Laser Cutting - Problems 9MM Ply

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#1

I have recently being doing some laser cutting using 9mm ply from the space’s materials shop. However, I’ve been having problems, specifically with cutting.

The SMLS 9mm presets in Ruby aren’t coming close to cutting the material - I’ll grab the full settings when I try again tomorrow. The settings are configured for a single pass for cutting, I’ve found I have needed five or six to get through. This has also led to some flare-up when cutting on subsequent passes.

I appreciate it’s difficult to give guidance without a better idea of the settings, just wondering if there’s any obvious I’m missing?

FYI @lasertechs

#2

Is the laser properly focused? I’d assume so, but worth asking just in case that was overlooked.

Do you have problems with other materials and settings e.g. 4mm ply?

#3

It might be that the 9mm settings haven’t been tuned very well

Feel free to have a play with the settings (being careful with things like flame/smoke etc.) and see if you can help find better settings for it

#4

I have noticed that the laser is out of square in the z axis (laser to bed) both back to front and left to right.

So if you cut a piece of say 10 mm acrylic the cut edges are not square to the faces.

Not sure if this is down to the laser mounting being out of square or the lens not perfectly central in the holder.

Best way to demonstrate this error is to have the bed fully down. Mark on a piece of paper where the indicator dot hits then raise the bed. And re- mark
This is the error.

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#5

I spent a while tuning settings this morning. Having done some Google-based research I started with the following settings:

  • Power: 100%
  • Speed: 0.2

This did a great job, but it was still a mm or less too shallow and was causing break-outs when trying to remove cut sections. I then adjusted to the following settings:

  • Power: 100%
  • Speed: 0.1
  • Z-offset: -2 mm

This worked great, like a knife through butter! I was a little anxious playing with the z-offset parameter for the first time, given it changes the focus of the laser. Do we have any concerns with z-offsets?

P.S. This post reads as if I tried two settings and magically the second was the one that worked. Rest assured there was a lot of trial and error in between!

#6

I’ll take a look when I am in the space

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#7

The z-offset only applies to your settings only, none others, so if you’re experimenting then it’s fine. Before it begins cutting, you’ll notice the bed adjust for the z-offset, then once done it goes back to it’s previous state. Just make sure not to set the z-offset to a number that will make the bed/materials collide with the laser head and you’ll all good to experiment.

#8

Might be worth summoning @SquigLeah who makes the awesome frog jewellery?

She’s does some really interesting stuff with multiple passes at lower power to do gradual cuts. Two passes with lower power seem to produce better results than one pass at high power?

#9

Just to add to this topic - I’ve also been having issues with cutting through 9mm ply cleanly with any of the predefined settings. @jwa I tried your today and they came the closest, but still didn’t quite cut through and, after tweaking them to cut through, the walls were definitely out of of square.

Furthermore, I noticed that what @lewisss mentioned above still holds. Not sure if it’s been fixed in the interim and got messed up again, but here’s a video of me marking the position of the laser dot with a sharpie and moving the bed down that shows the dot moving diagonally, not just defocussing/getting bigger:
https://drive.google.com/file/d/1ViG_ldZCXUjITr89euWQTY0hX9yaxYpD/view?usp=drivesdk

Then I also noticed that there’s a wobble in the honeycomb, so here’s a video showing that:
https://drive.google.com/file/d/1VilhYm0T28VsNHXRs_MyJp1OrpoPZLkr/view?usp=drivesdk
It’s definitely seated in the rails properly, you can see I can’t move it side to side, but pressing on on of the corners makes it wobble very noticeably.

I then took the honeycomb out and noticed a couple of the screws holding the rails in place are sticking out:

IMG_20241026_172052
IMG_20241026_172052.jpg2896×2172 4.38 MB

IMG20241026170931
IMG20241026170931.jpg3072×4096 5.94 MB

IMG20241026170936
IMG20241026170936.jpg3072×4096 7.02 MB

@lasertechs any thoughts on this? I don’t want to touch anything without permission, obviously, for all I know those screws have been deliberately made to stick out to level the bed at some point or something like that, but at first glance it seems like that could be causing, or at least contributing to, the issue of the bed being oit of square with the z-axis?

(also if there’s a better way for sharing videos on discourse, do let me know)

1 Like
#10

I will let lasertechs answer, but those screws can get loose over time, and they should be flush not protruding like this… I have had to tighten them many times.

We may want to put a tiny bit of blue (removable) loctite on the threads… @lasertechs?

#11

Can confirm - the screws should be tight/flush. I’ll look at the bed again tomorrow - it seemed ok yesterday during inductions.

#12

I’m still at the space and I’m happy to tighten the screws down myself now then, if that’s permitted. I can then do another check for parallel afterwards

#13

Go ahead :slight_smile:

1 Like
#14

I tightened all the screws and it removed all the wobble in the honeycomb, but unfortunately it looks like the table is still out of square with the laser beam:
https://drive.google.com/file/d/1VnSH2Tt-6Fb9vDB4B53qzBRsoUjO6JUm/view?usp=drivesdk

Not sure whether that’s a mechanical or optical issue and not sure how much that affects cuts at the ~< 10mm material thickness we deal with, but I guess it’s good to be aware?

#15

The drive links to the videos are not public, so I can’t comment.
Please can you make them public?

Thanks
Brendon

#16

Just changed permissions, let me know if there are still issues

#17

I am wondering if the laser is out because the lens is not perfectly centred in the holder. Are we still using the 3d printed ones?