In my experience most people go with what has worked best for them in the past.
As I travel around the country and visit manufacturers who have used mist collection, it’s not unusual to see a variety of different kinds of mist collectors from different manufacturers in the same building. Was it a case of “that didn’t work, try this” or was it the flavor of the week.
There’s a variety of mist collection equipment available: media, centrifugal and electrostatic precipitators being the most popular.
The question is what works best for “my” application. There’s not an easy answer to that, however. Each application can be different. Different cutting oils, pump pressures, materials, speeds and feeds, and cavity size all can play into what will do the best job.
Then you have to decide on how much maintenance do you want to endure. There are media filter style collectors that will need to be serviced a few times a year, and other media types that have long life filters that don’t require as frequent a service interval. There are centrifugal separators that require periodic pad replacement and could require drum replacement if they go out of round, causing the machine to vibrate which may transfer to the machining center. As for electrostatic precipitators, they require periodic cleaning to maintain peak efficiency.
In my mind, for most mist applications especially those with high pressure mist, electrostatic precipitators work well. I’ve seen applications where a double pass or triple pass electrostatic can handle up to 2000 PSI with oil or water soluble coolants. Even very light oils for high speed grinders are collected effectively with an electrostatic.
Here are some mist collectors to consider.
Electrostatics can also be effective on smoke, but there may be applications, like heavy hogging, where a post filter may be considered. Check with the manufacturer before applying one to this application.
Another application that electrostatics seem to do well is on EDM smoke. There are many sinker and wire EDM applications where you can draw the smoke over the bed of the dielectric fluid and collect it effectively. If you’re using kerosene fuel as a dielectric, caution should be used with any collection device, but I hope you’re not using kerosene. Depending on you dielectric, there can also be an odor that gets released. Many collectors have a carbon after filter option that can solve that problem.
Bag collectors will work with low pressure applications where pump pressures are in the 50-200 PSI range. Higher pressure applications may require multi-stage filters for maximum efficiency. I have also seen bag type mist collectors work well on Blanchard type grinders so long as you can capture the mist. The collection hose needs to be draped over the guard in many instances, but it can be accomplished.
Here are some bag collectors to consider.
Long life mist filters generally have a fairly high efficiency but still may not “get it all”, and need a post filter. One manufacturer makes their systems with a standard HEPA post filter which makes them expensive to buy. And replacement filters, when they come due for replacement, are also very expensive.
The bottom line is that for any mist collection application, there may be several ways to solve the mist collection issue.
Make sure to touch base with a qualified distributor if you’re unsure which way to go.