Thoughts on a small dust collection system for my workshop?

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With all of the recent discussion about dust (and the danger of fine dust), I’m hoping to get some thoughts regarding a dust collection system for my workshop.

I’ve seen the Festool CT, which looks good (?) - but it’s expensive, and for some reason you can’t get them in Canada anymore.

What I’m imagining is a small, portable wet/dry vac and a dust deputy. Is this a common setup? One thing I’m not clear on is what small wet/dry vacs come with a Hepa filter. I have been doing research, and it appears as though only the larger vacs can be fitted with a hepa filter?

And I’ve also been throwing around ideas in my mind as to how to make this work for my shop… I have a butchers block type wood table that my Nomad sits on, and I am wondering if I can cut a hole in the table directly under the Nomad, figure out a way to secure the hose to the hole (and perhaps come up with some sort of device that creates a wider surface area of suction that I can attach to the hose and have it sit under the nomad?), and then figure out a way to temporarily seal the Nomad to the table (so I can move it if necessary - so not a permanent seal.)

Thoughts?

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Be careful of the wet-dry vac you get. I have a rigid wet-dry vac and although it can use 0.3 micron filters that are “made of HEPA” material the filter and the vacuum are not HEPA rated. As far as I can tell some vacuums leak air around the filter that is being “sucked” in and that results in the non-HEPA rating. I’m assuming any vacuum that is certified for cleaning up lead paint would have the appropriate HEPA rating for CNC. An alternative to Festool is Fein, but those don’t get as good of reviews on amazon FWIW.

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I don’t think you’d be happy with a shop vac setup. They’re just not made to run for extended times you’d likely have on some milling jobs. You could investigate some of the lower cost dedicated collectors from Delta, Jet, Grizzly, Shopfox, etc. If you’ve got some kind of local woodworking equipment seller go talk to them and see what they have. A number of places have flanges for the sole purpose of hooking up dust collection hoses. If you start getting elaborate and running hoses to different machines then do a little research on restriction and grounding the hoses. Having ungrounded lines can lead to fires and even explosions.

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As I’ve commented elsewhere, something like a Festool is top notch, internationally rated and industrial quality… and while it is good idea to go that way, if you can’t, there are equivalent solutions.

The key is a vacuum element with a HEPA filter rated at 0.3 microns. There are many shop vacs that meet this requirement. The 0.3 micron requirement is what the EPA, UL and EU say is safe (it’s also what a firefighters mask is rated).

NOTE: Ensuring you’ve got a real, safe HEPA filter is a bit of a challenge. The vendors tend to lie (well… it’s just like a HEPA filter; the fine print is that it is HEPA but at 5 microns (which is worthless)).

Dust eventually plugs up the filter and it needs to be replaced. Trustworthy HEPA filters are EXPENSIVE, especially if you’re replacing them frequently.

The solution for that is a cyclone dust separator. Use one ahead of the vacuum element (and it’s HEPA filter) and very quickly one crosses over cost wise (cyclone purchase vs. multiple HEPA filters).

NOTE: Empty the cyclone OUTSIDE, upwind of the canister, put preferably with a mask on. I can point to an inexpensive 3M mask that is appropriate if one wants this information.

So, you’re completely in line with a good approach. How to do this within budget and space requirements is the challenge! :wink:

I’ve seen shop vacs with acceptable, inexpensive HEPA filters here in the States. They need to be rated for long running times. I’ll search around and post what I find. No need for a Festool unless you want to go all out (disclaimer: I own a Festool CT 26 with the Oneida cyclone that mounts on top).

An alternative is to get a shop vac that hoses for in and out. Don’t use the internal filter and make a filter box yourself (wood or plastic, this is pretty easy) that goes on the output. A box, a few fittings and some glue/caulk and you’re there.

Removing the the particles from the enclosure is… a challenge. The conventional CNC approach is a dust head and a vacuum line going to it. Vents in the enclosure to equalize the vacuum (which may not be necessary depending on how “leaky” and “noisy/breezy” a Nomad is when pulling a vacuum on the enclosure.

The STL files for a dust head has been posted recently. Have to learn to glue polycarbonate but this isn’t hard - check out TAP plastics videos on how to do this.

This approach has trade offs - the particles are picked up as they are generated (nasty ones and many of the visible ones (less after job clean up), the vacuum is isolated to the tool pretty closely (you get a bit of cooling), you can’t see the tool because it is inside the brush, one has to go through the enclosure, the enclosure needs tubing fittings, some cleaver routing is necessary for the tubing due to the small size of the Nomad enclosure.

Disclosure: the dust head is my bias. I used it for years and helped many do it this way many times. I will be building and installing on in my Nomad once it arrives (REAL SOON NOW). I plan to post plans, pictures and directions on how I pull this off. How, exactly, I’m going to do this remains open until I can stare at the Nomad for a few hours and test/design/test things.

If one is only interested in the nasty stuff, one could have the vacuum plug from underneath. This requires a seal (“rubbery material”) to isolate the vacuum. This is fairly easy to do. Tradeoffs are: each to do from below, not very hard from the side (at the base), the big stuff is left and has to be sucked up separately, the large and nasty particles are now attracted to underneath your machine and cleaning it exposes the owner and environment, the particles will tend to get onto the guide bars underneath faster.

This approach is, strictly speaking, all that one needs for safety. There is much to be said for this.

My main concern is the accumulation of nasties underneath. The clean cycle exposes the indoor environment to the nasties. The build up on the guides underneath is also a concern but much less so.

mark

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I spent a lot of time looking at small dust collectors and separators. I teach air safety for CNC and know a fair amount about how filters are rated, how vendors cheat, and the EPA rules.

I have a monster large dust collector/dust separator pair - in a garage location. Small machines call for small solutions.

One solution, one that does not require a HEPA filter at all, is to use the EPA rules. If one has a cyclone in front of the vacuum, dump the output air OUTSIDE. After all, 95+% of the particles are gone…

… just make sure it can’t come back inside!

If one can vent outside and not bother people nearby with the noise, this is an acceptable solution. To be nice about it, I would put a 5 micron filter on the output, just to prevent any visible “snow”.

Fein is “so so” to “minimally ok”. Festool is universally praised, albeit somewhat expensive.

Dust collection in the piping, conductive piping, ground wires in the piping, how to clean the pipes and so forth, are definitely issues. Yes, a dust explosion is possible but my back of the envelope says the Nomad is highly unlikely to get enough dust suspended to allow for this.

mark

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I did some looking around and there appear to be several common approaches:

A) Use a cheap shop vac with a HEPA filter.

Who cares if it wears out - they usually last well over a year for hobby usage - just replace it!

B) DIY - se a commercial quality blower - not expensive - and make a HEPA filter box for it.

C) Fein/Festool

D) Aw… what the hell - go for a large, commercial unit.

A shop that I do business with uses A and often has them last for 2 years or so. They ARE sure of their HEPA filters though.

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Try Amazon? Can they ship to Canada?

mark

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How really household vac with hepa differs from shop vac? Sorry for such a question but I really like to hear the answer here. Thanks

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Hi @anton42!

Nothing to be sorry for - this is a good question.

While the air flow rate and depth of the vacuum certainly differ across vacuum devices, there is a factor that greatly affects the choice of a device. This factor is how long is the motor designed to run.

Home vacuums are just not designed to run for hours - minutes usually. Shop vacs are set up to run longer - a hour or so but not much more. Formal dust collectors are designed to run for many hours per day, day in and day out.

Expect to wear out a home vacuum pretty quickly if you use it as a CNC dust collector. A shop vac is going to last longer - a year or two. A dust collector (e.g. Festool CT 26; Fein xxx) can run for hours every day for years and still be fine.

While it is worth it to go with a formal dust collector - certified air safety - they are pricey and out of range, budget wise, for many.

The vacuum element takes air in - causing a vacuum - and spits air out. We do not want the particles in the air to spit out with the air, hence the filters. With CNC, the particles can be very small - too small for the eye to see - and very dangerous to lung safety. We need a filter that removes the nasty stuff or the filter isn’t really doing much for us.

The HEPA filter - 0.3 micron rating - is a standard to ensures that one has the filtering necessary to protect your lungs. The UL, EPA, and EU recognize and accept this; fire fighters masks use HEPA filters.

So, a home vacuum with a HEPA filter is a fast way to go through vacuums. Probably not what one intends. A shop vac tends to be cheap so one goes through them once in a while - as long as the HEPA filter is real and installed so it doesn’t leak - it’s not to expensive or painful.

HEPA filters are… expensive. $60 or $80 is not uncommon. We use a cyclone in front of the vacuum element to remove up to 99+% of the particles before we hit the filter. The cost tradeoff is often rather fast, especially if one machines a lot of wood or Renshape.

The air flow rate and depth of the vacuum ARE factors that are important for particle “lofting” (ensuring they are picked up by the vacuum). It is very, very hard to get acceptable, honest ratings for those for a (home) vacuum; less difficult for a shop vac and easily known for a dust collector.

Another factor is… noise. Our Nomad is designed to be inside the house, one would not be happy with a very loud vacuum element running for hours.

A great deal of math and physics goes into a good vacuum. With a small format machine like the Nomad, we’re not going to achieve near perfection. The good news is we can do quite a bit to ensure air safety. A Festool is cool but we don’t have to break the bank to achieve very good results.

How to design an acceptable system depend on venting - where does the output air go. If one can always dump it outside (and ensure it doesn’t come back in!) the task is much simpler and cheaper than if the air is dumped inside.

Keep asking those questions,

mark

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Thanks Mark!

So what I’ve done months ago with my Nomad at home (sits on the desk inside the room) is taped all the holes near the doors with paint tape. That really helped to prevent wood dust from comming out. I was not aware that wood dust is dangerous but just intuitively wanted to keep it inside.
I did noticed that soft wood chip is relatively large and heavy comparing to hardwoods.

I am using home vac with cyclon and hepa to clean after job is finished. I usually wash hepa filter once a month as it says in the manual.

Just sharing my setup in a hope of correcting my mistakes. I am real CNC noob and Software Engineer by day.

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So what I’ve done months ago with my Nomad at home (sits on the desk inside the room) is taped all the holes near the doors with paint tape. That really helped to prevent wood dust from coming out.

A barrier is a barrier. :wink:

I was not aware that wood dust is dangerous but just intuitively wanted to keep it inside.

Unfortunately this is something that is often missed when learning/doing CNC machining.

Eye, ear and nose protection are all issues. The Nomad is off to a great start with it’s enclosure and spindle - eye and ear protection. The challenge is that the enclosure is filled with nasty particles - nose - and is emptied inside the house.

At a minimum, let the Nomad sit for a few minutes after everything stops moving. That helps the heavier particles to settle. This doesn’t help with the dangerous stuff which are still aloft (most do not come down (which why they are nasty to your health)).

If one doesn’t apply negative pressure to the enclosure - which would constantly remove the nasty stuff - I would advise vacuuming the air first. Open the door slowly and vacuum your way in. Get as much of the air clean as possible before attacking the visible stuff.

The HEPA filter will make sure the stuff you’re removing doesn’t come out the other end of the vacuum. A cyclone provides a lot of insurance that the nasty stuff is removed and extends the life of your HEPA filters.

Ideally, we want that negative pressure… and we don’t need the tape.

That means pulling the vacuum from underneath or from a hole in the enclosure. To pick up more of the particles - as they are generated - requires a dust head.

@FlatBaller posted a very nice one - it even helps cool the spindle! When my Nomad arrives (REAL SOON NOW) I will modify that one or come up with something similar. Either way, I will plan to post all of the parts, where to get them, directions on how to assemble the dust head and the CAD/CAM for it.

If I’m right - I have to stare at a Nomad, in person, for a while and take some measurements - the dust head and tubing will not be too hard to do. The cost will be low too…

I did noticed that soft wood chips are relatively large and heavy comparing to hardwoods.

Softer woods tend to “tear” and “peal” more easily than hardwoods (but there are some hardwoods with interesting properties (e.g. Red Oak)), hence the larger particles. None-the-less, the 10K RPM spindle is generating particles you can’t see, nasty ones. To some extent particle size depends on the RPM, number of flutes, feed speed, material hardness, cooling/lubrication and factors that some thought turns up.

I usually wash HEPA filter once a month as it says in the manual.

The washable ones are nice. They do eventually clog up or wear and need to be replaced… but they last a long time. Remember that emptying the cyclone or cleaning the filter should be done OUTSIDE, preferably with a mask… or stay upwind.

mark

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Wouldn’t it be best to…

  1. Seal any large holes in the Nomad
  2. Include a small blower inside the Nomad with enough air velocity/flow to blow chips from the bit toward a vacuum pickup.
  3. Build a small recirculation loop that pulls air out of the Nomad, through a cyclone (a small Thien type would work fine), then back into the Nomad, dropping the larger particles in a collection bin. This system could be designed to turn on based on a settable duty cycle (on time / off time) so it only runs enough to keep the cabinet from getting to full.
  4. Include a small bleed fan in the recirculation loop upstream of the cyclone to HEPA filter air needed to create a negative pressure in the Nomad. This part of the system could be low enough CFM to not be loud at all.
  5. Let the HEPA loop run for a minute after machining is complete to clear any residual fine dust.

My guess (I haven’t run any numbers yet) is this recirculation loop could have a flow rate well under 40 CFM which means the cyclone could be VERY small. I recently designed a cyclone that achieved 99.7% efficiency with just a 7" dia x 12" tall footprint and that was for a 140 CFM flow. For reference, a Dust Deputy was only 0.1% better and twice as tall. I believe I could design a system for the Nomad using a much smaller footprint using a much lower flow (less noise) pump. Making it intermittent would make it last much longer even with an inexpensive air pump.

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  1. Seal any large holes in the Nomad

Specifically, seal enough such that a good negative pressure is maintained without too much noise. Small cracks tend to “whistle” and drive one nuts. In the worst case, drill extra holes.

The rule is to have as much area for air to come in as for air to go out.

Not having taken possession of my Nomad yet and designing the vacuum system for it I can’t yet say what, specifically, is necessary.

  1. Include a small blower inside the Nomad with enough air velocity/flow to blow chips from the bit toward a vacuum pickup.

Designing a vacuum for CNC is a complex business. I’ll leave the details out for now; we can descend into the details as necessary.

It’s not only about vacuum, it’s about air velocities and low turbulence. The turbulence of a separate blower will most likely defeat the effects of a properly designed vacuum system where the vacuum is close to the milling.

The best air flow to ensure particle lofting is a big vacuum with plenty of air velocity… nothing else. This is well established physics.

I’ve pointed out elsewhere that a properly confined vacuum may benefit for additional help like the propellor designs others have be experimenting with.

  1. Build a small recirculation loop that pulls air out of the Nomad, through a cyclone (a small Thien type would work fine), then back into the Nomad, dropping the larger particles in a collection bin. This system could be designed to turn on based on a settable duty cycle (on time / off time) so it only runs enough to keep the cabinet from getting to full.

A Thien dust separator is a low cost, less efficient design than a cyclone. They are easy to build and MUCH BETTER than nothing. They are rarely more than 85-90% efficient and it is hard to build them such that are very good at preventing the smallest, nastiest particles from passing through. On a really tight budget, the Thien design is the way to go; anything else go cyclone.

The reason to NOT use a duty cycle - continuous vacuuming - is that particle creation is continuous. Designed properly, the vacuum and high air velocity will loft not only the small, dangerous particles but any particle created by the machining.

Many woods, especially hard woods and tropical woods, contain viruses and volatile chemicals that also serious health issues. We want to collect as many of these as possible, and minimize our contact with them. A close loop will concentrate these nasties in the enclosure and loop.

No commercial systems I know of, nor any system I’ve designed or used is a closed loop. It’s just too hard. We’re not designing to handle Ebola in a level 4 isolation room. Open ended is much easier, much cheaper, and more than satisfactory. The EPA only discusses open ended systems.

A duty cycle definitely makes sense if all one is interested in removing the small, nasty particles.

  1. Include a small bleed fan in the recirculation loop upstream of the cyclone to HEPA filter air needed to create a negative pressure in the Nomad. This part of the system could be low enough CFM to not be loud at all.

Turbulence disrupts the effectiveness of vacuum generation and practical transport. Fan blades are some of the worst things one can use. Sorry, this is the physics of it.

Effective lofting of particles requires a fairly high air velocity. Low speed air flow is MUCH BETTER than nothing.

  1. Let the HEPA loop run for a minute after machining is complete to clear any residual fine dust.

This is most certainly a necessity for safety. I’ve stated the need to do this in several places. :wink:

mark

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I have designed, built and tested cyclone and laminar flow hood systems. I understand the physics required, including flow velocities needed for efficient particle separation and the nuances related to flow velocity and particle removal. The way I look at it, the goal of this group is not to design a Class 1 clean room… its to improve a desktop CNC at a price point that is attractive enough that people will actually use it.

My cyclone design is more compact than a cone cyclone and is only 0.1% less efficient which wouldn’t matter for a recirculating system. It also has a much lower pressure drop for any given flow rate.

A one or two CFM negative pressure HEPA system would work on a system as small as the Nomad. It would be essentially silent compared to the Nomad itself. There wouldn’t be any noise issues to speak of.

From a safety standpoint, a 1-5 CFM HEPA system would be enough if the user didn’t need something to clear debris. Connecting a very small/cheap blower to a hole in the wall of the Nomad and into a prefilter and a HEPA filter would work fine for that.

The return on the recirculation could be used to clear the chips from the bit.

Its easy to overthink these things. Its important to consider that 95% of Nomad users won’t use any kind of filtering system nor will they be seeking EPA approval. What is needed is a simple, cheap, small, practical system that people can afford and that they will see enough value in to use.

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If you are going to modify your Nomad, make sure it gets all the big chips too. Having to clean it after each job when you already are cleaning the air is kind of silly. Using the design I posted, you can build a very functional dust head for under $25. Just add your own vacuum source.

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One concern about “big stuff” — ensure that it can’t come free and jam the machine, possibly breaking a bit or worse.

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The dust head solution is a well known, well understood and effective solution. @FlatBaller has a good solution.

With a good vacuum and brush on the dust head one will be removing the particles, nasty and larger as they are generated, solving the dust accumulation and air safety issues at the same time.

The open loop approach also solves the need to seal the Nomad tightly. It proves negative pressure to keep everything in. Yes, I may make sense to caulk up a few places to improve the vacuum; I have to play with a Nomad to be sure about this.

mark

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The “big stuff”, in this discussion, are particles one can see.

@WillAdams is pointing out that one must be careful about confining pieces from moving when they are cut. That is ALWAYS required. Anything that can come loose during cutting may go flying, ruin the finish, damage a tool or cause untold damage.

mark

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Well, I got a bit over-ambitious about what I could do with my Nomad over the holiday weekend. Replacing the bed ended up being more than I could manage, but I did put together the first iteration of my dust-collection system.

Basically, I picked up a Fein vacuum (as linked in a previous post in this thread) – I just couldn’t swing the price of a Festool, and frankly I just don’t use the Nomad enough to justify that. I also picked up a Dust Deputy, and some hoses and odds and ends. So, voila! (apologies for the Portrait orientation)

IMG_20151129_182155974.jpg2340×4160 2.08 MB

IMG_20151129_182204088_TOP.jpg2340×4160 1.69 MB

I wasn’t trying to do anything as ambitious as FlatBaller’s dust collector on the head – I mainly just wanted to maintain some negative pressure inside the enclosure. So the Fein connects to the Deputy, which just connects to a ShopVac utility grommet that I mounted to the back wall of the Nomad using a 2.5-in hole saw. The clear plastic tub under the Deputy is a pet food container with an “airtight seal” around the lid – I wanted something smaller than a 5-gallon bucket, for when I have to empty it.

So, then I put my prop-nut on for maximum air turbulence, and sent my .250" flat fill to planing down a 5"x8" piece of pine lumber. While doing this before, I had definitely noticed some bronchial irritation and a definite smell of wood dust filling the room. This time, nada – sitting right next to the Nomad, I couldn’t smell a thing, and no lung irritation at all. In fact, there’s probably not enough airflow – there’s a definite “suck” when I pop the door a bit, and the sawdust near the door jumps back towards the vacuum port. I might need to prop the door open just a tad.

The downside: while the vacuum is handling the floating dust, the visible-size sawdust is still (50% or so) settling inside the Nomad. Which I mostly expected, at this phase. The bigger problem is the airflow noise – when I used the Fein by itself, it was actually quieter than my normal household vacuum. But after adding the Dust Deputy, the airflow noises got so loud they drowned out the Nomad’s milling noses, and could be heard a few rooms away. Definitely an issue for watching TV while the system is running.

What I need to do next:

  1. trim down the hoses – they’re much longer than I need, right now.
  2. Try out the system without the Deputy – I know, it’s bad for the HEPA filter, but at these noise levels, I may not have a choice. Or maybe there’s other noise-reduction possibilities?
  3. How important are static-grounded hoses? I’m just using regular ShopVac hoses, right now.
  4. Look at how much work would be involved in adding on FlatBaller’s head-mounted vac box
  5. Find a simple way to branch or quick-connect the vac hoses so I can free up the Fein to hand-vacuum out the resting sawdust when a cut is finished.
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Nicely done!

  1. trim down the hoses – they’re much longer than I need, right now.

Shorter is better as there are frictional forces - to the air flow - against the walls of the tubing.

  1. Try out the system without the Deputy – I know, it’s bad for the HEPA filter, but at these noise levels, I may not have a choice. Or maybe there’s other noise-reduction possibilities?

It is pretty easy to kill a great deal of noise via a box lined with Whistermat. Even 3/4" of the stuff can drop sound levels by 20 dBa or more.

Can you get an app that shows the dBa and the spectrum of the noise? If the noise is strongly unimodal, we can use a Helmholtz resonator to kill the noise. They are easy to calculate and build.

  1. How important are static-grounded hoses? I’m just using regular ShopVac hoses, right now.

Important. That said, you don’t need conductive tubing. You do it yourself. Run a copper wire through the tubing and out to ground.

  1. Look at how much work would be involved in adding on FlatBaller’s head-mounted vac box

It’s a very nice design. @patofoto and I are close to releasing a alternative design that one can try too.

Directing the vacuum to the work site will pick up most of the visible particles. Remember to let the vacuum run for a few minutes after the job is done to drain off the nasty, invisible particles.

  1. Find a simple way to branch or quick-connect the vac hoses so I can free up the Fein to hand-vacuum out the resting sawdust when a cut is finished.

Definitely something worth doing. I pop the Festool at the machine and plug in a different tube - with brushes and such to clean up.

The bigger problem is the airflow noise…

Hmmm… that is a bit unusual. Given your report about a serious negative pressure in the enclosure, I think a fair amount of the noise is due to not enough air getting into the enclosure.

I expect to create some holes when I mount my dust head. The area of the holes should equal the area of the tubing.

mark