I recently got my first CNC machine (desktop 3018) and have quickly come to the realization that I NEED dust collection. I have a shop vac. Two actually. But they are extremely loud. And the systems I have seen in my searches are really large (for a shop), really expensive, or both.
So, having a CNC, I decided to build my own. And the first piece of the puzzle is finding a suitable motor.
My thoughts, for now are to keep it small. Thinking a 5 or 6 inch diameter impeller (see pic) with at least 8 veins (if that's the right word) powered by a 24 (maybe a 36) volt motor. For tubing (single tube), I'm thinking 2" diameter. And shouldn't need to be longer than 2 or 3 feet. And I'm not looking for suction enough to to pick up bowling balls. My main concern is capturing the fine dust that gets all over the room.
Therefore, I'm looking for a higher RPM motor with a bit of torque that runs fairly quietly (brushless?). As I have no experience with motors, I ask you folks for opinions/advice on selecting a motor. Any specific model that would fit the bill? Also, if I'm overlooking something or getting the cart before the horse, speak up.
However 4 inch or 3 inch duct is a common approach and inline fans work quite well.
For smaller stuff I also use a cyclone separator to save big time on dust bags.
Advantage is that they can often be situated away from the source.
Design of fans is all about back pressure and flow rate - there are design curves for this sort of thing, basically what you have to avoid is stalling the airflow over the blades, if that happens the fan stops working. High back pressure is going to mean faster speeds and more noise, and you'll eventually be designing a compressor not a fan if the back pressure becomes too high, so you want to avoid long narrow ducts, small collection bags with dense filters. Moving the air faster than necessary will increase the back-pressure too, from Bernoulli's equation.
Note that this device often seems to increase the suction of a vacuum cleaner and having partially collapsed a 45 gallon steel drum with one I would say that was true so a sturdy pail is a must depending on the HP of the vac used.
Standard vac hoses or cheap pool hose will work fine up to about 5hp vac. Or feel free to get jiggy with it and some plumbing fittings.
My main one doesn't even use a vac at all just one of those quiet inline duct fans with a reasonable CFM and although only about 70% useful does keep down an awful lot of the lighter stuff. In the garage that's a different matter. Also use a cyclone on the central vac and so far not needed to even shake out the bag (16 months and counting) Just empty the pail.
Pic below is the sander in the garage which does a little more than 90% sep.
Always appreciate your wisdom from experience, Bob. A small, and hopefully quiet, cyclone under the bench the CNC sits on is exactly what I'm shooting for. I just don't see a need for a full size unit like most use. This little CNC is all it will be used for.
MarkT, thank you very much for your insight. I've been looking around for info on calculating sizes, design etc. I think to actually design one properly would take an engineering degree. But I think for what I'm looking to accomplish, trial and error will have to suffice.
I think it will be a fun project though. Anyone know anything good or bad about the 775 motors? Seem like decent speed, torque and sound levels.
One in the house for the machines has two pieces of pool hose to a box at that outbound side powered by a computer fan to provide the initial suction then both hoses run up to a "Y" adaptor then to a larger adaptor.
Between that and the outbound flow is a chap 110v Fan I got in a surplus store which then goes to another adaptor and a 4" flex pipe meant for a dryer before it pops outside.
Fantastic at pulling laser fumes out but as I said not as good as I really want just yet.
Will be going with a better dust head but will more than likely make it myself.
Have a big dyson vac that I rescued from the tip that I intend to use with it that will also get some tweaks to throw the waste into a pail.
This shows the basic inlet side of one of the machines and will take some more bad pics tomorrow.
As for the 775 motor that tend to be the same as the use for the cheap spindles and having burnt a couple out I would say avoid them for all except the lightest or intermittent use.
ballscrewbob:
As for the 775 motor that tend to be the same as the use for the cheap spindles and having burnt a couple out I would say avoid them for all except the lightest or intermittent use.
That's what my gut was telling me. That whole "You get what you pay for" thing.
Would also agree with Mark that for something quite specific you need to be aware of CFM numbers cross flows, volumes etc etc.
That said most of these small CNC things will happily accept a "wing it" approach. although I must admit to having had some industrial experiences with cyclones in a few different uses / approaches from just water and debris sep to wet-gold-sep and some dry-sep powder uses.
You may still need to VENT to atmosphere after initial filtering so that is something you will need to consider.
Otherwise you may just end up re-circ on super fine particulate which is never good.
I have put some thought and research into everyone's suggestions and the idea of an inline fan system seems to be getting the most attention in my brain. Aside from larryd's suggestion (I'm too pretty for those! ), I think I can get it to be quieter than most other options without taking out a bank loan.
I've found a fairly affordable unit that should do the trick for now. I have thought of another use for one that's unrelated to CNC or Arduino. So, if I decide to upgrade to a better unit, it won't go to waste.
ballscrewbob:
Sly giggle...Ok a dang good guffaw Thanks larry...
If going with an inline fan make sure it has a decent CFM.
That's the key with those and may involve some detective work.
Bob.
The one I'm looking at is only 200 or so CFM. Going to have a HEPA filter in front of it too. Should do "OK" for the fine dust that I'm concerned with for now. I'll more than likely upgrade after I get through the holidays and 4 birthdays in the first 2.5 months of the year.
ballscrewbob:
Just a regular square fan.
Slang from Ikea flat pack
Alrighty then. Never heard it out that way.
Talked about it to my long time bud. Seems he has an inline fan on the shelf in his garage that I can have. Brand new still in the box from his days as an electrician. All I know at this time is that it's a (likely 6 ") 110v and having the pot/knob to adjust speed. But hey! The price is perfect!
