Nicely done, JefffH. But I’ll probably hold off a while trying another Grbl configuration… I need to tidy up this machine, test it a bit more, and get it to my daughter. It seems so much better behaved – and much quieter, being belt-driven – and I’m for the first time able to get some decent images out of Lighburn that actually match pretty closely those I got from Victor’s ImageToGcode for the same feed, power, resolution settings (“Laser engraving – not really getting great results” thread)…
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The black stripe is where my PWM’s GND wire pulled loose from the pin on the controller… and the laser was on full-blast. Be careful with these things, folks!
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I continue to be impressed by that cheap, little, CNC V3 shield… it is so simple and versatile. I had used it, without the Uno, for my Inexpensive LinuxCNC Interface board set and it was perfect for that application… and it is, here, as well IMHO. Uses the same little step-stick drivers we all know and love, the fourth driver is easily jumpered to clone any axis or be independent, and hooking a laser to this thing is dead-simple… just use Grbl 1.1 or later and use the Z+ and GND for PWM (the green and blue wires), with no pin remapping necessary…
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To stay OT a bit, I’m really wondering if this controller set CLOSES my closed-shapes because the PWM pin (Z+) for laser control is a simple, straight (wire only), connection to the D11 pin on the Arduino. The other CNC1610 boardset I used is an integrated controller (which I haven’t probed and have no schematic for) and has connector “ports” for laser power and modulation. Maybe there’s some “funky” circuitry between the Arduino and PWM connector pin that causes some [integrated?] controllers to exhibit the problem? Or, it could be the laser’s driver board, I think… I’ve got another 2.5 watt Eleksmaker laser ordered, so maybe we’ll see.
Anyway, I am really starting to like Grbl 1.1 (with laser mode M3/M4 control) with this simple Uno/CNCshield boardset… and Lightburn seems to generate gcode that works well with it. It has my daughter’s “stamp of approval” as well… and that helps
I agree. The Uno is underrated by many but the GRBL development community has really forged ahead with it. I have wired an Uno with a Shield as above, wired it to a group of TB6600 stepper drivers, and taken a Uno CNC shield and wired it ‘backwards’ to provide a compact stepper driver for MACH3 on my MPCNC to run 4 axes.
I have read in a Lightburn forum somewhere that Marlin is not as good at laser as GRBL is. Partly because of the Laser mode, as well as a pretty significant cost difference. I do prefer my Rambo for printing but used Unos and Megas for everything else. I have programmed an Uno with Estlcam as well to open up many of it’s functions. Since it only takes a couple of minutes to swap the wiring for the steppers it’s worth it to me.
Alright! Eleksmaker laser machine delivered to daughter… new machine takes its place on the “workbench”. Speaking of “work”… here’s how an old man works hard… without really working hard
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All within “eyeshot”; … slippers, a darkened room, a movie, Prusa MK2S printing a Pi case, MPCNC “Joe” lasering an MPCNC logo… or cutting earrings for daughter, a Pi 3B+ and CNC.js for control, and Tux to keep an eye on things. Tuckers me out, just thinking about it… maybe I need a nap
The issue you saw with the dwell command being issued before M3’s has been fixed for a while, and will be in the next release.
‘Beam drag’ is a phenomenon that happens when cutting really deep material, like thick acrylic, where the material has to heat up before you can effectively cut it - you end up with a ramp into the material at the beginning of the cut. If you’ve ever seen a plasma cutter or waterjet work, they’re similar - once you’ve gotten through the material it’s easier to continue cutting. This happens even with constant power and low speeds.
A dwell at the start (cut through) deals with it effectively, but can leave a larger entry point in the material, whereas using a little overcut handles it more cleanly, and doesn’t require the use of extra material like lead-in / lead-out would.
What you were seeing looks like a warm-up delay or something, but that would be in the laser module or driver itself, and since you didn’t see it with Marlin (using the same module?) I’m at a loss as to why. I have seen constant current drivers in the past that were repurposed from LED flashlights that include an R/C delay to prevent a huge current rush when powering up, but they short the resistor to bypass it when using it with engraving lasers. If you had one where they forgot to short it, it could explain the slow initial startup you’re seeing.
The last results you posted from M3 & M4 modes are what I’m used to seeing - M4 generally produces much better surface engraving, and fewer hotspots, while still having good cutting performance.
If you ever have questions or issues, please post in our forum or send an email to support at lightburnsoftware.
Wow! Thank you, Oz, for your response. After swapping out machines with my daughter – an Eleksmaker A3 with 3.5 watt Banggood laser for the original, “problematic” T8 CNC1610 mini-mill with Eleksmaker 2.5 watt laser – I removed the CNC1610’s Nano-based controller and put it on one of my MPCNC’s… where it has performed flawlessly so far. No problems at all with that machine’s 3.5 watt Banggood laser, Ligntburn, and Grbl 1.1h and all the little test cases I’d created early in this thread… so everybody is “off the hook” except the 2.5 watt Eleksmaker laser/driver, which I haven’t gotten around to testing yet.
My daughter and I both really like Lightburn and all it’s integrated features. I’ve not used it for machine control yet… but just to create/compose designs and generate gcode. I really like using the Pi/V1Pi combo to control these machines… maybe I ought to try Lightburn on a Pi 3B+?
Thanks for all your hard work on Lightburn. I’m signed up on your forum and from what I’ve seen/read so far I appreciate all your timely support.
After seeing the laser stuff run properly… I see the overcut stuff more as a “band-aid”, conveniently provided by Lightburn (who must have seen this problem somewhere along the way…). It works to cover the gap but with M3 leaves a little “hotspot” (as Oz properly called it) out where you tell it to end the overcut. The problem, of course, still exists… but it isn’t Lightburn or Grbl’s fault. Pretty sure now it’s probably the little driver module fixed to the 2.5 watt Eleksmaker laser… which I still need to test, to be sure.
There are a few libraries used by LightBurn that I can’t easily get on a Pi (or at least couldn’t - I haven’t checked in a while). It’s possible to run it on a Pi running Win 10, but it’s a pain to set up and is pretty slow. I occasionally test LightBurn on small single-board computers & mini-pc’s that you can purchase for around $100, and it works well enough there - I’ve coded it for speed where possible, because a lot of people use old systems or laptops for machine control.
