DC chip vs fine dust collection

[ian maybury]

No prob Dave, I had a look at the Dylos and most certainly am not knocking the use of particle counters. The point was just that the fine end of the dust produced by most machines comprises only a small part of the output, and also of the permitted airborne dust in the case of the 1mg/m3 limit. They seem to work very well, and are basically the only show in town so far as making objective measurements is concerned. I just wish i could afford one right now...

What I was trying to point up was more the personal sense that very much in keeping with Chris' comments above that dust collection (while very well known field in the professional engineering sense) is for us DIY guys not an exact science. (this page of technical topics by Camfil Farr gives a feel for how well developed the topic is in industry: http://www.farrapc.com/articles/This one here on recirculation of filtered air make some interesting points: http://www.farrapc.com/articles/recirculating/)

There's a learning curve involved for most of us, and the task is made significantly more difficult by time/budget limits, varying dust collection capabilities and needs on different machines, and the poor availability of good performance data and design information for most of the available dust system hardware.

The consequent reality that it's not always easy to (without experience) precisely predict outcomes using the fairly basic data and design rules used at this level - especially if using minimally specified equipment to save money. ( the latter part of no 6 here shows for example how the output of a marginally specified blower can be very sensitive to small changes in system resistance/pressure drop http://tiny.cc/ljbh3)

So while if we could each afford to go to a professional supplier and contract for delivery of a system guaranteed to meet regulatory requirements it'd all be very straight forward, the reality for most of us is that there's inevitably a degree of ongoing investigation/development/trial and error ('development' is perhaps upmarket trail and error) involved in getting to a good a dust system.

We're probably not doing badly if in selecting the core components and configuring our systems (blower size, filter capablity, duct size, dust separation capability - plus layout) we find our way to a system that works well (maintains clean enough air in the workshop to be so far was we know safe) on our major applications, and is capable of being tweaked into working well on the remainder.

i.e. It's probably not unreasonable to say that while a few bugs are pretty inevitable, the key requirement in planning a new system is to try avoid painting ourselves into a corner that's not easily recovered from. (installing a system that can't do the basic job, or hasn't got the legs to enable ongoing improvement)...

ian