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Work related post: Eliminating static charge

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Nik

Tue Dec 09 2014, 05:47AM

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

The plant at which I work has a problem with static charge accumulating on one of the products which causes one of our robots to go into a difficult to resolve fault. I would like to hear anyone's thoughts if you have idea on how to resolve the problem.

The process involves unrolling a metalized paper foil with a hot melt glue backing over a hot roller and onto a stone wool substrate. The foil/wool combo is then cut into individual pieces and then stacked, after stacking it is shrink wrapped with plastic and travels down several hundred meters of conveyor belts and metal rollers. When the shrink wrapped stacks get to the end of the conveyor system they are stacked by robots which are easily (it seems) disrupted by static discharge.

At the moment there are a bunch of ground straps hanging over the conveyor system just before the robots, they drag over the shrink wrapped stacks before they are picked up by the robot. Once every 20-30 stacks the robot will get a spark and lock up, requiring a lengthy re-start. As far as I can tell the unwinding of the foil and subsequent cutting and stacking acts like a mechanical voltage multiplier, adding up the voltage of each piece as they are stacked up and then shrink wrapped in plastic. I don't have any measurements with an electrostatic voltmeter but it will give you one hell of a shock from ~15cm.

My first thought is to add grounding brushes after the cutting process and before the stacking process to limit or completely eliminate the charge before it gets to the stacking process. My supervisor is hell bent on getting an "electrostatic expert" (salesman) to build a solution involving HVAC power supplies, compressed air and a regular maintenance contract but it seems like over kill for static build up.

If you have any ideas (or questions) let me know what you think. I'm gunning for the grounding brushes before the stacking process myself. Sorry if I was too vague in any part, there are limits on how detailed a description I can give :/ Thanks company secrets that everyone and china already knows.

Sulaiman

Tue Dec 09 2014, 06:02AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

investigate anti static shrink wrap ?

johnf

Tue Dec 09 2014, 07:00AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

Negative ion generator to dissipate charge

Shrad

Tue Dec 09 2014, 08:13AM

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

haha I have seen that already on similar processes

just put the cheapest christmas garland which contains shiny metallic pigment at places in the process where it can touch the material, hanging from a grounded cable or armature...

the garland touching the material will evacuate charge, and you can multiply it along the chain...

the idea comes from a major vinyl adhesive plant I have worked in which used electrostatic and UV treatment, so that was a major issue

Nik

Tue Dec 09 2014, 10:08PM

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

Thanks for the ideas, I like the Christmas garland, it should go on sale in a couple of weeks and we can stock up.

Ionizers were talked about but with the amount of dust in this plant I'm not sure how long they could go between cleaning.

Antonio

Wed Dec 10 2014, 12:00AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Try to increase the moisture in the air around the plant. Verify if the robots are properly grounded.

BigBad

Wed Dec 10 2014, 03:27AM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

It's probably the hot melt glue that's the real problem. The metal is easy to discharge, but the hot melt glue is an insulator and cannot be earthed.

A static eliminator bar might fix it maybe.

Hazmatt_(The Underdog)

Wed Dec 10 2014, 04:49AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Yea We have moisture control in our cleanrooms. Minimum 35% RH.

zrg

Wed Dec 10 2014, 09:13AM

Registered Member #4762 Joined: Sun May 06 2012, 05:59PM
Location: Russia
Posts: 93

In USSR they used powerful alpha radiation source to eliminate statics. Plutonium based. Extremely simple solution, but looks like not an option here, according modern tendencies of eliminating radiation hazard :)

Shrad

Wed Dec 10 2014, 09:19AM

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

in that factory I worked in, they had corona rolls for vinyl adherence to a backing, thermal adhesive deposition, thermal polymer printing and speeds as high as 120m/min with heaters, coolers and vacuum pumps... I guess there was also a great static buildup there

as they had put garlands everywhere they could, I really think it was effective

when I first asked about this, the guy I worked with told me they had huge problems of the same kind you mention, and it led to replacement of much CMOS logic boards in robots and PLCs

they had a bunch of things replaced by pneumatics with antistatic tubing, but the rest had to be tamed using this trick

since then they had no more statics problem

they were also using frying oil as lubricant for the machines as it was far more resilient than industrial grade designed for the same purpose and discounts were high for big quantities...

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