Z control for Galvo

LightBurn Software Questions
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Hey G’day people,

For the LB software engineers,
I see this question has been asked a few times but there was no real definitive reason as to why or why not this could or couldnt be implemented.

So we all know the board that comes with most galvos is not a lot to talk about so not asking for the impossible from the board itself but rather for those of us that have an external controller for raising and lowering z axis and for using the rotary which is controlled by another controller via the general fiber laser builds.

So my question is this in Lightburn, we can micro control the rotary move left move right we can micro manage the splits.

Now if we can do all this with the rotary why cant we just do the same with z axis?

Before anyone says awww we have hashed this before can’t do it.

A great introduction to the list of many things we can do with Lightburn was the cleaning pass - full cleaning pass and partial cleaning pass.

We have a simple on off switch you ether want to use one or the other then a simple add a number how often you want to do your cleaning pass, every 1 4 10 or whatever passes.

Great so thats out of the way.

How about the same principle for Z control, a toggle do you have a z controller Yes. Excellent how many micro mm do you want to step down each pass… .1 .01 .001 etc.

If you could please tell me why this wouldn’t work, if you can determine a cleaning pass every x moves why couldnt you do the same for Z control?

Z control could be limited to say 2/3/4 mm so we dont get stupid entries and they could be limited to micro control only numbers say .1 or less to a number that would be practicable and workable?

Would love an reasonable answer for this not a generic nup cant be done.

And if its just a question of coding time (because it takes too many hours to do this not worth our time) an honest reply to that would be appreciated as well.

Cheers avagreatday all and greetings from the colonies downunder.

Just as a by the by I have sat there while my laser was working doing a 2.5d engraving for an hour or so just tapping the button every 20 or so layers moving the galvo head a hair depth down. The result was exceptional in comparison to just leaving it rely on its focal depth depending on the lens your using. But who wants to stand there for an hour plus tappety tapping on the button.

There is a difference and the price of the dynamic focus galvo heads are off the planet at around 5000k USD thats not good value and exludes probably 99% of the rest of us galvo users.

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Z control isn’t strongly supported in EZCAD2 based devices - and the vast majority of galvos do not have Z control abilities (in software) as a result.

With a small dev team, we must focus on the features that affect the largest number of users. Z control simply isn’t the top of the list at this time.

With that out of the way, I hope this honest reply satisfies. We do have a Feature Request page (hyperlinked) that already has this suggested - you can vote for it here: Live Z Axis on galvo laser · LightBurn

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Hey Colin,

Thanks for an honest reply, I was rather hoping that with existing code that you have eg the cleaning passes that there might have been a way to leverage that.,

But fair enough… ty

As a by the by I have no idea but I cant log into that link you sent me. On perpetual logging in… I even switched off my vpn not happening not to worry.

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Why not just use a Nano or PicAXE controller and a relay to do this for you? A pot to control the time delay is all the control you would need.

Your Lightburn login does not work. You need to create a separate login for Fider.

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MikeyH well thats thinking outside the box… good idea…

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I am seeing a strong need for a way to do Z-steps. I’m experimenting with how successful the 300w MOPA is at cutting sheets with significant thickness. I keep going out of focus. Other than that, the main prob is the cut will slant at the same angle the beam is taking from near the center of the galvo lens to the cut, so the slant gets more pronounced the further the cut is from the bed’s center.

I do see how it would not be that straightforward to implement. My hardware doesn’t have a Z-motor.

One thought was that it doesn’t necessarily NEED to be implemented in the BJJCZ. It’s a very simple step command that happens outside of each pass, it’s not dynamic. So we could in theory have a separate ESP32 on USB getting told to issue a step pulse.

That does make some sense, because the Z also needs a manual up/down and it sure sounds nice to implement a TOF range finger to adjust the focus. But that sounds far beyond what the BJJCZ could implement, so pretty much the whole thing would be moved to an ancillary system anyways.

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Dannym,

Well this is my argument as well, there are many things that can be leveraged having a stepper controled Z Axis. Its an easy build, using the 4 pins on the back of I dare say every fiber laser out there which hooks you up to a rotary, whack an aeroplane plug (as I call them) and take the wires to a normal stepper controller give it some power add a power supply to the box, a couple of buttons and up and down she goes.

But because nobody explores beyond ahhh what do I need a motorized z for when I can wind the handle just as quick.

The code my belief is already there, whats the difference telling a rotary (which is a more complex set of codes) to do lots of wonderful tricks turn come back remember where you were last, steps, line width etc etc.

There is code already there that every X passes do a full or partial cleaning pass, no whether your telling the laser to do x y or simply now move the z distance down by .o1 whats the difference.

Your quite right regarding the cutting something Ive never really thought about because we jerry rig that with WOBBLE, lets just make the cutting wider to allow for this or that.

We dont need to hook into the fiber lasers mother board if the facility isnt there so be it. But we could be a little more inovative with other things."

At least I got an honest answer, sorry to much coding time not much interest and yup, click here make the suggestion, but the annoying thing there is to make a suggestion you have to make another login (right yup we all want to do that dont we) something else to remember, so you can well imagine people who have an interest in sharing an idea or asking for a request, (I admit like me) yup you know what Im not making another login when it SHOULD BE A PART OF THIS FORUM.

So things go no where, which is convenient and I say deliberate… but thats only my opinion.

Don’t hold your breath, unless people take up on the topic and start thinking outside of the box it wont grow legs.

The coders could though be a tad just a little bit more progressive and say you know what we could maybe do somethings with that rotary port not just x but as you suggested cutting, as well.

Sorry people not trying to be nasty I just have a different way of expressing myself.

Nice call anyways, love the idea!
Its not hard to implement my belief.
Same as it wasnt hard to add full cleaning passes instead of partial cleaning passes.

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I’m with you guys. Been running mine that way for some time.

Uno and UGS

PS I seem to be able to access the suggestion area once logged in to LB forum.

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I think most of us could find a way to make what we want work if this screen had a “Start Pass” or “Finish Pass” IO optionand maybe a “Pass Delay”…

From there we could use the IO to trigger what ever we wanted…

Heck be “extra Fancy” and add “Pass Start” and “Pass Finish” as Outputs and “Start Pass” as an input… Then to be holistic add a “use Pass Controls” to next to “use Rotary” on the marking screen…

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Well maybe someone will look at that and say hey you know what time to do this…

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From someone who isn’t related to the Lightburn people, I think this has little to do with Lightburn. These are output by the controller and Lightburn is giving you a way to use these.

You assume we have great knowledge of these JCZ controller, which we don’t…

I don’t even know if the controller knows anything about layers…

Why don’t you send a note to them at

Beijing JCZ Technology Co., Ltd. Wuhan Branch
Address: 1101, block B, building 1, modern service industry base, Huagong science and Technology Park, University Park Road, Jiangxia District, Wuhan, Hubei Province

And ask for a fix or maybe some useful information… about anything would be wonderful.

I’m also very sure that if these outputs were available, Lightburn would probably allow access to them.

:smiley_cat:

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Yah, lightburn can do things with those inputs and outputs given you get to configure which pin gets which I/O… These are programmable pins…

And EZCad 2 DOES support Z axis so “something” happens every layer line…

Lastly you make a pretty big assumption that the stream of data Lightburn sends to the controller over USB is a fire and forget… I highly suspect its a “discussion” given you can pause at any point, you can stop, you can restart… Like the controller isn’t “give me the job and then go away”…

And Pins being programmable (you choose which pin is assigned which input our output action) makes it HIGHLY likely you could fire a signal out of the pin any time you wanted…

Also, unless you have a Galvo and need/want Z axis control, why are you jumping in on this… Or did you just wake up and decide to choose violence this morning rather than be supportive or quite on a topic that doesn’t affect you…

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I have a galvo and would like Z axis control. Like seeing it discussed on the front page so often!

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Jack thank you for hoping on to the conversation, what you are offering doesn’t really help the discussion much.
It sounds like you are simply saying go away and ask for a fix.
If I were to do that, and write them a letter and lets say by some miracle they said hey yup we have a fix there it is.
Its still up to the marvelous coders at Lightburn to implement a use for the fix given.
Also I think you missed something as well, there is a stepper controller found in most Fiber Laser machines. Separate to the JCZ board, which runs the rotarys.
My question was if we can control a rotary you know left right x amount of steps this way or that.
Why wouldn’t we be able to control a z axis, when we are not using the rotary.
If you enable rotary in LB and asked it to rotate left or right you Z axis would move up or down.
Not real rocket science.
Colin the support manager did give an honest reply and hat off to him for doing so.
Quote
“With a small dev team, we must focus on the features that affect the largest number of users. Z control simply isn’t the top of the list at this time.”

Now Colin did not say it couldn’t be done, its not on the priority list.
Having said that if enough people asked for the feature, and unfortunately making a second login to request a feature for me doesnt work but this forum is good enough.
The good people at LB do look at it, if enough people realised the benefit and value of having a Z Axis control they would ask.

Z Axis isn’t just about moving the galvo up or down.

The advantages it give when cutting material are enormous,
I dare say people with fiber lasers do a lot of engraving and those particularly that do 2.5d engraving the benefit to the quality of work that could be achieved with z axis control would be staggering.

Naught to do with JCZ just a little out of the box thinking and I believe it wouldnt be hard to implement.

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Dannym just as a by the by, you can add an external box with a stepper and controler. then just plug it into you JCZ board.

There are fiber lasers that dont ship with a controler in the case, but you can buy an external case as an addon.

As a by the by, 300w Mopa, you need water cooling? What’s the thickest material you have cut with it.

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Well, funny you should ask. I was playing with it and got as far as 6mm… but there’s a catch which explains “why you don’t do that”.

It’s about parallax, the angle of the beam vectors towards approx the center of the lens overhead.

If you are cutting out a circle directly under the lens, you can get a straight-walled circle cut out. I took a 10mmx10mm square stock, made a 3mm circle in the exact dead center of the beam field, and quickly got about halfway through, but then it got very confusing how to focus is. If you’re too high, you will get a lot of sparks again as the beam focuses on the outer wall and erodes that. And we tune in the initial focus primarily by looking for the point where you get biggest sparks and loudest cut. That’s all you have to go by, it works at first but not as depth builds up.

And if I want to cut a horizontal straight line 2mm wide 6mm deep, it’s possible if it runs under the center of the lens. You have to adjust the focus down as you go because the depth of focus is under 0.5mm on the std 110mm lens. Anything not in focus does not cut.

But let’s say that line is 40mm from the center of the lens. The first 0.1mm cuts down 2mm wide. Then, the edge on the lens side starts occluding the cut. At 0.25mm-0.5mm deep you have to drop the focus to continue cutting. Well, the wall on the far side from the lens is straight down, but the near wall is clipping on the corner at the surface. And, it’s out of focus, so the laser won’t just round it off and make a slope on the inside wider than you wanted.

Rather, the laser has no effect on it and it occludes the beam from reaching the 2mm wide bottom. At first it occludes 0.5mm on that side, then as you try to go deeper it occludes 1mm, then none of the bottom has a line of sight to the center of the lens and none of the beam can see the bottom.

Net result, the cut is 2mm wide on top, the far wall starts straight. The inside wall starts with a 2mm width but goes narrower matching the slope to the center of the lens, the line of sight. So, my case described a straight line across the bed rather than a circular trench, so that angle varies down the line.

I did wonder “ok, let’s cut down expectations- what if I want to cut out a straight-walled oval directly under the lens?” Could I do Offset Shape inside of my oval 5mm wide on one layer, cut that for awhile, then another layer doing Offset Shape 4mm inside, then 3mm, etc?

Kinda works, yes. You’ll get the straight wall. You could do the same thing without Offset Shape and just try to hog out the whole volume inside the oval, it would just take longer.

But it’s not perfect, if you let the bottom go further than you intended before dropping the focus… well, I said anything not within the 0.25mm-0.5mm depth of focus doesn’t cut, right? Still mostly true. But say your bottom is now 0.25mm below the surface and you lower the focus 0.25mm. Then it erodes down to 0.5mm and you aren’t keeping up exactly with the handle. Well, the beam will tend to undercut the outer wall with, again, the line-of-sight angle to the center of the lens. Only a small amount, because, again, anything more than something like 0.25mm-0.5mm from the ideal focal plane can’t cut.

I did wonder about building an XY linear stage to move the work underneath to make it capable of more. Maybe I could drill 3mm holes in different places… cuts where the whole ablation area is a single shape under the lens center… more important, I could make small hex shapes for nut inserts. It could have some value over a milling machine because no bit radius round the inner corners.

But, so far, 1) I can’t really picture when this would often be of significant value. 2) it’s still very limited in the shapes it could cut 3) it would be really complicated to reliably manage the focus as the cut bottom drops. 4) it’s pretty slow 5) it could easily undercut the walls and so not a high accuracy solution and 6) how would you ever manage cam, and hardware+software machine control?

Can’t see a practical path forward, EXCEPT I could see a wild idea where you could limit the beam to doing the “wiggle” where the galvoes are making a small circle over and over very quickly, and more slowly moving the circle down a line. With “normal” bed, that method doesn’t change the fact that once you have that slant going when the cut isn’t directly under the lens.

But if you kept the beam doing the “wiggle” only straight down and moved the work underneath, yes, it could cut tracks without a slant.

That’s as far as the idea got. I can see some reasons even that wouldn’t cut as well as you might think, and, again, is there a case where this is better than just putting it on a mill? You could change the “wiggle” shape to a square and make a true inside corner. But, stiil, very hard to set up, limited in size, material, speed, etc and I can’t think of a task that even needs this.

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I have ran up against this very thing, stepping down 0.25mm increments didn’t take long before I started to notice a big hit in ablation. At first I didn’t catch on to the fact the beam was being occluded.

XY table / Z column only using the galvo’s wobble to create the kerf. That is something not that difficult to achieve. Have to manually turn the laser on and off using the LB controls and run continuously until cut was complete.

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I hear what you’re saying. There are many ways to perhaps overcome the problem. Not doing anything resolves nothing at least you have tried something and get a result which is better than no result.

I think we need to start somewhere and as soon as people understand the problem and are faced by lets call them brick walls, solutions will start to appear.

However its a two way street, there is no open source solution where the community at large can experiment on a resolution so if it’s closed source you then have to wait and depend on the software vendor to come up with a trick or two to get it all moving.

Personally I think LB is the key and their Devs are pretty clever. The solution is there we just need to support the Devs and they need to support us.

Because there is no percieved needs, doesn’t mean there isn’t a need. It just means people currently are not aware of what they have in hand.

I do hope that the Devs at least have a small look at this and offer us a tidbit that we can look forward too.

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I was looking at the 3d heads that have an auto z control at the galvo end I think the brand was taste or sino galvo one of those or something else. The killer for me is the price, its just excessive for what it offers.

One of the prices was in excess of $5000 USD worth more than the source and in some case the whole machine.

I don’t see the technology in the head that can justify the pricing.

We have had CnC’s for how long almost since day dot in control of z height, Co2 Lasers now for many years able to do 2.5d engraving again z height control, and fiber laser with well no z height control other than manual or over priced solutions.

Maybe its just a situation where we live with the pain until someone comes up with the magic cure pill.

Who knows maybe AI might come up with a solution for nothing. :)…

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Here’s the rub: When you’re trying to cut thick materials in multiple Z steps on a galvo-style scanning laser, you do run into a brick wall (as Danny explained), and that brick wall is geometry. The only way to solve that problem is by using something other than a galvo with the usual F-theta lenses.

Playing around with the concept in my head, I did hypothesize one potential way that it might be possible to engineer a galvo-style scanning laser to be able to cut thick things in multiple Z steps. Instead of an F-theta lens, you’d need an optics path that was basically telecentric on the exit side. With the resulting beam paths being normal to the surface of the work, moving Z would be workable. Of course, the work area would be necessarily limited to the diameter of the exit of the lens, but you could then couple that with an X-Y table to cover more area, like splits with a rotary.

Alas, there’s currently no such optics setup available, but perhaps it could be engineered, and it’d be a really cool thing to work with if it’s ever created. The scanning speed of a galvo with the basically-normal-to-the-surface beam path of a gantry. It’d be the Reese’s Peanut Butter Cup of lasers! Of course, it wouldn’t be a galvo with an F-theta lens at that point.