How to Engrave Photos Inside Crystal with the xTool F2 Ultra UV

Engraving a photo inside a K9 crystal looks incredible, but when I started, my results were all over the place. (No F2 Ultra UV? You can still put a photo on the surface of K9 crystal with a regular F2: here's how I do it.) After a lot of testing, I worked out that the settings matter less than you'd think. Measuring, placement and how you convert the photo make the real difference.

This guide covers the whole process on the xTool F2 Ultra UV, from building the riser and calibrating, to converting a photo and engraving it. It pulls together three of my videos: the full workflow above, setting up inner engraving and calibration, and the crystal settings I tested.

Jump to: What you need · Build the riser · Fit the lens · Calibrate · Check your crystal · Position it · Set up xTool Studio · Convert your photo · Import and place · Settings

What you need

• The xTool F2 Ultra UV with its inner engraving lens and the riser (both come with the machine).
• A blank K9 crystal. One comes in the box. You can buy more from xTool or other suppliers, in lots of sizes.
• Isopropyl alcohol (I use 99.9%) and a lint-free microfiber cloth.
• Calipers or a ruler, plus a pen and paper to write your measurements down.

Build the inner engraving riser

In the box you get two interlocking legs, a top plate, a bottom plate, the adjustment arm, a hex screwdriver, three thumb screws and eight countersunk screws.

1. Slot the two legs together and stand them on the desk.
2. Sit the top plate on, writing facing the front, then turn the whole thing upside down so the holes line up.
3. Screw in the first corner with a countersunk screw, then the opposite corner, then the last two. Doing opposite corners first pulls it square.
4. Fit the bottom plate with the numbers facing the front, using the other four countersunk screws. Go round once more at the end so everything is tight and sits flush.
5. For the adjustment arm, screw one thumb screw through the threaded hole in the arm until it comes out the other side. The arm only fits one way, with its grooved edge in the corner. Screw it down into the threaded hole on the corner until it bites. Loosen it to slide the arm, tighten it to lock.

Keep the other two thumb screws handy. They hold the riser to the bed.

Fit the inner engraving lens and the riser

1. Power the machine off first.
2. Hold the existing lens by its knurled edge and turn it clockwise. It drops down and out. Put a lens cap on it straight away and set it somewhere safe and clean.
3. Take the end cap off the inner engraving lens. The side marked Assembly face has a small circle on it. Have that circle facing you.
4. Push the lens straight up, centered, with both hands until it won't go any further. Then turn it counterclockwise as far as it goes. It's fiddly the first time, so don't worry.
5. Take the last lens cap off and put it on your other lens too, so both its ends are protected.
6. Put the riser in with the writing facing forward, lined up over the threaded holes in the bed. Screw both thumb screws in a little before you tighten either, then tighten them both down.

When you turn the machine back on and open xTool Studio, you'll probably get a screen walking you through what you've just done. Click Got it.

Calibrate (do this every time you swap lenses)

xTool recommends running a calibration each time you swap either lens. There are two.

1. Inner engraving Z axis calibration

1. Click Start calibration. Studio asks you to screw down the riser. Tick Secured.
2. Use the K9 crystal that came with the machine. Measure its height in the position shown and enter it as the Z axis value. Mine was 50 mm. Leave the refractive index at 1.5. Click Next.
3. Loosen the thumb screw on the adjustment arm, line up 35 on the scale with the arrow, and tighten it again.
4. Clean the crystal with alcohol and a lint-free cloth. Fingerprints get in the way of the laser.
5. Push the crystal into the corner against the arm, close the lid and click Engrave.

It engraves a small cube with Top written on it. Click Next, take the crystal out, and measure from the top of the cube to the top surface of the crystal. Mine was about 21 mm. Enter it in millimeters and click Confirm.

This uses up one crystal, but you can reuse that same crystal every time you recalibrate.

2. Inner engraving work area calibration

Run this one too, especially if an engraving ever ends up in the wrong place or looks distorted. You need some tape, the test card and the calibration card.

1. Click Start calibration and tick that the riser is secured.
2. Take the adjustment arm off and tape the test card flat on the riser on both sides, so it can't move.
3. Turn off the lights in the room. Ambient light affects the reading.
4. Click Engrave, then Take photo, then Next.
5. Swap the test card for the calibration card, tape it down and click Take photo again.

Studio shows the result against the reference. Check that every single dot overlaps. If it does, click Aligned, then Confirm.

Try the built-in tutorial

Studio then offers a tutorial project, which is a great first engraving. It uses an 80 x 50 mm crystal at 35 on the arm, the Inner engraving mode and the K9 Inner Carved Glass material. The design is locked in place so it lands correctly, and the material's own settings are already applied. Mine took about 3 minutes and came out as a galaxy you can see from every side.

Check your crystal

Not every crystal sold as K9 is genuine K9, and it has to be the real thing. A quick test: shine a UV torch through it. If the light passes through without making a cloudy haze inside, it's genuine.

Next, measure it yourself. Everything is made to a tolerance. My "50 x 50 x 80 mm" crystal measured 49.4 x 49.5 with a height of 78.24, and my "60 x 60 x 100 mm" one came in at 60.1 x 60.4 x 99.55. If you type in the advertised size, your image won't sit in the center. Write your numbers down.

Then clean the top surface with alcohol and a lint-free cloth. The laser goes through that face, so you don't want fingerprints in the way.

Position the crystal on the riser

There are two ways to tell Studio where the crystal is.

Option 1: the adjustment arm

Center the crystal on the grid, then slide the arm until it touches the crystal. I always aim for a round number so it's easy to remember. In this case it was 25. Tighten it and note the number.

Option 2: corner coordinates (big crystals lying down)

These days I engrave crystals lying down. When the crystal stands up, the laser scans side to side and has to step up again and again, and I find the image comes out less accurate. Lying down gives a better finish.

With my 60 x 60 x 100 mm crystal lying down, it took up almost the whole riser. I centered it so there was one row of grid squares showing on each side, sitting right on the edge lines. Then I read off the bottom-left corner from the numbers on the grid: X 5, Y 85. The scale stops at 60, so count on in fives to the corner. If your crystal is smaller, just center it and read off your own numbers.

Set up the project in xTool Studio

1. Click New project. Studio beeps and tells you it has detected the inner engraving lens. You may also see a notice saying it can't work. Don't panic, that's just because the flat surface mode doesn't work with this lens.
2. In the top right, click the mode (it says Process on flat surface) and choose Inner engraving. Click Next, as the riser is already fitted.
3. Keep the box shape selected and enter your measured dimensions.

If your crystal is lying down, swap two of the numbers: the long side (its height when standing) goes in the Y box, and the side that's now pointing up goes in the Z box. For my 60 x 60 x 100 crystal that's X 60, Y 100, Z 60. I noticed Studio rounds these to whole numbers anyway. Leave the refractive index alone. Nine times out of ten you'll keep it at 1.5.

4. Click Next. Either choose Use positioning piece and enter your arm number, or choose Enter Bottom-Left Corner Coordinates and type in your X and Y.
5. Click Import canvas. Your crystal now shows up on the canvas, and you can rotate the view to check it.
6. Click Material in the top right, choose K9 Inner Carved Glass and click Apply.

Convert your photo into a point cloud

A normal photo is 2D. To engrave it inside a crystal you need to turn it into a 2.5D image, which is made of thousands of tiny points. That's called a point cloud. Remove the background from your photo first (or let the generator do it), because a clean subject gives a much better result. I've used two tools for this.

Option 1: xTool's AI 3D Model Generator on Atomm

Go to atomm.com, sign in, click Craft Lab and open the 3D Model Generator. Set the processing size to the width and depth of your crystal (I used 50 x 50), upload your photo and click Generate. It costs credits (six when I did it), and you get one free conversion a day.

You then get two sliders, and these matter more than anything else:

• Strength adjusts the contrast and sharpness. The default is 49. I tested from 1 up to the maximum of 70. At 1 there was very little contrast and it looked bad, at 70 it added contrast and sharpness, and 49 looked pretty good to me, so I keep it.
• Dot spacing is how far apart the points are. The default is 0.03 mm. Smaller spacing means more detail, but too dense and the dots crowd together and look cloudy, almost burnt.

I engraved the same photo at 0.03, 0.04, 0.05 and 0.06. At the default 0.03 it came out washed out, too detailed, and a bit burnt. For my photo, 0.06 was clearly the best. It was also the quickest: about 30 minutes, against an hour and 40 minutes for some of the denser ones. Every photo is different, so try a couple of spacings.

Click Export and download the file. It saves as a PLY file.

Option 2: GenMake (what I use now)

For my latest crystals I've been using a separate tool called GenMake. It isn't free, but it was handing out some free daily credits when I made the video, so check its current pricing.

1. Click Generate and drop in your photo.
2. If you like, use its prompt to optimize the photo for crystal engraving in an AI tool. I used ChatGPT. It's AI, so check the person still looks like themselves. A normal photo will probably be fine too.
3. Choose Keep background if you've already removed it, otherwise pick a background remover.
4. Pick your crystal shape and size from the list (mine was the 60 x 60 x 100 mm block).
5. I keep the Standard 3D effect and set the mask to 0, then scale the image up as big as I can while staying inside the F2 Ultra UV's engraving area.
6. Choose a quality. I go with Premium. Then generate the final files and download the xTool Studio version (a PLY file).

Import and place the point cloud

1. In xTool Studio, click Import on the left and double-click your PLY file. Rename your files to something you'll recognize, they pile up quickly.
2. Don't resize it. Studio sometimes scales it automatically when it comes in. Click Scale at the top and then Reset initial params to put it back to the true size you generated.
3. If it hangs outside the grid area, Studio won't let you engrave it. Don't just drag it smaller. Shrinking squashes the points closer together and stretching pulls them apart, and both can ruin the result. Go back and regenerate at the right size instead.
4. Want it bigger? Regenerate with a bigger processing size. I made one at 90 x 90 on Atomm, and it filled the crystal with the points still the right distance apart.
5. Use the view buttons in the bottom left (front, top, left, right) and drag the arrows to move it where you want it. I keep mine in the middle.
6. To add a name, click Text on the left, type it in and use Auto fit. Then move it from the side view so it sits in front of the image instead of blocking it.

Crystal settings

I love testing my own settings, but for files from the Atomm generator, xTool's own reference settings for K9 Inner Carved Glass were the best I found. They come up automatically when you pick the material.

For text, I kept the default settings it offered: Dotting method, 50% power, 180 dot duration, 0.05 layer height and 0.03 point spacing.

If you're curious, click Processing plan before you start and drag the slider. You'll see how the laser builds the image up layer by layer. Then click Process, Start, and press the button on the machine when it beeps.

My advice from all this testing: keep the reference settings and put your effort into the photo and the point cloud. Dot spacing and strength are where the results are made. Don't be afraid to buy a few extra blanks and try things.

My tested settings for other materials on this machine are on the xTool F2 Ultra UV settings page in my free Laser Settings Library.

What are you putting in a crystal?

Let me know in the comments on the video how your first one turns out, and which converter you went with. If a step trips you up, tell me where and I'll do my best to help.