CO2 Laser Tube issue.

[wctx1977]

Hi everyone!

Last night I was trying to cut some white makrolon (similar to plexiglass) and the first pass it did ok, then the second and after, it just started making a charred line and not cutting any deeper. I found out that this material was going to be a pain to try to cut is with the machine. So what I did, I stopped the job, reduced the speed to 5 mm/s and increased the power at 60% with PPI setting to 300 and then I loaded and started this new sarting and restarted the job. I noticed that the laser would look very bright at the line spot but it would not cut any deeper. Then I learned that the black charred line would not let the laser to penetrate anymore as it was crystalized already.
Well,, after that I decided to changed the material for clear plexiglass and noticed that this material would behave very differently and would not create any charring line along the cut. BUT!, I noticed that it was cutting very little for such a slow speed and power setting. I cleaned all the mirrors and lens to make sure that wasn't the problem. After that it was cutting the same, no improvement. I tried to put a piece of paper in front of the laser tube at a several settings and it seems very week. So for that matter I think my tube is dying prematurely and I don't like the feeling of that.

I hope some one come up with another idea of determining that my tube is definitely going dormant or to see what I can do to improve the output power.

Please guys let me know what you think about this and what you guys suggest. Thank you!

[Tech_Marco]

If current is right and power looks weak, then the tube is pretty much 'gone' There is no other way you can tell other than burning something direct from the laser tube without it passing through mirrors or lens. For the K40, 18mA is max. In fact, the K40 tube is NOT 40W but 31~34W at most. So, 16mA is good.

Where did you get the laser tube from? How long has it been used? Got picture? Is it an orange label "TL" on the laser tube? If you paid $22 or less from eBay, the chance is that the tube is low quality made. The beam sport is not 'round' but deformed like "8". Divergence is very high and light beam lose power quick when traveling for a distance.


Marco

[wctx1977]

Hi Marco,
Thanks for your quick response!

I was afraid to hear that but I was expecting it. This tube is the one that came with the machine from china and I already knew it was low quality but I didn't expect for it to go so quick as I think I have used it for 60 hours total at the most. The tube does not have any labels or tags that give any kind of related information.

Perhaps the water flow is not adequate may be I need to get a better pump along with the tube when I can afford it.

Question Is there any temperature meter for this machines to monitor the water temperature? And maybe one that cuts of the power when it reaches the threshold to protect the tube for overheating?

[Tech_Marco]

You want to keep wataer cool. A CO2 laser tube works well at this range: 20'~32'C but prefer at 25'C (room temperature). For a laser tube over 60W, you better to use a water chiller. I do carry a couple thermometer or termperture controller (with alarm). You may think about it about.

Water temperature will not cause so much impact on power but the current. Remember that the K40 is having a 35W laser tube (not 40W). I did mentione it many times. So, 18mA is the max and you sure don't want to go over it. As matter of fact, the 16mA should be set to the limited to aovid over current.

It's very difficult to get a high quality 40W laser tube (35W, 700mm) because low profit margin. Manufacturers are not willing to spend much time on quality control or using better lens/mirror for it. The goal is to 'dump' as many as possible. Due the nature of the K40, the size is limited to 700mm (or 770mm is most), you can't really do nothing on it. However, if you're a handy man and willing to take time to work on the K40. The best solution is to cut a hole on the case to make it possible to accomodiate a standard 850mm or 1000mm CO2 laesr tube. You will see the gain of power! I think this would be my next project. Upgrade the K40 power from 35W to true 40W or 45W!

Marco

[wctx1977]

Thanks Marco for the info and I think I prefer to do it the way you say as cutting a hole in the case is not a big deal. One question, can I still use the same power supply with the true 40w or 45w tube? What is the largest size in length this power supply can handle or in other words, what would be the best match, a tube that I should not to worry about overpowering with this power supply?

Also that is good that there is a temperature controller available from you and definitely I will be adding one of those.

Thank you again Marco for your support.

[Tech_Marco]

If you're talking about my power supply, then here is info I can tell:

Model: Max Current: Target tube: Max power output:
40W 22~24mA 40~50W 60W
60W 24~26mA 60W 75W
80W 26~28mA 80W 95W (Ideal for Reci 100W)
100W 30~32mA 100W 120W
120~180W 32~35mA 130~150W 200W

To make laser tube last longer, it's better to drive it below 85% with 25'C water temperature.

A lot of folks may question what's the difference of my power supply and other power supply on eBay. eBay power supply seems cheaper. I can tell you that the parts it used in my PS are difference. Ours can handle peak power for hrs without an issue. For 100W or higher PS, you hardly found 'leaking' power. I know my supplier well as I made input how to improve it. For example, I just made an suggestion to replace choke and thermistor to make it runs better on AC110V. Running at 110V is not easy for CO2 laser as higher current is required. Beside this, quality capacitor, high voltage power supply, number pair of transistor, and burn in test are all counted.

Temperature controller:
Dual display
http://www.lightobject.com/JLD612-Dual- ... r-P43.aspx

or
Single display
http://www.lightobject.com/JLD7100-PID- ... r-P44.aspx

You can use the built-in relay for alarm. Once it detect water go over 32'C, it should trigger the internal relay for action like cut of the power or turn on flash bacon or buzzer. You name it


Marco

[wctx1977]

Hi Marco,

My LPS is the one that came with the machine from factory and it looks like this...

Is this the kind you sell, is it a good one? ... If i get the 60w tube, will this ps work ok with it?

[Tech_Marco]

Sorry I can't tell. Even though it looks similar, the internal circuitry, components, and quality play the role.
Plus, I don't think the K40 can accommodate a 60W laser tube which is too big for the K40 to use it.
60W tube should be in 55~60mm diameter while a 40W tube is 50mm. The length of a 60W is 1.2M (ft) but a 40W is 850mm (2.8ft).
It's not difficult to fix the length but the diameter of the 60W will give you a big trouble. So, forget about thinking to upgrade to 60W for the K40. Focus on a 40W tube!

Marco

[wctx1977]

Thanks Marco for pointing that out. I did not pay good attention about the diameter and now that I see the difference chances are I will have big trouble with it.
I will go with the 40watt tube. I just need to save some money to buy that and other things from you.
Thank you again!

[Meshal]

photo.JPG

Hi Marco,

My LPS is the one that came with the machine from factory and it looks like this...

Is this the kind you sell, is it a good one? ... If i get the 60w tube, will this ps work ok with it?

Just curious about that green element sticking at the right side, is it for grounding purpose ?

[Axeman]

photo.JPG

Hi Marco,

My LPS is the one that came with the machine from factory and it looks like this...

Is this the kind you sell, is it a good one? ... If i get the 60w tube, will this ps work ok with it?

Just curious about that green element sticking at the right side, is it for grounding purpose ?

That looks like a big fat Capacitor. For what...I'm curious.

[Tech_Marco]

That is a high impedance resistor. It exist on most K40 machine. The reason it is there because the original power (open case, non pwm) is no good. I believe it has bad triggering voltage that is too high and it may cause damage on the laser tube. That's why they put it there in series with the laser tube to limit the surge current. If you have a quality power supply like the gold case or ours (black now), you don't need to have the 'green monster' installed . But there is no harm to leave it there, though.


Marco

[todmaerin]

However, if you're a handy man and willing to take time to work on the K40. The best solution is to cut a hole on the case to make it possible to accomodiate a standard 850mm or 1000mm CO2 laesr tube. You will see the gain of power! I think this would be my next project. Upgrade the K40 power from 35W to true 40W or 45W!

Marco

You're supposed to stop tempting me, Marco. I promise I'm going to let this factory tube burn up first

-Tod

[Tech_Marco]

However, if you're a handy man and willing to take time to work on the K40. The best solution is to cut a hole on the case to make it possible to accomodiate a standard 850mm or 1000mm CO2 laesr tube. You will see the gain of power! I think this would be my next project. Upgrade the K40 power from 35W to true 40W or 45W!

Marco

You're supposed to stop tempting me, Marco. I promise I'm going to let this factory tube burn up first

-Tod

Tod:

Even "worst" to the tempting, I'm working on an extension cage to let K40 to use 850mm or 1000mm (45W tube)

I'll work on a template by using it you folks can make screws holes and the tube hole without guessing. By sticking it on the side, what you need is a drill bit to make four screws to mount the case (about 12" long, 5.5" wide). The most troublesome part is to open a 100mm (4") hole to let the tube to extend out from the case. I'm ordering some cheap cheap hole saw from China see it works out. If so, then making K40 (32W) to become a true 40W or 45W is not a 'Dream'! Don't underestimate the 8~10W power increase, it make things a lot of difference! You can cut through 6mm acrylic with speed 2mm/s or 20mm MDF! The default 32W tube barely can do 4mm acrylic or 15mm MDF. And, you can use 63.5mm or 68.5mm focus lens to make the cutting edge better.

BTW, from a test on a 80W tube I recently did on 9mm acrylic. I found that if you want to eliminate the vertical line on the cutting edge, you don't want to run the laser too fast even though it still can cut it through. I tried 5mm and the surface was much better. I was using 75mm lens, 80W SP laser tube


Marco

[NickWL]

Hmm Marco, that's interesting. My K40 tube cuts acrylic surprisingly well - doing 6mm at 5 mm/s, but it won't go through 6mm MDF at all.
Any ideas why?
Nick