we’ll focus the laser using the knob on the laser head. At this point its time to don your glasses and make sure the red shield is in place on the laser head. When you click the “Frame” button at the bottom of the screen, the laser will trace a bounding box around your file. It will also turn the laser on at a very low power. It’s not enough power to mark most materials, but it’s something to be mindful of. With the laser homed, focused, and our job framed, we’re ready to start cutting. Click the green play button to the left of the progress bar and pass count field.
As the laser runs you’ll see the gcode in the terminal as it’s sent to the laser. You’ll also see an estimated time at the bottom of the screen, and a progress bar with total time at the top of the screen. If you need to stop a job, press the red Stop button next to the progress bar. If you want to pause a job, click the red octagon with a white hand in it at the bottom right of the screen. If you stop a job you won’t be able to resume it. If you pause a job you can click the circle with a walking figure in it to resume the job.
This is what you’ll see as the laser runs. You can stop the job with the red square in the upper left, or pause it with the red octagon in the lower right.
Below is a picture of my engraving using the photo and settings described above. There’s a lot of room for improvement, and the small size of the photo coupled with the texture of the wood limits the amount of detail that can be achieved. In addition to the variation in tone, the finished image has a mild 3D effect to it as the darker areas are engraved deeper than the lighter areas. This image took about 15 minutes to engrave.
The result of my first attempt at engraving a photo with LaserGRBL
I decided to try again with slightly different settings. This time I set my speed to 2250, and increased the size to 75mm. I also lightly sanded the wood, and rotated it 90 degrees so the grain would be aligned with the laser’s direction of travel. As you can see below, these changes made a big difference in the quality of the engraving. This engraving took about an hour.
This larger engraving took more time, but the results are much better than the sample above.
Throughout my testing I experienced some stability issues. The computer would randomly lose its connection to the laser, causing the job to stop part way through. After rebooting and reconnecting the laser the software was sometimes able to recover and continue the job, but these stability issues would worry me on larger jobs. I was able to reduce (but not eliminate) these issues by changing the streaming mode to “RepeatOnError” and the threading mode to “Quiet” in the settings page. These changes dramatically increased the run time of the jobs I used for testing. These settings account for most of the increase in time between the samples shown in the photos above.
While much more limited than LightBurn, LaserGRBL is definitely a valid alternative to LightBurn. I found myself missing features like vector engraving and the ability to separate processes by color, but I was able to achieve similar results with both software packages. In my opinion the advantages offered by LightBurn are easily worth the $60 price tag, but it’s not strictly necessary to run the TOTEM S. My main concern with LaserGRBL is the stability issues I experienced. I haven’t been able to diagnose the cause of the issue, and without identifying and resolving the issue I would not feel confident using LaserGRBL for long jobs or jobs on materials that can’t be replaced as easily as a sheet of plywood.
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