[HoneyBeeWorks]

Hi,

We bought a G-350 laser cutter in January and it has been working without missing a beat. But this week it has stopped cutting effectively.

It's been cleaned every day, is cooled by a 150 litre tank that is temperature monitored (never more than 15c).

We used to be able to cut 3mm acrylic at 65% power and 8mm/s. Now at 65% power and 4mm/s it isn't cutting through.

The laser seems to scream/whistle intermittently when firing and the laser cuts through intermittently as well.

Has the tube gone? We have less than 150 hours on it!?!

If the tubes only last 150hrs this is totally uneconomical.

Anyone any ideas?

Thanks Neil

[gfacer2]

Its possible - Laser tubes IMO do not seem to live up to their stated hours. First things to check are that the lens is clean and not cracked. A cracked lens can cause issues (and yet it will still sort of work).

It could be the power supply or the controller and if you have a spare power supply it might be worthwhile to test it by swapping in the new one. The controller can be tested by a multimeter at the power supply - one connection is a full voltage from the power supply and another is the % voltage of power (ie 50% power would have a voltage of 50% of the full voltage line). So that's pretty easy to test once you figure out (laser power off) which line is which.

Another possibility is scratches or dirt on the mirrors - and depending on your cleaning regime - once a day cleaning may be too much if it includes the mirrors. Scratches can cause the beam to lose power on its way to the lens.

So to recap - its usually the tube. But to quickly and easily tell it helps to have a spare power supply. Then you can quickly isolate the controller/power supply/tube when issues occur. I don't have this either but its ideal and I should (we have 2 locations and 2 lasers so that's our alternative back up plan). It also helps to have spare mirrors and lens for maintenance and troubleshooting.

But I think way too often it is the tubes that fail early especially on new machines- though I think 150 hours is low for sure. I swear sometimes its like they price it low because its using factory seconds for things like the tube.

PS - I would not assume a replacement tube is only going to work 150 hours (unless you are over powering it - do you have a milliamp meter on it?) They should last a lot longer than that.
PPS - I think also there are no 50W tubes - there are only 40w tubes that have a max power of 50W (which they advertise even though it will kill the machine fast). What I am not sure about is what those machines use for a power supply. 65% seems low if its a 40W power supply for the cutting you described but if its an 80w power supply it might be too high - this is where the milliamp meter comes in so you can see what the power usage is and compare it to what the tube can take.

[HoneyBeeWorks]

Thanks gfacer2,

Lens isn't cracked. I had it out and inspected it before posting. Simlarly mirrors are clean and unscratched. The daily cleaning regime consists of cotton bud and acetone to just get any dust off the mirrors/lens.

In terms of the power supply/control board. Somewhat reluctant to poke around with that. 16k Volts is kinda scary for the none electrician!

It seems to be a 50W PSU though i am basing this purely on the fact I can see inside it through some of the vents on the PSU and see a label that says 50W. I wouldn't put it past them to change a label, but one inside the PSU seems a little far even for them...

The reason for the 65% power setting is that is what the laser seemed to cut best at. We tried it at everything from 20% - 95% power and found 65% cut the cleanest and fastest. The tube is only 800mm long and it looks like the chinese fit a cheap 40W tube in these G350s that really only work at about 35W. That would makes sense as 65% of 50W is 32.5W....anything more we are over driving the tube and the power was lower.

I suspect the short life is a combination of factors: 1.The tube arrived fitted in the machine which made me suspicious...plus the machine was filthy. I suspect this tube has been used. 2. It's a cheap tube and wasn't up to the job in the first place.

So I've ordered a 850mm 50W tube from Coletech and will see if it makes a difference.

Regards Neil

[gfacer2]

Excellent conclusions. Coletech is a good vendor, we've bought from them before. My brother just broke his 80w tube from them (cooling malfunction) after a few years of service.

As for the power supply, you don't test the high voltage side, only the terminals on the other side. In theory you can test the controller at the controller side but all our connections are glued on so its more practical at the power supply. If you keep the laser power off when testing it's fine. No high voltage or even 110v



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[robertk925]

On my Shenhui SH-G350 65% is also the max. usable power setting, equating to 20ma on my retrofitted ammeter.

I am surprised that you need 65% power & 8mm/s to cut 3mm thick acrylic. I use 65% power & 6mm/s to cut 6mm (1/4" here in the US) acrylic, and I believe 55% power and 12mm/s to cut 3mm (1/8" US). I probably have 2-300 hours of cutting time on it since I bought it last year.

Perhaps your tube has been losing power for a while?

Have you seen the Sarbar Multimedia videos on Youtube? A lot of useful information about this machine on there.