60W laser upgrade

//60W laser upgrade

It’s no secret that my SH-G350 laser machine, a.k.a. 50W eBay laser cutter, is not really a 50W.

Yup, it’s one of the biggest scam on the eBay.  What you get is actually a machine with 35-40W watt 800mm long CO2 tube, that’s being overridden with higher current to work like 50W.

A while back I purchased a cheapest laser power meter I could find: Mahoney Co2/YAG 100W power meter probe.

100_Watts_CO2_YAG_Laser_Power_Meter

Thing looks like an oven thermometer, and it actually is a thermometer of sorts. It measures by how much laser beam heats up the probe, which expands a spring inside, which moves gauge needle.  But hey, it works and works well.

Upon testing my CO2 laser tube, I noticed very strange behavior. At 100% power, I was only getting about 25 Watts of power,  but at 80% I was getting closer to 50 Watts. Also above 85% machine was making a high pitched “screaming” noises. Later I learned to associate these “screams” with sudden drop in power.

All of this was due to the fact that, I didn’t actually have a 50W CO2 tube, but rather a 35-40W one. It just couldn’t handle high current and would drop power. In the process I was also greatly shortening it’s life span.

I’ve also measured current with my multimeter and here’s what I found:

Power setting

mA

10%

3.13

60%

18.85

70%

21.74

80%

22.17

90%

22.47

Normally CO2 tube in the 30-50Watt range should not be powered by anything above 20mA. So anything above 60% was overrdriving and quickly killing it.

Soon I started to experience “scream of death” at lower and lower power settings.  First it was happening at round 80%, then I could not longer cut anything above 75% and eventually even at 60% I would get intermittent power drops leaving me with half cut acrylic…

That was an excuse for me to finally get a real 60W laser tube upgrade as well as new quality Power Supply.

I ordered both (SP tube and 60 Watt PSU) from LightObject, which is a reputable laser equipment re-seller from California.

First thing that arrived with PSU. Few days later Fedex brought this really big and tall box to my doorstep.

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Can you guess what was in it? 🙂

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A very well packaged, both within a box…

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A beautiful 60W, 1250mm long CO2 laser tube.  Some water droplets were sparkling inside. Tube was tested very recently.

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It actually had labels on it, unlike the one that came with laser machine. Strangely tho none of the labels mentioned power rating…

This nice piece of paper, had very interesting information about this specific CO2 tube.

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Surprisingly, it mentioned output of 60.2 Watt at 14.2 mA current. Which is great considering it’s rated for 20-22mA. Does it mean I can get 80 watts at 22mA?  I don’t know, but I might try it some day 🙂

And here’s back of the power supply. All terminals are same as my old one, some just reversed. Which means I shouldn’t have problem with connections. Physically mounting it, would be a little challenge as this one is much bigger then the one that came with SH-G350..

 

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In the following weeks I will be slowly preparing to install new components into my machine.  There are few challenges that I need to overcome, such as building extension enclosure for a much longer CO2 tube (which will be protruding from side of the machine), getting all wiring done, and mounting tube inside.

I don’t want to just re-use ghetto mounts supplied with machine (which are basically pieces of thick rubber pushed onto tube with some metal bends and bent machine screws).  I was told about this awesome tube hangers, which I modified today to fit my 55mm thick CO2 tube, and already started to 3D print the parts.

Another upgrade will be an analog Ammeter to monitor laser tube current.

ammeter

 

I will keep you posted on my progress!

2019-01-26T21:28:01+00:00November 13th, 2015|Laser machine|6 Comments

6 Comments

  1. SR March 2, 2016 at 2:41 am - Reply

    Are you interested in selling your power meter?
    Ive been looking for one for some time. (or heck rent it too me!)
    Sam

    • bratan March 2, 2016 at 3:09 pm - Reply

      Sorry I’m not selling mine 🙂 Why not just get one on Amazon?

  2. Warden September 8, 2016 at 1:54 pm - Reply

    Oh, my. I have the same Shensui laser that I’ve enjoyed for the last year. Lacking sufficient instructions (and not speaking Chinese), the learning curve has been mostly trial and error. While I’ve done some pretty incredible things with this machine, I was frustrated at the cutting speed and power. Intuitively, if you want it to cut deeper, increase the setting. But as you appropriately found and shared, it was killing the tube.

    So, as a test I changed my most common project that was cutting 6mm acrylic with 4mm/sec at 85% power to 6mm/sec at 40% power. I was shocked! It cut much better (and faster).

    This comment is to acknowledge your investigation efforts and how it helped renew my spirit with this machine. Knowing that I really have a 35W (not a 50W) tube and how you explained why I was having the issues will help on many future projects.

    A true 60W tube will be in my future shortly (just as you’ve done).

    I plan to add a Milliammeter to my system. Would you be able to provide the wiring instructions? (Again, thank you)

    • bratan September 8, 2016 at 3:02 pm - Reply

      Yup, decreasing power percentage might seem illogical, yet it will give you more actual power since tube is not “confused” by over-current. Kind of like blasting music thru speakers at too much of a power will distort sound… At least it’s my theory 🙂
      As for ammeter I wrote a small post how to connect it here: http://lensdigital.com/home/?p=1453
      Good luck with your future upgrade! At some point I measured output of my 60W tube and by the time I get to the nozzle I only getting about 45W, somewhere along the way I’m loosing the rest. But honestly I didn’t spend too much time on it, as I can still cut everything I need and engrave 🙂

  3. Ed_ September 26, 2016 at 11:21 pm - Reply

    I have the same laser cutter and I had the same issue with the actual output dropping at higher settings (documented at http://www.rdworkslab.com/viewtopic.php?f=11&t=339) and get the highest output at 30-40%. A really good test of power is shown at https://youtu.be/WbBPps42iHc?t=7m53s where you cut into the edge of a piece of acrylic held up like a fence at different power settings and get a bar graph of actual cut depth.

    After using the 60W tube for a while how does it compare to the original tube?

    • bratan September 30, 2016 at 2:22 am - Reply

      I get a lot more power (obviously). But due to losses somewhere along optical path, actual cutting power only marginally better… I can cut most materials 5-10 mm/sec faster…

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