I lay the laser module down flat on the worksurface, connected to the PWM module (it reads 001, photo timing drops one digit), and +12V power… that’s all that’s needed. I use a wooden block and ruler and slide the laser module back and forth to quickly find focus…
Get your measurement from bottom of housing to the wooden block or make any focus adjustments… and then go make a gauge block (or step-gauge) to enable setting the proper height when mounted on your machine!
Oops sorry David, yes I should stop playing around with editing my posts
I didn’t get the PWM module with my order, but your explanation makes sense and I can just order one if need be. Watching some youtube videos as well shows a lot of people using Lightburn to do a low-power fire test and then use a USB microscope to dial in the focus. Or focusing via firing on piece of wood set on an angle and picking the best looking spot/measuring the distance.
Thanks for answering my lasering questions (and everyone else asking in this thread)!
To me this method seems the same as just raising and lowering the laser in its mount to see where the best focus spot is and then measuring the result. The problem is that I cannot tell any difference between 15mm and 25mm using this method. I’m not sure if the issue is me, or the issue is related to the dual-beam A40640. The method that I have the most confidence in is the angled wood as kcny suggests. I still cannot tell a difference near the focus point, but I can match out-of-focus areas of the line and pick the midpoint. I also used LightBurns’s focus test. My best guess between the two was 18mm from the metal housing.
There is a different little board I’ve gotten with some Neje laser modules… that doesn’t have the PWM generator or digital readout. But it does provide a variety of ways to connect power and PWM (TTL) to your laser module. Most of the time I just leave it out of the system and connect directly to the laser module… but it can be handy (I’m actually just testing this laser on my machine prior to installing it on my daughter’s machine…) for testing and, more subtly but important however you do it, it provides a convenient way to insure a common ground when using different power bricks to provide power to your controller (which provides the PWM signal) and the laser power.
It provides a two-wire TTL connector, a three-wire +12V/GND/TTL connector, and even screw terminals to allow easier(?) connection to different controllers. It also provides a “TEST” button but, unfortunately, it fires the laser at full-power and is IMO of limited utility. Or, you can just go ahead and mount your module on your gantry and connected to you controller and simply focus it in place, controlling the power with Lightburn/CNCjs/etc.
By hook or crook, get PWM connected so that you can adjust to a very low power dot and you can use any focus method you want, on or off the machine.
When I have a fully-implemented Z-axis, I often use Ryan’s focus script to find the BEST focus when my laser is already in place and operating on a machine. You start with the Z-axis height too close to the material to possibly focus and then run the script. It burns 10 lines, each 2mm higher than the one previous, leaving the Z-axis 20mm above where you started. If the best focus point is found within the 20mm you traversed you should see a “gradient”… thicker lines surrounding thinner lines. Then you count from the top down to the finest/thinnest line and lower your Z-axis by the linecount you counted times 2mm; i.e. 6 lines X 2mm = 12mm below where you finished. I personally believe that this is the best way focus a machine that is fully-functional and has a true Z axis.
The method I showed above can be done as soon as you unbox your laser module… especially if the PWM board is included. No engraving machine is needed. Just lay it all out on the table, hook the laser module to the PWM board and plug in the power brick, Then use the buttons on the PWM board to turn on “TEST” mode and it comes on at the lowest power setting (001) … you should see a dot. Sliding the module by hand, against a guide or some sort (a wooden ruler is great!), you slide back and forth to quickly find the general area of minimum dot. Fine tune by making smaller back and forth movements and you’ll quickly zero in on the best/smallest dot… just like tuning the note with a trombone slide or cello string.
Sure the same thing can be done when mounted on your machine. I just find it easier to look down on it all from above rather than bending down and looking sideways to try to read my measurements or make an adjustment.
There’s many different ways to do this, of course. I just like what Neje has done to supply everything needed to do a quick and dirty test of the laser… right out of the box.
Do you (or, anyone else) have any idea how small the kerf actually is? (I’m assuming it’s the 40640?) I’m asking because one of the possible requirements that I would have would require cutting out 3mm x 3.5mm windows that are separated by 0.55mm in both x and y directions. Material is thin, 0.020" laserboard. Can the 40640 do it?
(Customer is currently using a CO2 laser system at the local makerspace, but, we are interested in more control of the process. )
The kerf on my laser (a A40640) is 0.2mm, though it varies a small amount depending on the material. Here are three luminaries I cut for Halloween to give you and idea of the kind of detail it can do:
The carved areas are all about 6" tall. I just measured, and the thinnest areas on the koi were .45mm thick, and the thinnest lines (around the teeth) of the Attach on Mars face were about 0.65mm. But with that said, it’s not a slam dunk. If there is any tension in the material, it can curl up and get in the path of the laser and ruin the cut. And as mentioned above, when I turned off my air assist, the bag caught fire.
So I think you are pushing it if you have a lot of windows with only 0.55mm of separation, but it is theoretically possible. It will depend on the nature of your material and how you present it to the laser.
LOL! During my laser “travels”, I had always been keeping an eye out for a good “bed of nails” design… when I came across a video (no clue where I saw it now) where a guy had found a “goth” apparel shop online (Ebay?) where they sold all this spiky stuff, popular with “those” folks. Anyway, a bag of 100 metal studs and screws was inexpensive enough I bought a bag. Printed a plate with counter-sunk hole pattern and assembled it (very tedious!) into a bed of “nails”. Unfortunately, when I packed for the move back to East Texas I lost track of it and only found it a couple of days ago… I had never had a chance to use it!
Anyway, playing with this big diode laser, destined for my daughter’s laser engraver, I’ve been trying to get my miniFoamRipper machine set back up for actual use again. Bought a 24" x 24" steel sheet from Lowes and I’m hoping now to start doing productive stuff again… it’s been a welcome diversion
I just grabbed a sheet of the white honeycomb light diffuser stuff from home depot. Not quite as fancy, but it’s worked well for ‘through cuts’ on the laser. Plus it’s plastic, so no reflections. It does burn through over time, but I’ve yet to have to replace it.
I picked up a sheet of steel lath from Home Depot last week for use as a laser bed for larger laser projects. It was $15 for a 27" x 96" piece. I have yet to use it (I have a smallish piece of aluminum honeycomb for smaller projects), but it looks like a good fit as a larger laser bed. From what I’ve read, you don’t need much separation below the material when laser cutting.
Thanks for your comments and photos of your work. My friend uses Lightburn at the makerspace, so I’m sure he’d stick with that. And, he tells me that he’s familiar with the necessary offset for the kerf width. And, clearly your experience (and of others) confirms the need for air assist.
I think the primary concern was whether the optical limits (inherent beam shape, etc. of the 40640 laser would allow these dimensions, and your results indicate that, while challenging, it should be possible.
So, back to the OP’s original question… is the Neje A40640 laser module any good or not? Given a couple of days to play with it… I say “Yes!”
It’s performance far exceeds any other diode laser I’ve ever had… and how long it lasts remains to be seen. After a bit of testing to find best cutting speed for 3mm (1/8") birch ply, I was able to cut everything but the heart-tree in the following photos in a single pass at 200 mm/min and 100% power… the heart-tree required 150mm/min and 100% to get all pieces to fall out without breaking small branches.
They’re very effective and are easily spread around to support any size workpiece… and a bag of 10 heatsinks is reasonably inexpensive to solve what in the past has been a nagging problem. I’m hoping they should be easy to clean with a cleaner of some kind… any suggestions?
These cuts are easily done with my CO2 laser and much faster, of course. But this diode laser setup is IMO much easier and convenient to use and not so slow as to be “painful”… i.e. the ~140mm x 140mm heart-tree took only 33 minutes, and way less for the other pieces. I’ve also cut several ~5mm materials in my testing as well… some in one pass and others with only an extra pass or two at most. Numerous videos are out there showing folks cutting far thicker material than that… so I’m really looking forward to playing with this Neje A40640 laser module further. I think it will really “up” my daughter’s game when I’m ready to move it to her machine…
