laser tube safe working current ?

[Ron Gosnell]

Hi Folks,

I am a little confused by the specs on my new laser. I don't want to abuse it.

It has a SPT C130 laser tube in it. The question is ...in the table below it states max current is 23-30 ma. That's seems to be a wide range for max.
I set my controller to max out at 65%. That puts out exactly 27 ma on the amp meter. Is that good or is it too hot ?

Thanks in advance,

Gozzie

Specification & Parameters of 130wLaser Cutter Tubes


Laser cutter tube Model

SPT-C130



Laser cutter tube Length

1650mm



Laser cutter tube Pipe Diameter

80±1mm



Laser cutter tube Type of Cooling

Water-cooling 15-25°C



Laser cutter tube Impulse Frequency

100% to 5KHZ



Laser cutter tube Gross Weight

4.8Kg



Laser cutter tube Carton Packing

1780*170*160mm



Laser cutter tube Wavelength

10.6um



Laser cutter tube Mode of Excitation

Electric excitation



Beam polarization mode

Linear reasonably



Beam Divergence Angle

3.1mrad



Laser cutter tube Light Beam Quality

≤1.1



Laser cutter tube Stability

10%



Laser cutter tube Lasing Mode

Much lower order film



Output Power Stable Value

130W



Laser cutter tube Max Output Power

150W



Laser cutter tube Starter Voltage

26~28KV



Laser cutter tube Working Voltage

20~23KV



Laser cutter tube Starter Current

6~8mA



Laser cutter tube Max Working Current

23~30mA



Laser cutter tube Spot Diameter

5±1 mm

[Bert Kemp]

I by no means know for sure but I think your loosing a lot of power that way. If your controllers set at max out of 65% and you set power setting to 100% your still only getting 65% power to your work. I was told to set my controller to 100% but to keep the pwr setting below 90% Kinda like having a governor on a car to keep the car from getting to its max speed. What goods it if you have a car that can go 200mph but you have it set to never exceed 125. Take the gov off and only run the car to 190 to conserve the engine.

[Glen Monaghan]

This is a matter of philosophy. Your [system, be it laser, car, airplane, lead-acid battery, etc.] is capable of X but operating at that level will quickly wear, use up, overheat, or otherwise degrade the [system] so you want to keep it, for example, 90% of X or less, so you have two choices. Either you install a governor that independently sets the desired limit despite what you say, or you have no governor and rely on the operator knowing not to exceed the limit. The governor may simply cap your command, so saying anything above 90% is capped at 90; or it may scale everything, so your 0-100% input value gets scaled down to 0-90 for the laser.

The good thing about the governor is that it protects the system from a naive, inattentive, or spiteful user who might unwittingly or purposefully push it into the redline and cause premature failure. The bad thing about the governor is that it prevents the operator from intentionally pushing the system into the redline under compelling conditions. Some early fighter planes had physical stops installed on the control stick to prevent cocky young pilots from pulling too many g's because high g's weakened the airframe and could eventually result in structural failure, but it also prevented a pilot from intentionally over-g'ing the plane under life-threatening conditions such as a dog fight or imminent crash. You may have a high value cutting job where you need to eek that last bit of power and speed out of your laser in order to meet an extremely tight deadline, and the value of the job far exceeds the cost of subsequently replacing the tube, but the governor gets in your way...

So, if you want to protect the system from your own mistakes or from misuse by a less experienced/responsible user (such as a new hire at a business, or a junior member in a co-op), install the governor. If you can take responsibility for yourself and are ready to deal with the consequences if you screw up, skip the governor and make sure you always pay attention to what you are doing.

So, you ask what good is a car that can go 200mph but is set to never exceed 125, and then you say to remove the governor and limit yourself to 190 to conserve the engine... Well, if your buddy borrows the car or a thief takes it on a joy ride, they might ruin the engine by pushing the limits too high. The alternative there is to keep the governor but adjust its limit from 125 to 190 so no one accidentally or intentionally exceeds "safe" rpms.

[Ron Gosnell]

Thanks Bert. I guess I may have said that wrong. I think we see it the same way.
I took the 30ma max rating times 90% which is 27ma. I then kept raising the power levels to find that 27ma reading. At a 65% power level on the controller I got a 27ma exactly on the meter.

What bothers me is should I do 90% of 30ma or 90% of 23ma. I chose the first because the other would be way low on power... but will 27ma burn out the tube too fast.
It's rated for over 9000 hours but at what power level ? I think the manufactures should be more specific. 23-30 ma is a large spread.

Glen that is an excellent explanation for the reasons of governors.

Gozzie

[Bill George]

That 27 mA or whatever is continuous duty, correct? Like when cutting material It should not come into play when engraving. Or otherwise think of it as a 87 watt machine.

[Ron Gosnell]

Hi Bill,

Yes that is a continuous cut. Straight line without any corners to keep it stable for testing.

Gozzie

[Bert Kemp]

Nobody's is going to borrow my laser maybe the car was a bad example but it illustrated the point well I thought. I know that I personalty will not exceed 90% pwr on my machine fact is to date I have never gone above 65% power. But thats me I can afford the extra time to run a little slower at lower power . I understand that in a business environment you want to run as fast as possible, so setting the controller is probably a good idea. Especially if your not the only one running your equipment.:)



This is a matter of philosophy. Your [system, be it laser, car, airplane, lead-acid battery, etc.] is capable of X but operating at that level will quickly wear, use up, overheat, or otherwise degrade the [system] so you want to keep it, for example, 90% of X or less, so you have two choices. Either you install a governor that independently sets the desired limit despite what you say, or you have no governor and rely on the operator knowing not to exceed the limit. The governor may simply cap your command, so saying anything above 90% is capped at 90; or it may scale everything, so your 0-100% input value gets scaled down to 0-90 for the laser.

The good thing about the governor is that it protects the system from a naive, inattentive, or spiteful user who might unwittingly or purposefully push it into the redline and cause premature failure. The bad thing about the governor is that it prevents the operator from intentionally pushing the system into the redline under compelling conditions. Some early fighter planes had physical stops installed on the control stick to prevent cocky young pilots from pulling too many g's because high g's weakened the airframe and could eventually result in structural failure, but it also prevented a pilot from intentionally over-g'ing the plane under life-threatening conditions such as a dog fight or imminent crash. You may have a high value cutting job where you need to eek that last bit of power and speed out of your laser in order to meet an extremely tight deadline, and the value of the job far exceeds the cost of subsequently replacing the tube, but the governor gets in your way...

So, if you want to protect the system from your own mistakes or from misuse by a less experienced/responsible user (such as a new hire at a business, or a junior member in a co-op), install the governor. If you can take responsibility for yourself and are ready to deal with the consequences if you screw up, skip the governor and make sure you always pay attention to what you are doing.

So, you ask what good is a car that can go 200mph but is set to never exceed 125, and then you say to remove the governor and limit yourself to 190 to conserve the engine... Well, if your buddy borrows the car or a thief takes it on a joy ride, they might ruin the engine by pushing the limits too high. The alternative there is to keep the governor but adjust its limit from 125 to 190 so no one accidentally or intentionally exceeds "safe" rpms.

[Bill George]

I am assuming you just put a red line on the mA meter and be done with it. That's why tachs have red lines. Bert I agree with you nobody but me runs my machine.

[Jeff Body]

My question would be why are you hitting 90% mA at only 65% setting?
When you have it set at 65% do you feel like you're getting the full power of an 80w tube?
Do you feel like it should be able to produce more power?

[Jerome Stanek]

My question would be why are you hitting 90% mA at only 65% setting?
When you have it set at 65% do you feel like you're getting the full power of an 80w tube?
Do you feel like it should be able to produce more power?

His power supply is over powering his tube. At 65% he is getting what he should at 90%. He may be able to adjust the supply down to where it puts out the correct voltage.

[Ron Gosnell]

His power supply is over powering his tube. At 65% he is getting what he should at 90%. He may be able to adjust the supply down to where it puts out the correct voltage.

If anyone knows how to do this please advise. That would be the ticket.
I'm not experienced on laser power but at 27ma I believe it's hitting 100 watts plus. 4" lens.... speed =6..... power= 65%.... just cuts through 3/4 pine board on testing

Gozzie

[Dave Sheldrake]

The PSU will be able to provide current for a range of tubes, (a 150 watt supply will run a 130 - 180 watt tube) so is likely set to run the bigger tube in it's range. There is a small screw hole on the PSU that allows access to a potentiometer to adjust peak current and gauge output.

The PSU is likely set by the factory to pump 30mA to power a 180 watt tube (the figures look about right) and has not been checked by the seller before being sent out.

27mA on a 1650mm widebody tube will be fine.

[Dave Sheldrake]

His power supply is over powering his tube. At 65% he is getting what he should at 90%. He may be able to adjust the supply down to where it puts out the correct voltage.


^^^^^^ This :) spot on and a lot better than my reply :)

[Ron Gosnell]

Thanks Dave,

I feel much better about the 27ma now.
I'm going to look for the pot and try to adjust it for everything to match 27ma at 100%
I'm a little OCD about things like that.

Gozzie

[Jeff Body]

My question would be why are you hitting 90% mA at only 65% setting?
When you have it set at 65% do you feel like you're getting the full power of an 80w tube?
Do you feel like it should be able to produce more power?


His power supply is over powering his tube. At 65% he is getting what he should at 90%. He may be able to adjust the supply down to where it puts out the correct voltage.

Makes perfect sense now.

[Keith Winter]

I'm wondering how important this is to turn down the power supply?

Being my laser is from the same company (Thunder) and same wattage as Gozzie's I have the exact same issue. I have to run it at about 70% of power which gives me 27mA.

The power supply is already mounted and impossible to get to the screw hole to turn the power supply down by adjust the petentiometer without demounting it and the attached wires and boxes. Will it shorten my tube life if I do not turn down the power supply and just run it at 70% instead of turning down the power supply and running it at 100%? Or is running it at 70% an ok solution?





The PSU will be able to provide current for a range of tubes, (a 150 watt supply will run a 130 - 180 watt tube) so is likely set to run the bigger tube in it's range. There is a small screw hole on the PSU that allows access to a potentiometer to adjust peak current and gauge output.

The PSU is likely set by the factory to pump 30mA to power a 180 watt tube (the figures look about right) and has not been checked by the seller before being sent out.

27mA on a 1650mm widebody tube will be fine.

[Dave Sheldrake]

Output is control Keith, why the tube gets 27mA doesn't matter so long as that is what it gets...reduce the PSU output or reduce the settings on the screen doesn't matter :)

[Lee DeRaud]

Specification & Parameters of 130wLaser Cutter Tubes


Laser cutter tube Model

SPT-C130



Laser cutter tube Length

1650mm



Laser cutter tube Pipe Diameter

80±1mm



Laser cutter tube Type of Cooling

Water-cooling 15-25°C



Laser cutter tube Impulse Frequency

100% to 5KHZ



Laser cutter tube Gross Weight

4.8Kg



Laser cutter tube Carton Packing

1780*170*160mm



Laser cutter tube Wavelength

10.6um



Laser cutter tube Mode of Excitation

Electric excitation



Beam polarization mode

Linear reasonably



Beam Divergence Angle

3.1mrad



Laser cutter tube Light Beam Quality

≤1.1



Laser cutter tube Stability

10%



Laser cutter tube Lasing Mode

Much lower order film



Output Power Stable Value

130W



Laser cutter tube Max Output Power

150W



Laser cutter tube Starter Voltage

26~28KV



Laser cutter tube Working Voltage

20~23KV



Laser cutter tube Starter Current

6~8mA



Laser cutter tube Max Working Current

23~30mA



Laser cutter tube Spot Diameter

5±1 mm





Off-topic, but am I the only one amused by the word "reasonably" appearing in a spec sheet?

[Ron Gosnell]

At this point in time I am very comfortable with using 65% as my max setting. It still runs right at 27 ma at 65%.
Like Keith I cant get to the power supply potentiometer to adjust it.
I don't know if we lose any resolution by only being able to adjust our settings between roughly 10 and 65 %
but I haven't noticed it. I don't do photographic work and work mainly with wood so it probably doesn't matter much anyways.

Gozzie

[Keith Winter]

Thanks Dave and Gozzie!


At this point in time I am very comfortable with using 65% as my max setting. It still runs right at 27 ma at 65%.
Like Keith I cant get to the power supply potentiometer to adjust it.
I don't know if we lose any resolution by only being able to adjust our settings between roughly 10 and 65 %
but I haven't noticed it. I don't do photographic work and work mainly with wood so it probably doesn't matter much anyways.

Gozzie

[Matthew Grant]

I realize that this thread is a bit old, but I wanted to reply (for future searches) that using a 70% power setting to limit the max current is absolutely fine.

The supply is not overpowering the tube, it is just able to deliver more power than that tube needs. You set the max PWM duty to set the max current, just as OP has done.

I personally would not recommend messing with the pot inside. You get the same effect by limiting the PWM duty with more flexibility.

[Timothy Kamp]

I realize that this thread is a bit old, but I wanted to reply (for future searches)
Short answer - adjusting a pot or using a software limit are acceptable.

I have several of this same 130w tube by SPT. I've logged what I calculate to be pretty darned close to 3000 hours on it since Oct and we run it HARD at 28ma. It's cutting at pretty close to 90% duty cycle (very little travel time between cutting, lots of continuous lines) and until it burned out because I overheated it (forgot to turn chiller on), it was still cutting very strong. One of my machines has a potentiometer wired back to the power supply to adjust the output current from 0-5v, which works well. I set all my cut files to 99% power, and dial back the pot until it's dead at 28ma max current on the ammeter. My other machine lacks the pot to adjust, so we played around in the software to adjust the software max to about 72%, which turns out to be 28ma on the machine's ammeter.
The biggest downside that I see with the pot solution is if someone walks up to the machine and inadvertently turns the knob, I could overcurrent my tube when I start up the next job if I wasn't paying careful attention. Alternatively, since the machine max power settings are diffferent, I can't use cutfiles between the two machines without altering the power settings. One of these days I'm going to disable the pot for commonality's sake, just haven't gotten around to it yet.

[Phill Barnes]

Ron, don't you mean CDO?