problems with print on reverse of sheet

[richck]

We have recently been printing a job on an SM52-5 that when backing it up we have been having problems with the image slurring/doubling, the job has run perfectly on the first side. The stock is 170gsm gloss (which is a good quality stock) and is set up work on turn, it has quite alot of coverage. Every other job we have done has been fine,on all other stocks. So i'm inclined to think it is some thing to do with the paper, but don't understand why the first side would run fine. We had an engineer in the other day and he agreed it could be something do with the paper, he adjusted some of the grippers but we still had the same problem. The only thing i can think of that might of affected the paper (4 pallets SRA1) is that before it got to the press it wasn't brought into the pressroom to acclimatise and was left in a storage area for 4 days that gets cold and very damp, and we had non stop rain for 4 days, then it was straight onto the press. Would this have had that much affect on the paper?
Thanks.

 

[rapid3]

Do you have an IR dryer? What temperature were you running your loads?
Also, if the job was a S/W or W/T, try running the back on the same side
guide as you ran the front to eliminate that.

 

[richck]

Yes we have IR dryers usually set at around 32c. We've run it on both lays and it doesn't alter anything.

 

[rapid3]

After you print the 1st side, does the paper develop either
a tight edge or wavy edge?

 

[richck]

Yes its a bit wavy, but it was wavy before we printed the first side. like i said in the original post we've printed lots of other jobs without a problem, its just this one stock.

 

[rapid3]

Are you using the 1st printing unit to bump or are you running black in it?
We had similar problems on an SM74 when running black in the 1st unit
with unstable stock. Bumping in the 1st unit & running black in the 2nd unit
helped.

 

[richck]

yes just using the first unit for dusting, black in the second. When we get running on the second side and get sheets without the slur the fit is spot on, there just doesn't seem to be any sequence to it when you look through the sheets.

 

[vaithi47]

why dont you run the same job w/t on a different stock.if there is no slurring then you can be sure that it was the paper if not it is some problem with the m/c

 

[Tahir]

problems with print on reverse of sheet

we have faced the same problem with same gms of paper ,the formate was work & tumble , gripe side changed . So i turned the plates gripe side & kept paper grip same ,it works but some sheets remain with same problem . i also print this job on 150 & 135 without any problem

 

[turbotom1052]

when you lay a few sheets down on the inspection console during the backup do you notice that the sheets dont lay flat? are there areas of the sheet (usually around to perimeter) that are kinda baggy? this would be consistent with what richck suggested in that the edges are wavy or tight. if this is the case im thinkin your probably SOL sometimes the misregister can be minimized by controlling how it enters the infeed. not familiar with sm52 but on the larger speedmasters a careful and precise application of smoothing paddles or holdowns can help smooth the sheet out before it enters. the tighter you can put these paddles down on the sheet without affecting its register and side guide pull the better chance you have of minimizing your problem. ive also gained a little control over this by using streamers to control the sheet during its entire trip down the feedboard. my understanding is that a sm52 can be set up to feed sheets individually as opposed to a stream feed??? have you tried doing this?my first thought too was how much heat you applied but if your certain that you didnt overheat the sheet then id say in the future you might want to look at your climate control in the pressroom and try to be more conscientious when it comes to properly acclimating your stock before printing. these are the most likely causes for what your experiencing.