. For a cyclone I currently have cheap Chinese ‘knock-off’ which seems to work pretty well with my shop-vac.
Virtually all shop vac are crap when it comes to filtering. They get the big stuff and let the nasty stuff through. That you have a cyclone is a real plus.
Cyclone dust separators vary in efficiency. Any reasonably designed on is going to remove 90+% of the particles and virtually all of the larger particles. The small ones are harder to catch and so some get past. Better cyclone, better particle catch. Regardless, no cyclone can come close to 100% for all particles sizes.
The Thien Baffle is an alternative to the cyclone. It is remarkably efficient… but as good as a good cyclone. It’s main advantage is that it is nearly trivial and inexpensive to build.
The cyclone is removing a HUGE amount of the problematic stuff, reducing your exposure. Since the risks are cumulative, you’re doing a great job reducing your risks.
The output of the cyclone could be dumped outside (where humans aren’t) and you would be done. No exposure! All that is necessary is a 5 micron filter (essentially an easy to clean cloth bad) to prevent “snow” below the exhaust port.
The output of the cyclone inside (where humans are) is where things get dicey. The cyclone can only do so much and the nastier stuff is the stuff most likely to be released. We need a better filter. This is where the 0.5 micron rated HEPA filter comes in. This ensures that the nasty stuff is caught, that the exposure risk is lowered to extremely low levels.
My reason for looking at the 'Ultimate Dust Deputy" is because just recently I brushed by my dust hose when the CNC was cutting MDF, the hair on my arms and legs stood up as a result of the static buildup. I know that static and dust is not a good combination.
Anytime particles move in air, especially when they are hot or chemically active, they generate electrical charge (static). This can build up until a discharge and fire and explosion are possible. The explosion risk is pretty small for the machines where talking about. Fire is an issue.
There is another danger… discharge into your dust collector. Today, many dust collectors use microprocessors and they don’t like static. The original Ultimate Dust Deputy for the Festool (long since replaced with the current model) was made of a plastic that generated static and they regularly destroyed Festool CT series dust collectors.
Needless to say, Oneida and Festool quickly figured this out. They offered retrofit kits for the existing machines and redesigned to use static dissipative plastic.
I admit bias, I have one, and I too say that these are excellent devices.
To solve machining static, one must start with a solid ground. The dust collector must be grounded. The dust separator must be connected to the dust collector AND ON THE SAME GROUND. With small tubing, static dissipative tubing does the job. Static dissipative tubing can be expensive; it’s a bit of a luxury item in that it takes care of things (“one stop shop”).
There is an alternative way to solve this… bare copper wire through the tubing. Make sure it’s not “magnet wire” or covered in varnish. Bare. Run the wire through the tubing to the same ground as the dust collector. If you dust separator is metal, ground that too!
Do not run the ground all the way to the CNC machine… this can create a “ground loop”. Start at the enclosure (or dust head) and run the wire all through the tubing to the same ground as the dust collector.