extracting mdf dust

[DaveL]

I bought two pleated 20 m2 filters that filter to .5 micron and built a mdf and stud device to hold the filters in place similar to one of the links on Bill's site. What a difference - just complete the job this weekend. The extractor works much better - the suction has improved as the air has more area to escape and the fine dust blown out of the top bags is removed .
The filters were £47 + VAT each - well worth it.

Barry,
thanks for this information. I have been looking at these filters for the output of my cyclone, if you found that they work OK on you collector I will get some for it.
I am going to built an mdf manifold for them. I want to put them into the roof space of the shop, keeps them out of harms way and should help to move the hot air down from the roof in the winter. :roll:

 

[ivan]

The problem with Camvacs (and any other universal motored high revving vac) is low airflow. The 3 motor Camvac only moves about 300 cu.ft.min.
Wouldn't be much good on a sawbench cutting mdf, although a single motor would do for a router (see Bill's cylone pages)

 

[Barry Burgess]

Dave they work well and my dust extractor is using more amps on startup as there is less resistance. I have sent you pictures via your e mail

 

[Barry Burgess]

Ivan is correct the Camvacs fail the Bill Pentz tests and the minimum pipe size should be 100mm or more. The Camvacs I have seen are using 2.5" pipe
If your extractor is 2HP or more - putting a simple bin extractor before the system take a load of the extractor but you lose airflow with smaller motors
Barry

 

[wrightclan]

I have replaced the lower bags with plastic and used gaffer tape to prevent leakage from the bags.
Barry

Rather than having to tape it up with gaffer tape every time, you might try sticky-backed foam weather seal. The kind you might use to seal up a drafty door or window. You run it around the circumference of the extractor and the pressure of the band clamp seals against it. ( Not my original idea, it was an idea sent into some woodworking mag, but I can't remember which one or when.) I've seen it in Poundland for--you guessed it-- a pound. Their stock is always changing, but you might try them.

Thanks for the link on filters, I have been looking for something similar to build my own cyclone.

Brad

 

[Barry Burgess]

Thanks Brad I will try that

 

[Sonic]

I enter this debate with some temerity here, as I have yet to install a complete extraction system - I make do with a portable 2-bag extractor that I use mainly on my Router table & P/T (so I may be talking out of ignorance).

Is it not true that even the best extractor set-up will not catch all of the dust ? And if that is so, then particularly when working hazardous materials such as MDF, it would be wise to use a personal respirator of some sort. I speak as someone who suffers fairly severe allergic reaction to dust of all kinds (it gives me blinding headaches the following day), so I am very aware of the need to avoid exposure. My worry would be that people who do not get this "early-warning" sign might expose themselves for years to harmful amounts of dust, only to discover the consequences too late.

Colin S.

 

[Jake]

The problem with Camvacs (and any other universal motored high revving vac) is low airflow. The 3 motor Camvac only moves about 300 cu.ft.min.
Wouldn't be much good on a sawbench cutting mdf, although a single motor would do for a router (see Bill's cylone pages)

His calcs assume you are using a HVLP extractor, so aren't valid for an HP Camvac.

 

[Jake]

Ivan is correct the Camvacs fail the Bill Pentz tests and the minimum pipe size should be 100mm or more. The Camvacs I have seen are using 2.5" pipe

Mine is 4" - I think it is an optional choice on most of their machines.

The pipe size calculations on Pentz's site again assume low pressure, anyway - much of the reason he stresses the need for big pipes is that the low pressure nature of the vacuum means that air resistances are much more important than they would be at greater pressure.

 

[Barry Burgess]

Jake with a vacuum type approach I prefer to use a mini cyclone to separate the majority of chips and heavier dust into a 65litre container with the air outlet going to the vacuum. I have built both a single and double cyclone(like Dyson) attached to 2000W vacuums that work very well with dust using 1.5" pipes but don't handle large chips well. These let very few particles through to the vacuum. I have also built a number of dust buckets and still use one as a pre filter to my extractor. The cyclone has proved it's self over a number of years for separating dust and chips effectively.As Bill's site said it is important to get the ratio's right. My large cyclone is under construction at present.

 

[Barry Burgess]

Sonic the problem is the bags. I have found replacing the top bag with a filter you do not get that fine dust being blown out across the workshop.

 

[Jake]

Jake with a vacuum type approach I prefer to use a mini cyclone to separate the majority of chips and heavier dust into a 65litre container with the air outlet going to the vacuum. I have built both a single and double cyclone(like Dyson) attached to 2000W vacuums that work very well with dust using 1.5" pipes but don't handle large chips well. These let very few particles through to the vacuum. I have also built a number of dust buckets and still use one as a pre filter to my extractor. The cyclone has proved it's self over a number of years for separating dust and chips effectively.As Bill's site said it is important to get the ratio's right. My large cyclone is under construction at present.

A 3 motor Camvac will suck any size chips you want - I rescued a 10" screwdriver from mine the other day after a careless floor-sweeping. Edit: With machine and screwdriver still in nice condition, being as it hadn't been through an impeller.

Cyclone's are all good and well if they are engineered correctly, but personally I couldn't be bothered to spend time building one. I'd either stick a good conventional extractor outside with big ducting, or look for some other solution. The Camvac won for me - I can't have an outside extractor. I'm not claiming it is perfect, but it works well enough for me -

I was just pointing out that you'd need to do a lot more work on Pentz's underlying calculations before it would be fair to say that they objectively disqualify the Camvac as a valid solution. I don't know whether the calculations once rejigged for the static pressure and consequent acceptable duct size would 'pass' or 'fail' the implicit underlying test stripped of the LP assumptions, and I'm not going to start trying to work it out!

I think the 800CFM is entirely theoretical anyway - the table is based around one having replaced all of your ducts and extractor hoods with the same diameter outlets as the duct pipe. I haven't done that with any of my tools and I'm not about to start - if I was doing woodworking 8 hours a day 5 or more days a week, I would I hope have a different attitude.

 

[Jake]

Oh, and if your extractor hoods haven't been replaced with 6" outlets, I note that a higher pressure solution will suffer less detriment than a low pressure fan with or without cyclone - evening out any CFM differential that may exist 'at the fan'.

 

[prawnking]

what a debate its very interesting too see all the different opinions.
now after reading the info on bill`s website and looking at the replies i now dont know which way to go, the camvacs look pritty good, but cyclones do too.
my mane prob is if i was to run 4 - 6 inch ducting all around my shop to satisfy bills recommended requirements i wont have any room left for woodworking.

jake how often do you need to replace the filters etc or do they just need blowing through outside with an airline.
also its not just the fact of wearing a suitable dust mask to prevent breathing in mdf dust its that it needs to be extracted from the workshop otherwise like bill says it can take hours to settle and its easily disturbed and also gets onto your skin and clothes,

how far do u go?

:? :?

 

[Jake]

jake how often do you need to replace the filters etc or do they just need blowing through outside with an airline.

The filters are (1) an elasticated cloth that fits over the edge of the drum and under the lid and motors (2) paper bags that are fixed over the motors with elastic bands and (3) cloth covers to the motor inlets.

The cloth bag gets kind of shaken out when the bin is emptied (which is err, not every night of use as it maybe should be) but I don't really worry about too much, figuring that a bit of build up helps the filtering really.

The paper bags are changed when they have visible dust on them (which takes a good long while - 10-20 hours use at a guess).

The cloth covers I've never touched.

 

[Barry Burgess]

Jake thats the problem with both impellor or vacuum based systems you have to get the air out of the system with as little dust in the air as possible.
The bigger the square meterage of the filters the better. This can be seen if you connect a clamp meter to the electrical cord to the device and measure the amperage used. You can see the difference when no filter is inserted. The motor runs best. Most of the extractor makers like the motor running at the lower amperage as they have no come backs during the warranty period.
I use 40m2 for a 3HP motor and that is about idea but performance is inhibited if the filters are filling up. Anyway of letting as little dust as possible to get to the filter is the best system. I always use a big filter before the dust goes into the extractor
Barry

 

[Jake]

The air can't get out of a Camvac without being filtered, as it has to go through all three filters before it goes through the fan-motors.

I can't detect any difference on the Camvac between a clean and a dirty main filter - not that I've measured current draw, but just from suck or sound.

The high pressure helps here as well, as the resistance of the filters has a negligible effect on performance compared to an LP impellor machine with a clogged filter - that's why, as you say, the area of filter matters on such machines, precisely because they are low pressure and thus susceptible to significant drops in performance and throughput if they encounter air resistances.

 

[Barry Burgess]

The air can't get out of a Camvac without being filtered, as it has to go through all three filters before it goes through the fan-motors.

I can't detect any difference on the Camvac between a clean and a dirty main filter - not that I've measured current draw, but just from suck or sound.

The high pressure helps here as well, as the resistance of the filters has a negligible effect on performance compared to an LP impellor machine with a clogged filter - that's why, as you say, the area of filter matters on such machines, precisely because they are low pressure and thus susceptible to significant drops in performance and throughput if they encounter air resistances.

Jake - I started out the vacuum route and bought a clamp meter - to be a little more scientific than you and your sound. Shock - the meter was right and my ear was wrong . I have been there and tried most of the vacuum options and then I started to test the Pentz options.
My test was very simple - what was the results in the gym after a day in the workshop?
Most days I was na*****, so I started to experiment with the options.

 

[Jake]

Jake - I started out the vacuum route and bought a clamp meter - to be a little more scientific than you and your sound.

Fair enough -I did deliberately make it clear I was being pretty subjective. I'll have a play - but surely what actually matters is airflow rather than current though? Are they directly linked in a linear manner?

Shock - the meter was right and my ear was wrong .

Interesting,but inevitable I guess. To what degree? What sort of vacs did you test, and did you measure the effect on the airflow?

I have been there and tried most of the vacuum options and then I started to test the Pentz options.

Out of interest what machines did you test?

My test was very simple - what was the results in the gym after a day in the workshop?
Most days I was na*****, so I started to experiment with the options.

I don't suffer that problem - well, rather it makes no difference whether I have or haven't been making dust the day before, so I can't be that scientific I'm afraid.

Interesting discussion.

 

[Barry Burgess]

Jake
I tested a total of 7 vacuum cleaners with both of my mini cyclones. I started with a 600W B&Q shop vac upto a 2000W and included two different Dysons. What I was trying to do was to separate the maximum amount of dust out of the air and allowing very little to get through to the vacuum filter as their filters are too small to be of much use. I went back each time to attempt to improve the cyclone separation. The 2000W achieved the best results and as that was the largest domestic vacuum I could find I started on the extractor route.
I tested a 1, 2 & 3HP extractors with the idea of preventing as much dust and chips as possible from reaching the extractor. I knew what a cyclone would be likely to achieve the best result but I started out with a dust bucket and played with ways of preventing as much as possible from reaching the extractor. I ended up with the 3HP extractor and a combination of 2 dust buckets achieving the best result for me but the cloth bags were still not working. To get rid of the fine dust I replaced the lower bag with a plastic one and replaced the upper one with a filter.
At this point I have achieved the best I can expect from a dust extractor but it is failing the principle of dust seperation as too much goes to the filter.
Its now time to concentrate on dust separation and the prevention of most dust getting to the filter so back to the cyclone approach
I bought a clamp meter after reading Bill's site and for flow rate tests I use a bucket of mixed chips and fine dust and time the rate to empty the bucket
Hope this helps as I did not set out to prove one was right or wrong but to just improve my lungs.
Barry