2 questions - "ghosting" and laser tube


2 fast questions. (laser - K40)

1: what can couse this kind of “ghosting” which You can see on photo? I did not change anything at all except adjustable bed. Then i must remove all the “skeleton” with mirrors and other stuff.
After installing a new bed i align mirrors, create tamplate to engraving and cutting (50.8 mm ruler…), and now i have this. Did not change anything, just tried lowering and rising Air Assist - nothing changes… now i have always this strange shadow. One thing - this shadow is on the opposite side then AirAssist. But why this wasn’t visible before???

2: how can i check my lasertube lifetime? I have 3mm thick plywood and after 7-8 runs with this settings (20mm speed, 50% power on machine, 100% power in lightburn, 49.3mm distance to lens) and i cannot cut it. Before after 2-3 runs, plywood was cut.
Never used laser on more than 15-16 mA (55% on K40). Can it be end of this laser tube? What brand You will propose? What do You think about aliexpress tubes? Same kind of sh@#? :wink:

You say that you have not changed anything on the machine except the whole transport system …
I would think that your laser head is not at a 90 degree angle and the mirror adjustment is not quite right. The extra frame you get probably comes from the reflection of your laser beam of the inner wall from the nozzle. It will also be the explanation why you can not cut 3mm plywood properly. But, beyond that, look at the tube itself while it is in operation and see what color is inside the tube. Is it white or only very little pink then you need to find yourself a new one. But first try to get your mirror adjustment in place especially no.3 and the nozzle angle itself.
As a side note, I cut 3mm BB-plywood at 750mm / min and 8mA with my 2 year old 40Watt (30-35) no name tube.

uh… You mean 750 mm in one pass??? 8mA??? :sweat: :sweat: :sweat:
I must set to 10/15mm, 2-3 passes at 100% in LB and 50% on K40… I bought K40 2 months ago, for today i did not have any comparison to my K40, but Your settings are unreachable for me. BB - You mean birch plywood, right? Have the same.
I have one photo, it was taken 3-4 weeks ago.

Can i look at laser directly from above, when laser is working, or should i just take photo behind the cover?

You do not have to be scared at all, it is not the actual laser beam you see in the glass tube it is “only” ionized gas which then generates the (invisible) laser beam itself …
Be careful not to mix the units of measure together, I’m talking about mm / min, you should also always specify the unit of measure.
Have you been able to control the angle of your laser head ?, You can sometimes also feel this error if the nozzle itself gets hot during operation - it must not be.
I use good quality interior Baltic plywood, 3 and 4 layers. Plywood is available in many many different qualities, especially Plywood with waterproof glue, usually dark, is not so good for our small K40 :wink:
But if your tube is not bad and after fine tuning and with the right speed, you should easily cut 3 and 4mm plywood.

By the way, I will not be able to judge the color of your laser from this image. But you will be able to see quite clearly live, whether the beam is purple / pinkish or colorless white - very slightly reddish …
Your laser tube stand mounting looks significantly better than mine which is just a thin piece of tin with tape and 2 screws.
Have you fitted an ammeter or do you just stick to the 55% max in LigtBurn?

First of all - thank You very much for help. :slight_smile:

Ok. My fold, didn’t saw mm/min. I’m using mm/sec as default lightburn setting.
“Angle of your laser head” - You mean laser tube? Didn’t touch it at all.
I’ve cleaned all the mirrors and try to set them right, but didn’t touch the lens.

First off all was air assist + amperemeter. I think it’s a must have for K40. 55% is ~16 mA, i’m trying not to exceed this value. I think, Lightburn, when i’m setting 100% (in software) is my 55% at k40. So 100 % LB + 55% K40 is 16mA real. I don’t want to change machine setting. I hope it is clear (sorry for my english). Never use more than 60% (for short testing) on K40 (near 20mA).

First of all is ghosting, as You said - it can be some reflections inside a nozzle. How to fix it - do not have any idea. Aligment is complicated, and i knew, it will be much more complicated if i’m also redisign bed which is very poor quality in k40 out of the box.

But this 8-9 pass is weird. I have nice, clean cut after 1-2 pass. But just for 1-1,5mm, then - it is over.
I think it’s waterproof plywod, as You said - much darker inside plywood, but - still very strange. Just cannot cut more.

Here is my new bed. Nice quality, found on Amazon.

I’ve found company nearby with some lasers. Try to contact with them tommorow and ask for help. Too much variables for me, but… it is what i ask for.
Thanks for help! I Do not want to take Your time. Have some clues, now it’s time to experiment :slight_smile:

No problem at all, that’s why we have this nice forum.

No. it is the nozzle itself that is most often not at the right 90 degree angle. The laser tube is the last thing you should adjust if you can avoid it, (on the other hand, it is not a bone fracture to do so, it just requires caution and patience.)

No, it is actually easier with your new bed to ascertain / find the error (if there is an error)
Find a piece of easy to engrave material, adjust your bed all the way down, and make a test shot (as little as possible), now put your bed all the way up under the nozzle and shoot again. The points will of course vary in size due to focus mismatch - but you should clearly see if the die overlap is central or not. (It requires that your bed is stably bolted to the machine itself.)
If you have found that there is a misalignment, you must loosen the plate itself which holds the nozzle and get some very thin metal, under in the opposite side of the deviation. Then you start testing again and find out if it fits or not and adjust a bit again.

Will you be so kind and give me the link, I would like to see closer on it. Are you happy with the bed?

I think it’s innaccesible outside amazon.de. i had to use special delivery company, which have address in Germany, then they re-send it abroad. Very good quality aluminum, adjustable, very good design and well packed for transport. Maybe honeycomb is a little too thin? You can easly deform it, if You use too much force when You, for example, push it. Definetly recommend.

Edit: hope link is visible.