Lowrider 3 Z axis options for co2 laser

LowRider CNC Advice
#1

Hi,

I’ve just bought a LR3 and long term, would like to be able to switch between CNC router and laser.

before i build a table and start bolting the LR3 to it, i’m after some advice…

For laser, I am considering using either a fiber laser or co2 laser, but these usually need mirrors between the laser tube and the “head”. For x-y this is fine, but z would require the laser & mirrors to move with the head. I’ve seen other CNC builds move the bed rather than the CNC / laser head.

Has anyone else done this? how did you get around it?

#2

Here’s one idea, but it’s a Primo.

Primo 40W laser.

A

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#3

The neje 10W lasers are pretty strong diode lasers.

With a CO2 laser, it is a real safety hazard, because the beam can be misaligned so easily and fire off somewhere. If you were to build it into a Low Rider, you would want to make it so a misalignment would not be possible, which would mean riding the tube on the gantry. I haven’t used a CO2 laser, but I have heard that is a tough choice.

I don’t know much about the fiber lasers, except they are very expensive.

The diodes are super easy though. You can make a mount that fits instead of the router. They operate on the same 12V.

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#4

As an owner of a strong CO2 laser (100w) in its own dedicated machine, I second what @jeffeb3 said!

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#5

I’ve found it easier to move the work up and down to focus on different thickness parts in my K40 than to try and move the mirror and lens on the gantry. The mirrors are “fiddly” to get right, so you don’t want them experiencing off-axis movement. The glass laser tube is rigidly mounted in the case and does not move as it is fragile and requires liquid coolant (in my case distilled water). Ideally, the beam is kept in a single horizontal plane throughout it’s manipulations. The first mirror is rigidly attached to the case and turns the beam to be parallel with the Y axis. The second mirror is fixed to the end of the X axis and turns the beam to be parallel to the X axis and aims it at the mirror in the head. The head contains a third mirror that points the beam down toward the work, and the lens that does the final concentration/focusing of the beam.

I think this would be hard to accomplish on a LowRider because the X axis is attached to Z and designed to go up and down. While not impossible to accomplish, there’s going to be complexity in the coolant delivery, and you’ll still need to bend the beam around to get it onto the work. And the fragile tube will be in constant motion.

It would be easier to recreate the standard mirror configuration on a Primo as fixing the second mirror to the X axis would be fairly easy, and the tube and first mirror could be mounted to the table outside of the movement envelope. I’d split the components in the head. I’d want the third mirror at a fixed height relative to the second (X axis) mirror, then have the lens assembly on the moveable Z axis allowing for easy changes in focus height, but this would require very close tolerances so that vertical movement of the lens doesn’t result in the beam ending up out of the prime focus center of the lens as it moves up and down.

And, as others have said, the area should be fully enclosed with safety interlocks. I managed to burn my finger while using the test button adjusting mirrors. It happened ridiculously fast, and hurt a lot. Haven’t needed to relearn that lesson.

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#6

I can’t recommend it as a good idea, but you could run the mirrors in a way that will get there.

Mount the laser parallel to the X axis at the edge of the table. Use 1 mirror at 45 degrees to bounce it parallel to the Y axis, say just inside the Y rail.

Mount another mirror on the YZ plate to bounce the laser straight up, inside the XZ plate.

The third mirror is on the XZ plate bouncing the laser back along the X axis towards the tool head.

Now, if your Y axis goes out of square because of the motors being out of synch you will miss the third mirror and burn a hole in your ceiling. If your Z axis is oit of square you will miss the tool head and burn … something. This is why its a bad idea.

It could be possible to mount the laser tube to the gantry. This at least avoids the possibility of motor misalignment causing bad things™ from happening, but that’s a whole new kettle of fish to have the laser tube mounted on a moving platform. I think a laser tube inside the beam braces would look awesome, but in a “holy crap that’s dangerous” kind of way.

Another thing to keep in mind is that those morrors need to stay clean even regular dust on them will damage them when that laser hits it. Those mirrors shoukd stay inside an enclosed machine where they are not exposed to dust, let alone possible chips from a CNC milling operation.

I want to run a CO2 laser at some point, but it’s not going to be on a V1 chassis. It will br a dedicated machine.

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#7

Really interesting, thank you

#8

Ive been looking at the diode lasers, but havent been able to find anything that suggests they can do 1" thick mdf or ply or 4-6mm steel.

#9

Thanks everyone, i appreciate the replies and information/ suggestions/ warnings. I was hoping it might be simple’ish to raise / lower the bed than the z axis but sounds like alot more reading / design needed.

#10

That is a pretty high bar! 1" mdf and 4-6mm steel needs a very expensive laser. If you did the shopping, I bet you would find that the cost of a laser capable of that much is going to make the CNC machine look like an accessory.

I haven’t shopped for them in a long time, but that sounds like a $10k+ machine to me. If not more.

If I am wrong, please educate me. I would love to see a machine like that in action.

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#11

Re. Cutting 1” MDF — my 100w CO2 laser can cut 1/2” MDF, with some considerable scorching. Cutting through 1” is a tall order requiring a majorly powerful laser and the only way diode based could do it is if you had an array of them. That’s the only way to increase power of diodes past a small amount - increase number of diodes.

#12

Yeah. I have cut through 1/4" plywood with the neje 10W (marketed as 40W). It has two diodes, IIRC. Definitely simple to add and a couple hundred bucks.

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#13

The challenge with cutting thick materials is that the laser has to be focused to a very small spot in order to concentrate the energy, which is the job of the lens (or set of lenses). The spot of focus, at least on my CO2 machine, tends to be small both in area (viewed from above) and in depth (viewed from the side) but it is wider outside the area of focus. With different lenses you can tune the size and shape of this focus zone to get a little more depth of cut, but then you need to lift the material (or lower the lens assembly) in order to cut through thicker material. When the kerf gets deep, the edges of the kerf start blocking the light that’s still on it’s way to the focus point. This diminishes the power at the focal point, and you’re on the downward slope of diminishing returns.

Section 3 of this article explains this better. In the final image in that section they use “tolerance” to show the effective depth that the focused beam will cut for a variety of possible lens combinations.

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#14

Thanks for the feedback everyone, its interesting to hear real world examples and theres plenty here to think about / use to make decisionson. (Ty). Fiber lasers are now becoming more commonplace and subsequently a little more affordable… i dont know too much about sizing one for my needs yet, but thats part of the journey… really appreciate you all taking the time to share your experiences

#15

Another one that just popped up in my feed.

40W Co2 for under $700

A

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#16

Heh. Would take a lot of modifications…