Yea, I’m not gonna get into an argument of comparing each others sword lengths. I think the point here was to help the OP who may or may not have an adjustment pot on their PSU. It’s pretty common for folks to add mA meters to their machines and adjust cuts by actual than percentage.
Dan
Here’s a link to a youtube video for mA meter install:
And this is same/similar to the ammeter I installed on my 50 watt:
https://www.amazon.com/dp/B07CN2G4GN/ref=psdc_14244481_t1_B07M7NB4BJ
Dan
I guess that’s common with the K40/50W eBay laser.
Not with industrials. Most don’t even have a meter. None of the US RF units have a power. meter, nothing professional does, either.
I was surprised my latest came with one - I asked the vendor why and he didn’t know, but said Americans all wanted them so he was now fitting them 
After reading some of these post, it got me wondering if I was really getting the power I was expecting.
I said I could cut 6mm acrylic at 50% power and 20mm/S. Well that 50% power setting was really like 90% of my tube 23mA. From this, I found a few issues. When I last set my power supply I did this by setting it to give 26mA at 99%. So 50% should be around 13mA, but it was 23mA, something not right. Well, I found that my Ruida is only putting out 4.7V, so the PWM is never going to integrate to 5V, or 99% of that. My LPSU uses the same input for analog control and PWM, this tells me it probably has a cheap low pass filter to change the PWM to an analog control voltage. I bet that the analog output of my Ruida controller does the same thing.
So for a while now my power control was very much not linear or anywhere close. I just readjusted my LPSU to give 13mA out when set to 50% power. This gave me just over 25mA at 99%. I can live with that, but I still want to figure out why my controller is only doing 4.7V instead or 5V.
So the reality is I cut 6mm Acrylic at 23mA and 20mm/S. I dropped to 15mm/S and was at 17mA.
So whats the point of this? There was a comment that % power is somewhat irrelevant, which is true. But you might also want to be aware of your tubes rated power vs current and what you are really getting at different power setting. In my case I discovered that something was wrong, what was wrong might explain why I have been having an issue getting grey scale engravings to work well.
Now another issue pops into my head, I need to know how fast the LSPU integrates the PWM, this will dictate an engraving speed limit, but that’s yet another issue.
I hope the OP got their answer, but there were other good thoughts in here.
Bought a meter, waiting for Amazon to deliver, will update back when they do 
Get one of these, or you’ll always be guessing: https://www.bell-laser.com/product-page/mahoney-co2-laser-power-meter-probe-0-200-watts
I have a Boss LS1420 65w and cut 1/2" acrylic in 3 passes running about 9mm/sec at 90% power.
Please note that my first try I used rubbing alcohol to clean the surface after and it caused the acrylic to shatter fracture. Don’t know why but it crackled just sitting on my desk. I figure the alcohol must have reacted with the acrylic.
Here is a great article with a video to explain what happens…and by the way you figured correctly
That it called “Crazing” in the industry, any alcohol, acetone, ammonia based cleaner will cause this. I would suggest using a spay bottle of water with a few drops of dish soap in it.
Just slightly dampen a cotton cloth with it, if it leaves wet streaks you are using to much.
That is how I clean acrylic on a daily basis.
Added note: use compressed air to blow any dust off before you clean, so you don’t scratch the acrylic.
After some back and forth with the dealer it was the PSU, bought a new one, setting it up today - will update in a little while
If you go to Edit > Machine Settings, then all the way to the bottom in the Vendor Settings area (unfold it) there’s a section called ‘Laser’ and in there are Min & Max power values. It’s possible that the factory set yours to less than 100% to prevent you from nuking the tube.
Hi Oz,
That’s not it, laser setup is all good. I looked at the PWM with a scope and all looks well.
In the end, I now have the LPSU adjusted and the laser is working fine, gray scale engravings are now working well with the laser power being more linear.
Thanks
Joel
Ok, replaced the PSU and… same 
Put a 4mm piece of acrylic, speed 12mm, power 95%… 10 passes to cut a circle and still it didn’t cut through!
Checked the laser tube, there are no cracks or damages… how else to check if it’s damaged?
what else could be wrong?
Stilll waiting for Amazon to deliver my am meter 
What is the Min power setting when you do this?
Sounds like the tube is not outputting what you think it’s outputting.
The only way to know 100% is to test the beam using one of these exactly as @Bonjour suggested above
Cheers
Sasquatch
I set both min and max to 95% just to be sure…
I bought one of these:
https://www.amazon.co.uk/gp/product/B07CZ1MNXZ/
Should arrive in the next 6 days…
@NewbDudey. That’s only going to help you monitor your ability to identify if you are overpowering your laser. You still need to be able to identify that your laser is outputting the wattage you’re tube is ratted to output at. The only way to gauge the lasers true output power is by using the device I and @Bonjour suggested you use. This device absorbs the lasers beam and tell you the exact output power of what your laser is emitting.
Cheers
Sasquatch
@Sasquatch, that’s an expensive diagnostic tool. Maybe I buy one and make it available for rent (with a deposit of course). 
I do want one of those toys for myself though.
