Laser Finally arrived. Now what?

LowRider CNC Advice
43

Looks like you’re getting a “better” expected grid.
Hopefully that was with both dialing in the focus, and possibly the changing of material.

Only thing I can offer as an opinion, is to stick with one material as you get things dialed in and learning your machine. Changing that variable will cause you to chase your tail if you’re not careful. Manufacturing vendors using different glues as just one example.

My path, I elected to work on focus first, using only poplar to start. Once I felt I knew the focus distance, then I did the grids, to dial in power and speed for engraving. Then learned how changing materials, effected my engraving speeds and power based on materials. Then I moved onto cutting. I will freely admit, that was my journey based on the machine I started with. If I started with a different machine/laser, I might have focused on cutting first.

My opinion is the learning curve is steeper than most tube videos imply, and a DIY laser has more to learn about, than a ready to burn, higher priced manufactured machine. In my case, it could also be the user. :blush:

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I think I’m going to stick with 1/8” as most projects I have planned call from 1/8”. Would you say this is probably good, assuming I run in the 10mm/s range? Or do I have room for improvement with my focus?

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IMO (as not an expert), I think it would be hard for anyone to tell much about the focus remotely. With that said, I feel positive about this without a photo engraved, or a straight line results from the ramp test. (Still not an expert) With that said, I would do the ramp test, jumping right into cutting without knowing if your focused, to me is jumping in the deep end without knowing if you can swim or not.

Looking at neje’s wiki, it seems that lens screwed in all the way, is a long focus, and out is a short focus. Their documentation and YouTube video on their wiki shows them setting up for high density MDF, I’m assuming less than 20mm per their documentation, distance of the brass lens 2.5 mm from the case to the knurling, bottom of the aluminum 5mm from the material, 300mm/min, 80% power, 2 passes, resulting in a clean cut. They are on a honeycomb bed, with air assist. By the hiss sound, I’m assuming compressor not pump. At least my pumps don’t hiss like that (ones on actual fish tanks). The hole their air is coming out of, is very small, so…

The focus you are looking for, is the equivalent of playing with a magnifying glass and sunlight. Hopefully you were able to experience this at a younger age. Glass too far away, light beam was wide and out of focus, to close same result, but within a sweet spot area, the light spot, was bright, round, and caused things to smoke, or burn. Of course we also had to account for the angle between the sun, and the object we were trying to make hot, and make sure the lens was parallel to both source and target.

Same thing here, however you don’t need to adjust the lens all the time, once you know your focal distance for z. And you shouldn’t have to worry about the angle assuming neje did things right.

The ramp test, creates a straight line, with a variable z, where depending on the angle you setup, could start from not burning anything, to burning a wide line, that gets narrow and focused, and then out of focus, and wide again. Aka, the material is on a angle, I would set it up, assuming you do the settings they used, where the material will be 10mm from the bottom to 0mm, and burn a line on the piece of wood. You might be able to add some speed, being we aren’t trying to cut, but mark a line. Fast enough to make a mark, slow enough for it to have some color.

My only problem with the ramp test is, it can be a bit of a challenge figuring out the measurement where the line is the thinnest, and most focused. At least it was in my setup. Which is why David’s in my opinion is more “scientific”, once you know what you’re looking for. But if you’re new…. How do you know what to look for. David’s method you’re looking for the laser “dot” to be the smallest with the cleanest/clearest defined sides. FYI, diode lasers beams are more of a square that a circle.

Does that help?

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@JamochaTrilby

You rectangle test looks like you’re probably using too course of a change on the power or the speed.

Take things a little slower: Start with some smaller changes in speed, and more of them. Do engraving first to get in the ball park for line and fill. As noted above, stick with one material until you can get goo, predictable results.

Once you know the focus distance, you focus on the top of the material for lines and fill engraving.

If you’re trying some cuts, start with the same settings as your fine lines. Focus about halfway through the material thickness. Plan on multiple passes, up the power a small amount and the speed, maybe, down a little. Air assist is a must.

One thing to consider is the expected life of the laser: the higher power will let you go faster, but will shorten the life of the laser module. I’ve seen recommendations of using less that 75% whenever possible. That means slower speed, more passes, and less power for deep cuts.

This is the way I have gone about it, I hope that helps.

Mike

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Well in a fun twist for the day the laser will not fire now. I took it off the machine to run the router while I was testing the focus, upon hooking it back up it won’t fire the laser. I believe I have it narrowed down to the PC9 pin or the ground pin as I tried both mini boards that came with the laser and I get the same result. I can also fire the laser with the mini boards via the test button and if I just jiggle the ground and Ttl wires on board end or laser end all I get is a weak beam similar to when I want to test the focus. If it is the pins can I re map the board to choose another pin?

Edit: oddly enough I tried a test gcode that I ran earlier today just to rule everything out and it worked as normal. So something about this file is a dud. I did create it on my computer in my house instead of the laptop I use in the shop.

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48

For inline commands, you need a ‘M03 I’ at the top of the file. Typically, this is put in the Lightburn start g-code section, so it is automatically added to the file. Does the copy of Lightburn you have on the computer in the house insert the ‘M30 I’? You can use a text editor to examine the g-code file to verify.

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49

Your cut test does not look right to me. There is too much smoke damage on the surface, and the lines look a little thick. I’m thinking you have one or more of:

  • Air assist is not being very effective
  • You are not raising your material on some sort of grid. The smoke and particles need somewhere to go.
  • Your focus is still not right.

The A40640 has been reved, but, with the original model, in all the YouTube videos the focus distance was around 20mm. For my personal laser, my focus distance is 19.8mm measured from the metal housing. I don’t remember whether the YouTubers used the housing or the red window as their reference. In the original version of this laser module, the red window hangs down a bit beyond the metal housing.

tried Home Depot 1/8” ply

I’m sure plywood varies a lot, but I find my Home Depot’s 1/8" plywood tough to cut. That is, my cut settings for this plywood are not much below the settings I use for Home Depot underlayment (5.4mm as I measure it). In my laser projects, I’ve used up around ten, 4’ x 8’ sheets of underlayment. I’m still on my first sheet of 1/8" ply.

It is pricier than buying 4’ x 8’ plywood from Home Depot, but you might consider getting some Basswood plywood. It is notably easier to cut and engrave than plywood from Home Depot. I recently purchased this 1/16" pack from Amazon.

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50

I need to get my piece off my mdf for sure, I am looking into options now, so that could part of my issue for sure. I cannot say if its the air assist, but once I fixed the line on it yesterday I noticed an improvement, but it could still be an issue. As for the focus, I am still in the weeds on it I guess. What I have been doing for my adjustments is I sit my LR as low as it will go, then I take a piece of black cardboard and place it under the laser on my MDF spoilboard (once I get a proper laser bed I’ll put it on there). I slide the laser up and down on the bracket that it came with to adjust it.

I gotta say, getting this thing focused its really frustrating.

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The ramp method recommend previously is easy and effective. You place some item below the laser, but at an angle. You then cut a long line on the item. The line will get cut with varying height because of the angle (the ramp). The line will be an elongated hour glass shape, going from wider (thicker) cut to narrow, and then back to wide. The narrowest point is your location of best focal height. Position your laser over that point, and measure the distance.

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I watched the video posted yesterday and then totally forgot to do that test! :upside_down_face: I’ll have to do that next and see what I get.

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So update: things seem to be okay, I’ve cut out the project I wanted.

Is smoke a big issue with laser cutting, I mean I understand that using a laser on wood will generate smoke, but this hour long cut basically filled my garage with smoke. Is this an indication my air assist isn’t enough?

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Air assist and smoke removal are two different things. My machine is in a space open to the outside, so I’ve never had to address the smoke removal issue. Without an enclosure, I’m not sure what the best approach would be for smoke removal.

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I cut in my garage without an enclosure, but I run some big fans to ensure many air exchanges. I even have a little 4" fan I use to blow the smoke away from the bed (super low tech, I just find a spot it won’t interfere and set it there.)

Even if I want my garage door down, I put it up just enough to clear a fan so I know I can push air out. I’m able to do that year round though. I get that many climates make that impracticable.