Double spot on new laser

New K40 laser, original mirrors and lens (will be replaced soon) I cleaned out the swarf and dirt from inside the laser head, set up the mirror alignment as close as I can, now if I send a pulse onto white card I get a nice spot in the middle but also a fainter spot about 4 or 5 mm away. When engraving text this gives a speckle of light dots around the words.
Any ideas where I should start looking for the solution?

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One of the possible causes could be the lens which has some damage or is not placed correctly in its position. Another possibility of error is the reflection of the laser beam on the inside of the nozzle, either for the same reason as I mentioned before, or because the laser head is not set vertically 90 degrees.

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I forgot to say that it is not necessarily bad original mirrors and lens in a new K40, I used my machine for approx. 4-5 months before I replaced them and by this time they were not in useless condition yet.

The most likely explanation is that the machine is badly aligned such that the beam is clipping the hole below the lens causing the beam to split a little bit. Post a photo of the spot in question might help. If you are able (and I understand that a K40 doesn’t have adjustable height bed) send a picture of a pulse spot at normal work table height and one lower than normal below the focal point.

Hi,
I think you are correct, I went back and re checked the alignment, I thought I had it correct but after doing it all again from the start everything is now perfect. (it’s a learning curve!)
Now I am going to have to remove the X - Y assembly in order to modify the bed to allow (manual) Z axis adjustment so will need to do it all again! (starting to feel more confident about it now though)

On a related subject, when I unpacked the laser, I put the big cardboard box it arrived in on a table on the other side of the workshop, I was standing behind the machine trying to adjust mirror number 1, couldn’t see the beam marking the paper anywhere near mirror number 2, then smelled smoke and saw a hole being burned in the box about 4 feet from the floor. Luckily no damage done and no one was hurt, but it could have been nasty, I am surprised that the machine was sent out with the mirrors so badly out of alignment, I can imaging someone expecting to just unpack it and use it getting hurt

I’m pleased no one got hurt. But I am not surprised at all… I have had mains electrical shocks off unearthed K40s, K40s that scrapped down the side of the case when moving internally. You get what you pay for, when you know what these parts cost and how many people need to get a little profit off your $400 K40 there isn’t much money left for safety or finesse and it certainly doesn’t meet the standards of most countries in terms of conformity, even if someone wrote CE on it.

The first thing I did when I got the machine was check the earth connection, seemed ok, but on looking closer it had the usual problem of the paint not being removed from the bolt fixing it to the case. Currently rewiring all the mains electrics and replacing the cheapo “universal” sockets on the back with proper UK sockets.
Also upgraded to the Cohesion control board and after a litle messing around with the bed size it works perfectly with Lightburn.
I knew what to expect when I bought it and feel reasonably confident about sorting the issues but I know some people will spend £400 and not have a clue what to do

That is the main problem. Not everyone is as lucky with their K40, where all the electrical is properly made and even the focus makes sense right from the start, as was the case with my machine. But as long as you are aware that you can be challenged to work with your newly purchased machine and you have the necessary knowledge, it is in my opinion the best possible and affordable start to a laser journey that can open many new doors.
When I count all in all that I have spent on my old K40, I do not get at 500 euros (without my 5000er cooling machine), what is it just one of the well-known American laser machines in the same class costs? Based on my experience today, I would even have “saved” the money for my 5.5 watt Eleksmaker and gone straight to a K40, although this machine also has its daily value. A K40 is a fantastic starter machine and can handle even smaller productions if the workpieces are not larger than 230x320mm.

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