Machine: K40 Nano M2
Firmware: I have a new board and I’m using whatever it came with
Software: Lightburn - gcode version
First many thanks for such a great resource. I sincerely appreciate all of the contributors. I will advise that I am a complete noob, having just stood up this machine about a month ago, having spent every weekend and many evenings with it, and enjoying every minute spent.
I’m interested in dialing in my machine a bit for engraving; birch and acrylic mostly and I use a lot of chipboard for test runs. I’ve been surfing and reading many posts, running several tests (ramp test, standard testers), and am happy to provide additional info as needed.
I realize settings will change based on media and machine, but I’ve noticed some oddities with my K40 for which I’d like some advice/direction.
Here’s my machine, so you know which K40 variant I have
Power, enable, and test buttons and most importantly, ammeter.
And my laserboard; ribbon cable on the y-axis variant.
I noticed that my “engravings” using greyscale were not offering much variance, somewhat akin to what I found in this post, with similar results on both clear acrylic and chipboard.
After reading that post I did a few things.
First, checked the response to %s of the power setting
- Set the pot to 10mA. (test fired to home in on 10mA)
- Via Lightburn, entered GRBL commands to set to mm, pick a spot, cut a 10mm line at 10% power at F600
- G0 X0 Z0
- G0 X0 Y10
- G1 X10 S0.1 F600
With this I noticed that the ammeter on my K40 seems to be run quite high relative to power %. With these settings; 10mA / 10%, that line cuts at about ~4mA, at 20% it’s ~5mA. In fact, issuing and monitoring the commands from this post, the ammeter pegs quite high across the board, topping out early on the high end at 70%-100%.
I didn’t expect the output to be linear, so went poking around a little more and came across this article (which is a doozie) and that’s where i read (vs learned) about the complexities of PWM frequency and how it might be adjusted. However, even with a PWM setting of 400, the ammeter still pegs at about 3-3.5mA at 10%, 4-4.5mA at 20% with the pot still fixed at 10mA output.
So to explore a little further I did a few more experiments to get a better sense of things, this time with the pot at 10mA, speed of 50mm/s, and power settings between 1% and 5% (from comments on that 1st article), looking at two variables (independently), PWM [200|400] and DPI [254|400]. The results are interesting but raised more questions.
First, you’ll notice that the media is card stock. I picked it because it’s white and would show any marking better than birch or chipboard.
On the right, there are two groups of 5 experiments, 1% to 5% of 10mA, at 50mm/s, 400pwm, 400dpi (top) and 254 dpi (bottom). There are a couple of okay gradients there (e.g. 2% 254dpi), but more questions than answers.
- At 1% in both test sets, there are few if any shaded cells and interior lines.
- In each case, there are a number of cells that were never touched. They’re completely devoid of any markings. Even in the 10mA, 50mm, 400 pwm, 400 dpi, 5% case, there appears to be room for additional gradient, but none exist in 4 of the cells. It appears to fall off.
- Also, as the power decreases, these void cells increase in frequency. Makes some sense empirically, but I expected a uniformly diminished gradient over the entire area with a power decrease rather than an increase in absence of engraving. I think the net is the same, it just didn’t manifest as I expected. It seems like I’m hitting a power floor/cliff that results in a full drop in output.
On the left, there are two groups of 3-4 experiments (I didn’t do the later ones as they were just burning up the media), 1% to 3/4% of 10mA, at 50mm/s, 200pwm, 400dpi (top) and 254 dpi (bottom).
- At 1% in both test sets there is absolutely nothing, the ammeter barely wiggled at all.
- Again as the power decreases, these void cells increase in frequency. More dramatically though, there appears to be vary little variance.
- In this case with the PWM at 200 the media is really just burned up, with very little opportunity for a gradient. In reality I’d rarely if ever use this for media, but it is interesting to note the effect of a 400 over 200 pwm setting all other things being equal.
So my questions are these.
Am I on the right path? How else might I make adjustments on the low end?
At 10mA and 10% the ammeter registers ~3-3.5mA, even with a PWM of 400. From what I’m reading that seems high, with an ideal of around 1mA. I’m not expecting perfection/absolute linearity, but want to understand this response and anything else I might do to drive it lower, perhaps additional settings. Thoughts/Suggestions?
It also appears that there is some power threshold below which results in zero effect on the media as illustrated in just about every case. I think that’s obvious, but I’ve also noticed a minimum power % setting for a layer. Wondering if that might at least bookend the drop off? Thoughts? Anyone use that setting?
Any other suggestions are welcome.
I’ve also provide my device settings here:
And the settings of the last sample that I engraved for reference.
10mA pot, 3%, 50mm/s, 200 PWM, 400 dpi
Thanks for your time.