OK. When I last left off in my UN-closed closed-figures saga…
Once I delivered my daughter’s little T8 Mini-mill, turned laser engraver… I dragged out an Eleksmaker A3 3.5 watt laser machine I had built up before. Got it set up and running with Mega/RAMPS/Marlin — as before — and then went to my stash and found a Uno/CNCshieldV3 board set to play with. Converted the Eleksmaker to a Grbl v1.1h set up… and hooked up the 3.5 watt Banggood laser it had mounted.
What do you know? This unit seems to handle every previously-problematic test case without difficulty... all closed-figures are closed. Not a problem at all. So Lightburn is fine… and Grbl is fine. Apparently the CNC processor/controller and/or laser driver are the culprit(s). Note the M3 and M4 labels in the following photos… in Grbl 1.1h laser mode, M3 is the CONSTANT power mode and M4 is the newer DYNAMIC power mode. Look closely at the corners… and note the darker M3 burns (first photo left) whereas the M4 burns (right) show the effect of reducing power as each cut accelerates and decelerates at the corners.
I think I’m going to tidy this machine up and swap out my daughter’s machine. She said she prefers Lightburn’s all-in-one, ease of use, features over Inkscape/Jtech and is looking forward to the larger work area of the Eleksmaker machine.
This machine seems so much better behaved and, being belt-driven, is very much quieter. And, for the first time, I'm 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” MPCNC/V1Engineering thread)…
The black stripe in the following photo is where my PWM’s GND wire pulled loose from the pin on the controller… and the laser was then on full-blast. Be careful with these things, folks!
I continue to be impressed by that inexpensive 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. It 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 (if you need +5v PWM, verified with a scope)…. just use Grbl 1.1 or later and use the Z+ and GND for PWM (right-most green and blue wires), with no pin remapping necessary…
I’m really wondering now 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 (the one with the problem?) 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 also helps that it has my daughter’s “stamp of approval", so...
All is right in my world again… and I am at peace 😉
— David