Thread: Advice on opening up machine ports

Originally Posted by DoctorBobski

Anyway, to my question. I'm going to be running 150mm main pipe for my ducting and I have read here I should open up the ports on my machines to 150mm also. I have been thinking however, some of my machines wouldn't have enough inflow to pull that much air. For example my table saw. The airflow is only pulled through the slot around the blade and also through a few slots near the motor. I'm not sure if I'm understanding airflow right but isn't it pointless to open up the port as the restriction will still be the space around the blade?

Yep it is somewhat pointless which is why you may also need to get out the angle grinder or nibbler or plasma cutter and cut some extra holes in the cabinet. Ideally these should be done to create a cross flow across the dust entry point. These can be done with care and coarse grilles can be place across these openings so that enquiring fingers/hands don't explore these openings. If grilles are used then the holes need to be correspondingly larger to ensure sufficient air can still get through.

In this example on my BS the opening at the top LHS creates a cross flow through the entire cabinet and feeds out at the bottom right hand corner (the port cannot be seen as it its behind the machine). This works very well and there is very little saw dust left in the cabinet.

The other duct that is visible in the picture is supposed to clear the bottom blade guides but that is near useless which is why I jam a third 100 mm piece of flexy up under the table and draw dust directly across the blade/guides at that point.

Am I not better off making a dust extracting blade guard above the table with as big a port as I can make (100mm?)and add that to the cabinet port making 2x100mm ports? Should I then have another 100mm port open to ensure flow along the 150mm duct (making 3x100mm inflow)? Same goes for my bandsaw. .

In terms of collecting fine dust you are better off cutting holes in the cabinet and tackling the dust at source if you can.
However I would still recommend a minimum of 100 mm ducting for a TS blade guard
3 x 100 mm ducts (~400 CFM each) are needed to equate to one x 150 mm flow (~1200 CFM) but the air speeds will be so fast in 100 mm ducts that you can use 4 x 100 mm (4 x 300) and sawdust will not fall out of suspension.
Likewise 1 x 150 mm (800 CFM) and 1 x 100mm (~400 CFM) will also work.

I have recently purchased a mobile 3hp Carbatec UB-3100 cyclonic dust extractor. Yes, I know I should have got a clearvue but I wanted something mobile with a filter as I don't have anywhere I deem safe to extract outside (only over my kids play area) and I also occasionally move my machines.

The filter on the CTC is very at removing fine dust but it does eventually reduce the flow rate so regular cleaning and emptying of the dust bin is required, even if the dust bin is not full. This is a real benefit of venting unfiltered cyclone air outside - not to mention the noise.

One issue with the CTC is that they are older designs and so they generate more back resistance to flow and they won't filter the dust as finely as a Cleavue. The other issue is moving DCs around invariably leads to leaks. I have not see a single mobile DC that has not had a leak. I assume this is because they get "bashed about" during moving. I know this is not possible for many folks with limited shed space but for those planning a new shed this is something to bear in mind.

RE the issue about "venting outside over the kids play area": moving air and fine dust through a DC raises its temperature which means that when it is pumped outside it is usually warmer than external air and so it will rise. If possible this can be aided with the use of chimney . The slightest breeze rapidly dilutes the warm dust so overall the risk will be very low most days of the year. The only time when this would not work is if there was an atmospheric inversion but that is usually only a few days a year in most places.

Thanks Bob! Interesting about the extracted dust rising. That hadn't crossed my mind and I didn't come across it in my research. I might have gone for the CV had I known. No going back now though and I think the Carbatec is going to be a huge improvement to my old 1hp fabric bagged chip extractor. I'll certainly be minimising any movement of the extractor now. Thankfully it only has to happen when I breakdown sheet goods on the table saw. Might be able to make an argument for a tracksaw now (but honey, the dust extractor might leak if I move it, the tracksaw means I don't need to).

Would there be any sense down the track in trying to rig up some pipe from the bottom of the filter to the outside of my shed? Or even getting rid of the filter and porting?

Watching with interest, especially the bit about venting the dusty outside.

I know it should be self explanatory, but would you have any photos of how others have ducted up an external vent whilst maintaining rain protection, etc? There's an external window right next to my dusty, if I had more ideas...

Originally Posted by DoctorBobski

Thanks Bob! Interesting about the extracted dust rising. That hadn't crossed my mind and I didn't come across it in my research. I might have gone for the CV had I known. No going back now though and I think the Carbatec is going to be a huge improvement to my old 1hp fabric bagged chip extractor.

Yes, it will certainly be a major difference.

I'll certainly be minimising any movement of the extractor now. Thankfully it only has to happen when I breakdown sheet goods on the table saw. Might be able to make an argument for a tracksaw now (but honey, the dust extractor might leak if I move it, the tracksaw means I don't need to).

Provided they have the impeller on the output side of the system cyclones have less of a leakage problem than regular DCs. This is because this design places the entire cyclone under negative pressure so it's only the positive pressure side of the impeller that is a problem. Usually these sections of the cyclone are higher up and out of the way compared to the impeller, filter housing and bag locations which are at knocking height on regular DCs.. Vacuum cleaners are even worse as they all get bashed into other machines or objects as they are hauled around a shed.

Would there be any sense down the track in trying to rig up some pipe from the bottom of the filter to the outside of my shed? Or even getting rid of the filter and porting?

Venting outside is the biggest improvement any woodworker can make to their dust extraction system. The advantage of a cyclone is no enclosure inside a shed is needed and the outlet can be just ducted outside.

The need for a filter will depend on the cyclone. Some cyclones will still emit a small amount of visible dust which means they might have to use a filter. If you can remove the filter this will improve the flow and could be directly ducted outside will via a chimney. This will also improve the flow especially as the filter clogs up.

There are always noise issues. A major benefit of getting a DC outside is the noise is no longer in the shed. Even venting outside may direct a substantial amount of noise outside but there are simple mufflers that can be made for this.

Originally Posted by johnredl

Watching with interest, especially the bit about venting the dusty outside.
I know it should be self explanatory, but would you have any photos of how others have ducted up an external vent whilst maintaining rain protection, etc? There's an external window right next to my dusty, if I had more ideas...

Remember if it is a regular DC and you want to vent the DC outside it needs to be put inside a cupboard or enclosure because (unless you live on a big block and don't mind sawdust scattered all over your yard) the filters cannot be removed and the air from the filters and bags has to be collected in some way or other. Leaks are also usually more of a problem than the fine dust that a bag emits. Putting the DC inside an enclosure and venting that outside takes care of all this.

To vent through a window and protect from rain etc all that is needed is a waterproof box (painted wood) that fits into a section of the open window with an opening at the bottom of the box.
Several members have done this. One member called Zelk did a very tidy job of this and has posted some photos about his setup.

(QUOTE)Would there be any sense down the track in trying to rig up some pipe from the bottom of the filter to the outside of my shed? Or even getting rid of the filter and porting?[/QUOTE]

A friend has the 2hp version and he is finding that the separation of the dust into the waste bin is not as good as it could be causing the filter bag to also fill over time(probably caused by the design of the cyclone cone which is much shorter than the Clearview) You may find that too much dust is piped outside the shed if you dispense with the bag.

Originally Posted by safari

(QUOTE)Would there be any sense down the track in trying to rig up some pipe from the bottom of the filter to the outside of my shed? Or even getting rid of the filter and porting?

A friend has the 2hp version and he is finding that the separation of the dust into the waste bin is not as good as it could be causing the filter bag to also fill over time(probably caused by the design of the cyclone cone which is much shorter than the Clearview) You may find that too much dust is piped outside the shed if you dispense with the bag.[/QUOTE]

It's a chicken and egg situation with these 90º injection angle, short, small, impeller cyclones. Flow is not high/fast enough, separation is not as efficient, this injects dust into the filter which further reduces the flow etc. About the only way to make these work properly it to regularly clean the filter and at the same time empty the bin even if the bin only contains a cupful of dust. see https://www.woodworkforums.com/f200/using-pressure-determine-filter-cleaning-time-187330

Thanks for all the advice. I think I'll leave the cyclone as is for the moment and see how it performs once the ducting is in. The unit has an auto clean for the filter so hopefully that will mean I don't need to get the compressor out too often. In relation to noise the Carbatec is quiet out of the box and I can easily have a normal conversation standing next to it. It will be interesting if it gets even quieter if I do decide to duct the exhaust outside.

Originally Posted by DoctorBobski

Thanks for all the advice. I think I'll leave the cyclone as is for the moment and see how it performs once the ducting is in. The unit has an auto clean for the filter so hopefully that will mean I don't need to get the compressor out too often. In relation to noise the Carbatec is quiet out of the box and I can easily have a normal conversation standing next to it. It will be interesting if it gets even quieter if I do decide to duct the exhaust outside.

That's good that it has the auto cleaning feature and what you will find is that the air being sucked through ducting has a certain sound volume that cannot be avoided, not to mention the sound of the wood working machinery that cannot be avoided.

One thing to take advantage of when you have a good filter is to use it to scrub the air in the shed of any dust that has escaped the DC into the rest of the shed during a wood working process. This means leaving the unit on for 10-15 minutes after machines have been turned off and this is when you do want the DC to be quiet. To scrub the shed efficiently requires an air intake that is diametrically opposite the shed to where the DC is located so that it sets up a circulation within the shed. If the intake is too close to the DC all the DC does is to scrub the air close to the DC but does not draw much air in from the rest of the shed. When the DC is outside this is easily done by opening all blast gates and also using the entire shed as a duct and either using a door or placing a number of small vents on the wall opposite the wall of the shed the DC is located against, to act as air intakes to the shed.