Which Power supply for 45W C02 Laser Tube?

[WolverineX]

Hello from the UK!
May the 4th be with you!
New to the forum, just have a question before I make a purchase from the Lightobject store.
I am looking to buy the 45W C02 tube for my chinese Shenhui SH350 laser cutter, I have prepared for the longer tube (1m rather than the original 850mm) but I am in doubt as to which Power supply I should buy - the 20W-45W PSU or the 40W-60W PSU

45W C02 Tube - http://www.lightobject.com/SP-45W-CO2-S ... -P751.aspx
20W-45W PSU - http://www.lightobject.com/20W45W-PWM-C ... -P885.aspx
40W-60W PSU - http://www.lightobject.com/40W60W-PWM-C ... -P886.aspx

I am not confident as to how I would set the power supply units to match the desired 45W tube, is this something Lightobject could do before they ship?

Regards.
Ian

[jeckardt]

I posed the same question to Marco. He said either would work but that the 20-40w had ample highend for 1M tube and would do better a low settings than the 45-60w one. I bought the 20w one.

[WolverineX]

Thank you for the reply.
Isn't there some kind of potentiometer on the PSU to vary the output to the laser tube - dangerous thing that, a doofus like me searching the internet! I have read that some (not all!) Chinese Laser machine suppliers crank up the power in the PSU to make the tube act more powerful that it actually is.
Here's the article I read...
http://www.instructables.com/id/How-to- ... CO2-Laser/

Question is do I need to adjust anything or are the Lightobject PSU's already set to the wattage of the Tube?

[jeckardt]

The "20-45W" PS delivers max 22mA
The "40-65W" PS delivers max 25mA

The 1M (45W) tube max current is 18mA, so the smaller supply provides plenty. The larger supply offers more at the high end which you can't use anyway, and per Marco is less stable on the low-current end, so it's a net loss.

There is no adjustment necessary to either power supply. The controller is what is responsible for controlling the current.

The pot on the panel of the stock K40 adjusts how much current is allowed to go to the tube -- you just adjust it while running until the current meter reads what you want it to (and less than 18mA for this tube).

If you have a DSP, then you set the "max power" setting to something like 80% for the 20-45W supply to limit the max current the supply can provide. For the 40-65W supply it'd be something like 70%.

[WolverineX]

Brilliant! Thanks for the information! I'm going to order right away!

Cheers!
Ian.

[WolverineX]

All ordered. Should be here in a couple of weeks...can't wait to get lasering again!

[Tech_Marco]

To make it last longer, limit the current to 16mA.
Water temp:20~25'C


Marco
(@China)

[WolverineX]

There is no ampmeter on my machine, and I have no testing equipment but I could get an electrically competent friend to check the current as per the link I provided in a previous post!?

[Tech_Marco]

http://www.lightobject.com:80/Small-DC- ... -P932.aspx

Connect it in series with the LPSU on the ground side
Do not connect it on the hot wire side


Marco

[WolverineX]

Thanks, and that does not need a 'shunt'?

[Tech_Marco]

No external shunt needed. Built in


Marco
(@HK)

[WolverineX]

Just a quick update, tube and power supply arrived well packaged and in one piece. They are both fitted, and the machine is working better than it ever has! Very pleased with my purchase and LIghtobject.
Now only around 12 months to go before I need to order another tube! Best get cutting!

[WolverineX]

Well quite a bit more than twelve months - The tube has started to lose power on my final job of the day! Upping the power to 60% and two passes still couldn't cleanly cut 3mm ply! Time to order another 45W tube.