Laser power lost randomly for a short time?

Hey guys.

I’m not sure if laser power is lost but it seems like. I have a 130W (100W) Reci on a 90x60 machine. Here are two examples of what I’m talking about (the back of a 6mm plywood panel):

This is cut with 20mm/sec and 85/85 power, so should definitely be enough for 6mm plywood, but you can see some areas where it just didn’t cut. The material is a bit thicker than 6mm and seems to have more glue holes than the material I used before. Mostly it doesn’t cut because of the glue holes but sometimes also without. Here’s an example of a 5mm panel front from better material:

This shows that it just didn’t cut what I haven’t taken out. You would just break it anyway.

For the 6mm items, I bought other material, but this was even around 7mm thick and it turned out that it was “water resistent glue”. See what happens:

The engraved areas burned black and the cuts didn’t even reach the surface. Just gave up on this one, believe it is the water resistent glue.

But the other material shouldn’t be any issue. So I wonder why this is and here my recap of the setup:

  1. My laser path seems to be excellent, as with the head on all four cornes the pulse matches in the middle and over each other. The vertical path the same, laser dots match high and low and are exactly in the middle of the lense.

  2. My bed seems to be leveled, as I masured the height of all corners and the difference was 0.5 mm on one edge.

  3. I’m using a CW-3000 chiller, it shows 17 to 21 celsius normally. I have purchased a CW-5202 which will replace the smaller one as I have read somewhere that the laser can lose power due to a small chiller. Not sure about this, but replace it anyway.
    I use anti-freeze.

  4. My Laser tube is quite dirty with residue on it. Guess this is not the reason, as the laser shouldn’t care about the dirt.

  5. Mirrors and lenses are clear, 2" plano-convex lens, convex up. I bought another 2" and 2.5" to check if the lens is the reason. Tried the new 2" but it was worse (original below the new one):

    I found out that the new one is a miniscus not a plano-convex, so maybe a direct comparison is not right. Have to check again.

What else could be the reason for the bad cuts ? Can’t think of anything.I’m more than frustrated now, as this is going since the purchase early last year, sometimes better sometimes worse. I just can’t find a pattern to help me solve the problem.

So any thoughts on this would be really appreciated.

TIA. Peter

I usually cut at max speed with minimum power or on the verge. I’ve seen the same thing on my smaller 50 watt machine. Air assist will make a better cut.

I’ve made it a habit to do a number of test cuts on unknown or different batch of plywood. The kind of glue and the ‘voids’ also impact the cut.

If I understand you, you’ve been doing this and now it’s not performing as usual.

You did not specify if you have any kind of wattmeter or mA meter to help us make any good suggestions.

The tube looks dirty, hoping the rest of your machine is a bit more tidy… Hope the output end is clean. Generally, the output hose should be pointed up, so air will evacuate the tube with the coolant flow

Looks like it’s out of focus. You should ramp test the new lens…

Might want to read this… there is a section specifically about the use of antifreeze.

I use 50% mix of distilled water and propylene glycol (food grade). Good to 19 F.

My laser runs higher current for a specific power percentage when it’s cooler out. I normally run it about 25 C, many run it around 20 C.

Good luck


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Yes, as I said I need to check this one again. It was on the (tested) focus as the other (plano convex) lens.

Anti-Freeze: I use this:

According to the article, it’s not the recommended thing. What does it mean, it can short down the tube ? Power or Lifetime ?

And I have read about theaquarium heaters. Nice, but you then also need a pump to circulate the water. I’m not sure I want to drill a hole into the chiller. But now, as I have two, I can experiment with the CW-3000 and use this one in winter if it works. :wink:

What you want it good insulation anywhere there is high voltage. If the coolant in your system has a high conductance, the hv can get into the coolant. Anything that is touching the coolant could be at a hv potential.

I can’t comment, as I’m clueless as to your location which is the basis of how you pick a chiller/coolant. What kind of ‘cold’ do you get where you are…

There are commercial coolants that are very good, but relatively expensive.

The 5200 series, I’ve been told, adds about 60 watts of heat to your system if you let it run. If you use a heater then you have to let it run. Running warm water through a cold tube could be disasterous.

There has been talk of an aquarium heater that slips into the ‘hole’ in the top of the 5200. I saw it around one of these laser sites.

Good luck


I’m not sure what this means for the coolant and the laser tube. I have also seen this aquarium heater thing, along with the water pump that’s needed. And I was uncertain if this is the best solution. Because I’m totally with you, saying that having 25 degrees warm water running through a very cold glass tube might not be the best idea.
I’m located in the middle of Germany, where it can freeze 6 months a year, usually between Nov and Apr. So I have to do something. On the other hand, summer can be > 30 degrees and even more in my garage then.

But apart from the cooling problem, I still have the power loss and I have no clue why that is or what I can do against. With the older lens, I’m on the best focus due to my ramp test.


All the 60 watts of heat means is that it’s like having a 60 watt aquarium heater. You didn’t mention how cold it gets there. We can get into the 20 F range, but below that is rare.

This has/is an issue with liquid coolants. If it gets 30 C there in the summer, that is way too warm for your tube to operate and will shorten it’s life. The 3000 series are a radiator with a blowing fan, so it will ‘heat’ the tube at least to ambient temperatures.

The two lenses should perform pretty much the same. If I’m looking at the photo there is a big difference between the beam size so something is amiss in the setup.

At this point the only thing I can think of, if you’re sure it’s focused is to ensure it’s operating in the proper TEM0 mode.

How does the beam look coming out of the tube or at mirror 1 (m1).?

Good luck


Plywood has its own live and plywood with exterior glue is something the devil has invented to tease laser people with :wink:
But I would have thought that an 80 or 100 Watt laser could handle the task. For the most part, my 60Watt laser cannot. When I run into a piece of “unknown” plywood and there are areas that splash and crackle when cutting, I discard the whole piece, I do not bother to spend time sawing out with a knife and finishing holes and black spots. I like to buy airplane plywood with interior glue (it’s the light glue), here I have no problems at all with 6mm material.
Regarding your coolant, the absolute best thing for the laser is to run with clean demineralized or distilled water without addition. In a closed circuit, no pollution usually occurs. When you need to protect your tube from freezing it is another thing. Try searching here in the forum, I remember that theme has been discussed before. It is very important to find an antifreeze that has the correct electrical properties. I do not know exactly how it works but with the wrong coolant and or mixing ratio you can reduce the power of the laser significantly, I have tried it myself.

In winter it gets usually -5 to -10 degrees.

It’s a bigger dot like shown in TEM0 cell

So this is maybe one valid reason for lowering the power and the plan is to install the 5202 during summer with only distilled water, so I should then see a difference.
However, I’m still wondering why it is losing the power just for some short time and then everything goes well again.

I often have bigger items, that is maybe 6 on an 80x50 cm board. Usually all items have at least one or two burning marks or holes between the layers. As wood became 3 times expensive from last year, I can’t affort to throw all into the bin. The really bad ones, of course. But it is anyway far from what I want,

Where do you buy this from ?

No I don’t have this.

That’s right, wood prices have risen a lot, also here in DK. I buy plywood here in DK from a small but fine supplier, I do not know if he “exports” abroad.
It’s called “aeroply” and not airplane plywood, as I have written before :wink:

Nor in the power supply itself?
It is, in my opinion, a necessary tool. Without it, you do not have a real chance to see what is going on.
Does not cost much and is very easy to assemble.

When writing 85% power, how do you know you are not running over the limit of the tube?
55% is approx. 16mA with my machine (60Watt) I do not go higher because here is approx. the max power of my tube, i.e., 20mA gives me no more power but reduces the tube life somewhat faster.

I’m not an electrician… so no clue how to calculate this and what it really means.
Normally I run at a max. of 80% which is recommended as a max by the chinese vendor. 85% was a desperate try :frowning:
And also no clue how to install a mA meter…