Before we get too much further into dust collection, I’ve decided that it’s time to get some actual numbers on our requirements. I apologize in advance for the novel this post became. I’ve found this article from Wood magazine, which gives us a baseline. In particular, I’m looking at this section:
I’m going to work from the router table example, since it is probably closest to the Maslow. This would give us a required airflow of 195 CFM from the tool. This means that even a 2 1/2" hose is throttling the dust collection flow a little. A 3" hose would give us the required flow for the tool.
Side note: The Rigid R2200 has a 1 1/4" dust collection port on it. That means that either Rigid is expecting very little airflow is needed for the tool or they simply didn’t engineer the dust collection port correctly. I’d believe that its the latter, because when I use my router freehand dust gets everywhere, even with a shop vac connected.
So let’s get into the math. As far as calculating flow, I’m more interested in the rectangular calculations rather than the round ones since my chute’s interior is rectangular. The formula I’ve derived from the article is:
A = (W * H) * 28
Where:
A = Air flow in CFM
W = Interior Width in inches
H = Interior Height in inches
There is 68mm (2.677") currently between the inside faces of the linear rail blocks. We should probably factor at least 0.4mm (0.015") clearances between the rail mounts and the outside of the chute. We have to factor a 3mm wall thickness to get the inside. So the interior width of the chute as it is currently drawn is 61.2mm (2.409").
So:
A = (2.409 * 3) * 28
A = 7.227 * 28
A = 202.356 CFM
We need the section of the chute to be 61.2mm (2.409") x 76.2mm (3") consistently. The issue here is consistently.
Where the chute meets the hood body is really the issue. The opening starts at 113.49mm (4.468) wide, and is 15mm (0.59") tall. This gives us an airflow at this section of 74 CFM, which is less than half of what we’d need. I can’t make this part taller, which would be the easiest way to solve the problem. Right now, we have 8mm between the bottom face of the collet and the stock top. That is with the spindle lock mechanism against the dust hood window. In order to accommodate 1/8" tooling, the most I can comfortably push that is to 12mm. That would give us closer to 94 CFM, which is better, but not great.
The other option is to cut a relief in the top face of the sled to increase the height of the opening. Routing 1/2" into the face would give us 156 CFM, which gets us to the 2.5" requirement. That is factoring in the 4mm we gained by increasing the height of the dust hood. This adds a whole lot of complexity, though, because now the sled has to be machined on both sides for all the required features. I’m not sure if that would ultimately be asking too much of beginners.
This post has already gone on for too long, but I’d like to touch on another related issue:
I was able to look at the center of mass of the model. I had to make the HDPE pad on the bottom steel to approximate the weight correctly. I have the sled massed at 13.6kg, or just under 30 lbs. This is roughly where Fusion thinks the center of mass would be with the router at the bottom of the axis:
I’m definitely going to need to raise the linkages by at least 3/4", though I’m thinking that 1" might be safer. This is going to make it hard to move the linear rails to be over the linkages and still have the router be able to plunge through a sheet of material.
I could probably keep this going but I’m going to end this here.
The TL:DR here is that I’m going to have to do at least some redesigning. I like @dlang’s point of shortening the travel to lower the center of mass more. I’m agreeing with him that 3" of travel is a good amount for most needs.