Static, static, everywhere...

[bbates]

So we deal with a lot of static. Our material can be completely free of it, via ionizing bars and still it will gain static just as it sets in a room. So severe that 50+ 12" x 48" sheets can be picked up and held vertically by holding on to just one sheet.
What is/are some of the tricks you all use? Is there any resources that you can recommend to talk to about this in more detail? I'm hunting for a better grip on the causes and potential solutions.

 

[Seeking Knowledge]

bbates,

Have you tried introducing humidity?

I find those ionizing bars to hocus-pocus. To be fair, I have only used the ones from Meech and they never worked. I once called their tech support to ask how to use the two dials on the box and how to figure out the sweet spot and the response was "just keep changing the dials until you find what works".

 

[bbates]

Yeah, we try to keep our humidity between 50% and 55%. Much higher and the curl is unmanageable.
We have two ionizing bars on the end of our machine. According to the operator the material does not have a charge as it come out or the machine, but as it sets on a table, untouched, it builds up a charge. I am a bit skeptical, but do not have enough experience/knowledge to call anyone out. Do you have any experience with the air blown ionizing bars VS. the proximity method?

 

[Seeking Knowledge]

I would be a bit skeptical too. What material are you dealing with and what is the printing process?

 

[bbates]

Toner printing, silicone liner, poly with poly over lam. Lotsa points of friction and pressure, both candidates for nasty triboelectric charge introduction.

 

[dabob]

We run a lo tac (aka cling) plastic stock on a Xerox and yes there is a lot of static build up but just think of the free electrons floating around inside of a modern "copier/digital press" . . .

 

[bbates]

Exactly, I'm trying to think of a way to completely nullify the charge after in leaves the print machine. But I am beginning to think it is a magnet and eliminating it may not be possible.

 

[Al Ferrari]

The method of combatting static by raising the humidity requires that a sufficient time elapses for the printed sheets to equilibrate to the environment. This should also take care any curling due to uneven moisture content from one side compared to the other (there could be other causes for the curl, such as the influence of the roller transport system in the printer.

Al

 

[bbates]

Our material is even more sensitive than that. Our liner is very thin compared the poly on it. Too much humidity has effect even when plenty of adjustment time is given. The optimal printing humidity is between 50 and 55%.
We can experiment with higher, but what happens when it goes to the client where humidity is not controlled?

 

[Al Ferrari]

Well, What I wrote applies only to uniform like sided material. If you are using material that is NOT uniform and like sided, then all bets are off. Sorry, but I have no suggestion for your problem.

Al

 

[ondemandbindery]

Where is the main sore spot? Feeding Printed material or the ending result meaning a delivery?

JW

 

[bbates]

Feeding is good. The post-print material is where all the charge resides. Our machine introduces heat (fuser), pressure (rollers) and friction (plasma coated plates). We stuck two ionizing bars on the end of the machine, one above and one below the output hole. The operator claims that the material is static free immediately after output, but gets more static as it sets?

 

[Cornishpastythighs]

Not sure if this is any help to you but when we ran problem sheets on the sheetfed presses we used to hang that metalic christmas Tinsel and make sure it dragged across the sheets, make sure it is grounded. It could sometime mean the difference between running say plastic sheets or just going home and downing a large scotch.
Good luck

 

[bbates]

That tinsel is not robust enough to fight the amount of charge that we are generating. We were thinking of even ionizing the whole production room!

 

[Seeking Knowledge]

bbates,

Is it possible to change the rollers that used when laminating? If they are rubber try polyurethane or vice-versa. Have you tried a different type of laminate? Have you tried to Ground the table that the parts are siting on?

I too have used the Tinsel when laminating and it seems to help a lot.

 

[bbates]

The rollers are mostly plasma coated, our adhesive is really nasty stuff so everything but one tension roller is plasma coated (non-stick). The non plasma coated roller cannot be anything else, unfortunately (I've asked). We have few option with material for our method of printing and the needs of our clients. The table is not grounded but we have set them on those antistatic mats and that was grounded, but the charge still built.