Dust Sniper (quiet extractor system)

Step 15: In Use, Evaluation, Maintenance

Lets evaluate the DS in relation to the design goals which were: 

1) Effective removal of dust from hand-held tools and bandsaw 
2) Little or no noise
3) Provide strong but wheelable work surface

1) The removal of dust thus far is excellent. The dust is sucked up and separated by the cyclones into the collection barrels. Because the separation efficiency is so good suction remains very high - no regular cleaning filters or changing of bags required. Obviously the collection barrels need emptying occasionally, but being many times bigger than a bag or standard shopvac canister, this is an easy and infrequent chore. Thus far, I have only had to change a vacuum bag after I got carried away and let the barrel become full, which resulted in the dust quickly clogging up the vacuum bag and suction becoming very weak.  

So yeah, it might be worth me trying to make some kind of warning sensor that tells me when the collection barrels are approaching fullness to avoid similar problems in future. I already put a viewing window into one of the collection barrels, problem is that the static causes it to be obscured with dust, so that's little to no help. Some of you have already made some good suggestions on how to overcome this little problem in the comments. Of course any other ideas are very welcome...  

2) Noise wise I am better pleased that I expected to be. When the DS is all closed, shut up and operational, I can't really hear the noise of the vacuums at all! The noise of the air rushing through the hose is pretty much all that is audible. So jackpot on the sound front. I can't tell you how nice it is to be able to clear up the shop and suck up dust without a loud noise. It makes nice quiet, well balanced power tools more worthwhile ;)

Now bearing in mind  there are many differing and complicated techniques of sound measurement, the audiophiles may want to look away now. In a blissfully and probably horrifyingly simplistic manner, I used a mobile phone with an in-built 'sound meter' to do my measuring.

Sound of both vacs out in the open - 85dB
Sound of one vacuum in the open - 83dB
Sound of both in the DS - 61 (but varies a lot depending on where the end of the hose is situated - the air rushing in at the tip is almost the only precipitable noise) 
Sound of one in the DS - 55 

3)  The work surface is nice, functional, and sturdy enough to dance on. I do need to add a breaking mechanism to the wheels, so that I can lock it in place better.

Parting Thoughts

The DS has been a long project for me, with plenty of help, research and tweaks needed along the way. Still, it has come together in the end and with any luck this instructable will help you guys avoid some the mistakes I made. Already a number of you have said you will be making your own DS, so I look forward to feedback, build photos, and areas of development. If it improves the working environment (and health!) of one of you, my fellow makers, hackers and craftspeople, then great!

Comments

[wiml]

Thinking laterally about bucket sensors: perhaps you could put a small tube into the collection bucket near the top, connected to some not-very-strong source of vacuum. When the bucket fills, the sawdust blocks the tube, making the pressure in the tube drop, which then ... um ... raises a flag, or triggers an electronic pressure sensor, or the like.

Or, alternately: isn't the interior of the bucket at below-atmospheric pressure? The tube could be connected to 'outside' air though a small hole. When the bucket is not yet full, airflow into the bucket keeps the tube below atmospheric. When the bucket fills past the tube, airflow stops. Let's see if I can attach a sketch of this idea... I can't decide if it'd be horribly finicky and impossible to implement, or if it would be perfect and elegant. :)

Electronic pressure sensors are around $15 new but maybe there's a good junk source for them...

[bongodrummer]

Hi Wiml,
Interesting ideas, thanks! Things are complicated a bit because the storage barrels themselves are in a partial vacuum (which fluctuates depending on whether the end of the vacuum hose is blocked or partly blocked). It is necessary to maintain the seal on the barrel so that the cyclones work right. My feeling is that adding another 'not-very-strong source of vacuum' would open a whole can of worms (big malicious ones at that).
An interesting idea though, thanks for sharing.

[jeff-o]

I wonder if you could put a small digital scale with a remote readout under the barrels. When the barrel hits a certain weight, you know it's time to empty it.

Any kind of optical sensor inside the barrel would be obscured just like the window, and other sensors are out because of the static. But yeah - weight would probably work.

[DeadlyDad]

How about using a simple, light flap and a cherry switch, along the inside of the barrel at the 'full' line. Have a spring on it so that it normally sticks out when the system is off. When the system is in operation, the flap will be forced against the side. If the flap doesn't swing back out when the system is turned off, something is blocking it, and the barrel can be assumed to be in need of emptying.

[bongodrummer]

Hay Jeff-o!

I am not sure I am understanding you with this. The barrels 'float' off the floor, so that the DS can be wheeled around. They are screwed onto the base of the cyclones - their lids are firmly attached so the cyclones and everything remain stable.

Or did you mean putting the scales inside the barrels? That might work, if they were inside some kind of plastic bag - but then again the partial vacuum created would probably disrupt readings...

[jeff-o]

Ah, true. I forgot that the barrels were connected to the cyclones. Perhaps with a short flexible tube (flexible ducting?) between the two it would work.

[bongodrummer]

A bit of flexible tube would get around that yes, although there is another problem with the weighing method, that was pointed out to me on one of the forums. That is, the material sucked up is often of very different density. Between different woods and plastics, and different shapes (ie shavings, fine dust, etc.) the weight of a barrel can apparently vary a lot.

[jeff-o]

I was thinking of that. And yeah, if you're sucking up plastic and metal along with the wood then it could be a problem. But really, they shouldn't be mixed in the first place (sawdust can be used for other things!) And as for different density woods, unless you're doing a lot of work with ebony and cocobolo, I doubt it'll present much of a problem. In most cases, people will be using oak, pine, maple, and poplar. Set your threshold for a bucket full of oak sawdust and you'll be good to go!

[bongodrummer]

I am not sure we can assume wood density is so homogeneous, but you are definitely right about keeping materials separate (one of the reasons I wanted two collection barrels). I have no first hand experience, but I can quite easily imagine the shape of the particles would make a fair difference though. I know a barrel load of shavings from the power planer feels lighter than say 3/4 of a barrel of proper sanding dust - I haven't actually weighed it, so I am just going from my feeling here.

But also consider: my Handbook of Hardwoods claims the weight of European Oak usually falls in the range from 640kg/m3 to 820kg/m3, having an 'extreme but possible' range of 600 to 900kg/m3. And that is within one species. Pine is often round 500kg/m3. That in mind, I think density issues would be worth considering with the weighing approach. If you calculated in a good safety margin though, I expect it would work fine as an indicator - barrels don't have to be full before we empty them after all.

[jeff-o]

It's true, the barrels don't have to be full. So, you'd make a "best guess" estimate of what weight the barrel should be when it needs to be emptied. Then over the course of a few "empties" you could adjust the threshold up or down accordingly. I think you'd find the weight would, on average, be about the same assuming you use the same types of woods and processes on a regular basis.

[bongodrummer]

Agreed.

[Pazzerz]

I guess with all the problems with densities, the best thing would be to do what we do every time we vacuum the house: Visually check the container and empty it prior to use. A bit old fashioned, but it works.

[dcorbett]

WAY AWESOME!!! I loved the reed switch auto on/off idea. Plain to see you put some extra effort into this one.
Try ultrasonic for measuring the level in your bucket.
The transducer can be mounted at the top (to provide "analog" measurement), or on the side (use as ON/OFF or "dump alert").

[bongodrummer]

Thanks. I must admit I had to do some reading to find out about ultrasonic sensors, and the idea seems good. One concern might be the dust flying into the barrel interfering with the sensor's reading, while the DS is in use?

Sounds like it could be worth pursuing though. Any ideas for cheap/salvageable sources? My first thought was the car alarm doodars that clip on inside at the edge of the windscreen - probably plenty of them floating around at scrap yards or still in cars with alarms that have been permanently disabled or taken out. Would that be any good? Other ideas?

I still want to try the simple idea of using grounded antistatic bags over the viewing window (as MadScott and wingman358 suggested).