Poor performance and rendering quality
Hello,
I'm having trouble with slow X axis speed with the miniGerbil on a K40. I'm also not thrilled with raster quality. Here's the situation:
- Using the stock m2 nano controller, I was easily achieving great quality 300+ mm/sec raster speed on the X axis with K40 Whisperer.
- Replaced the m2 nano controller with the miniGerbil. Switched to Lightburn (config below).
- I tried to up the X axis max speed from the default, but setting $110 to anything above 13500 (and trying speeds over 225 mm/sec) and the head just stutters and barely moves.
- I did accidentally slam the laser head against the right side a couple times during the install as I was trying to get the right homing location, so I wondered if there was some mechanical problem. Checked the tension on the x axis belt, seemed fine.
- I swapped out the miniGerbil with the nano to see if there's a mechanical issue with the stepper motor or belt tension, but the machine operates buttery smooth at high speeds with the stock controller and K40 Whisperer.
Some things I've tried:
- Followed troubleshooting here, with no luck: https://awesome.tech/mini-gerbil-debugging-movement/
- Maybe it's a current issue? I tinkered with the step sticks (https://awesome.tech/adjusting-stepsticks/), but didn't notice any improvements. Put the step sticks back to default locations.
- Read about the $28 setting, so tried tinkering with that, but I saw no change to max speed. Does the controller need to be restarted when $28 is changed?
So is there any reason why the miniGerbil can't move the head as fast as the stock controller? Could it be Lightburn?
Also, even at the max speed I can do (225 mm/sec), the quality of raster engraving is quite poor (jagged edges). Even at 600 dpi I'm getting jagged edges. I dialed in the scanning adjustment offset (-.15 gets me closest), but quality is still not nearly as good as at 100 mm/sec. Laser is in sharp focus. Stock controller had much cleaner render, even at high speeds.
I'm at a loss...any thoughts or insights are most welcome. Thanks
My settings below ($101 is at 133.041 because I'm using a rotary attachment atm).
$0=10
$1=255
$2=0
$3=2
$4=0
$5=1
$6=0
$7=0
(ATC M6, pulse/ff)
$8=100
(ATC Tool Td, milliseconds)
$9=100
(ATC M6 Td, milliseconds)
$10=1
$11=0.010
$12=0.002
$13=0
$19=0
(Softstart, milliseconds)
$20=0
$21=0
$22=1
$23=3
$24=2000.000
$25=10000.000
$26=250
$27=2.500
$28=5
(Spindle freq. 0 to 15)
$30=1000
$31=1
$32=1
$100=157.000
(x:stp/mm)
$101=133.041
(y:stp/mm)
$102=160.000
(z:stp/mm)
$103=160.000
(a:stp/mm)
$104=160.000
(b:stp/mm)
$110=13500.000
(x:mm/min)
$111=5000.000
(y:mm/min)
$112=5000.000
(z:mm/min)
$113=5000.000
(a:mm/min)
$114=5000.000
(b:mm/min)
$120=4000.000
(x:mm/s^2)
$121=500.000
(y:mm/s^2)
$122=3000.000
(z:mm/s^2)
$123=3000.000
(a:mm/s^2)
$124=3000.000
(b:mm/s^2)
$130=500.000
(x:mm max)
$131=320.000
(y:mm max)
$132=200.000
(z:mm max)
$133=200.000
(a:mm max)
$134=200.000
(b:mm max)
Hi Matthew,
thanks for your detailed post. Good news, I'm confident we can sort this out. We could write posts back and forth on those details (in the normal way) if you like. Or, if you have an example image file you don't mind being public, we can bring it to life with actual results of various settings - this will help communicate a few key insights that will resolve what you're currently seeing.
Is that sounds ok then please attach your .jpg or.png file, and your .lbrn project file. I'll then run a few engravings and post photos of the results here.
Regards,
Dan
Hi Matthew,
I've published a quick blog emphasizing key things for grayscale engraving. It's really just a 'do this' kind of guide and we'll write an expanded version that explains more of the underlying calculations etc. But check it out let me know what difference it makes.
Cheers
Dan
Hi Dan thank you for the followup. Your blog post was very helpful in understanding the relationship between line interval, laser beam size, and speed. In fact, the jagged edges I was describing above are certainly from a combination of the speed and the size of the laser beam, which I see now, so thanks for that.
On the other hand, in my case I'm not working with greyscale engraving, but rather working with powder coated stainless steel tumblers, which leaves me with a different problem: Although raster engraving can burn off the powder coating at about 127 dpi, this leaves the edges of the shapes with effectively the same resolution, an artifact that is easily discernible to the naked eye and looks pixelated.
Seems to me that there are two solutions to this:
- Increase the DPI. Because the stepper motors have a finer resolution than the width of the beam, by overscanning the steel remains unaffected but the edges benefit from finer apparent line intervals. This is why my quality indeed improves at even 500+ dpi. But this seems to require a line interval of approximately 0.042 to get the quality I'm looking for, and that makes the jobs very long indeed.
- Run a fill & line pass, which clears the powder coat fill first, then sharpens the edges with a line pass, smoothing over the jagged edges. After dialing this in, it can produce a nice result; this seems like the "right" way to do it, but unfortunately my rotary attachment seems to lose accuracy over time during complex line passes like this, so that the lines track worse and worse with the fills as the lines are drawn.
I'm still perplexed why faster speeds are not possible, even if they are not ideal. And this problem exists even when using the "Move" panel in Lightburn and trying to up the speed. For some reason, the Lightburn/miniGerbil combo just isn't allowing me to go faster, even though with K40 Whisperer/nano controller I can go much faster
Alas, maybe I'm expecting too much from my equipment. 🙁 Thanks again.
Hi Matthew, i would suggest to improve the rotary function. You can replace the rubber bands on the rotary wheels so there is more friction between the tumbler and rotary wheels. One issue i had with my rotary was misalignment of the supporting wheels and driving wheels. When the axis are not aligned then the tumbler skips. Next you could insert a dead weight into the tumbler to give it more grip on the wheels. You might need to reduce the acceleration for the spinning y axis. What happens if you run multiple cycles? Is the tumbler shifting? Can you run one cycle, pause align and run the second cycle? Maybe that requires the assistance of a laser pointer somewhere fixed and shining onto the tumbler surface and a fuducial e.g. sticker or marker. Let us know your findings.
Thanks for the feedback Matthew.
If you could upload a good quality photo of the artefact you're concerned about we can advise.
I imagine you're using high power, so the issue could be the tube delay. Fortunately that can be fixed in Lightburn, see
https://github.com/LightBurnSoftware/Documentation/blob/master/ScanningOffsetAdjustment.md
For us to help you best, it's essential that you provide all parameters of your burning (including power level) and an example file as well.
Regards,
Dan