Custom 1500x1000mm CNC for Smart Mirrors: UV vs CO2 RF Galvo & Tiling Controller Advice⁠

[G.G.21 (GIO)]

Title: Custom 1500x1000mm CNC for Smart Mirrors: UV vs CO2 RF Galvo & Tiling Controller Advice

Hi everyone,

I am currently building a custom large-format CNC machine dedicated to smart mirror production. My main goal is to remove the back amalgam/silvering from mirrors to create:

1. Perfectly transparent, clean windows for touch sensors and clock displays.

2. Frosted/sandblasted effect borders around the mirror for LED backlighting.

My Custom Mechanical Build (Parts already purchased & assembled):

Working Area: 1500mm x 1000mm.

Base Frame: Welded 80x40 (3mm thick) steel square tubing. The rail mounting holes were pre-drilled on a precision CNC router for perfect alignment.

X-Axis Gantry: 80x40 (4mm thick) aluminum extrusion.

Linear Motion: HIWIN HGH15CA linear guide rails.

Drive System: HTD3M 15mm timing belts (with inner steel wire core to prevent stretching) and 20-tooth pulleys.

Motors: NEMA 23 (57BH100) Closed-Loop steppers with LCDA257F drivers.

Z-Axis: Motorized 100mm travel GGP ball-screw module with a DM542 driver.

Current Board: I initially bought an MKS DLC32 v2.0 (GRBL), but I now realize it won’t support a Galvo head.

The Dilemma:

Because the heavy motorized Z-axis on a standard flying-optics/gantry setup would cause too much vibration at high engraving speeds, I have decided to mount a Galvo Head on my X-axis gantry. Since some of my LED borders span the entire mirror, I will need to use Tiling / Split-marking to cover the 1500x1000mm area.

I am debating between two laser sources:

1. 5W UV Laser (355nm) with a Galvo head & 300x300mm F-Theta lens.

2. 30W/50W CO2 RF Metal Tube with a Galvo head & 300x300mm F-Theta lens.

My Questions for the hardware experts:

1. Tiling/Stitching: Which setup (UV or CO2) is more forgiving when it comes to edge distortion (barrel distortion) and aligning tiled segments seamlessly on mirror amalgam?

2. Processing Quality: For the LED border light diffusion, is the thermal micro-fracturing (frosted effect) of the CO2 RF laser significantly better than the cold ablation of the UV laser?

3. Controller Choice: Since the MKS DLC32 is out, what controller board (e.g., specific JCZ / EzCad boards) do you highly recommend to perfectly synchronize my mechanical closed-loop X/Y steppers with the Galvo head using LightBurn’s Galvo features?

Any advice, controller recommendations, or shared experiences with mirror processing would be hugely appreciated!

[jkwilborn (Jack Wilborn)]

@G.G.21

amalgam/silvering from mirrors

These are made from a mixture of tin and mercury. Industry has absorption cells a laboratory works with to determine dosage where these are used in manufacturing.

You can find some information here.

Tin-Mercury Amalgam Mirrors

Personally, I wouldn’t recommend you lase these without some research to ensure it can be safely done.

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If it’s glass a uv or co2 is required, a fiber won’t mark clear glass. If I change my lens, the spot size is related. If the change is doubling the spot size (by a lens length change), you will cut the apparent power by 1/4. It’s a 4 times greater area. Spot size for my fiber is ~15 microns (0.015mm) using an F100mm lens. If I change to my F254mm, the spot size is now ~31 microns or over double the size. It requires an F420mm to give me a scan area of 300x300mm, spot size is nearly 50 microns.

Ensure what these mirrors are made of, it may limit your choices. A fiber is recommended by some, but I don’t know what kind of damage it does. I know it goes directly though the glass of a mirror.

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I don’t know what closed loop motors you have, these is generally no way to tell the control board there is an error and it it’s fixed or fatal.

I don’t know what you want Z travel, that’s more mass on the X axes, which means you have to slow not only the X acceleration values but also the Y as it’s not added mass to the gantry.

Is there some reason you didn’t use closed loop for the Z axes?

@G.G.21

Because the heavy motorized Z-axis on a standard flying-optics/gantry setup would cause too much vibration at high engraving speeds, I have decided to mount a Galvo Head on my X-axis gantry.

A flying head is mounted on the X axes gantry… can you clarify? How fast are you expecting to go?

A co2 with a galvo usually has the metal tube mounted with the galvo.

A fiber uses an external glass fiber to pipe the output of the source to the galvo. Since fiber wavelength passes through glass it’s no problem. You can’t use a glass fiber to carry uv or co2 wavelengths. I personally don’t know how they get the source output to the galvo using anything other than glass. I’m sure there are materials, but I see co2 with the source mounted along with the galvo head.

Since I really don’t know what you’re doing exactly, it’s likely over my head, but you should put more time into exactly what the process is and what materials you are using before choosing a laser of any kind.

UV lasers are not really cold, they call them cold lasers as they work at a molecular level, but they still get warm according to one person I know that has one, I do not.

@G.G.21

edge distortion (barrel distortion)

I’m not sure on what you mean here, you’ll have to elaborate. If you have a flying galvo, you need software to drive it. It’s much more complicated when both the galvo beam and the galvo itself is moving.

Lightburn has one, but we haven’t heard much about it.

I have no clue if/what JCZ does for control boards. Might be a good question for the Lightburn people about how the flaying galvo actually works.

Good luck…