[BrentFerguson]

Hello fellow members.

I have searched high and low on this forum for my answer before posting this, I did find some great advice on comparable threads but no definitive answers.

My issue has to do with gradual power decreases with my Shenhui 690 laser (90watt RECI tube).
Put simply, the settings I would use when I first purchased the machine in January barely mark my substrates now.
I only ever mark wood and as an example when I etch bamboo I used to do so at %26 power, 370mm/s speed, results were perfect.
Now, just 8 weeks down the track, to get a comparable result I have to run it at around %38 with the original %26 barely making a mark on the surface.

Obviously over time tubes will decrease in power and results like these would be typical, the problem is, its only been 8 weeks!

The 1 contributing factor that just may really help narrow down the possibilities is the fact that perhaps coincidentally (but probably not) I had the exact same thing happen on another Chinese laser (not Shenhui) that I used to own.

I maybe off in my potential diagnosis but I feel it has something to do with the grounding of the machine or the power that is being supplied to the machine.

I am far from any electrical expert so have steered clear of fiddling with what I dont know but understand that as the power cords have 3 prongs they should essentially be properly grounded?

There is the usual ground point on rear of machine which has good contact with one of the garages steel support beams.

The machine is in a 40+ year old garage which is why I thought initially suspected some sort of power issue to be the cause but I could be well off the ball there.

All mirrors and lens have been checked and regularly cleaned, the lens had a dark spot on it but replaced with new piece and wasn't the culprit of the poor results

Your suggestions would be greatly appreciated.

Please keep in mind im in Australia, assuming replies may come from the US please forgive any lengthy delays in replying, I appreciate any and all guidance.

[fixtureman1]

Have you checked to see if your mirrors and lens are clean also did you check your beam alignment. What is your amp meter showing for power. Not sure the software you are using but on mine sometimes I have to boost the minimum power to get the correct high power to work.

[Labmaster]

Maybe you have permanetly overdriven your CO2 Tube.

Especially on chinese machines yoi should be carefull aand stay within limited power setting.

For example, if the Tube at maximum power draws 30mA you should better stay at about 25mA. (or lets say 70% of the max setting)
This all higly depends on the safety measures that the manufactorer has done.
It should be good practice to limit the powersupply to a safe operation range where the tube nevers get to the extrem areas, unfortunately most of the chineses guys do not care or the powersupply do not have an option for adjusting such things. In this case you have to take care about this yourself to stay within a safe level.

A always overdriven tube could easily quit within hours where when driven in safe ranges it could last for years.

best regards,
Walter

[BrentFerguson]

Rarely draws anything over 10mA so I dont think this could be the case
Like I said though im no electrical expert im just going by what the inbuilt ammeter reads.

On small bursts of etching it hovers around 3mA or up around 10 for larger areas,

[DavidYoung]

I always used Reci Tubes upto last year, they seem to have lost the edge when it comes to quality, we also find they do lose upto 20% power in the first couple of months, but then it seems to level out and can run fairly stable for upto 4 years ( i have one 80W still putting our 50W after 4.5 years)
Recntly we hve been using SP tubes, the quality is better than Reci, the 100W can output 125W and after 2 years the 100W tube is still outputting over 85W at the head. You really need a power meter to see whats going on, although a mirror can look clean, minute scratches can lose 10% power or more, 3 mirros like this and you are down 30%. We had a visit from Synrad R&D in Germany Last year to trouble shoot a Synrad 80W that was only putting out 50W at the head, The mirrors were losing most of it, Now we check using a Synrad power wizard so you can see any drop between the tube output window and the cutting head. We had a similar power fade with the Reci DY10 Psu on one of the other machines, tweeked the pot up but within weeks it dropped again, had to replace it in the end, and its still going 3 years later

What software you running? Lasercut has power table offsets, which can affect output powers.

[BrentFerguson]

Some interesting point there grumpygnome thankyou. Im just using rdworks. I imagine changing to the SP tube requires replacement of power supply also but anything else?