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Two dots?

TFMvdBroek

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So I got this 5.5W laser from aliexpress (OXlasers) rigged up to my 3D printer for some engraving/cutting.
Yesterday when trying to focus the laser I noticed a second dot next to the main dot.
What is the cause of this? and can it be fixed?

Thanks guys :)
 

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RA_pierce

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It could be internal reflection from one of the optics. Do you have any secondary optics attached after the collimating lens?
 

paul1598419

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What does this secondary spot do when you try to focus your laser? Does it move or does it focus just like your primary one? I need to get a little more information before I can hypothesize a cause.
 

TFMvdBroek

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The second spot focusses with the main spot but it also seems to move slightly (1-2 mm) when rotating into focus.
The rotation of the second spot is not nearly as fast as turning the ring.
 

smallfreak

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What is the cause of this? and can it be fixed?
This looks like some internal reflection. If it´s of considerable brightness, which cannot be judged from the image, I would complain and ask for replacement. You could try to mask it off, but it may well be that it does not infere at all with the intended use.

Any hint that the beam is not fully aligned? Since the spot follows the motion of the lens, it might be the lens being mounted wedged or the ray is reflected off the rim of the window. In this case the components are not well aligned.
 

smallfreak

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If you insist to take it apart instead of ask for exchange, you could unscrew the lens (remember which part is facing forward), blacken the lens edges with a black felt pen and do the same with the interior of the lens chamber and window ring.

When you reseat the lens, make sure it is centered and lies flat on the seat before you fix the mounting ring. This should remove most stray reflections.
 

smallfreak

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(y)
Take that offer. You certainly will get the entire focusing part, with the lens mounted in, not the lens itself. So it is a simple screw off and on replacement. Getting the LENS out of the case is tricky, as you need the right tools to unscrew the mounting ring without making the problem worse. And there might be one or two (or more) spacer rings inside that tend to get damaged, swapped or lost during the process, especially when it‘s not a single lens but a 3-element ensemble - where you wish you have a Vacuum pickup.

So when you can get a replacement lens, you might take your chance and try to disassemble the current one. You might learn something and you have a spare to play with.
 

paul1598419

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Since you are using this as a cutting or engraving laser, I wonder if you haven't deposited some smoke fragments on the diode's widow. That could explain the issues you are having with it. Anytime you use this laser where smoke can get to it, you need to use a fan to blow it out of the way. I'm not so sure the lens will help you. Good luck.
 

TFMvdBroek

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Since you are using this as a cutting or engraving laser, I wonder if you haven't deposited some smoke fragments on the diode's widow. That could explain the issues you are having with it. Anytime you use this laser where smoke can get to it, you need to use a fan to blow it out of the way. I'm not so sure the lens will help you. Good luck.
Should I clean it with some air ?
 

paul1598419

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If some smoke has deposited to the diode's window there is likely no way to remove it unless you decan the diode. Anything deposited to a burning diode's window gets burned on there and people have tried all sorts of chemicals trying to remove it with little or no success.
 

steve001

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So I got this 5.5W laser from aliexpress (OXlasers) rigged up to my 3D printer for some engraving/cutting.
Yesterday when trying to focus the laser I noticed a second dot next to the main dot.
What is the cause of this? and can it be fixed?

Thanks guys :)
It could be a speck of dust. Have you visually inspected the diode window and lens with a magnifying lens?
 




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