Thread: Modifying a 3HP DC-7 Dust Extractor

Originally Posted by HeadScratcher

I removed the Y piece for the second bag and rotated the housing 90 degrees. Even without my cyclone connected the air flow is pretty crap. Would I be correct in assuming that the single bag is restricting the air flow too much?

Yes it will definitely slow the air down, but not as much as using the chip catcher which will reduce the flow by around 20%
The chip catcher will help keep the filter clean BUT less flow means leaving more fine dust behind in the shed so its pointless doing this in the first place.
You could use one pleated filter to improved the flow a little.

Your MAJOR problem is using 4" ducting - this is to put it bluntly "A DOG".
The max flow a 4" duct can sustain with a conventional DC is ~425 CFM. Then Using one bag at the chip catcher means the flow will be under 300 CFM
The only way to catch the majority of fine dust at source is to use 6" ducting all the way.

The other problem I have is that I a trying to make it quieter so I don't annoy my neighbours with all the machinery running at one. Any suggestions on how to make it more efficient and quieter at the same time?

The motor needs significant cooling so it cannot be insulated by itself. About the only way is to put it inside an enclosure but it sounds like you have no room to do this.

Thanks BobL, I have actually been thinking about putting the motor in a box above the thein separator and opening up the top to 6", so it's a straight path.

I am trying to keep the footprint as small as possible, but I am not so concerned with height. I currently don't have any 6" pipe so I just cobbled it together with what I had.

Time a proper rethink. Yes the airflow is so bad at the moment I don't even have it going through the separator. Down the track I want to build a new cyclone top for the bin.

If you had to guess which was causing the greatest restriction one bag or 4" pipe which would you say?

Originally Posted by HeadScratcher

If you had to guess which was causing the greatest restriction one bag or 4" pipe which would you say?

Well a 2HP DC only uses one bag and with 6" ducting all the way (including the flexy between the impeller and the filter housing it can pul 800CFM

As soon as you put 4" ducting anywhere in a standard DC system it will throttle it down to 400 CFM

The chip separator will drop it another 20-25%.

Ok well it looks like a 6" upgrade is the biggest priority. How do you go about losses when connecting the 6" pipe to some kind of machinery?

I am currently using this on my CNC and cant physically fit a 6" pick up to the CNC. At best I can do about 50mm.

Edit:

If I made new spindle holder brackets I could put a wider oval shape in there.

Originally Posted by HeadScratcher

Ok well it looks like a 6" upgrade is the biggest priority. How do you go about losses when connecting the 6" pipe to some kind of machinery?

I am currently using this on my CNC and cant physically fit a 6" pick up to the CNC. At best I can do about 50mm.
Edit:

If I made new spindle holder brackets I could put a wider oval shape in there.

That could be useful but my understanding about CNC is that it is really important to clear the chips so you might find this deteriorates if you make the pick up wider (i.e. air speed will drop too far)

After small ducting, small machinery ports are the second dust elephant in the room.
There is no question that machine cabinets and ports have to be opened up to take advantage of 6" ducting so get your angle grinder out and start cutting!

Connecting a DC to a 50 mm port will only pull about 70 CFM through that port so if you have a DC that uses 6" ducting that means you have ~1000 CFM available to use elsewhere

With point dust sources like power tools and CNC there are two requirements
1) the chips, best picked up with a vacuum cleaner (VC)BUT these generate a whole new raft of issues including making more fine dust than they pick up
2) and the fine dust, which wafts around a shed like a fart in sports dressing room which requires large volumes of air to be collected (1000 CFM

To reduce the amount of fine dust a CNC injects dust into a shed a VC needs to be located (or in an air tight chamber that is vented) outside the shed.
At the same time as collecting the chips from a CNC using a VC I would advocate employing a second bigger bell mouth hood directly above and as close to the cutter as possible to collect the fine dust.

AND very importantly don't turn the DC off after you finish with the CNC. Leaving it running will help clear the shed of fine dust.

How long do you keep it running? That depends on the size of your shed, the size of your DC and ducting, what you are cutting, and how long you cut for. A light cutting session in a small shed for just a few minutes should only need a few minutes of post cutting air extraction. heavy cuts in a large shed for a hours or so would need hours to clear the shed.

On my DC I have an semi-automated delay period so that when I switch it off it takes anywhere from 2 minutes to 24 hours to turn off the DC after I switch it on.

Some really good points to think about, as I am in the finishing stages of making the CNC there are still some final touches going on. One of which is going to be a light plastic canopy that goes around three sides, to stop sawdust being thrown out so far, and making cleaning up easier.

If I can only use part of the suction at the tip, I might just make a range hood style top to fit over the table and feed a 6" hose into the top.

The design of the CNC would lend itself to that.

Ok got a little carried away again, but was thinking of upgrading the idea to something more like this, with inner and outer walls and some filler in between.

Originally Posted by HeadScratcher

Ok got a little carried away again, but was thinking of upgrading the idea to something more like this, with inner and outer walls and some filler in between.

The DC cannot be physically connected to either the inner or outer walls of the enclosure or the vibrations will be transferred direct to the outer skin. The DC should be isolated inside the enclosure and only the wheels or legs should sit on something like a thick layer (50 mm) of carpet or soft runner or similar. Several members have experience this problem including myself. My enclosure is outside but I rested the DC on the frame of the enclosure and it was noisier than I had hoped for. By isolating the DC from the enclosure the sound level dropped by 5dB.

Also your sound baffle for the exit air needs more turns. Something like 7 180º turns if you have room. Mine has 5 because that is all I had room for,

Thanks BobL, I was up till about 4am this morning playing with different designs, and with a bit of careful rejigging I managed to fit the it the separator in the box as well, saving me space.

You saved me a lot of effort because I was thinking about hard mounting it to the back wall. How about sitting it on 4 car valve springs on the bottom?

I read in several other posts about making the frame box work rigid, and was planning to use lots of pine bearers. For insulation I was thinking of using acoustic Gyprock for the inner layer, some acoustic bats, and then some MDF on the outer layer, and maybe even some colourbond on the very outside so it could be left outside.

Does the colourbond make any difference?

Originally Posted by HeadScratcher

Thanks BobL, I was up till about 4am this morning playing with different designs, and with a bit of careful rejigging I managed to fit the it the separator in the box as well, saving me space.

Your plan doesn't seen to be any different than the one in your previous post. A DC attached to internal walls is going to transmit the noise to the outside wall.

You saved me a lot of effort because I was thinking about hard mounting it to the back wall. How about sitting it on 4 car valve springs on the bottom?

I thought about spending the DC using spring but was advised against this by an acoustics specialists at work. Springs work for very low frequency but not for higher frequencies. Springs on top of about 10 layers of carpet would be better.

I read in several other posts about making the frame box work rigid, and was planning to use lots of pine bearers.

You need to be careful about adding too many studs and noggins - you need enough so they wall is not "drummy" but no so many that it takes up valuable volume that needs to be occupied by insulation.

For insulation I was thinking of using acoustic Gyprock for the inner layer, some acoustic bats, and then some MDF on the outer layer, and maybe even some colourbond on the very outside so it could be left outside. Does the colourbond make any difference?

The acoustic insulation sounds good. The Colorbond is purely for weatherproofing. The Colorbong can also "Drum" so it needs to be fastened direct onto an under material like an MDF or chipboard layer. with more fasteners than usual.

Refining the idea even further... I still want to put the motor up high but want to also decouple it from the outside frame (inside not as bad, as it has more material to resonate through before reaching the outside) I am working with the idea of semi floating the motor.

The two green horizontal panels would connect to the side walls but not the front or the back outer walls, so any vibration would have to be transmitted to the centre walls before reaching the outer walls.

If I can get some kind of hard dampening plastic between the motor mounts and the mounting panel that would be ideal. With the blower sitting horizontally Styrofoam pieces could cut and placed top / bottom to ever so slightly support / align the motor through the blower housing, and the blower outlet being foam (or something else) mounted to the down tube, with the rest of the system directly attached to the cabinet.

Originally Posted by HeadScratcher

Refining the idea even further... I still want to put the motor up high but want to also decouple it from the outside frame (inside not as bad, as it has more material to resonate through before reaching the outside) I am working with the idea of semi floating the motor.

The two green horizontal panels would connect to the side walls but not the front or the back outer walls, so any vibration would have to be transmitted to the centre walls before reaching the outer walls.

If I can get some kind of hard dampening plastic between the motor mounts and the mounting panel that would be ideal. With the blower sitting horizontally Styrofoam pieces could cut and placed top / bottom to ever so slightly support / align the motor through the blower housing, and the blower outlet being foam (or something else) mounted to the down tube, with the rest of the system directly attached to the cabinet.

I tried that and it didm't work anywhere near as well as loading it onto the floor. The DC was too heavy and compressed the isolating material sufficiently so sound was still transmitted through the isolating material to the outside walls. The best place to load the DC in the enclosure is on the smallest most constrained area of the enclosure i.e. the floor. This is deadened by the entire weight of the enclosure and can easily be made extra stiff/heay because is the lowest part of the structure - it could even be lined with a couple of layers of bricks and foan if needed. Then all that is needed is ~50 mm (compressed) of isolating material (old carpet tiles/ dense foam/even corrugated cardboard) between the enclosure floor and the DC.