Power loss, new 50W laser

[roig12]

Hey Guys,

I got my machine for about a month and used it only about 5 times for a few single cuts of squares in 2mm acrylic.
I used to cut 2mm acrylic at 20% power 10mm/s
Today I cut again and the power was a bit lower since I needed to break the squares at the cut areas and then it got worse by only engraving.
I tried realigning the mirrors (can it affect power if power seems even at the whole cutting surface?), water was a bit warm (maybe 30c, just slightly warm when I stick my hand in) so I changed to new chilled water and nothing.

A few things to note...
I looked at the laser tube while it's working for the first time and the side where the laser starts from doesn't start from the middle, more like an angle from the positive wire direction but it's not arching at the exit side, it goes straight out.

Can it be that I changed from distilled to tap water before I started cutting today? my distilled water was dirty and didn't have any more of it so I used tap water and the first cuts were good until it start loosing power after about 5 minutes of cutting.

I didn't understand how to set up the laser "nozzle", it can go up and down but I didn't see how it affects the power and didn't find any explanation on the internet.

Can I damage the tube by going to about 35c water temp for about 10 minutes of use?

I don't know if it has something to do with the power loss but it does seem to happen around the time I got the hinge that holds the machine's lid open loose and it fell on the rail and the X axis got stuck in it and the servos started going grrrr for a few seconds until I got it all fixed.

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[roig12]

bump...

[robertk925]

Ok, lots of things to check. To answer your specific questions:

a. Not sure if I am visualizing what you are describing, but assuming you didn't make any adjustments to the tube then it shouldn't make any difference.
b. I don't think tap water would immediately affect things unless you have a lot of minerals in the water, and even then it would take a lot of time unless it is somehow causing the laser to "arc".
c. The height of the nozzle doesn't make any difference, assuming the beam is not hitting the nozzle. It does affect the air assist however.
d. A water temperature of 35C seems really high. Not sure if would permanently damage the tube, but it will definitely affect the power output. I usually keep my water temp at 19-20C.
e. Did you perhaps bend the rail? If so, it may be subtly changing the distance from the laser head to the table.

Power loss comes down to 7 primary things, in order of ease of checking/correcting:
1. Incorrect lens focus (i.e. wrong distance from lens to material, table not parallel to X/Y axes, and/or warped material)
2. Water temp
3. Dirty lens
4. Dirty mirrors
5. Mirror alignment
6. Tube failure
7. Power supply failure

I would start with #1 and work your way down the list. On item 5, if your mirror alignment is off then the beam may be hitting the nozzle, which will definitely affect the power.

[roig12]

Ok, lots of things to check. To answer your specific questions:

a. Not sure if I am visualizing what you are describing, but assuming you didn't make any adjustments to the tube then it shouldn't make any difference.
b. I don't think tap water would immediately affect things unless you have a lot of minerals in the water, and even then it would take a lot of time unless it is somehow causing the laser to "arc".
c. The height of the nozzle doesn't make any difference, assuming the beam is not hitting the nozzle. It does affect the air assist however.
d. A water temperature of 35C seems really high. Not sure if would permanently damage the tube, but it will definitely affect the power output. I usually keep my water temp at 19-20C.
e. Did you perhaps bend the rail? If so, it may be subtly changing the distance from the laser head to the table.

Power loss comes down to 7 primary things, in order of ease of checking/correcting:
1. Incorrect lens focus (i.e. wrong distance from lens to material, table not parallel to X/Y axes, and/or warped material)
2. Water temp
3. Dirty lens
4. Dirty mirrors
5. Mirror alignment
6. Tube failure
7. Power supply failure

I would start with #1 and work your way down the list. On item 5, if your mirror alignment is off then the beam may be hitting the nozzle, which will definitely affect the power.

It seems like the beam is being blocked/hitting the nozzle from the inside since it gives me the same power output when at 20% and 90%.
I looked at the tube and the purple laser seem much brighter when on 90% compared to 20% so it means that the tube outputs more but doesn't increase more when it hits the material.
So I did the alignment with the mirrors and got the x and y axis to hit at the same spot of the tape when it's closest and most further on the axis.
Then I got to the laser head and I notice that if it's not aligned it gives 0 output, so I play with it a little and it hits the material BUT I have no Idea if part of the beam hits the nozzle...the dot comes out pretty much in the middle of the hole that faces the material (stuck a piece of tape there real hard to emboss the opening to see how aligned is it in the little hole).

[fixtureman1]

Do you have an up and down table. My beam was coming out at an angle when I had it centered going into the final mirror. I had to adjust the beam to hit the upper part of the final mirror to get the beam to go straight down I checked this by removing the lens and raising the bed all the way up and did a test fire and then lowered the bed all the way down and did another test fire to see if the beam hit the same spot. Before I adjusted the final head down it did not hit the same spot.

[robertk925]

One other thing to check in the future so that you don't damage your laser tube. Laser tubes have a maximum amperage that they should be run at. However, these Chinese machines are not calibrated so that 100% power = the maximum amperage. On my 50W blue-and-white eBay laser, a power setting of 65% gives me the maximum amperage (20mA) recommended for my tube. The only way to check this is to install an ammeter. Running your laser tube an higher amperages will most likely damage it. Also, increasing the amperage too much above the tube max doesn't actually generate more power, it can actually generate less power. So running at 90% may not give you the results you expect.

[roig12]

Do you have an up and down table. My beam was coming out at an angle when I had it centered going into the final mirror. I had to adjust the beam to hit the upper part of the final mirror to get the beam to go straight down I checked this by removing the lens and raising the bed all the way up and did a test fire and then lowered the bed all the way down and did another test fire to see if the beam hit the same spot. Before I adjusted the final head down it did not hit the same spot.

Thanks alot, will sure try it and update.

One other thing to check in the future so that you don't damage your laser tube. Laser tubes have a maximum amperage that they should be run at. However, these Chinese machines are not calibrated so that 100% power = the maximum amperage. On my 50W blue-and-white eBay laser, a power setting of 65% gives me the maximum amperage (20mA) recommended for my tube. The only way to check this is to install an ammeter. Running your laser tube an higher amperages will most likely damage it. Also, increasing the amperage too much above the tube max doesn't actually generate more power, it can actually generate less power. So running at 90% may not give you the results you expect.

I never ran it above 20% other than the last test I did when it was on 90% just for a few seconds.

[automationtechinc]

Pls call us, our Engineer will help you
https://www.automationtechnologiesin...ser-engraving/

[grawley]

The color of the tube can change internally with an increase in power from the power supply. If there is an internal alignment problem (within the tube), the output power may not significantly increase. To do a quick check, carefully (without letting smoke deposit on the tube), do a mode burn, prior to any mirrors. A mode burn is an unfocused laser beam burn into a material, such as acrylic (be sure to blow on it, using your own wind or from an air compressor.). Time the mode burns at each power level to determine if you are getting more power and a faster burn into the acrylic between the two power levels. Also, 20% may be too low, and you can try 30%, as often times these tubes loose the low power first then higher later (sounds backwards, huh?). Also, keep in mind that the percentage that you type into the controller is mathematically linear, but the laser output power is a curve (so it does not match, but does a good job of giving a general indication of more and less power).

[engraving_hub]

I always run mine at 75% and above. I increase speed not decrease power.


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[roig12]

I always run mine at 75% and above. I increase speed not decrease power.


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I think it's better for the tube to run longer on low power than for shorter periods on high power but I may be wrong.