Odd change in laser penetration


#1

So, I’m trying to cut this file, one i have cut many times before, and it’s not working.

Imgur

In the photo you see the back of the piece.

The outline cut first, and fine.

The slots cut second and, obviously, not so fine. Each of the three panels should be basically identical.

The origin is in the bottom-right of the piece, beam from the bottom-left (piece is upside down) and the slots are narrow rectangles that are cut from left to right.

Pertinent details:
3mm poplar ply, usual supplier
40W Blacknose laser
Settings 10 speed, 90% power (usual settings for ply are 15 & 70%).
Optics are clean.
Optics are correctly aligned.
Focus is correct.
Laser is in a sunny conservatory, but the problem was still there at 0630 today, when it was cool and shady.

Any ideas, folks? I have paying work to do…


#2

Hello Mark

Ruling out the things you’ve mentioned like coolant temperature, dirty lens or mirrors and alignment, or material variances, the most likely answers are as follows.

  • your tube is dying
  • you’ve adjusted the height of either your lens or your bed and not noticed
  • material is affected by humidity or is not flat.

Also don’t put your laser above 70% power on your model.

Dominic


#3

We had a similar looking issue to that which was down to alignment, but not in the usual sense I would have expected. Our spot was in the centre of the mirrors when checking but in a different location when taking the position to the other side of the bed (if that makes sense?)

Is your spot on mirror 3 in the same location between the corners of the bed?

Ian.


#4

Ooo, or the bed isn’t level, that could also explain it.

Ian.


#5

The tube is nearly new (guess who installed it?), but I’ll turn down the power & the speed, see if that helps.

What’s the best way to store ply (600×400mm)?


#6

Ian,

The spot seems to be in the same place, and checking focus across the bed it seems flat.


#7

Tube was replaced August 2018. Basing it on what you said these are the likely causes. Have you checked for good flow and air bubbles?

What the ambient temperature of your conservatory? Even at 6:30am? What do you use for cooling? A box of water or a chiller?

Bear in mind I have customer who can burn through a tube in 3 months.


#8

Three months? Ouch! My previous one lasted 5 years!

The chiller said 22C this morning, 32C yesterday. I’ll check for bubbles after the tennis…


#9

SCHECK FOCUS DISTANCEACROSS THE BED IF THE BED IS NOT LEVEL IT WILL ME THE FOCUS TO OBJECT CHANGES REDUCING THE POWER TO HIT THE WOOD

sorry cap lock on


#10

Did you get a resolution to your issue @Kiteman?

Curious if you identified the cause or not.

Ian.


#11

Yes, I’m also curious to know.


#12

I dialed it back - reduced the power & slowed it down, and no problems since.


#13

Fab! Glad you got it resolved :slight_smile:

Ian.


#14

Hey @Kiteman, would you remind me what cooling system you have? I don’t recall if you have a chiller or a big box of water? It’s worth monitoring the temperature. Remember that the ambient chiller can only cool to the temperature of the environment and needs to be kept topped up.

Good luck and I’m pleased you are getting satisfactory cuts again.


#15

Damn is it bad weather for the ambient chiller at the moment…

23 at power on…

Ian,


#16

Beat you-> 25C

I’m half way through a lampshade prototype, and a marketing piece, but I’m reduced to retreating to the shade with a stubbie of beer…


#17

Damn fine idea that man!


#18

Update: the temperature has climbedto 32C.

Second stubbie…


#19

It says “CW3000 Industrial Chiller”.

I haven’t even thought about switching the actual laser on…


#20

At 32 degrees, it’s not worth turning the laser on. Quality of cuts seems to deteriorate rapidly above about 28 degrees I seem to recall?

I suspect @Smokey would know better :slight_smile:

Ian