New JTech Laser - basic questions

I just bought a JTech 14W laser. While I won’t be doing production for a good while, I didn’t see any reason to start small and buy a replacement later.

Are there any good guides about dealing with power compared to speed? I know it’ll change depending on how deep I want to burn or cut. I’m starting with wood. First cuts will be on scrap 3/4" plywood. For starters, I’m trying to get an idea of the range to work with so I can make a mark and not cut through the wood and my wasteboard and so on.

Also, I’m wondering if it’d be a good idea to get some kind of metal plate to put down under wood that I’ll be cutting. (I’m thinking I’ll be putting designs on wood, then cutting them out.)

I know a lot of this is experimental, but I don’t want to damage my Shapeoko. (I know wasteboard gets replaced, but I also have rails for bolts so I can fasten projects down.) I also don’t want to be spending a lot of time gradually increasing the power level or speed until I’m finally making a mark.

Also, I’m thinking, with a strong laser, since, ultimately, one issue will be speed, should I focus on using a faster and constant speed and adjusting the laser strength or are there reasons to sometimes adjust speed and other time adjust strength?

Also, how do I precisely measure the offset between the laser and the CNC router so I can take that into account on projects where I want to use both?

I have the 7W version…it can’t cut anything even remotely close to 1/2", much less 3/4" - but maybe the 14W is different. I’d be interested to hear how you do.

EDIT: Looking at the JTech site, he says: Cut 1/4″ plywood, 1/2″ dark acrylics, 1/2″ MDF, no problem! This is with the Air Assist upgrade. They show 3/4" Pine 10 passes, but I don’t know if you’re going to get 3/4" Ply with a reasonably clean cut.

As for putting a metal plate under the board - I’d be careful about anything that might reflect the laser…although the focus won’t be there, the beam can certainly damage someone’s eye if it starts bouncing around your shop.

So it can cut it, but after a number of passes - but it’s worth testing. 10 passes is a lot, but it also depends on workflow. It might be easier and faster to do 10 passes (if it’s not to large an item) than to stop it, re-zero it, then cut it out with an end mill. I’ll have to play around and test it.

Thanks. I figured it’d be so unfocused that as long as I was wearing eye protection, it shouldn’t be an issue, but it’s more of a factor than I thought it was.

Mount your laser package per instructions. Use a good Vbit to cut a “target” crosshair pattern. Note the machine coordinates. You’ll need them to find the offset. Then switch to your laser. Use your jog controls to move your laser test spot until it is as close to the center as you can visibly get it.

Then burn the same pattern crosshair pattern with the laser. Look that your burned pattern matches the Vbit cut pattern and adjust the XY accordingly. Possibly cut another Vbit crosshair pattern when you can’t see a difference anymore.

Note the machine coordinates. Subtract the two coordinates and you have your offset.

NOTE: there are other ways to do this that could be easier, but this is one way. For instance, you could just reverse the cutting vs. burning operations and use the Vbit to locate the burned crosshair center. YMMV :smiley:

I put that offset into my postprocessor. gSender has a laser offset field to do this for you when you burn something that you designed without an offset.

FYI. Here’s how I changed my JTech 7W so it stays put and goes on/off easily and predictably on my Shapeoko XXL.

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In Lightburn, you can create a Macro to jog the offset using GRBL command.

I was going to do the exact same procedure you recommend - burning the crosshair first and then zero-ing a vbit on it - but I didn’t get around to it. My plan was to create two macros in lightburn to jog the offset in both directions.

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I’ve also been thinking about what may work for a quick centering tool for the J-Tech laser. Maybe I could print something that works a bit like the BitZero. This wouldn’t provide feedback. It’d fit over the corner of the material, like BitZero. Make it 1/4" thick for Z adjustment. Then have walls sticking up that I could just “slide” the laser up against with jog controls. That way once it fits in place, turn on the laser for positioning and that provides a visual check.

This would be a different way, but since, for now, I have to use UGS for the laser and CM for CNC, both would have to be zeroed anyway.

I’d prefer your method, though, and if there’s one program I can use for both GRBL for the CNC and GCode for the laser, I would love to use that and your method to set the offset. That’d speed things up a lot!

What does that add over the current system? Tighter tolerance?

You need to checkout Lightburn it is 1 of the best laser programs you will find for the money. They have a fire button you can turn the laser on at low power then move to the point you want to start.

I’m using LightBurn, but I have a major issue. I’m using a Pi with a touchscreen to control my Shapeoko. It’s in the middle of the floor (for multiple reasons) and far enough away that connecting it to my workstation is a not viable as a long term solution. While LightBurn does work on Linux, the Pi on my Shapeoko uses only a 7" screen. CarbideMotion is fine on that. UGS is okay, but frustrating. (It’d be easier if I could find out how to store the window layout so I wouldn’t have to change it each time I run it.) But from using Lightburn on a workstation, I would not want to try to deal with that interface on a small touchscreen.

So for the foreseeable future, I’ll do all the design work on LightBurn to produce GCode files that I’ll load with either CM or UGS (and I’m now looking into gSender) to do the actual control.

I am looking into USB over IP. I can connect through wifi or the fiber optic cable through the ceiling (major lightning issues - need to use fiber instead of normal cable through the area above the ceiling) with that, but I have more to learn about it - like if it monopolizes a USB port or if I can easily stop it or use the same port locally while it’s running.

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Maybe read a bit more about those two things.

Repeatability mostly. Unless I bump a clamp, nothing ever changes even if I take the laser off and on.

Yeah, doing a LOT of reading on all this - and video tutorials. (Personally, I prefer written with photos - easier to reread what I need to and to skip what I don’t need.) Dealing with the CNC alone was one thing, but so much to learn about dealing with a laser AND about dealing with both on the same system.

@Tango I recognize that I don’t fully understand your setup…but can you utilize Dropbox to share files over IP, rather than converting to USB? I do this between my design station and shop tablet and it’s very convenient.

Granted, yes, it’s a strange setup!

I have a NAS RAID I use for my 3D work. I have a big screen iMac in my study, in the house. My workshop is in the barn, with the Shapeoko and two 3D printers. I like to do most of my work in my study. It’s more comfortable and the dogs are often sitting on the daybed nearby - plus I have the daybed for naps! :wink: The rest - well, if it helps in terms of understanding the situation, it’s here. It may all just be tldr stuff.

The barn is over 300’ away (500’ or more on foot). In the workshop I have a Mac Mini, so I can do design work there. I have 4/0 line in a trench to the barn, along with a conduit for fiber optic cable, a water and sewage pipe as well. All 2’ underground. Normally what I do is get all the design work done in my study, save it, then go down to the barn when I’m ready to print, etch, or cut. Because of the lightning issue there (and it is real, I’ve had to replace ethernet switches after lightning strikes), I’ve replaced ethernet cables in the trenches under the main floor in the barn. (It was a big parn and there were two 2’ square trenches running the length of the floor, one near each side wall, for pig waste. That was 30 or more years since it was all in use and I’ve bleached the hell out of those trenches! Now they’re tunnels under the concrete floor.

Most of the blowouts happened to the switch connected to the cables running from the fiber optic converters, through those trenches, to the “tech closet.” Once I pulled those cables and put in more fiber, the blowouts stopped. I’ve had a similar issue with ethernet running above the ceiling for the 2nd floor, so I’ve been replacing that with fiber. The Shapeoko (and my table saw) are in the middle of the shop floor, so I have outlets in the ceiling with a box on the ceiling for a UPS, the fiber converters, and stuff like that.

So far, since I switched to fiber in the ceiling, I haven’t had anymore blowouts up there, either.