You've done your material tests, your text and logos are coming out perfectly, and then you drop a photo onto the canvas. Suddenly speed and lines per cm have gone, and you're looking at dot duration and DPI instead. If that's thrown you, you're not alone.
Once you understand why xTool Studio swaps the settings over, it all gets much easier. I explain it in the video above using my dog Ted as the test image, and everything is written out below with screenshots so you can come back to it.
Jump to: Vectors and images · Power, speed and lines per cm · See the lines for yourself · Dot duration, power and DPI · What happens when you push DPI · Why it matters
It starts with the type of file
The settings you get depend on what you've selected. On my canvas I've got a pink logo, some red text and a photo of Ted. The logo and the text are vectors. They can come in as SVG files, DXF files or just text you type in Studio. The laser sees a vector as lots of little lines that it joins together to make the shape.
The photo is an image. An image is made up of lots of tiny dots, and the laser has to place every one of them to build up the picture.
This is the simplest way I can put it:
- Vector = drawing lines. The laser moves at a constant speed with a constant beam of power. That's why you set speed and power.
- Image = placing dots. You tell the laser how many dots to fit into an inch, and how long to spend on each dot. That's why you set DPI and dot duration.
Vector settings: power, speed and lines per cm
Select a logo or some text and the panel on the right shows the settings most people learn first:
- Power (%) is how much power the laser beam is putting out.
- Speed (mm/s) is how many millimeters the laser travels in a second, at that constant speed.
- Lines per cm is how many lines it lays down in 1 cm of space. In this example it's set to 120, so it puts 120 lines inside every centimeter. Turn it up and you get more lines packed in, which gives a denser engraving.
The numbers in my screenshots are just there to show the idea. They aren't settings for any particular material, so don't copy them for a job.
See the lines for yourself
This is the bit that made it click for me. You can watch exactly what the laser is going to do before you press start.
- Turn Output off for everything except the design you want to look at.
- Click Process. You'll get the estimated time for the job.
- At the bottom of that screen, click Preview processing path.
- Zoom right in, then drag the slider along the bottom (or press play) to watch the laser build the design up.
Zoomed out, the logo looks solid, which is how it will look once it's engraved. Zoom in and you can see it's really lots of separate lines. Here I've set lines per cm to 350, and the estimated time was 3 minutes 24 seconds. Press play and you can see it lays one line at a time, each one a constant line of power.
Then I cranked it up to the maximum of 800 lines per cm. The estimated time went up to 7 minutes 39 seconds, and I had to zoom in a long way before it stopped looking black, because the lines are packed so tightly. But it's still engraving one line at a time. That's the key thing to understand about vectors.
Image settings: dot duration, power and DPI
Now turn Output off for the logo, turn it on for the photo and select it. The panel changes to Dot duration (µs), Power (%) and DPI.
I can see why this is confusing. Speed is easy to understand: you either go faster or slower. Dot duration doesn't look like it has anything to do with speed. Here's what each one means:
- Dot duration tells the laser how long to spend on each dot. It's measured in microseconds.
- DPI (dots per inch) tells it how many dots to fit into an inch of space.
- Power is the same as before.
For this example I set Ted to 600 DPI with a dot duration of 900. When I clicked Process, the estimated time came up as about 19 minutes.
Open the processing path again and zoom in. At first it looks like it's doing lines, just like the logo. Zoom in further and you'll see it's adding lots of little dots along each line, building the picture up one row of dots at a time.
That's why dot duration matters. Increase it and the laser spends longer on each dot, which can give you a stronger engraving. Go too far and it can wash the image out instead.
What happens when you push DPI too far
To show you the difference, I cranked DPI up to 2,000 and hit Process. The estimated time jumped to 3 hours 32 minutes.
In the preview, Ted looks almost completely black because there's such a high concentration of dots. You have to zoom in a really long way just to break them up into individual dots. That many dots in a small area will most likely come out black and burnt. More isn't always better.
Why this matters
A lot of people, new or experienced, assume that once they've got settings that work for one type of file, they'll work for everything. They won't.
You can have one set of settings that's perfect for logos and text on a material. If someone then asks you to engrave a photo on that same material, you need to go back and test again for image settings. Here's how I'd approach it:
- Check whether your design is a vector (SVG, DXF, text) or an image (a photo or other picture).
- Use speed, power and lines per cm for vectors, and dot duration, power and DPI for images.
- Use the processing path preview to see what the laser will actually do, and keep an eye on the estimated time.
- Run a test on a scrap of the same material before you engrave the real thing.
If you'd like a head start, my free Laser Settings Library has nearly 300 settings I've tested on xTool machines, for text and logos and for photos.
Still got a question?
If something still doesn't make sense, ask me in the comments on the video and I'll do my best to help.
