Humidity Question

[Yookaroo]

Weather is mighty cold and being in Canada our humidity has dropped drastically. We have a job that is having difficulties backing up on card stock, the sheets keep jamming in the feeder nowhere else.


I had always thought humidity would cause in machine jams and toner issues, we called a tech who said the humidity is the cause case closed. Im fine with it we will manage after a few hundred jam clears we will be done.

So my question: Will humidity cause feeding issues?

 

[Steve_S]

What is the material you are printing on? We generally only have issues with low humidity on uncoated paper. We're also at altitude (6200 feet) which causes some additional weather-related issues.

 

[Yookaroo]

Printing on 12pt coated 2 side

 

[Bill2618]

I find the curl is more of an issue for jams in the feed tray on hvy stock. Try decurling the lead edge by hand.

 

[Yookaroo]

I think in hindsight we should have printed the side with just the text as opposed to the side with all the images.

I had just always assumed that humidity effected the machine not the feeder.

 

[rath307]

I think static is you issue with low Humidity static builds up on the paper.
This causes sheets to stick together hence feeding issues. We notice this
issue on our sheetfed presses, Digital presses and copiers. We try and keep our Humidity at 40%

 

[Yookaroo]

Well, turns out our cutter cut our stock all grain long instead of short. By hand curling the lead edge we can get a stack of sheets without a jam.

Just so happens our Konica Tech was in and noticed it, too bad our Xerox tech said it was the humidity and didnt look further could have saved us some time.

Funny one for all you guys our tech took all the rollers out of one of our trays, then tried to print, she was like see your papers no good then complained about the humidity and left. We found the rollers on top after she had gone!

Im having the worst luck with technicians this week

 

[dabob]

Technicians are a strange bunch . . . I once had a tech that told me to leave the machine turned off for a half hour . . . "to let the memory leak out" . . . we're still laughing about that one

 

[Corey]

Static electricity is a huge problem in Canada at this time of year. Common effects include printing defects like overspray and ghost tracks, feeding of multiple sheets that cling together in a stack, static shocks are another problem particularly on laminators. Fun for the operators!!!!

Adjusting humidity isn't always the solution because some of the newer substrates aren't hydroscopic, which means that cannot absorb water!!!! The Static String or Static elastic are anti-static cords that work for this. On the delivery, you just place a cord so the sheets can pass over in a space of air.

 

[John W]

It's the change in humidity that causes problems; as long as it remains reasonably constant, mechanical set ups will continue to be fine as long as the RH doesn't drastically change. The stock must be nearby to get used to that RH too.
A cheap and awesome way to get cosistent temp and humidity is to install a water cooled air cond, duct heater, using existing or new ductwork and house type humdifier for the room(s) in question. The air cond fights the duct heater which both dry the air while the humidity adds the moisture back in. Need 3 controls; cool, heat and humidity (human hair if possible). For a room about 18x24 feet, this sytem can be bought and installed for about 10 grand. You can keep the temp within 1 degree C and the humidity within 2-3% year round. Water cooled means no rooftop condenser so the system works 24-7 no matter the outside climate. Get the RH measured with a sling psychrometer at various times to find out your variance. Done it twice with no regrets ever! That 10 large pays back within a year with no jamming happening!
John W

 

[jdsmurf1]

We have found that humidity and static play a big role in feeding stock depending on the substrate. We run a lot of plastic and forced us into humidity control and we run constantly between 45 - 50%.
Low humidity has caused major feeding issues. Also as in the last post, acclimate your stock to the press conditions is critical.

 

[Tron]

Your feeding problem does sound like static. We tell our customers that they need to maintain a pressroom humidity level of 50-55%. This is also the spec stated by PIA/GATF.
Stock coated on both sides is more likely to be effected by static in a low humidity enviroment.

Do you have any anti static equipment on your feeder? If not, you may want to consider this since the geographical area which you are in suffers from low humidity for at least four months out of the year. If you get a static system make sure it is a quality system and not a "fly by night" static bar. Ionized air helps as well.

The easiest way to determine static is to purchase a static meter to see how charged your loads are or ask your pressman(woman) if they are getting shocked on the press when taking out sample sheets. If yes, you have a static problem.

One other point that helps in winter is to make sure that your paper has 24 hours to climatize to your pressroom prior to running it.

 

[GTurner]

Humidity is an issue. I work and live in Denver, Colorado. Our summers are our optimal period for humidity but our winters have low humidity. We have to change our standard paper settings on our copiers to accommodate this issue. The other thing we do and it seem to help the most is not do the pre-press cutting until we are ready to run the job. If we do, we will wrap the paper.

 

[mdc1239]

You could try brushing a laundry fabric softener sheet around the edges of a ream of paper - we found that helped remove some of the static in the paper.