Thread: Building better dust extraction

Originally Posted by mic-d

Stage 2 will be to connect all the ducting together to make 2 drops from the ceiling. One with 3 x 4" gates to service the combo machine, the other with one 4" gate to service the bandsaw or drum sander. I will be fitting one hose permenantly to the saw cabinet and one to the overhead guard ( which currently doesn't have DE capability, but I bought a 3" flange to fit to it) the other will have a quickfit coupling to use in jointer/thicknesser mode or on the spindle moulder. 8" duct will run up to the ceiling and a short way across then branch for the first 5" drop and reduce to 5" for the run to the other drop. l

Before you get fixed on these duct sizes you might want to have a think about what Bill Pentz says.

Bill recommends a minimum of 28 sqin of collection area (ie a 6" diam duct) to catch the dust from any single action ie one action on one machine. That is the minimum cross section that will provide the volume and air speed needed to catch the dust from a single dust making activity.

3 x 4" ( 37 sqin) drawing from a TS blade is OK, but 3 x 4" ducting to separate parts of a combo machine is not.

1 x 4" to either the bandsaw or drum sander is definitely not OK.

even 2 x 4" (ie = 25 sqin) is not considered sufficient onto one action on one machine)

1 x 3" + 1 x 5" (ie = 27 sqin) is considered borderline and is the minimum he uses.

It seems such a shame to run 6 and 8" pipe around the shed and then hobble every inlet to a 4" duct. I'm completely revising my DC set up in light of this information.

Pretty much am fixed on those sizes Bob as I already bought it. The dust extraction engineer did all the calculations and selection for me, I defered to his greater wisdom. Don't really see what else I can do given I have one 4" outlet on all my machines. The tablesaw has one on the cabinet and soon to be one 3" on the guard, can't do 4" on the guard. The jointer thicknesser has one 4" shroud, the bandsaw and drum sander all have one 4" outlet. They are all pretty much hobbled by design, according to Bill's doctrine. I go up to 5" asap and 8" asap. Don't know why he chose 5" over 6", perhaps it is because my dusty would have marginal velocity with a 6 and 8" combo. I don't really know and to be honest, it's got to be an improvement over what i got at the moment.

Cheers
Michael

Originally Posted by BobL

Before you get fixed on these duct sizes you might want to have a think about what Bill Pentz says.

Bill recommends a minimum of 28 sqin of collection area (ie a 6" diam duct) to catch the dust from any single action ie one action on one machine. That is the minimum cross section that will provide the volume and air speed needed to catch the dust from a single dust making activity.

3 x 4" ( 37 sqin) drawing from a TS blade is OK, but 3 x 4" ducting to separate parts of a combo machine is not.

1 x 4" to either the bandsaw or drum sander is definitely not OK.

even 2 x 4" (ie = 25 sqin) is not considered sufficient onto one action on one machine)

1 x 3" + 1 x 5" (ie = 27 sqin) is considered borderline and is the minimum he uses.

It seems such a shame to run 6 and 8" pipe around the shed and then hobble every inlet to a 4" duct. I'm completely revising my DC set up in light of this information.

Originally Posted by mic-d

Pretty much am fixed on those sizes Bob as I already bought it. The dust extraction engineer did all the calculations and selection for me, I defered to his greater wisdom. Don't really see what else I can do given I have one 4" outlet on all my machines. The tablesaw has one on the cabinet and soon to be one 3" on the guard, can't do 4" on the guard. The jointer thicknesser has one 4" shroud, the bandsaw and drum sander all have one 4" outlet. They are all pretty much hobbled by design, according to Bill's doctrine. I go up to 5" asap and 8" asap. Don't know why he chose 5" over 6", perhaps it is because my dusty would have marginal velocity with a 6 and 8" combo. I don't really know and to be honest, it's got to be an improvement over what i got at the moment.

I agree that any small improvement is better than no improvement.

The 4" outlets on most machines really hamstring the fine dust collection performance of 3HP units and short of rebuilding the outlets, which is not always possible, there seems like there is nothing we can do. If a machine only has one 4 " outlet then adding an additional 4" flexy inlet, in the close vicinity of the dust making section of the machine being used will help catch some fine dust dust before it is sprayed all over the shed. In some cases it will be easy to do and it will be highly effective - for example adding a 4" flexy so the outlet is attached close to the top blade guides is a good decision. The blade going down into the wood pulls some air down with it. The air hits the top of the wood and circulates back upwards carrying invisible dust with it. Having a 4" inlet just at this location will grab that dust before it moves out into the room.
Bill Pentz shows this one on his ducting page - Bill's Cyclone & Dust Collection Research - Ducting

On a thicknesser, an extra flexy inlet immediately above and behind the fence near the blades is useful. When I use my DP to drill a lot of holes in MDF I hook two x 4" ducts either side of my DP table. I don't care all that much about the big chips it's the fine dust that I want to minimize in my shed.

I'm in a similar position to you, lots of 4" flexy and all of my machines (except for my bandsaw) having 1 x 4" outlets. My TS is just a contractor saw and I made the dust catcher under the saw from ally sheet so it will be easy to expand the outlet from 4 to 6" . My band saw has two 4" outlets so for the short term I plan on using the above solution but the 4" outlet underneath the table has enough room to modify to make a 5" outlet. For my thicknesser I will eventually bite the bullet and remake the shroud.

Originally Posted by BobL

I agree that any small improvement is better than no improvement.

Thanks for the backhanded compliment Bob. IMHO it's already a massive improvement. The noise level alone has reduced considerably by changing vacuum cleaners and boxing in the dust extractor, not even completely yet. Once the exhaust duct is in it'll be even quieter. Replacing the 5-odd metre run of inefficient 4" flex with shorter more direct runs of larger diameter duct can't help but improve the work flow efficiency and safety of my workshop. Exhausting the dust outside allows the dusty to work as an air cleaner too, up to this point I have had to rely on the vagaries of the wind. So now I can pull nice clean air, laden with super fine particulates from the road into the workshop instead. I'm not aiming to create a clean room and I'm not aiming to rework machinery that should have been designed better. I just want to do woodwork and be left in peace.

Cheers
Michael

Disclaimer
It may be construed from the title of this thread that I am giving advice on how to build better dust extraction. This is not the case. I should have titled it, 'Improving my dust extraction system'. The story and photos should only be considered as a WIP not a guide for how to setup dust extraction. I make no claims as to the adequacy of my system and none should be inferred. The information may contain errors, problems or other limitations.
Hopefully that keeps the dust extraction nazis happy.

RE: I agree that any small improvement is better than no improvement

Sorry if that sounded like a backhanded compliment and I didn't mention your major improvements, but I was making a general comment for anyone working on dust collection

I agree the noise issue is significant and if the DC cannot be located outside then and a housing inside the shed is worth doing. This is definitely worth doing as long as any housing inside the shed is made air tight.

Venting DC to outside, I agree, another definite major improvement.

Replacing 5 m long 4" ducting runs with larger diam pipe and then reducing that to a single 4" intake connection on a machine is in the small improvement category (and is the one I was referring to in my previous post) but still worth doing because if you decide to upgrade the machine outlets you already have the other ducting in place to do this.

G'day Michael,
Thought I might add my experience with dust collection to the mix...

A while ago, I made up a clear blade guard (how do you find working with you black one?) with a 4" port on top which picks up the vast majority of blade dust and keeps the area much cleaner. Keep the 'vast majority' bit in mind, though. I'm don't think it's possible to get every last particle, so even if my workshop was big enough to use my saw inside (I drag it out on its wheeled base and work in the breeze), I wouldn't without respiratory PPE.

My old man has the saw in the picture below. It's a great machine, except for the laughably inadequate dust port on the blade guard. I don't recall the specifics, but the port ID is probably 45 to 50 mm, at best. Hooked up to the second port of his 2h Hp dusty (with the other to the saw base), the blade guard port simply did not suck. Mr Pentz appears to be right on the money regarding minimum practical port sizes.

I second Bob's motion regarding venting your dusty outside the workshop if at all possible.

Cheers,
Mick

I will be adding some clear windows to my guard.
I will be exhausting the DE outside.

Originally Posted by BobL

RE:

I agree the noise issue is significant and if the DC cannot be located outside then and a housing inside the shed is worth doing. This is definitely worth doing as long as any housing inside the shed is made air tight.

Bob, why does it need to be airtight if the exhaust goes outside the housing?

DE extraction in a workshop starts at the machines before anything else. All the ports need enlarging to 150mm or at the minimum two 100mm ports into one 150mm line, for instance a 100mm line from the TS cabinet, another from the TS guard and Y join both together into one 150mm. While this does not quite equal one 150mm it goes close enough for all practical purposes.

Overblade guards are a pain. The best one is generally acknowledged to be the Shark Guard LeeWay Workshop, LLC -Shark Guard System but I like this one ZCI vs Dust Collection.

The reason I like the second one is quite simple, it addresses what I think is a problem for most overhead guards and that is airflow INTO the guard. Like all DE the air must be replaced and most if not all guards lack in this area. If we have a 100mm line pulling air out of the guard then we need an equivalent amount of air going in or we have no air flow and that little point is what most miss. No air flow means the dust drops out of suspension and drops on the table and once it is there then it stays there as a rule.

Most guards sit down tightly on the timber being cut so as the timber is fed in the inlet air is cut off because the air has no way of entering the guard, I am sure you get the idea. The second link above has at least some potential to allow air to flow in through the bristles and they also containing the sawdust. I will in the future, not right now as I just have not got the time make a guard with two 100mm pipes on it to create a very high air flow through the guard, one acting solely as an inlet. The problem of course is designing it so the whole thing does not become too bulky and unwieldy but I think I might have that sussed out. The inlet capacity only has to equal the exhaust side, it does not have to be round or any specific shape.

As for the guy who designed the system I might point him to BP's site and have him re-assess his thinking. I have some reservations about BP's site, it is so loaded with info that it makes what should be relatively straight forward decision appear very hard and I for one gave up on it for a long while due to information overload. I have repeatedly gone back there and slowly absorbed what he has written and it is all good stuff. Everything we need is in one place but I can see the problem it presents to Bill, a huge amount of information like this is difficult to present and he most probably has got it as good as it gets without spending huge amounts of money.

Modifying the machines is mostly fairly simple but some do present problems like bandsaws but then a bandsaw requires two extraction points so that works out. I suppose the hardest thing to do is taking a drill, grinder etc to something that cost a lot of money but in the end it is only rectifying a problem that should have been addressed in the first place and if you sell it then the next owner should see that as an advantage and thank you for it.

The hardest problem of all is attaching dust extraction to a machine that was never designed for it. Both my jointer and thicknesser are very old machines and luckily someone had done the work before me. All I had to do was enlarge the outlets to 150mm which was an easy task. making the pickups in the first place must have taken a fair bit of thinking about and I am glad I did not have to do it.

Originally Posted by Mini

Bob, why does it need to be airtight if the exhaust goes outside the housing?

If it is not airtight then contaminated air from the DE will bleed back through the holes into the workshop. My cabinet will be airtight by and large, but it seems like a moot point given that my collection system as designed by a leading woodwork machinery company will be farcically inadequate.

I think you are going to have problems. The heat rise from the motor and the heat generated by the dust collection action is going to create a very hight temperature in the cabinet. The actual dust collection process does produce heat, quite a lot of it which is a hidden gotcha for most people. In a high ambient temperature which you will have in summer it won't do the motor any good especially with all the dust floating around from the bags. I guess you are trying to contain the dust that escapes from the bags? I don't see any way to do that in a sealed area and stop the temperature rise. Yes I do, use an heat transfer method and some fans on it, getting fairly complicated, at least for most people though.

Originally Posted by mic-d

If it is not airtight then contaminated air from the DE will bleed back through the holes into the workshop. My cabinet will be airtight by and large, but it seems like a moot point given that my collection system as designed by a leading woodwork machinery company will be farcically inadequate.

You only have to look at the ports in the machines to see that the manufacturers either don't know what they are doing or don't care or perhaps both, they only pay lip service to our DE needs at best.

Originally Posted by Mini

I think you are going to have problems. The heat rise from the motor and the heat generated by the dust collection action is going to create a very hight temperature in the cabinet. The actual dust collection process does produce heat, quite a lot of it which is a hidden gotcha for most people. In a high ambient temperature which you will have in summer it won't do the motor any good especially with all the dust floating around from the bags. I guess you are trying to contain the dust that escapes from the bags? I don't see any way to do that in a sealed area and stop the temperature rise. Yes I do, use an heat transfer method and some fans on it, getting fairly complicated, at least for most people though.

Rubbish.
1) I don't have bags I have pleated filters. Not that this relates to your current argument, I just want to point out that I am getting sick and tired of people not reading posts carefully.

2)The motor has a fan for cooling, this fan takes air from nearby the motor and forces it over the motor. The air nearby the motor is a pool of air inline with the dust extraction system and is therefore continually being replenished from the air in the workshop, at workshop temperature, and then exhausted . The very same air that up until recently bathed the DE without a cabinet wall in between. Do you not see it is not a closed system? Even if there is a temperature increase due to the dust making activity, the duty cycle of most machines/operators is such that a large proportion of the time the DE will be sucking and no activity will be carried out. Any warmer air from a work cycle will be very quickly purged.
There is no cooling issue.

Originally Posted by mic-d

2)The motor has a fan for cooling, this fan takes air from nearby the motor and forces it over the motor. The air nearby the motor is a pool of air inline with the dust extraction system and is therefore continually being replenished from the air in the workshop, at workshop temperature, and then exhausted . The very same air that up until recently bathed the DE without a cabinet wall in between. Do you not see it is not a closed system? Even if there is a temperature increase due to the dust making activity, the duty cycle of most machines/operators is such that a large proportion of the time the DE will be sucking and no activity will be carried out. Any warmer air from a work cycle will be very quickly purged.
There is no cooling issue.

I don't think mini understands how this type of enclosure works as there is no cooling issue with these enclosures. There volume of air flowing through the cabinet is the same as that flowing through the dusty. This amount of air can carry a lot of heat. I run my DC in an enclosure that vents to the outside sometimes all day in summer