Another K40 newbie that needs helps (beam focus issues)
So I recently picked up a K40. It's one of the M2 Corel based ones with the LED light strip and LCD AMP meter, and the LCD tube temp readout. I have added air assist, an a manual adjustable honeycomb bed. For the most part I think I have the majority of it dialed in. moving the head across the gantry to the 4 corner and test firing, I am hitting pretty darn close together into the entry hole of the head.
But here is where i am having issues. When the head fires downwards, I can see two dots, and one is quite a distance away from the other (about 5-10mm between them) So somehow, my beam is losing focus from the entry point into the final mirror on the head, and down into the lens. I have used the 12mm lens that comes with it and an 18mm from LightObjects, but it seem to still be splitting the beam somehow no matter what lens is installed. I am not sure how to correct this.. or what is causing it. So with this ghost beam, my engraving is making shadows and i am sure the reason i cant cut is due to not enough focus of the beam.
I included am image below, where you can see a star, and then above it the ghosting effect caused by this beam issue.
Any advise on what to tweak next would be appreciated, or sugestions on how to trouble shoot this issue.
Re: Another K40 newbie that needs helps (beam focus issues)
I would check mirrors and lenses for damage or contamination clean with isopropol alcahol many youtube vids showing alignment routines but this ghosting should not be caused by misalignment, the reason you are probably having difficulty with your cuts most likely the lack of power, 40w means peak in these machines so 30-35w and run conservatively thats 25w, are you using laser compatable PLY and MDF or attempting to use standard cheap diy stock which needs far more power to achieve good cuts? The major mistake many make when buying lasers that are underpowered for the job is to begin burning away at materials leaving charred edges and poor finish laser cutting is ideally achieved by vapourising the material not merely burning and air assist used to prevent burning not to provide more oxygen to burn as many posts I see claim!
Re: Another K40 newbie that needs helps (beam focus issues)
At this point i am just using some generic thin wood, to test. not really concerned with cutting it, as my goal is to cut 1/8 acrylic and not wood. But wood was much cheaper for testing purposes to see how the beam is lining up etc. I looked at the mirrors and it looks like it may make sense to clean them up, and will see if that makes a difference. I did not physically see any dirt on the lens at this point, but i will double check.
How do you avoid getting your mirrors and lens from getting dirty, or is routine cleaning just part of the job, with a machine like this.
Re: Another K40 newbie that needs helps (beam focus issues)
I'd offer that a good exhaust keeps mirrors clean also.
I would look at the pattern out of the tube. It is suppose to be a 3mm solid circle
Just put some wood in the path of the beam during a test fire.
Also try to shine a bright light in the laser path, with the laser off, to see where the shadow comes from.
Re: Another K40 newbie that needs helps (beam focus issues)
Ok, i cleaned the Lens and the mirrors with a swab and alcohol, but the problem still exists with ghosting.
here is a shot of the beam on a small piece of chipboard. This was taken by placing the chipboard in front of the tube, before it ever gets to the first mirror. So this is the source of what is coming out of the tube. I measure it at about 2.8mm with my calipers, so that look decent.
Next I traced the path, and took test shots, on the Vertical (Y axis) This is taken right in front of the mirror inside along the upper left corner.
Then the Horizontal (X) axis, this one, i place the chipboard, right in front of the hole in the head, intercepting the beam before it had a chance to hit the last mirror. .. but these don't look as rounded... perhaps one of my mirrors prior to it getting into the head is the issue? Should these reflected shots of the beam also be perfect circles? The thing is, i am not seeing any double shots on these... so now i am wondering if the issue is something with the mirror in the head or the actual lens itself.
End result of testing... if i move the head pretty much anywhere, and hold down the fire button, i see two points getting shot out of the lens.
Below are a variety of shots from multiple placements of the head, I messed with the power levels a little, as well as the duration of time that i held down the fire button.. but end result is the same... double points are being shot out of the lens.
Since there are folks with a lot more experience with this then myself, you feedback is appreciated in this painstaking troubleshooting and fine tuning process.
On a side note, i have a 270 inline CFM vent fan handling the exhaust, so that seems to be doing a good job, also i have an air assist connected to the head gantry. I manipulated my height as well, adjusting my bed between 48mm-52mm but the results of the ghosting were pretty much the same.
Re: Another K40 newbie that needs helps (beam focus issues)
well it's night here now.. so no sunlight to try that out with, but I used an bright LED flashlight and shined it into the lens, both thru the head (bouncing it off the mirror that directs it to the lens. As well as i removed the mirror in the head and shined light directly down into the lens.
The result is below... I didn't expect to 3 individual points of light... Or is that the expected result, and based on the focal length of how far the light source is, those 3 beams converge into one single beam?
I tried this test with my LED flashlight on the 12mm lens that came with the K40, as well as the 18mm light-object one I purchased. But pretty much same results, I see 3 small dots, if i adjust the flashlight closer/further, the points of light do stretch out, or merge into an unfocused single shape. What am i dealing with here? I assume the desired result of light coming out of the Lens should be a single focused, and small beam...
suggestions for what to do next? anyone...
Gotta be honest, I didn't expect these kinds of problems with this machine.. I assumed mostly electrical/mechanical stuff, which I am fully capable of resolving... but the Optics side of it, is all new to me.. so not really sure how to troubleshoot this further, to get a functional machine.
Re: Another K40 newbie that needs helps (beam focus issues)
Make sure your lens is put in the right direction. The rounded side goes up.
Also check the alignment on a TON of parts of your bed. Whenever I see ghosting like this, it's due to the alignment being off. The laser will bounce off of the side of the nozzle and create two cut lines.
Re: Another K40 newbie that needs helps (beam focus issues)
Assuming the flashlight has 3 LEDs there doesn't appear to be distortion in the lens. Concave goes down and know how to align the machine.
Beam looks good out of the tube. Only thing left are mirrors. Could ghosting come from reflection of light from both sides of the mirror? Mirror mounting backwards or coating so thin it partially reflects light. Check that the reflective surface is in front on all mirrors. It isn't suppose to shin thru the glass like a normal mirror in your house. Also no holes or scratches in the mirrors.
Re: Another K40 newbie that needs helps (beam focus issues)
Hmm.. i will check the flashlight.. it very likely has 3 bulbs.. i didn't even think of that.
Are you saying the concave (rounded) side of the lens faces downwards? Everything else i have seen/read seems to say the flat side of the lens points downwards?
Re: Another K40 newbie that needs helps (beam focus issues)
So i have been continuing to make tweaks, and was able to make a cut of a 1/8in piece of acrylic (pic below)
That seemed to work, without any ghosting effect. But if i move my material to the upper left corner the ghosting comes back and is visible.
This cut took about 5 passes at 2mm a sec, so that seems like i am still not getting the focused power i need out if the beam...
So what am i dealing with here? Is this a focus lens issue, or mirror still? any more suggestions on further tweaking?
Last edited by method121212; 06-29-2016 at 06:13 PM.
Should be like this. Also keep in mind that if the last mirror has it coming in at an angle, the beam will go wonky through the lense and come out at an even more extreme angle. you want that beam to be coming down 100% vertically from the last mirror and through the exact center of the lens.
We've also noticed on cheap lasers that sometimes the nozzle after the lens is bent, unaligned, or even the hole at the bottom is too small. Use your alignment tape to make sure the beam is coming out of the last mirror correctly. If it is, and then it's not coming out of the lens right... I bet the nozzle is cocked and the beam is hitting the side of it before it exits.
*Edit* - According to your last post... it's definitely alignment. You have to align the mirrors on all 4 corners AND right in the middle of the machine. I know this is annoying and usually takes almost an hour to do... but it will be worth it. Keep tweaking tweaking and tweaking until it's perfectly aligned on all 5 of those places and I think you'll have an awesome little machine
Re: Another K40 newbie that needs helps (beam focus issues)
yea i believe mirror alignment is the issue now as well.
i used a level to test the entire gantry and head mount, and everything check out pretty close to perfectly square.
after further review, i am noticing my 1st mirror (the fixed one next to the tube) is not getting hit in the center.. it's off by a good bit.
I believe once i get that fine tuned, and then home in the other points, it will clean up most of my issues.
i agree it is a slow and annoying process, i just need to keep fine tuning to get it all dialed in.
Another K40 newbie that needs helps (beam focus issues)
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