Hi,
I have had our omtech 50w engraver for about a month and we have started to try acrylic engraving. Unfortunately no matter what speed/ power we use we seem to get little dots around the engraving, picture attached.
Material: Cast Acrylic (also does it on non cast)
Speed: 600
Power: 20
DPI:300
Material has a small layer of dawn soap before engraving
wow, thank you for your reply. that looks like a **** show! not sure what to do about this problem I would really like to do acrylic but changing a power supply that might fix a problem seems quite extreme, especially as the machine is a month old!
It’s very clear on the scope that the signal to lase isn’t active, but it’s lasing anyway. This can only be the lps. You could confirm it with a scope…
I wish I knew some other option. Ed thinks it’s just poor supplies that are lasing when they shouldn’t.
It’s possibly something else, but I doubt it…
If it’s only a month old, I’d go back to the vendor… A month out, and it’s already failing, isn’t a good sign as they generally don’t get better…
See if the vendor will replace the lps… all they can say is no.
Good luck…
in the light of trying, we masked up a piece and engraved it…and no dots? bit of a pain to mask the acrylic up and very strange but that seems to do the job. It does seem to be bouncing the laser, is there alternative ways to make the surface less reflective without using masking tape?
Thanks for your help btw! 
There is no reflectivity from masking tape… You are doing the same thing, it’s not penetrating the masking tape.
You don’t want reflectivity. It can/does damage the lens… I lost one of mine that way.
The masking material absorbs enough energy to prevent / reduce damage in the acrylic, so there’s no visible spot. If you examine the mask very carefully, you’ll find spots.
However, those random pulses extend far beyond the tube’s normal operating power, so some will punch through any masking material you can imagine: if the mask completely shielded the acrylic from the speckles, the normal beam wouldn’t cut through. A mask layer can certainly reduce the number of speckles, but won’t eliminate all of them.
Aaaannnnd a new supply probably won’t solve the problem, because so many people report random spots that (IMO) they come from the power supply design, rather than a manufacturing error.
And there is no guarantee that you will not have the same problem with the new power supply, I have had the same problem since my machine was new.
No, but it’s the only shot you have.
We know the lps is lasing when it shouldn’t.
Crap shoot?
No, certainly not. If you absolutely need a completely clean result on glass, acrylic and mirrors, this is an option. You can also buy 2 new lps - so you have even more chances … 
Does anyone know if it is “only” a problem with the “cheap” CO2 laser machines, or do they have the same problems with the expensive machines?
IMO:
Bottom line: as with all engineering problems, optimizing any single feature makes other problems worse. Injecting enough money lets you optimize any two features, but the relationship is definitely not linear.
As the Prophet Morgan said: If you must ask how much it will cost, you can’t afford it.
Which explains why nearly all of us have (relatively) low cost lasers shipped halfway around the planet … 
I really rarely see this issue. It a small percentage of the people have this occur… I don’t have it and there are really limited posts about it compared to other issues I see.
If you fix anything, you can see @ednisley has diagnosed and absolutely confirmed that his machine is lasing when the signals tell it not to. The only possible oru is the lps.
There are probably millions of people doing acrylic on these, with relatively few people complaining about this issue…
Add to this, the fact that these manufacturers make millions of these, they are bound to have some that do not come up to standards. These are sold off and the consumer get a new product… never aware it did not pass testing at the factory… They get it cheap, and sell it to you cheap … but it’s still new.
I’m clueless where any of the components came from that are in my machine…
I think buying anything from China could and has ended up worse than a crap shoot.
Opinion, of course everyone has one 
I think most people just don’t notice the problem or it’s not a problem for them, it’s fine for them (and me). I have had the problem with both of my CO2 machines. (Primarily when I make mirrors in acrylic)
As far as Chinese product quality is concerned, it depends on who places the order and what people want to pay. I don’t know how it is across the Atlantic, but here all the electronic hardware comes from China, including Apple’s phones and all their other products. China delivers everything in the quality and at the price that the West accepts and pays for.
Even not-cheap lasers produce speckles:
Apparently those “Call for a quote” machines have better supplies.
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