Thien baffle needs more suction (aluminium routing)

[Mustard]

Hi all,

After some large "offcuts" of aluminium from my CNC router threw holes in my Hare&Forbes (Aus equivalent to Harbour Freight) dust collector I decided to chop it up and make a Thien style collector using a 44 gallon drum and mounting the dust collector ring to the lid with the dust collector fan mounted to the top of that.
The separation of the collector works fantastic with absolutely no chips or offcuts exiting the fan. That said since doing the modification it has lowered the suction capability of the collection system just enough that it no longer sucks up the offcuts very well. As this is quite important so the offcuts don't foul my cnc router tip I need to find a way to increase the suction.

From what I have scanned across the multitude of information two things could effect this, the inlet position and the depth of the fan into the centre of the collector. Both of these are unfortunately quite hard to modify now I have built the collector so I'd like to know what I am doing before I attempt more modifications. Can anyone shed some light on the effects of these in laymans terms so I can judge what I am doing?

Also I was wondering if simply upgrading the fan to a higher Hp motor will help? Or if need be even replacing the whole fan unit with a higher CFM unit from a higher grade dust collector (I should be able to buy these as spare parts) will do the trick?

Any help is greatly appreciated.

Regards,
Mark de Jong.
Mustard Bikes.

[retired2]

I'm not sure I totally understand your separator design, but if it behaves anything like a conventional top hat, the sad reality is that separators impose a significant loss of air flow.  In fact, my test data shows that loss to be about 40%, and that is using a separator with all the bells and whistles to maximize performance. 

I have a bandsaw at the longest distance from my stationery DC.  Without the separator in the system, no saw dust escapes.  With the separator, there is a lot of dust on the table and floor.  That's what happens when you lose 40% of your air.  You are trying to pick up much heavier waste, so I am not surprised by your results.

It is possible you could make some changes that would improve things, but I seriously doubt you can solve the problem without a higher rated blower, i.e. more CFM and SP.

[Mustard]

Ok, that sounds like what is happening then. My design uses the middle section of your typical bag/filter type DC mounted to the lid of a 44 gallon drum. I cut the slots in the lid of the drum, which results in the typical Thien design. The top of the "separator" has a disc made from chipboard to seal it off with the original DC fan mounted with it's inlet in the centre of the separator.
Sounds like I might have to upgrade the fan though to get the suction I need.