Tophat CNC Design & Build -- Results of first bucket full

[BradD]

Hi Everyone!

My goal with this build is to improve the dust collection in my home shop, using as many existing resources as possible.

My "before" system is a Rockler wall mounted dust collector similar/identical to their current DustRight model connected to their 10-gallon separator with 2-1/2" hose connections. The shop contains a table saw, radial arm saw, 2 sanders, and last but not least a CNC router. The 2 saws connect directly to the DC through 4-inch hoses and blast gates, not using the separator. The sanders have 2-1/2 connections, and the router has handheld 2-1/2" dust collection. (You'll see in the videos I took.)

The 2-1/2 inch collection path is Dust Collector -> Elbow -> Wye -> blast gate -> 4" flex hose, 10 or 20 feet as required -> 4 to 2-1/2 reducer -> 2-1/2 inlet to separator -> 2-1/2 outlet to 10 or 20 feet of 2-1/2 hose, as required -> nozzle or machine connection. This setup is also used for floor cleanup. As you can imagine, by the time you get to the end, there's not much suction left.

Next: The new design. Stay tuned!

[BradD]

After studying this forum, I was pretty sure I had absorbed enough to draw up a plan that I could build on my CNC router that would eliminate parts, incorporate several important design principles and provide smooth airflow plus provide enough adjustability to experiment with different settings of the baffle plate and the height of the exhaust.

Let's look at a top view of the base plate:


This is a 2H design (4" hose inlet, 8" nominal height). The inlet transitions from 4"D to 2x8" rectangle, and intersects the window at a 10 degree angle. The window sits in a rabbet that puts it very near the edge of the baffle cutout. The baffle cutout is 1/8" off the bucket I.D. The base provides a large support area for a thin hardboard baffle plate, while staying back from the edge.

Now, lets look at a top view of the top:


The top outline is a copy of the base. The top provides a groove for the window, and an outlet hole for the exhaust.

The baffle plate looks like this, in 3/16 hardboard:


The baffle plate provides a 1-1/8" gap for the dust to fall through. The bottom edge gets beveled on the belt sander to reduce the thickness at the very edge by about half the thickness of the hardboard.

I'm attaching a DXF file of the drawings for your reading enjoyment.

Next: build photos and video

[tvman44]

What program do I need to open a .dxf file?

[BradD]

The first step was to cut the parts on the CNC. The material is 3/4 MDF, just because that's what I had. The MDF did provide me with plenty of fine dust for testing.  :P

The YouTube vid runs a little over 20 minutes with lots of CNC action: Enjoy!
http://youtu.be/wNUUT9ZkBcs

With the parts cut, it's time to assemble.
Bending the window, loose assembly:


Different angle:


I don't think I allowed the acrylic to heat enough to become really bendy. It formed a big arc with the ends about a foot off the table. This turned out to be a good thing, as the window later cooperated by springing tightly into its groove.

As I mentioned before, I sanded the underside of the baffle plate to thin the edge:


Edge-on view:


Fully assembled and ready to test:


Next up: Testing, results, recommendations.

[BradD]

What program do I need to open a .dxf file?

Most CAD programs will work. I'm don't know for sure, but Google Sketchup might work, and it's free.

Also try googling "dxf viewer".

Can anyone else help tvman44?

Brad

[BradD]

Before I get to the test video, I want to show a couple of pictures of the Rockler separator, showing why it's not an optimal solution:

The separator lid:


As you can see, the inlet blows sawdust straight at the outlet elbow. Also, the airflow has to make a 180* turn to leave.

Looking at the bottom of the bucket:


Here you can see that the swirl goes all the way to the bottom, creating the cool looking sawdust-scape.

Here's video of the first test run:
http://youtu.be/iTvZFy-N6Es
Success! ;D

Very little dust got to the filter bag. This picture shows what got thru:


I'm afraid my floor is the same color as sawdust, so it's hard to see. I'll say there's less than a quarter cup of dust that went to the bag. Remember, this is MDF dust, so it's pretty fine to begin with. I'm very happy with the result.

According to my Kill-a-watt, the DC draws less current now than with the old system. This is counterintuitive, as it stands to reason that more air moving = more amps. There is no doubt in my mind that there is more air moving than before. I should have noted the voltages before and after. Does anyone have a thought on this?

What needs improving? The edge of the baffle plate in front of the inlet sticks up and catches dust and larger chunks. I think I'll make a piece to go from the inlet ramp to the edge of the baffle plate.

Also, I would move the baffle plate support cutout more clockwise. I think if the baffle slot went a little farther around, collection might go faster.

I'm also going to make a clamp-y thingy to hold the outlet tube more solidly.

Phil, thank you for your separator design. It is a modern marvel. Check your email, you've got some bucks on the way.

Thanks to everyone looking. I welcome questions and comments.
Brad

[BradD]

I just filled up my first bucket load, and I wanted to show everyone the results. Just to jog your memory, it's a 10-gallon bucket from a Rockler Dustright Vortex. Wood dust comes from the CNC router, table saw, floor sweepings, etc. Wood is mostly a mixture of MDF, plywood and poplar.

Here's a top view of the bucket contents:

The inlet is over the lower left, and the swirl goes clockwise.

More of an angle:

The low point is under the inlet, the high point about halfway around. The center of the bucket is the lowest point with a conical wall around it.

Here's the dust bag dump:

This is about 2 cups of very fine wood flour.

another angle:


Here's a handfull:

This is very fine dust. Silky soft with no lumps or bigger pieces.

Overall, I am very happy with these results. The shop is staying cleaner and airflow remains high with so little dust going to the bag.

Thanks for looking!

[BernardNaish]

Great build. Did you really use acrylic for the walls or was it polycarbonate and how thick was it? If acrylic I would be interested to know why you selected it rather than polycarbonate. Thanks for sharing a very interesting design.

[BradD]

Hi, Bernard. Thanks for the kind words.

The walls are acrylic. I made the choice on very unscientific grounds:  It is reasonably priced and available in Home Depot stores.  A 24x48x.090 sheet is under $30. This link will get you to the product:

http://www.homedepot.com/p/202038048?N=5yc1vZbrdgZ1z0th74Z1z0xux8Z1z0z676Z1z0z6cb

I ripped an 8" wide piece of the sheet using my table saw. Set the blade just high enough to cut through and keep it flat on the table. I also recommend using a zero-clearance table insert.

Good luck on your build. Don't stress on the minutiae, follow the general guidelines and you'll end up with a good functioning separator.

Regards
Brad

[jgt1942]

What program do I need to open a .dxf file?

Most CAD programs will work. I'm don't know for sure, but Google Sketchup might work, and it's free.

Also try googling "dxf viewer".

Can anyone else help tvman44?

Brad

Sketchup will work. click File > Import > drill down to where the file is located. After loading the file click Save or Save As and save the file.

IrfanView will also work but you may need a plug-in which will be identified when you open the file.

AudCad will work - there are free versions you can find on the web.

[BradD]

Sketchup will work. click File > Import > drill down to where the file is located. After loading the file click Save or Save As and save the file.

IrfanView will also work but you may need a plug-in which will be identified when you open the file.

AudCad will work - there are free versions you can find on the web.

Good info, JGT. Thanks. I wasn't sure about Sketchup, because I don't use it. IrfanView is a pleasant surprise. I've used it in the past, but never knew it would do DXFs. DesignCad 3D Max is my CAD of choice. It makes and reads DXFs.

Thanks again!
Brad

[jgt1942]

BradD - Thanks for the info on DesignCad 3D Max. In the past I used Autocad only because my brother was using it and when I built my house the guy creating my house plans used Autocad. Thus my knowledge is super limited however I was able to show the guy creating my house plans a lot that he did not know.

I looked at DesignCad 3D Max and they offer a student discount (about 85% off) and as an old guy taking advanced woodworking at my local college I qualify. In that this makes it super cheap I may take a look at it however SketchUp has served my needs and I've found a bunch of add-ins that make it super useful some are free, some a small fee and some are super expensive. I stay away from the super expensive. I'm NOT an expert with SketchUp but is has been a great tool. It, and I'm sure any drawing tool, forces one to think things through.

[Paranoid2569]

BradD. Is there any chance of you cutting me out the 3 pieces on your cbc router and mailing them. I would gladly pay you for material, time and shipping?

[retired2]

Nice job Brad.  Two tips.  1) Lose all the flex hose you possible can!  2) Move that 90 degree a foot or two away from the blower with straight pipe.

Bonus tips: 3)  replace that 1xD plastic ell with two segmented ells opened to 45 degrees each.  4) add an air straightener in the straight piece of pipe in suggestion 2.

These may seem like insignificant changes, but your blower is probably rated at about 650 CFM and I don't know what the SP is, but if you intend to pipe all the tools with rigid pipe and tight ell's you are going to be looking to save every morsel of SP that you can.