When Do You Shut Down Machines For Bad Weather?
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    Default When Do You Shut Down Machines For Bad Weather?

    So we have several CNC profit centers that tend to be sensitive to partial and intermittent power outages. Historically, it's been the call of the department leads and the shift supervisor to run during times of significant risk of loss of power. We're kinda in the boonies, so this is not a particularly uncommon occurrence.

    When the remnants of Ida came through we had what was likely a crash due to power fluctuation on one of our main production machines being run on second shift. Since the operator wasn't quite up to speed on how to recover, several downstream problems happened resulting in the machine being down for the next four days.

    In hindsight, getting those few extra hours of production time at the cost of four days of downtime wasn't such a good bargain. So I'm wondering if anyone has a formal set of hard limits in place saying that if one or more of the following conditions exist, or are likely to exist, shut this machine down. I'm looking to establish a formally documented baseline so that we're all more or less all working out of the same playbook.

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    Do you have a local weather service that shows lightening strikes in your area?

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    One supposes that there will be all manner of procedures, which may or may not be applicable.

    But we have too little information. What exactly caused the four days of downtime? That's where I'd start.

    One dodge that comes to mind is to provide a UPS to power all but the axis, spindle, coolant pump drive motors, so even if power goes down and machining stops, the computers will know to cancel the program and not restart until the current work piece has been removed and any broken tools replaced, and the humans finally press the start button - this should be a matter of hours, not days.

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    Very rarely do we shut down our 20 cnc's for a storm. Only when it's a very,very nasty storm do we shut the machines down. In fact I think we've only done it 3-4 times in 30 years.

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    Quote Originally Posted by Joe Gwinn View Post
    But we have too little information. What exactly caused the four days of downtime? That's where I'd start.
    This was on a CNC turret punch. So since this happened on 2nd shift the facts are rather malleable, but I suspect the sequence went something like Brown Out cause the machine to error out. Operator tried to reset the control but managed to get the machine out of sequence from the controller instead and crashed the die transport hook into a partially loaded tool, bending the cylinder tang. Cylinder height had been misadjusted by someone mucking around in the machine at some point in the past, so clearances were critical. Proximity sensor that detects the presence of the die in station had to be re-adjusted once the proper die hook clearances were re-established and the turret control re-synchronized.

    Kind of a Daisy Chain of little and not so little things. As opposed to when Henri was coming we shut down and disconnected the night before and everything came back up nominal the day after the storm.

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    Hard to say. Normally we won't interrupt operations unless the area is in the middle of major weather and employees need to leave and take care of families. We've had some pretty nasty storms come through and didn't lose any power.

    On the other hand, ever since the big Texas Snow Storm in January, it seems like we loose power every couple months for anywhere from 10 minutes to four hours, and this is in blue sky daylight. I THINK.... it's due to them intentionally turning things on and off while improving the grid for increasing power requirements and bad weather demands, at least that's what I keep telling myself. It hasn't been too frequent, but still unpredictable.

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    It sounds to me like a user error. Machines go down for one reason or another. I would spend my time on a start up protocol.

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    I'm in Florida... Summer thunderstorms can shut down the whole plant/city for a few minutes.

    We just run until they stop.

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    I remember running 3 six spindle screw machines during a storm. I was standing near the bay doors and watching the storm. I saw a lightning strike about a block away, one of the transformers for the shop developed an arc across the terminals for about 5 seconds with that strike. The machines slowed noticeably then resumed speed when the arc died.

    A friend told me about a lightning strike on the line coming into his shop and seeing an arc develop from his big lathe and grow in size. He was amazed the arc went out from the corner of the lathe in a straight line. I told him the arc was growing like a Jacob's ladder and following the rebar in the slab. No mystery there. He had to replace or rewind ever motor in the shop that was plugged in. After hearing this experience I unplug all the machines and shop computers during heavy storms. I live on a 300 acre ranch and can point out more than a dozen lightning struck trees and fences. Also had to replace a span cable on one of the center pivots that was struck by lightning.

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    You could buy a lightning detector, We used to use them when doing any critical hoisting with cranes

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    This must depend on where you live and power dependability history. I don't normally lose power during a storm, but experience fairly frequent power outages for no good reason at all. They usually last between ten seconds and a couple minutes. Probably happens, on average, once or twice a month. Completely unpredictable.

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    It's time for a "green" investment along with any tax credits. Install a sizeable solar PV system grid tie with significant battery capacity and put your CNC machines on that. Effectively it gives you a UPS for them at taxpayer subsidized expense and "green" feel-good credits. It will also reduce your electric bill so you'll recoup some of the cost eventually.

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    Quote Originally Posted by wp6529 View Post
    It's time for a "green" investment along with any tax credits. Install a sizeable solar PV system grid tie with significant battery capacity and put your CNC machines on that. Effectively it gives you a UPS for them at taxpayer subsidized expense and "green" feel-good credits. It will also reduce your electric bill so you'll recoup some of the cost eventually.
    How to account for the energy usage to clean the SNOW off the panels 5 months out of the year ?
    Back feed them from the powerco, and heat them up ?

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    Many moons ago when I ran somebody else's shop, we had a really close lightning strike. I think
    it might have hit our pole outside, or one very close. Power went out and came back up, but nothing
    worked right.. The HIGH leg was 77v.. One transformer got fried.

    Nothing broke that day, but over the next week, lost the power supplies in 2 computers, and one machine,
    and had 2 driver boards go bad.

    If I can tell its cloud to cloud lightning, or its over that away in the middle of nothing, I won't
    shut down, unless I need an excuse to call it quits.. If its right near me and rolling hard, I'll
    shut it down for an hour so until its passed. An hour of productivity, I can make that up.. A
    $1000 driver board, that hour isn't going to pay for that, and I'm not big on gambling.

    When it was somebody else's money, I wasn't so cautious.


    There is an ap that my Dad and my better half have. Tells you where the lighting strikes are
    compared to where you are sitting at that moment. I should probably down load that.

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    Quote Originally Posted by crazygoat View Post
    Do you have a local weather service that shows lightening strikes in your area?
    Rig up a pole attached to a ground rod, away from the property.

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    The power at my house is very unreliable. It goes off at least once a month, even in good weather. We have some pretty bad storms and we unplug all computers, TVs, etc. when they get close.

    In the past, we've had a tree stuck by lightning, had a 2-week old TV fried, and a couple of phones. What a nuisance!

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    I'll add too that with all our storm related power outages, we've never had electrical damages to equipment, with the exception of damages to rooftop HVAC units and transformers upstream from our shop, BUT we also always install a dedicated ground rod next to every CNC machine and every PC is on it's own battery back-up surge protector. We might just be lucky though.

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    If you are running “profit centers” you should also have profit center protection. A bank of uninterruptible power supplies should give your people time to shut down the profit centers.

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    Quote Originally Posted by M.B. Naegle View Post
    I'll add too that with all our storm related power outages, we've never had electrical damages to equipment, with the exception of damages to rooftop HVAC units and transformers upstream from our shop, BUT we also always install a dedicated ground rod next to every CNC machine and every PC is on it's own battery back-up surge protector. We might just be lucky though.
    Hello Naeg;le,
    This is a very important subject that I have been interested in for quite some time. My shop is located in Northern California and in 30 years I can count 7 to 10 outages that include flickers of power disruption. I do all the wiring here and I do not use a grounding rod at any machinetool at my location. I would like to hear more from you and others of this practice.
    thanks

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    Quote Originally Posted by otrlt View Post
    Hello Naeg;le,
    This is a very important subject that I have been interested in for quite some time. My shop is located in Northern California and in 30 years I can count 7 to 10 outages that include flickers of power disruption. I do all the wiring here and I do not use a grounding rod at any machinetool at my location. I would like to hear more from you and others of this practice.
    thanks
    Many of the machine tool foundations I made drawings for had extensive grounding from the manuf.
    a grid of ground rods all around the machine, bonded with thermite junctions in place.


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