Thein/Cyclone Dust Separator

Preamble:

Having used sandblasters before, I am well aware of the dust that gets out of a cabinet and settles on everything in the work area. So, on this Instructable, I have shown my construction of a Thein/Cyclone dust separator complete with motorized blower to compliment my Sandblasting Cabinet. https://www.instructables.com/id/Sandblasting-cabi...

Now, there are dozens, if not hundreds of articles on how to build a dust separator and mine is just one-of-the-pack. Better than some, not as good as others. Inspiration was taken from Cosmas B. "Building a cyclone separator for a vacuum or Shop vac"

Since I don't have access to some materials and the machinery that this builder did, I fabricated it using different materials and methods. You may feel that some of my methods are a little unsafe, but I have been fabricating and repairing all manner of industrial machines and equipment for almost 60 years with only one incident (50 years ago) where I cracked a finger bone on a drill press with a foot-operated on switch. I learned to be very careful from that incident. Take your time and think twice before performing and machining procedures.

I've also added several drawings showing air-flow through smooth and corrugated pipe as well as round a 90 degree elbow. In a smooth pipe, the fastest flow of air is down the centre of the pipe because friction against the walls creates drag on the air. And you can see how disturbed the airflow is in the Cyclone separator drawing.

Corrugated pipe, such as a vacuum cleaner hose not only creates more drag, but also causes eddies in the air, severely slowing airflow. You may have noticed this when connecting the hose to an operating vacuum cleaner. You can actually hear the load increasing on the motor.

A 90 degree elbow creates its own problems. As the air is forced to change direction, it creates an area of low pressure effectively reducing the pipe diameter.

And... photos of my circle router jig.

So, smooth, straight pipes are best for any air or liquid flow.

I was unable to locate suitable tubing for the cyclone, so I used duct metal sheeting. I used my 'scoring' method of cutting the metal to the required size so that edges didn't become curled.

See my instructable “How to cut thin sheet metal and keep it flat” https://www.instructables.com/id/How-to-cut-thin-sheet-metal-and-keep-it-flat/

My preferred box cutter was broken, so had to use my spring-loaded one with extra care.

The dust collector is a 20 litre white pail upon which the cyclone separator sits with the centrifugal blower on top of the separator.

I used MDF for the 'wooden' parts because I had it and it is easy to cut. Make sure to use a mask when cutting MDF because it creates a lot of dust very fine when being cut . You will notice in some photos, that I often use 1” wide double-sided masking tape to prevent movement of work-pieces while routing, cutting or drilling. I simply clean the working surface and place the material on top. I made a circle-cutting template for my router from a piece of ⅛” plastic using a wood screw for the pivot point. Even if you use a purchased jig, you still need to check the actual cutting size on a piece of scrap wood before routing the actual piece. Remember to measure from the correct side of the cutting bit dependent upon cutting inner or outer circles.

The Plexiglas was first rough-cut with a sabre saw and then finished with the router. Before the top wooden form was routed into a ring, it was used to ensure that the plexiglas was the exact same size by cutting them one after the other, without changing the router settings. (hope that makes sense)

Boring out the centre of the Plexiglass was done with a fly-cutter in my drill press. (Do not try to do this with a hand drill. At best the Plexiglas may break and at worst, you could be injured)

Because my Plexiglas was ⅜” thick, I needed to bore out a ⅛” lip to ensure that my 1½” ABS threaded fitting would seat down effectively.

The Plexiglas top and the top wooden ring were temporarily taped together while six equally spaced pilot holes (screw root diameter) were drilled around the perimeter. Leave one piece of tape on each part for future assembly positioning. Once the pilot holes were drilled, the parts were separated and the Plexiglass hole were opened up to clearance size. To prevent wood splitting when screws are driven in, the pilot holes should be the 'root' diameter size of the screw you're using, so the wood wouldn't require a second drilling.

The sheet metal wall of the cyclone was unlatched and laid on a flat surface to facilitate marking and drilling 6 equispaced pilot holes around the circumference top and bottom. The sheet metal is now wrapped around the outside of the top ring and inside the bottom ring and taped firmly into place. The 6 top and bottom pilot holes (screw 'root' diameter) are now drilled into the wooden rings and then countersunk for the flathead screws. Do the pilots holes only as long as the screw you're using – no less, no more. Mark a reference point on both ends for final assembly location.

Having done that, remove the sheet metal and lay it back on the flat surface a drill out the 12 holes to less than the maximum screw head diameter. This will act as a 'countersink' for the thin metal. When the metal is wrapped back around the top and bottom rings, the screws will 'dimple' the sheet metal into the countersunk holes in the wood.

(A photo illustrates these sizes)

The centre tube that evacuates air from the chamber also supports the inside baffle. A hole needs to be cut into this pipe near where it is glued to the baffle. Photos show how I did this.

The 'inlet' pipe-support was made from 8 pieces of MDF. Each piece was centre bored to the OD of the 1-1/2 ABS pipe. Each piece was coated with good quality wood adhesive and placed on the tube. When all 8 pieces were on the tube and clamped, the tube was pulled out (to prevent becoming glued to the wood). The next day, the wooden block was squared off using my electric cut-off saw. The curvature of the sheet metal was drawn onto one side of the block and came out close to 10” diameter. Since my cut-off saw-blade is also 10” diameter, I set up two pieces of scrap wood on the saw table to allow me to cut closely to the curve. This is illustrated in 2 photos and you will notice at this point, the ABS pipe has been press-fitted (not glued) into the hole and will be cut along with the wood. It also served as a handle while cutting.

Consecutive saw-blade thickness cuts were made until the entire block was curved. Now for some sanding to correct the curvature of the block, and to fill a mistake I made during cutting.

Once the curvature was correct, masking tape was place on the cylinder the correct distance from the top of the cylinder. Then the block was correctly positioned on the cylinder and the pipe hole traced onto the masking tape. Allowing for the thickness of the pipe wall, the outline to be cut was hand drawn inside the traced line.

Now, I have been cutting thin sheet metal with a box cutter blade for many years, but you may want to practice on a piece of scrap first. Alternatively, you could drill a few small holes close together and use a mini hacksaw blade to cut the curve. Using a jigsaw may distort the metal and be dangerous to your well-being. It is relatively easy to punch through the thin metal by holding the blade against the metal and lightly tapping it near the cutting edge with a small hammer. Continue cutting around the curve keeping inside the line.

I have never cut myself using this technique, but I am not responsible if you do! When finished, the edges of the hole will be a little distorted. Hold a piece of curved wood on the inside and tap the outside of the cut with a small hammer thus flattening the defects against the wood. When that's done, use a rotary sanding drum in a hand-drill to smooth the hole edges and bring them out to match the inner pencil line.

Now you need to glue the pipe into the support block. I use LePage 'outdoor weatherproof glue' Wipe some glue on the outside of the pipe towards and including the back of the curved cut. Also wipe glue around the curved pipe cut in the support block. Insert the curved end of the pipe through the square end of the support block and push through until the curve of the pipe matches the curve of the support block. Clamp the curved end of the pipe to the block. Wipe off excess glue and leave overnight to ensure the glue hardens. (Because the pipe wont allow air to get to the glue, it takes much longer to harden as opposed to gluing 2 pieces of wood together). The next day, sand the glued joint until it is smooth.

Correctly position the support block onto the metal cylinder making sure that the curvature of the pipe matches the hole in the cylinder. Mark the outline of the block onto the cylinder. I now placed masking tape against the outside of the outline and marked 6 places where the block mounting screws will go. Drill these marks using a 'screw root diameter bit'.

Now apply double-sided tape to the curved part of the support block and place it back on the cylinder as before. Once again, make sure that the curvature of the pipe matches the hole in the cylinder. Now using the same bit, drill through the mounting hole from the inside of the cylinder.

If you hand-drill is too large, simply mark through the cylinder holes onto the block with a pencil and then remove the block and drill it. However, this may not be as accurate because drill bits tend to wander when drilling into wood. Slightly countersink these holes.

Now enlarge the holes in the metal cylinder to the size mentioned before, (for sheet metal countersinking), and as shown in one or two of the photos.

We are ready to assemble the cyclone unit leaving the plexiglas and centre baffle till last. When the plexiglas is mounted (be careful to NOT over-tighten these screws, or you will crack the plexi.

Finally, mount the centre baffle using the ABS screw fittings making sure that the air outlet hole in the bottom of the pipe is slightly behind the air inlet hole in the metal cylinder. Do not glue the ABS threaded fittings. You may need to dismantle it for cleaning from time-to-time.

I have tested the completed cyclone dust collector in conjunction with my sandblasting cabinet. I was using fine bi-carbonate of soda as the medium and was really surprised at how much stayed in the pail and how little was ejected through the blower. However, I have tied an old pillow case around the output tube of the blower to catch any fine powder that gets through

I hope you the reader, like what I have shown here, but if there is anything about this construction that needs some clarification, or you have any questions, please ask.

Also, if you notice errors in the text, I would appreciate your informing me. The spelling is UK English, not American English.