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  1. #1
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    Default WIP 150mm Auto Blast Gate

    I've been working on a blast gate prototype that is driven by a simple controller (arduino, photon or similar) and opens and closes with a simple servo motor.

    So far I'm pleased with progress. It is compact and quite simple to build, and is about $30 per gate in parts (with a bit of scrap and scrounging). It wouldn't be hard to incorporate auto start of DE when any machine is turned on, and that machine's gate to automatically open when needed. I'm not aware of any gates set up in this kind of way, but the butterfly mechanism is so simple, I'm wondering what I'm missing.

    So I've got a few questions:

    1. how much impact on flow will a disc have when the gate is fully open?
    2. can anyone point me to non-invasive ways of getting an input to say a machine is turned on? (I think a current sensing device might be the go here)
    3. what else am I missing?



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  3. #2
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    Bob will reply with more accuracy, but I suspect it would have a fairly significant impact on the airflow, as it is. Looks to be about 10mm thick ply? If it was sheet steel or (rigid) plastic sheet it would have considerably less impact.

    When the motor is not running will it have enough torque resistance to hold the disc in place against the airflow (when closed)? The airflow will be constantly trying to push it open.

    Like the idea though - very neat.
    Regards, FenceFurniture

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  4. #3
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    I think your biggest issue will be when you turn on the extractor, you may find your servo motor won't have the strength to keep the door opened.

    Also dust will build up around the pivot and prevent it from opening/closing.

  5. #4
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    It also doesn't seal so it may whistle like a banshee when closed.
    Those were the droids I was looking for.
    https://autoblastgates.com.au

  6. #5
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    Great to see other people tinkering with the automation side of DC.

    With regards to your machine input question, have a look at this thread - Current sense switch - For dust extraction automation

  7. #6
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    Good on you for having a go at this.
    Lots of people, including many engineers, ask me what I don't make blast gates this way.
    One engineer at the mens shed has asked me this on many occasions.

    To assess general efficiency, this back of the envelope calculation might help.

    A 150 mm diameter opening has a cross sectional area of 17670 mm^2
    What you have in effect created are 2 hemi-circular openings each of ~ 8835 mm^2
    This equates to a circular opening of ~80 mm in diameter.
    At nominal DC pressures each will conduct will conduct ~250 CFM, so a total of 500 cfm will get through both openings.
    Compare that to 1250 cfm for a 150 mm diameter duct and its a no brainer that it's an inefficient gate.

    Flow rates are determined by wall perimeter length to cross sectional area ratios
    In practice the wall perimeter of each opening is greater than the perimeter of an 80 mm diameter so the flow will be less than 250 CFM.

    The next most significant thing is what Tony Z says, curlies, strings and other things will get caught on it and further blow the air flow.

    It's worthwhile considering posting your idea before trying it out - we could save you a lot of development time.

  8. #7
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    I realise you want an automated gate, but the main reason you want it automated is because you want to prevent a machine from being used without dust extraction being available.

    In other words "no machine can be operated without dust extraction being available to that machine"

    A much cheaper solution is to turn the problem on its head.
    Don't allow a machine to start unless the DC is on and the right blast gates are open/close.

    Two of us members have found the easiest and cheapest ways to do this is to use a pressure switch connected to the machine switch with the pressure sensor tube connected to the DC ducting near to, or into, a machine cabinet.
    Making sure your DC is on

    It been working a treat at the mens shed. Some members gave me the devil eyes for weeks after I installed these switches at the shed but now everyone agrees that they have been very effective at making sure the DC in on to a particular machine.

  9. #8
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    Quote Originally Posted by BobL View Post
    Good on you for having a go at this.

    It's worthwhile considering posting your idea before trying it out - we could save you a lot of development time.
    Thanks for both encouragement and a reality check Bob. I enjoy playing about like this, so I'm happy to spend a few hours to knock together a rough prototype. I knew it was important to ask before I got carried away with an automated system with lots of bells and whistles.

  10. #9
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    Quote Originally Posted by BobL View Post
    I realise you want an automated gate, but the main reason you want it automated is because you want to prevent a machine from being used without dust extraction being available.

    In other words "no machine can be operated without dust extraction being available to that machine"

    A much cheaper solution is to turn the problem on its head.
    Don't allow a machine to start unless the DC is on and the right blast gates are open/close.

    Two of us members have found the easiest and cheapest ways to do this is to use a pressure switch connected to the machine switch with the pressure sensor tube connected to the DC ducting near to, or into, a machine cabinet.
    Making sure your DC is on

    It been working a treat at the mens shed. Some members gave me the devil eyes for weeks after I installed these switches at the shed but now everyone agrees that they have been very effective at making sure the DC in on to a particular machine.
    I got caught out several times today with either the wrong gate open or multiple gates open ... I'll have a good look at that set up Bob. Thanks.

  11. #10
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    From the research I have done, the automated dust extraction systems that are around fall into something akin to the ol' project triangle; Easy to install and reliable quality = expensive, Cheap to install = poor quality, etc. especially if the DC system is done with Bill pentz advice along with the advice on these forums.

    That's why I have gone for a decent controller, pneumatic cylinders and good quality blast gates (started off with self cleaning blast gates from the USA, but found the clearvue blastgates work just as well and are far cheaper - thanks Chris!). The system keeps me working without having to think about dust.

    I installed a system for the FIL and it worked out about 1K for the system for 6 machines - with room to expand easily and not too much more cost as the infrastructure is now there. Certainly not cheap, but I expect many years of usage for both him and I with little maintenance.

    Hard to get that mindset past being happy to pay big $$$ for the rotary sander saw thicknesser lathe with the inverter VFD drive system and the attached mortiser , but reluctant to spend the money on being able to make sure we can keep using these machines long into the future.

    Only had to work in a saw mill for a while to see how dust affects people after a while and needs to be dealt with now, not later.

  12. #11
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    Quote Originally Posted by maxxsinner View Post
    From the research I have done, the automated dust extraction systems that are around fall into something akin to the ol' project triangle; Easy to install and reliable quality = expensive, Cheap to install = poor quality, etc. especially if the DC system is done with Bill pentz advice along with the advice on these forums.

    That's why I have gone for a decent controller, pneumatic cylinders and good quality blast gates (started off with self cleaning blast gates from the USA, but found the clearvue blastgates work just as well and are far cheaper - thanks Chris!). The system keeps me working without having to think about dust.

    I installed a system for the FIL and it worked out about 1K for the system for 6 machines - with room to expand easily and not too much more cost as the infrastructure is now there. Certainly not cheap, but I expect many years of usage for both him and I with little maintenance.

    Hard to get that mindset past being happy to pay big $$$ for the rotary sander saw thicknesser lathe with the inverter VFD drive system and the attached mortiser , but reluctant to spend the money on being able to make sure we can keep using these machines long into the future.

    Only had to work in a saw mill for a while to see how dust affects people after a while and needs to be dealt with now, not later.
    I wasn't aware of the clearvue 6" gates until you mentioned them. Do you have details on how you automated them? Pneumatic? How did you control them? Thanks.

  13. #12
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    I haven't probably added enough detail on how I have done it, but my build blog below might give some insight.
    https://www.woodworkforums.com/f200/workshop-dust-extraction-install-build-blog-202966


    I use a PLC to control the system and 5 way/ 2 position valves to control the cylinders controlling the blast gates.
    Happy to help with any queries you might have.

  14. #13
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    I've been thinking about this over the past couple of days. These are the some things that are driving the grey matter:
    - needs to be simple (I have a tendency to overcomplicate)
    - needs to alert/remind/enforce only one gate open at one time
    - auto starting of DE would be nice (but needs to be simple)

    I don't have any of the clearvue gates yet, but plan to order some soon and test out an idea. If anyone has thoughts/experience of those gates and can comment before I get there, I'd appreciate it.

    Assuming it works with the gates, I'm leaning towards a string operated mechanism. Pull the string to open a gate, release to close. I'm not sure how well that will work, but guess it would need some kind of spring return tension, or weight and gravity.

    All the gates can then be operated from one central panel.

    If the gates are fitted with a simple microswitch, a light can show an open gate. Perhaps a two colour light could show red/closed and green/open.

    The string positions and lights on a panel give an easy visual. A simple code on arduino can show more information, like errors (ie. two gates open at once).

    The arduino can fire up the DE on demand.

    The lights can be extended to each machine and placed in proximity to switch gear, giving a visual go/no go without needing to tamper with same switch gear.

  15. #14
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    Some interesting ideas there.

    A gravity return might work by orienting the gate so that it slides in the vertical direction and then just adding weight to wither the top or bottom of teh gate.
    This assumes there is enough space for the gate to work in the vertical direction.

    I'm not familiar with the Clearvue gates but most gates I have seen have stiction issues sometime during their life so weights might have to be quite large to over come this.

    Rocker style gates gates operate in a horizontal/rotary direction so if your motors have enough torque you might be able to go back to your original rotary approach.

    If the gates are fitted with a simple microswitch, a light can show an open gate. Perhaps a two colour light could show red/closed and green/open.
    The same microswitch might be able to be used to tell the program what gates are open and closed.

    Quote Originally Posted by arniew View Post
    The arduino can fire up the DE on demand. .
    DE shouldn't be used just when a machine is running but run for some time after the last dust making activity to help clear fine dust.
    Some time of timer should be added wither as a physical timer to the circuit or in the Arduino program.

  16. #15
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    Quote Originally Posted by BobL View Post
    Some interesting ideas there.

    A gravity return might work by orienting the gate so that it slides in the vertical direction and then just adding weight to wither the top or bottom of teh gate.
    This assumes there is enough space for the gate to work in the vertical direction.

    I'm not familiar with the Clearvue gates but most gates I have seen have stiction issues sometime during their life so weights might have to be quite large to over come this.

    Rocker style gates gates operate in a horizontal/rotary direction so if your motors have enough torque you might be able to go back to your original rotary approach.


    The same microswitch might be able to be used to tell the program what gates are open and closed.


    DE shouldn't be used just when a machine is running but run for some time after the last dust making activity to help clear fine dust.
    Some time of timer should be added wither as a physical timer to the circuit or in the Arduino program.
    I’ve been happy to let go of RC circuits for timing and instead flash code to a controller. Much easier! What length of delay do you suggest for a DE and what about an air filter in addition?


    Sent from my iPhone using Tapatalk

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