Woodshop Dust Collection

Since you have the same email chain that I do, you know that the stated purpose of the meeting was an information download between old and new Board members. No mention of other issues. No post on Talk, advising the membership that other issues would be acted upon. No notice of any sort or character, that other actions would be taken prior to the meeting.

It’s nice to hear these statements about what you ran for, etc. But you are a Board member now. What you do, is all that really matters. In this case, you did the exact opposite of transparency. You did the exact opposite of include. And in adopting an action relying on the advice of a salesman with a vested interest in selling his product, and two well-meaning, but wholly unqualified individuals, despite earlier on-record statements by professionals advising that the unit is not big enough to do the job, cannot be described as good judgement, well-advised decision-making, or even common sense.

If we spend $60,000, and the proposed collector turns out to be inadequate, What then? What will be the consequence of your impatience and total lack of research or due diligence? The fire Marshall did not write us up because the dust collector was the wrong model. He wrote us up because the collectors weren’t getting the job done, and the shop was a dusty mess and a fire hazard. Will he close our doors for a couple of months until we can replace an undersized (again) collector? Other Makerspaces have been closed by the Fire Marshall for less.

Are you absolutely sure that the Collector you voted for will be large enough? You blew off the requirement for an third party engineers report. You blew off the advice of two separate members who were also Engineers. You relied instead on the estimates provided by a salesman with a vested interest in selling us his product. On what basis did you blow off your duty to make informed decisions in the best interest of DMS?

Beyond that, the two issues considered illuminate each other. It is a fact, that the Space will be squeezed tight financially in expanding. Careful and thoughtful decisions about money will be required, to avoid forcing DMS into insolvency. Yet, your first action, was to vote to spend $60,000.00, a significant portion of our available cash, on a unit where your only professional advice was, that it wasn’t big enough.

As to the rest, I don’t doubt that you intend to do the right thing, and want to be a good Board member. But that means you have to be accountable for the decisions you make. I’m sorry, that your first foray into it, was to get pushed into a bad decision. The new Board deserved better, than getting pressured by a false “emergency”, and bum-rushed into making a poor decision.

Unless you intend to pay to have the ductwork rehung twice, there’s no reason to buy right away. The new space won’t be available for move in before August. That’s four months away. I call on you to back up a little, get a real third party engineers report on the size needed, and buy a collector based on that, making dead certain you are spending such a huge lump of cash on the right unit. The $3K-$4K spent, will ensure we don’t get burned with a bad choice.

I’m not asking you to do what I want. I have proposed no collector. I’m asking you to do the right thing, and ensure your decision is the best you can make.

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As a lay person, but with a certain amount of science/technical expertise and general Woodshop experience, here is a back-of the envelope analysis interested people/parties should review and consider:

  1. A Dust Collector has a certain rated CFM at the collector; this is what can be found/read on the tin. The actual CFM at any machine port will be somewhat less, depending on efficiency, length, materials used, etc. for rest of system. So a D/C system rated at X will have an effective CFM of X-dX at the machine.

  2. If you have a system that has an effective CFM of X at a machine port when the first port is opened, and then open a second port, you are NOT then getting X/2 effective CFM at each port but X/(2+?), because the decrease in CFM is NOT linear. In our current D/C systems in the Woodshop, once a third port is open, NO port is getting enough CFM to effectively draw chips and dust. This is one of the primary reasons the place is a dust nightmare.

  3. Most of our big woodworking machines require significant CFM, as spec’ed by manufacturer. E.G. the two table saws, router, miter saw, large band saw, jointer, planer, drum sander, edge sander, all require ~800-1100 CFM *each. Applying a simplistic calculation (i.e. NOT taking into account CFM non-linear attrition), this is ~10,000 absolute minimum CFM required. It does not include the 4 lathes, or a few other machines that have a dust ports hooked up. I assure you, we are frequently busy enough that 5-8 machines (dust ports) are in use at same time. And this does not take into account the dust ports that are left open by lazy people and are not noticed/closed by others before they start their work on another machine. In reality, a system for current Woodshop configuration probably requires close to double this,as in 20,000 rated CFM, but IANAE.

  4. If there is an actual proposal(s) for a new system available for review on Talk or Wiki, I am not aware of it, and I have looked. Are we or aren’t we a transparent organization?


And a question, since I can’t locate proposal(s) to review: Is whatever organization/sales person that spec’ed current solution willing to guarantee that it will meet our current and future needs, that is a shop with 8+ machines running at same time that efficiently/effectively collects >90% of chips an dust we produce?

This is a good point.

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This situation like many recent ones highlight how important decision making has become in DMS leadership. That also extends to committee leadership and key volunteers.

There is no need to rush unless there was an expectation set with the Fire Marshall. We cannot knee jerk a solution and then not follow up either.

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It’s a fair bit more complicated that that. The overall static pressure of the system, the cumulative frictive loss of a given airflow, the actual pressure drop created by the fan, and the volume and weight of the material being transported, all need to be known in advance, to calculate the size of the fan needed on the other end (the collector size). That size is calculated by determining the system parameters, and then using the desired air velocity within the duct. Air velocity is the ultimate requirement. If it moves too slow, the chips fall out of the stream, and accumulate in the duct, or are simply not pulled out of the machine in the first place. If you open any of the machines, and look inside them, you’ll see the direct result of too-low velocity. If you’ve used the jointer, and had to stop and clean out the duct and hose because it was clogged, you can thank low air velocity as well.

There’s a pretty good explanation of the basic parameters to a system Here.

In order to correctly size a collector, an Engineer needs to first calculate the overall pressure conditions of the system as designed, and then determine what the worst case condition would be (i.e. highest expected number of users at stations at the far end of the system normally). This will dictate the size of the collector (with a clean exhaust filter).

Since there is no existing design, no one has done this, and therefore it logically follows that no one knows how big it needs to be. The salesman just did a wild-ass guess that it would be big enough. Then he chummed up a nonsense estimate on an external collector, which included a lot of made up numbers which favored selection of his product.

Speaking as an Engineer who has three years working in our woodshop, and having a working familiarity of our useage, current system performance, and future needs, I’m going to make an educated guess that the system needs to be about twice as large as the unit proposed by Andrew. But thats just a guess.

Conditioning all this, is that the Building Inspection Plans examiner that reviews our permit application, is going to require engineering drawings, and very likely require them to be stamped by an engineer. The Fire Marshall (who will also review the application) will likely want the same thing.

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I could not agree more. The scary thing, is that for the first time, we will be in a situation where there isn’t lots of extra money available to hide mistakes and poor judgement.

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Yes, obviously, hence my use of words and phrases like “back-of the envelope”, “simplistic calculation”, and “close to”. Engaging in analysis paralysis here won’t help. Conveying need that a better discussion and more expert consensus is in order, and that we are not in any immediate hurry, is what’s important (I think), and which last several posts have sufficiently accomplished (I hope).

What is the size of the unit that Andrew proposed?

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Here is an outdated list of tools and their manufacturer’s recommended flowrate. But hey, some dude is about to get a sweet commission on a collector that totally is gonna work dude.

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4000 CFM.

Teeeeeeeeeeee-wenty.

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The good news is I just figured out how to use most of our new expansion sq footage:

https://www.industrialvacuum.com/dust-collectors/stationary-dust-collectors/filt-aire-20000-cfm-dust-collector


The downside is we also need to build our own coal fired power plant.

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With the expansion coming up it kind of makes sense to me to at least wait and see where we end up settling. If woodshop gets repositioned next to the back wall, maybe by the ramp even, (cough @John_Marlow) this could become so much more of an easier issue to resolve. Then all the cost of tubing to an outdoor unit is minimized…

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Let me first say that I am not a technical expert in dust collection requirements nor systems. I do not have a preferred solution in mind. However:

(a) We cannot wait for expansion to solve our dust collection problem (not saying that we are waiting for that, just emphasizing that we can’t). Best case, by the time we get construction/installation completed and (whatever relevant portions of) Woodshop moved, it will likely be October or later. That will be nearly one year after the Fire Marshall’s review.
(b) Whatever we do needs to be something that we can either transfer or enlarge in conjunction with expansion, without losing any significant part of our investment.
© We shouldn’t install it in a location or in a manner that will be destroyed if/when we cut a hole in the Woodshop wall to connect with Suite 102. It is possible that we will sacrifice the eastern end of Woodshop to make a passageway into Suite 102 so that people don’t have to walk through a shop to get into the other suite.
(d) The DC system needs to be sized for the assumption that we will add additional equipment. At the very least we will add a duplicate planer, jointer, and probably another table saw - not in the near future but we need to size the system accordingly - or it needs to be something that can be modularly enlarged without losing our investment.
(e) @IanLee - we have permission from the landlord to install an exterior dust collection system if that’s what we want to do. I am not saying that is the right solution, and I understand it is not what was proposed to the board, but we have permission to do that if necessary.

The only analysis I saw that included CFM assessment concerned me, but I am not a flow engineer.

Perhaps we should spend a few dollars and pay an engineering professional to size the system for us …

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Needs more power. Let’s rewire it.

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Just another thought. Any reason we can’t use the existing DC in addition to the new DC? Use existing to be dedicated to 1 or 2 machines each and new dust collector for everything else? I am in the same camp as @John_Marlow that I’m not an expert but agree we can’t wait another 6 months.

I whole heartedly agree. It’s a system that needs to be engineered. Not just for the use now but in the future. In my opinion we are doing it backwards. The engineer needs to size what we need & make the equipment selection based off that need. I feel that this purchase needed to be fully vetted. I do not want us just throwing money out of the window.

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I believe that Andrew is tentatively considering using one of the older DC’s dedicated to the lathes (after the expansion).

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Is there any thought to putting the lathes in a separate “turning” room using their own collector? (For safety too) It also seems that a lathe needs a collector running for a long time, where the other tools are used for a shorter duration and not always at the same time.

We could keep the wood shop where it is, add a new collector now, and move the lathes out when there’s new space.

Maybe it is just me, but I’d also be more in favor of multiple smaller systems for redundancy (failure of one wouldn’t take down the entire shop) and to reduce duct distance.

Finally, are we also looking at air filters to collect airborne dust that the machine collection doesn’t get?

(Sorry if all of this has been covered before. I haven’t read every previous post)

There is some thought of that. That’s what Woodshop has requested.

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What a brilliant idea! This sounds like a plan that makes sense, ask an expert!

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I’m available tomorrow in the a.m.

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But then you would still have the issue with the HVAC returns in the woodshop…