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Work related post: Eliminating static charge

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Ash Small

Wed Dec 10 2014, 01:34PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

UV light can be used to eliminate static charge if the charge is negative, but I don't know how practical it would be in this case.

Shrad

Wed Dec 10 2014, 02:24PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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in that case (I guess this is insulation material fabrication as described, like rockwool or similar products) the bands seem to act as a giant van de graaf

if you allow a string of garland to pick charge under the belt at some places (so that only the small hairs of the garland are touching the belt) and ground the garland, I think it would suffice

are the belt rolling cylinders in nylon or PTFE, or any other insulating material? if so, maybe use some conductive ones? are the belts themselves well grounded?

did you check for potential difference between the robots and any other large metal frame in the process, which would indicate ground loops or inadequate potential equilibrium?

BigBad

Wed Dec 10 2014, 05:39PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Sticking the robot controllers in Faraday cages could help.

Nik

Thu Dec 11 2014, 12:08AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

All of the rollers used to move the product are metal however there are are a few hundred meters of conveyor belt used in the transport system. All of the conveyors run over grounded frames but I'll check them out for static next shift.

I don't know the polarity of the static charge (hadn't thought of it) but I will grab a neon bulb next time they run it and find out.

The plant is about 400,000m^3 so climate control is unfortunately out. If we could control the air it would be a lot nicer place to work than it is now (5 degrees in the winter and 30 in the summer). We do however have the same static problem even in the summer when there is very high humidity.

I agree that the charge is more than likely on the glue and that this might be like the x-ray scotch tape effect.

Thanks again for all the input. I'll be shopping for garland shortly >_<

Shrad

Thu Dec 11 2014, 08:47AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

Nik wrote ...

I agree that the charge is more than likely on the glue and that this might be like the x-ray scotch tape effect.

do you have the opportunity to test the area with a scintillator or detector of some sort?

I think even an old digital camera would indicate if there is radiation emission... this is worth checking

Nik

Fri Dec 12 2014, 01:02AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

To get x-rays the tape had to be unrolled in a pretty serious vacuum, the plant I work in unfortunately operates at around 1 atmosphere >_<

BigBad

Fri Dec 12 2014, 03:29AM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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I suppose in this situation the metal backing is your friend. If you can earth that, even if the hot glue on it is charged, the metal backing will create the opposite charge very close by and tend to cancel out the voltage practically everywhere.

So lots and lots of garlands; you want the metal discharged everywhere, and obviously, you don't want the garland to be a short to earth, it should really go through a resistor to slow the discharge to avoid creating a magnetic field/radio wave and EMC issues.

The thing I'm most interested in is the robot manipulator itself, when it picks up the sheet and lays it down, I'm thinking that MUST be earthing the sheet the whole time. If it's not, and it picks up the sheet in any voltage field, then as soon as it moves the sheet, there's electrostatic induction going on right there.

I mean Q=cV, charge is conserved and the capacitance will be varying if the capacitance is reducing then the voltage can go sky-high.

Shrad

Fri Dec 12 2014, 08:05AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

the problem is that before passing on the belt, the metal backing and rock wool are spliced in parts and piled, then are traveling unconnected from any metallic source

maybe BigBad is right and you just have to let a string of garland gently touch the metal backing when it comes out of the coating machine, so that it is discharged before reaching the belt

it would be the same as grounding your van de graaf bottom end

BigBad

Fri Dec 12 2014, 05:35PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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The metal backing needs to be earthed the whole time they are being piled; you do NOT want to be piling up any net charge.

If they have any net charge, as they come together the voltage will be going up, roughly proportionally, with each extra sheet added to the pile.

Shrad

Fri Dec 12 2014, 08:19PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

could it be an idea for a new type of static generator?

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