Why can't I set my power level to less than 35%?

[Preso]

I have a 40W chinese laser which has been retrofitted with an AWC608 DSP. I am using the original laser tube which still has plenty of power. I am also using the original laser PSU. My problem is that I cannot seem to run the tube at anything lower than 35%. It will work at setting higher than that but at 34% There is 0 amps showing on the ammeter and no marking at all on material under the laser. I have checked the settings in the software and I have set the maximum power at 80% but I can't find anything that would prevent the tube firing at lower settings.

Any Ideas anyone????

Regards
Preso

[Preso]

Hmm. I thought this would be a hot topic!!!
I must say I am puzzled. I thought after reading lots of posts on this forum that misbehaving laser PSUs were common enough. Usually the problem relates to tubes not firing at high power or tubes that lack power. My problem seems to be that I cannot get low power. I am sure someone can shed some light on this.
Come on .... As Mulder would say, "The truth is out there".

Preso

[Tech_Marco]

Ha..ha....At least I'm here
(doing shopping with my wife and my kids in Bay Area now)

I haven been thinking it but it since yesterday. It could be many reason for it

At least one thing you need to tell me:
What is current when it start firing at 35%

FYI, % doesn't mean anything but the output currently is everything.


Marco

[Preso]

Thanks for getting back to me Marco.
I just ran some tests using Lasercad. I drew a rectangle and set the line to cut.
Here are the results:
Power-------------Milliamps on meter

20-----------------0
30-----------------0
31-----------------0
32-----------------0
33-----------------1.3
34-----------------1.8
35-----------------2.4
36-----------------2.9
37-----------------3.3
I even graphed the results. It looks nice and linear from 33% onwards but below that it just falls off the cliff.

Most strange!!!

[Tech_Marco]

Then what is current when 100% is set?
Usually it is the power input issue on the PSU
But if you can get as low as 0mA and full output at 100%, I don't see a big deal. Just get used to it.

Marco

[Preso]

I'll check the power output at 100% however I really to want to get the laser tube to fire at low settings. There is no in between with the way the system is now. I either get 0 power (no heat) or 1.3ma. Sometimes I need to cut paper or mark really thin veneer without burning right through. A setting of 33% and 1.3ma is too high for this. Should I be able to get the tube to run at 0.5ma? I should mention that my laser PSU seems to be an 80W unit and my tube is only 40W. Could this be a problem?

Regards,

Preso

[Tech_Marco]

You shouldn't use a 80W PSU for a 40W tube! The tube could be damaged and you won't be able to fine tune output current. I don't understand then why you said that it was original tube and original PSU. If that's the original machine you have, then the manufacturer is shame of being ignorance.

If 1.3mA is too much for paper cutting, the your only chooice is to increase speed to offset the higer current output


Marco

[Preso]

Marco,
I am using the original tube and the original PSU. The fact that they are mismatched is an example of how badly put together this machine was. The manufacturer should indeed hang their head in shame! I checked the power at 80% and it was showing 26.4 ma. I only did a very short run as I understood that a 40W tube should not run at more than 18 ma.
I think I will do as you suggested and increase the speed. When the tube dies I may extend the chassis and fit a 60W tube and maybe a new PSU.

Regards,

Preso

[Tech_Marco]

You may enable the "PPI" that is designed to control output by sending pulse beam and the rate is fully adjustable. Since you're having a 80W PSU, it is not very stable when firing at low current say 2~3 mA. I believe that for a 80W tube an initiated current that runs at stable output should be set to 4mA or above.

Anyway, you should not set current too low as that will cause unstable output and it would be pretty bad for especially on engraving. I can't tell you exact amount of current needed because each tube, even though with same power rating, has it's own characteristic. I will take advantage of having higher speed cutting/engraving or using the PPI feature.


Marco

[Preso]

Thanks Marco

Regards,

Preso