When you go to large diameter hose like that you lose the velocity needed to pick up dust. I have a metal dust shoe off eBay. One end clamps around a 80mm spindle the other side I have reduced down from 4 inches to 2 inch shop vac hose size. It has a brush and snaps on and off with two clamps in 10 seconds. Zero dust in the air or on the table. Cost way less than $100, and it works.
Dust collector is a Shop Vac with a mini cyclone setup and that cyclone setup was $100 or so.
Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP
It doesnt make sense & hopefully someone that can explain it will chime in, but you get more vacuum / dust collection with the large hose. I think andrewwong2000's problem is he needs a brush to contain the dust. You can see the dust swirling around the brush until it gets to the vacuum hose. As soon as you reduce the diameter you loose the power / velocity / volume whatever you want to call it. If you are using a shop vac with a 2" hose you cannot go up to 4" but if you are using a harbor freight dust collector & keep it at 4" you have much more suction than if you reduce it down to 2". I would have ran 5" clean to the spindle if I didnt already have the 4 " flexable.
To increase velocity the size should be reduced. The CFM will stay the same for that small diameter, over a short distance. If you leave it small all the way back you Will lose CFM because of fiction loss in the pipe. Flex is a big loss anyway, it should be hard pipe whenever you can run it. Turns as 90 degree and fittings are a loss. This is from a HVAC guy who used to design ductwork as part of his job. You can do whatever you want.
Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP
You may be correct but why do all the industrial dust collection units use larger ducting? I agree that elbows & 90's reduce the flow, but I've had numerous people tell me to stay as big as possible as long as you can. The say it is opposite to water like I said I dont know but just what I've been told. I've also watched videos on you tube of people going from 2" - 2.5" to 4" if 2.5" is better I could have saved a lot of money.
Also it should probably be mentioned that you should run metal duct work & ground the flexible hose to the metal. They claim sawdust is more flammable than gasoline. I tend to agree since when my son worked at a Fiberboard plant they were having fires all the time & it didnt take much to start them. I'm so glad he is out of there
Gary
It's a little more complex than saying 4" is better than 2", or 2" is better than 4".
You don't want a 2" hose ith a dust collector, and you don't want a 4" hose on a shopvac. Neither will work well.
Imo, a shop vc is not ideal for two reasons.
1) The noise will drive you crazy.
2) They won't last long if you'll be running it for hours on end.
With a dust collector, you do want to keep the duxt size as large as possible, for as long as possible, with minimal bends, and as littel flex hose as possible.
I recommend a 2HP or larger dust collector.
A good dust shoe with a brush is critical as well.
Gerry
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Gary you missed my point for increased velocity to pull off the table or out of the shoe you need to reduce for a short distance. I said nothing about reducing the main line or home run to the collector. If you make the duct to big your wasting money on material. A 90 generally is equal to 20 feet of straight pipe, flex duct is terrible for loss. My wife hates it when I watch HGTV and see all the huge diameter flex duct used in some areas of the country for HVAC. Then they wonder why they do not get any air flow!!! Its good for a laugh. It takes a bit more skill to run sheetmetal duct but its compact and has smooth interior for great air flow.
You increase velocity to get the air flow where you want it. Next time your in a large commercial building look for the air diffusers they use to direct air flow. Some have slot diffusers mounted high in the ceiling but thanks to velocity, throw and spread the air makes it down to the area needed.
Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP
Sorry folks there is a strip brush surround but not in that particular photo!
The dust extractor is a 5hp 1500cfm cyclone.. i still have to wear hearing protection because of the spindle and dustie.
The 6” hose sucks huge amounts of dust and chips normally, but the strip brush gets sucked into the pipe restricting it a bit and it’s just physics that the hose isn’t near enough to the cutter on the far side where MDF dust is being thrown off the cutter and blowing through the strip brush.
There isn’t any real duct shape to deflect dust and chips, and optimise air flow with the flat profile dust hood.
That’s why I want to try a 3d printed shape and will post updates.
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You need a stiffer brush, and the brush should form a seal with the spoilboard. The purpose of the brush is to block the chips from flying away, so the vacuum can get them.
Gerry
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JointCAM - CNC Dovetails & Box Joints
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(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Andrew that dust collector is just for your router? My little Shop Vac with the 2 or 2.5 inch hose takes all my dust away even when doing MDF.
Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP
WMGeorge - ok I see what you mean. I run 5" round duct to above my table then neck down to 4" but that was because my KentCNC shoe is 4"
We have a dedicated 10HP dust collector with a 10" hose to the spindle. Depending on the operation, it gets between 50%-95% of the dust.Andrew that dust collector is just for your router? My little Shop Vac with the 2 or 2.5 inch hose takes all my dust away even when doing MDF.
I've seen roostertails of dust shoot out 10+ feet.
The spindle is actually inside the hose, and is cooled by the airflow.
Gerry
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http://www.thecncwoodworker.com/2017.html
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(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Gerry, that sounds awesome are you able to post any photos?
This doesn't really show much. It's a 15HP spindle inside the dust hose.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
That's awesome it looks as though it has a pneumaticly controlled dust shoe to allow tool change & different sized bits
Yes, I think it's 4 air cylinders that give you 4 different brush heights, which are assigned to the tools. The brush lifts all the way up for tool changes, and then it's lowered to the specified height after the tool change.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)