Author Topic: How long do you run your laser for?  (Read 1764 times)

mathyouw

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How long do you run your laser for?
« on: October 18, 2017, 08:02:15 PM »
I read somewhere that you can let a 2.5 watt laser run for 2 hours, but that you have to let it rest for an hour before going again. Is this true? How long do you let your laser run?

ThothLoki

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Re: How long do you run your laser for?
« Reply #1 on: October 18, 2017, 08:22:31 PM »
I have personally run my for over 3 hours before and have heard others post that they have run it for over 20 hours.

It all depends on the laser. My thought on this is that we can run it longer due to the fan on the laser module to help keep the laser diode cool.
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Starbrow

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Re: How long do you run your laser for?
« Reply #2 on: December 12, 2017, 01:31:06 AM »
For some of my largest engravings I have run my 2500 mW EleksMaker for 8 hours without issue. I should note that I keep it in my unheated workshop, so the temperature is below room temperature.
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Stonemull

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Re: How long do you run your laser for?
« Reply #3 on: December 12, 2017, 04:19:07 AM »
It is only the maximum temperature that matters, not the length of time.This applys to the power supply as well as the laser, I cannot see any way 2 hours could ever be meaningful, it will be as hot as it will ever get after 30 minutes or so, after that it does not care if an hour more or a thousand hours.
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Zax

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Re: How long do you run your laser for?
« Reply #4 on: December 12, 2017, 04:50:38 AM »
Diodes are designed to have long run times, as Stonemull said providing you have an adequate heatsink and cooling (fan) there is no reason it can't stay on for many thousands of hours.

The problem comes when the manufacturers over drive the diode with excessive current to get a little more output, which is converted mostly to heat. If a 6W diode is used at 5.5W it will last a long time, that same diode at 8W or 12W as some seem to do will fail prematurely (sometimes in just a few hours).

ROSS

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Re: How long do you run your laser for?
« Reply #5 on: December 12, 2017, 04:54:59 AM »
IF you are worried about it..change the fan to the same sized physically -  but a more powerful one....They are available at most PC shops....
.
Lasers are wonderful machines..not ONLY  can they cut a finger off BUT  they can also cauterise it at the same time.....

SAFETY -  IS NO ACCIDENT

mrehmus

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Re: How long do you run your laser for?
« Reply #6 on: December 12, 2017, 09:44:32 AM »
It is only the maximum temperature that matters, not the length of time.This applys to the power supply as well as the laser, I cannot see any way 2 hours could ever be meaningful, it will be as hot as it will ever get after 30 minutes or so, after that it does not care if an hour more or a thousand hours.

Not correct. Time and temperature have an effect on semiconductors. The longer they are too hot, the quicker they will fail, statistically.

That said, I run mine for five or six hours but I have an airconditioned shop so it stays at around 70 F max.
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ggallant571

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Re: How long do you run your laser for?
« Reply #7 on: December 12, 2017, 11:10:13 AM »
I think you both are saying the same thing. Stonemull is using 30 min vs 2 hours as an example. I have no problem with the numbers. It could be 2 minutes or 5 hours, the point is you must dissipate the heat or the device will self destruct.

I have used a number of devices during my career where the manufacturer gave specific maximum operating time before a cool down period was required. Others just shutdown when hot. I can't imagine any of the hobby laser vendors incorporating any type thermal measurement. Might cost $0.50US and need firmware.

Anyone care to guess what is going on my controller? 
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ThothLoki

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Re: How long do you run your laser for?
« Reply #8 on: December 12, 2017, 12:17:45 PM »
Anyone care to guess what is going on my controller?

A beer holder?
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ggallant571

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Re: How long do you run your laser for?
« Reply #9 on: December 12, 2017, 01:14:46 PM »
You are too slow. That was last year!!! Along with the cooler that kept both cpu and beer at the right temp.
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mrehmus

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Re: How long do you run your laser for?
« Reply #10 on: December 12, 2017, 04:15:26 PM »
I think you both are saying the same thing. Stonemull is using 30 min vs 2 hours as an example. I have no problem with the numbers. It could be 2 minutes or 5 hours, the point is you must dissipate the heat or the device will self-destruct.

No, we are not saying the same thing. He is saying that time and temperature don't matter, that only the temperature matters. Devices have a curve of temperature vs time to destruction. What applies to ICs also applies to any semiconductor.

Here is what Micron Technology states: The time frame and random field failures in the useful life of the IC can be predicted using statistics based on lab data from a sample of parts and will vary greatly depending on the operating temperature of the IC. This process is explained in detail in the following pages. 
If you want to read the entire paper, use this URL: https://www.micron.com/~/media/documents/products/technical-note/dram/tn0018.pdf
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nottingham82

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Re: How long do you run your laser for?
« Reply #11 on: December 12, 2017, 10:02:02 PM »
just finished a 27 hour burn.  still running fine.... on a side not turn on rapid skip blank ... otherwise you will end up with 27 hour burns.
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Stonemull

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Re: How long do you run your laser for?
« Reply #12 on: December 12, 2017, 11:04:05 PM »
pedantic much. yeh I wasnt going yo get into MTBF's and statistics. I was disputing the original quote of needing a rest after 2 hours, I call bollocks to that. To repeat myself its going to get as hot as it will after 30 minutes. Does it matter whether you have ooerated at 1.5hours out of 2 at full temp or whether you operate it for 20 hours straight and it was hot for 19.5 .. sure, by about 20% of total life, assuming that the high temp is of a level that reduces mtbf significantly. If not .. then it makes no deifference at all.

The point is that with active cooling the device is unlikely to get the high temperatures where rapid failure is expected unles the heatsinking is way sub par and at lower managed temperatures there is not a great enough reduction in MTBF that much caution is warranted.
Pulling numbers from my butt, maybe 20000 hours instead of 50000hours at 100C (junction) whereas a decent fan holds it at 70C and MTBF is much still closer to that 50000 mark.
If it is not still raising temperature after something like 30 minutes then the cooling has now matched the dissipated heat, if you can touch it confortably and there is decent thermal conductivity from junction to case then the laser is probably not going to explode any time soon.
« Last Edit: December 12, 2017, 11:13:37 PM by Stonemull »
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rolx

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Re: How long do you run your laser for?
« Reply #13 on: February 06, 2018, 09:18:49 AM »
@nottingham82 What in the world did you burn for 27 straight hours ?? :O :O

ThothLoki

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Re: How long do you run your laser for?
« Reply #14 on: February 06, 2018, 04:20:45 PM »
@nottingham82 What in the world did you burn for 27 straight hours ?? :O :O

Probably trying to see if he could burn slate  ;D
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