Engraving on large machine

Nothing in software seems to change this, so I assume it’s slop in the machine. Frustrating, but it is what it is. In this case, the wrong tool for the job.

George

Are you doing bi-directional scanning on that block? If so, it looks like you need to change the Scanning Offset Adjustment, in the Device Settings so the ends of the lines are even on both sides.

You could also try turning that off and confirm that the issue isn’t present at that time.

Thank you, yes that is exactly what I tried. No offset parameters seemed to change the ends. Nor did turning it off. That’s why I think it’s mechanical. There is a lot of slop in the laser head, I can easily move it 1mm in all directions while it’s at idle.

I have checked all the screws in the transport and rails. Motors too, they are tight. The belt could be tighter, but I don’t know the correct spec.

Still open to any and all suggestions.

George

Even with some ‘slop’, changing those values should show up in the engraving as a change. Every other line is consistent to itself, so their is consistency within the machine.

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Very good points.

It engraves the bottom line first and works upwards. The bottom line is always more left and short on the right. That is engraving from left to right IIRC, so turning on and off early. Next line is offset right, with laser moving right to left…once again early on and off.

Maybe try negative offset numbers?

George

Here is another post dealing with a similar issue. To set up ‘Scanning Offset Adjustment’, you need at least two entries for any others to be extrapolated. Start with two measured speeds, and if you need more after that then add them. Also, are you using “Flood Fill” for anything? It doesn’t work with that option enabled at the moment.

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Thanks! I added up to 5 different speed measurements. My last try was:

50mm .5mm

100mm 1mm

200mm 2mm

300mm 3mm

400mm 4mm

When that made no difference I gave up. Was not using flood fill, but will keep that in mind.

George

Had a busy Monday, but glad I was able to spend time working on this today. Everything with this machine feels like baby steps. LOL

Away from the shop now, which means I’m reflecting and considering the results. It seems like I’m just a few parameters away from engraving as well as this machine is capable. I’ll research and try to gain perspective on this. For example, I have no reference for what typical engraving parameters smaller machines use. It’s all trial and error.

If I can reel in the offsets on left and right during engraving I’ll consider this machine operating at it’s limits. I say that with some optimism, since only yesterday I didn’t realize how jacked the axis acceleration settings were.

Thanks everyone for your answers. Please keep them coming!

George

I’ve found that the machine is far more capable than my patience for adjustments!

What happens if you set the scanning offset adjustment to something ridiculous like 10mm at 100 mm/s? Then run it at 100mm/s. You should see a change. If not, the issue is somewhere else (the wrong setting area, not saving to the machine, etc).

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I wonder the same. I should have seen a change with the settings I tried. So I suspect more drastic will also not change anything. But, I can’t wait to try tomorrow.

I also wonder if there are machine settings working against the scanning offset. It’s so cryptic, you have to wonder.

My more pragmatic side goes right to testing in steps. Movement, calibration, belt tension and so on. The controller tells the machine to transit from coordinate A to coordinate B. If I can measure the delta between what the controller says to do and what the machine does I can start to work backwards and find the culprit.

Measuring anomalies during transit is obviously more challenging. I’ll happily rely on experience and anecdote here.

George

I have almost all the same issues discussed here. My laser is 1000x900 and 150 watts. I engrave anodized aluminum and cut some acrylic parts holders. I can now engrave clean “circle R” symbols but it took me months to achieve them. My major breakthrough came when I rebuilt the frame under my honeycomb bed using 2” square aluminum hollow stock. After installing the new frame, I could shim different areas of the bed. Getting really accurate distance from nozzle to bed everywhere made a huge difference in my output

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That’s encouraging! So focus was your major breakthrough, good to know.

How is your engraving on that large machine?

George

I replaced the head on my machine and had to make a mounting plate, (didn’t make it perfect!). After that I started to get the wobbly lines from resulting play in the head. I reduced the X and Y acceleration and that has helped a lot.
3000 isn’t crazy high, mine was set to 6000 and I wasn’t getting any wobble beforehand. I’m hoping that machining a new mounting plate will allow me to up that speed back up.
Do you have any play in the head if you try and move the nozzle in multiple directions?

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I do have some play. Enough to account for the resolution. But the offset is very consistent, so I get stuck thinking it can be addressed in software.

I did buy a new head, but I need hardware to mount in on the gantry. I’ll take a look at that.

Also, how tight should the belt be? Maybe I could lessen the slop tightening the belt a bit. Just don’t want to go too far.

George

this might shed some light on that.

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This one may also be of interest
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I’m going to stop linked videos in case I shouldn’t be! but he also speaks about some interesting points in Learning Lab 117 (you can skip to approx min 35)

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Fantastic videos, thank you! I’ll watch in full tonight when I can focus and digest.

George

I want to spend some time on the mechanical. Maybe fabricate the bracket to mount the new head. I see a lot of slap in the belt driving the Y axis also. Surely enough to affect cutting and engraving. I may look into mounting a constant tension pulley, like you find on motorcycle drive chains and belts. Slapping robs power and speeds wear.

George

I can’t say anything about your machines, but I have a 6090 and 1390 in 100W and 130W and they cut and engrave flawlessly.

There’s no issue with the mass of the gantry or head - the motors and drive are sized correctly.

Fine detail is no problem.

No issues with differing focus across the working area - I guess a lot of the 380kg is in steel framing.

Have you considered that there are aspects to your machine’s design that are sub-par?

Things to look at: how many power supplies have you got? Do you have a seperate 36v or 48v psu just for your steppers? What steppers and drivers are you using? Are the drivers set correctly? Are the steppers adequate for the task?

Shimming or otherwise adjusting your bed is the very last step I would take and only if you can prove parallelism of the beam path is out, rather than there being warpage due to the machine not being square and flat to the floor. On a heavy machine that doesn’t have as good a frame as it could, being one or two mm out can be enough to induce enough twist to make your beam-to-bed look like it’s wrong, when it’s really torsional forces from being out of whack.

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