Thread: Sanding dust control - sanding long thin curved things with ROS. Thoughts needed.

Are you using mesh sanding discs? If not, that change alone will probably solve all your problems. It may seem unpalatable to sell off the stock of paper sanding discs and upgrade, but once done you wouldn't regret it.

Hmm not mesh. Mostly nice Alox discs from Sandpaperman.
Actually my stock of pads is getting low at this time of year, so changeover is least painless now.

I was also wondering about using a flexible backing disc/ foam too. Maybe that and mesh might be a good starting point.

I can't see any way an ROS can capture the dust and I have had the same problem lately. For production purposes and to speed things up I would make a fixture to spin the paddle and use hand held paper to sand with and it would give a far better finish. All that is needed for DE is a long hood with multiple outlets in the hood hooked up to a DC. You could make the hood and the fixture to spin it in all in the same fixture with it all closed on three sides and only open enough to get the hand and sandpaper into. Drive the paddle from one end with an electric motor and the paddle would rest on a support at the other end or even clamp to the blade. You could get fancy and use a 3 phase motor and a VFD to vary the speed as needed if you want.

Originally Posted by elver

Hmm not mesh. Mostly nice Alox discs from Sandpaperman.
Actually my stock of pads is getting low at this time of year, so changeover is least painless now.

I was also wondering about using a flexible backing disc/ foam too. Maybe that and mesh might be a good starting point.

A sacrificial backing pad is definitely the way to go. The mesh allows the suction of the vac to collect so much more of the dust and the problem of the sanding material clogging is virtually eliminated. The finish is better too because of the lack of clogging. Hopefully you won't need to take any other steps to bring your problem under control.

Aldav - Mesh sheets ordered just now. Cant see a backing pad that fits my current sander 8 hole configuration now so will do that later.

Chris - my paddles are more flat bits than round bits, so spinning won't work for me. The hood with multiple dust ports to create extraction I think might be step 2 after trying the mesh sheets. I think reducing volume inside the space will be important as will reducing the number of open sides, so as to create a path of air ingress with a little velocity.

I honestly doubt that mesh sheets will make any substantial difference but the proof is in the making and it may make enough difference to be good enough.

Look at BobL's posts about bell mouth hoods. He has posted some nice photos showing the effects.

Originally Posted by Chris Parks

I honestly doubt that mesh sheets will make any substantial difference but the proof is in the making and it may make enough difference to be good enough.

I'll report back on whether I can tell the difference.
Given the low quality feedback many give downdraft tables I'm not keen to go there (or to a 'fume hood style box' without being able to move heaps and heaps of air.
I doubt my little 2HP chip collector will cut it. To make it work I think I'll need to keep it more boxed in than I can tolerate and still do the job well.

Pippin,

I've seen the benefits of the BMH. I might be missing something, but I'm not sure that they will assist enough given my little dusty. I sand over about a 1.5m sweep as I work. That might take a lot of CFM and hoods to be effective. My little 2hp dusty just wont cope?

If it was an oft repeated task I would go for a different approach.

Position and fix the ROS upside down with a BMH on 6" duct about 300mm directly above or at a slight angle away from directly above the ROS.

Then move the wood over the ROS rather the the ROS over the wood.

A modified 2HP DC on 6" ducting should be able to cope with this amount of dust.

Might even experiment with that some time and run the particle counters to see what happens.

Interesting thought Bob. Not sure I'd have the same control, only because I've been doing it the same way for a decade or more.. but it might be worth me giving it a crack.

My last job had downdraft tables for the metal finishers. They had 4' x 8' tops with 5hp motors moving 3,000cfm and they didn't get it all. I doubt you will ever get your 2hp to do the job you need.

I suggest you look into ventilation fans. I set a couple up beside my fathers lathe that I salvaged from ceiling mounted heaters in the plant. They were 16" across and had 1/4hp or 1/3hp motors. The fans were mounted just below waist level and when turned on were able to grab all the dust and a good deal of the shavings and blow them out into the woods behind the shop from a few feet away. They were great in the summer but not so much when the snows were on their way. If you can get a good sized fan or two and mount them just above bench height opposite you in the wall or in a window opening They will pull all the sanding dust you produce and when not sanding will ventilate the shed when doing other operations. They will pull enough air that you won't need PPE when you sand. The ones with self closing louvers would help keep the weather out. Example below.

ECOtronic EC Square Plate Axial Fan Series - fans - Fantech

Pete

Originally Posted by elver

Interesting thought Bob. Not sure I'd have the same control, only because I've been doing it the same way for a decade or more.. but it might be worth me giving it a crack.

It will take some getting used to but eventually you might find get more control??
Anyway, I usually prefer to handle the wood especially if its lighterthan the tool.

This is how I set up a belt sander to do what I'm taking about some 15 years ago.
I was surprised to see what level of control I could get.
No BMH those days and only a 1 HP DC. Dust everywhere!
Sander1.jpg

On long stock you'll have to learn to sand from each end so you'll have to flip the work but that's no biggie.

These days I have this 1000 x 150mm belt sander and I handle stock the same way.
I've sanded stock up to 2.4m long with this machine.
It now also has a BHM on the end of the belt
finished5.jpg

Vids of BMHs in action
150mm on lathe


100mm on DP

Bob, I did start off making my paddles just like that with a belt sander. Upside down in a bench, spurting a fine mist of dust _everywhere_.
I moved to finishing up the other way so I can see what I'm doing for fine work. Seeing the pass assists me in pace of work. I've not tried it with the ROS. The sweet spot on the ROS is smaller and clamping will take a little more thought than a belts ander, but I'll try and give it a crack.

What do you think of using large axial fans exhausting dust laden air? If there is room for large diameters are axial fans more efficient at moving air to evacuate dust, compared to our centrifugal systems used in dust blowers, or is the velocity too low to manage the speed at which the dust is exiting a 10000 RPM tool head?

Seems like these large fans are used in spray booths. Per m3/hr they seem more energy efficient, if your not trying to achieve large pressures to push air through a filter.