Correct laser tube and power supply matching

[Richard Nester]

We are newbies to SC, but have been using an FSL 120w CNC laser for about 4 years, relatively trouble free. After 4 years, the tube finally gave out slowly and we just purchased a new 120w tube from GoldenSign in Chino, CA. In the process, we have learned that there are many opinions about tube and PS matching. We currently are operating with a 150w PS. So we are wondering what the community thinks. We want to cut relatively quickly, but preserve the life of the equipment, too. We do a lot of wood cutting, and want to be able to cut through 1/2" Baltic Birch, although our mainstays are 1/4" and .20". 1/2" birch may be an unachievable goal. Additionally, the PS is running at a constant 42ma. That seems high. Thanks in advance for your advice.

[Dave Sheldrake]

150 watt tube should be no more than 35mA peak(32mA running), 42mA will shorten it's life and cause excess heat very quickly. Both voltage and current will be wrong by quite a bit Even tweaking the PSU down by percentage won't help a great deal as the output Voltage is fixed and still too high for the tube

[Richard Nester]

Dave Sheldrake, I thought that was the case. However, I am buffaloed by the wide variation in recommendations from places like FSL and Golden Sign. Golden sign says the 150 PS can be safely used down to 80w tube. FSL says we could/should use a 80 or 90w PS. Intuitively, neither of those choices seems right. Why isn't a 120w PS right for a 120w tube? Is the 42mA current a function of the PS itself?

[Ian Stewart-Koster]

The greater the overall power of the tube, the longer it is in physical length.
The longer the tube is, the higher the voltage needed to 'spark'.
Once the spark fires, the current is what does the work... and many tubes operate within a vaguely similar current range...roughly.

[Bill George]

I would take Dave’s advise to the bank. He has forgotten more about lasers than most of claim to know.

[Dave Sheldrake]

The greater the overall power of the tube, the longer it is in physical length.
The longer the tube is, the higher the voltage needed to 'spark'.
Once the spark fires, the current is what does the work... and many tubes operate within a vaguely similar current range...roughly.

Ian's pretty much got it covered,

Bejing EFR:

http://en.bjefr.com/

ZN Series

ZN-1250:
Length: 1250mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 95 Watts
Working Current: 26 Ma

ZN-1450:
Length: 1450mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 28 Ma

ZN-1650:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

ZN-1850:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 180 Watts
Working Current: 30 Ma

F Series:

F2:
Length: 1250mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 95 Watts
Working Current: 28 Ma

F4:
Length: 1450mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 30 Ma

F6:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

F8:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 170 Watts
Working Current: 30 Ma

F10:
Length: 2050mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 180 Watts
Maximum Power Output: 195 Watts
Working Current: 30 Ma

http://www.recilaser.com/en/products.htm

W Series:

W2:
Length: 1120mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 80 Watts
Maximum Power Output: 85 Watts
Working Current: 27 Ma

W4:
Length: 1400mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 100 Watts
Maximum Power Output: 120 Watts
Working Current: 28 Ma

W6:
Length: 1650mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 130 Watts
Maximum Power Output: 150 Watts
Working Current: 30 Ma

W8:
Length: 1850mm +/- 20mm
Diameter: 80mm +/- 2mm
Rated Power Output: 150 Watts
Maximum Power Output: 180 Watts
Working Current: <30 Ma

This may help explain it a little, always check tube length, tubes sold as 120,'s will sometimes be over driven 100's etc. The RATED power is the tubes useful, maximum, the PEAK is what the trigger current causes and if you try to run it at that it will die.

The 42mA is the current setting inside the PSU, most decent PSU's will pump up to 50mA and some companies don't bother setting them properly to match the tubes (time costs money etc) and some will deliberately overdrive a shorter tube to try and make it appear more powerful.

Stabilising caps in the PSU' a 40-60 watt usually has one, an 80 watt has two and 100 watt+ has three, but using a lower rated PSU you run the risk of blowing the internals pretty quickly as it's much like screaming a Ford focus just under the redline to get 130mph out of it

a couple of mA extra may get you the last possible Watt but there is always a cost to doing so :)

[Richard Nester]

Thanks guys. Invaluable. I have more questions, but they can wait.