slitting on press

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slitting on press

Postby gricey » Sun Mar 03, 2019 10:17 am

Hello,
I read your comments about Flexotecnica and I must agree with everything you wrote. I purchased a Flexotecnica EVO xd8 and yes I am highly impressed with the results and we are achieving things with it that we could of only dreamed of just 2 years ago.
However there is one constant issue that we can not resolve and it's the issue with slitting in line. We are a paper cup company using hot cup board and we will print and slit either 3 or 4 wide and slit each lane.
The in feed and out-feed web guides are Fife and we run and slit both from the edge of web at 400mpm. What we are experiencing is the web wondering constantly during the run and variation is 1mm-8mm. We have checked every roller is square and level. The tensions are indicating that they are steady, we've extended the web guide in-feeds and out-feed lengths but still we are no closer to solving this issue.sometimes we have issues with the web flapping and slack edging but it's the failure of the web guides to correct the web from moving that is mystifying me, They've both been serviced and calibrated.
I am sure you must of had similar experiences and i'm hoping you may have some advice for me to try to sort this issue.
Thanks for any advise you can give.
Gricey
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Re: slitting on press

Postby longtimefan » Sun Mar 03, 2019 10:56 am

Have you tried to run guides in center and see if still an issue? This would verify if from Fife or not.

Taper tension set right?

You just may have to turn up tensions at rewind

Cores enough air?

If there is a bow roller or banana roller, is it set right?

Rider roller, or lay on roller out of adjustment?

Cores under cut to eliminate any issues there?
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Re: slitting on press

Postby guy de cafmeyer » Mon Mar 04, 2019 3:45 am

The fact that you mention slack edges is already a major issue if it is paper .. or any non-extensible substrate , as these cannot be pulled out with tension .
Rather than using a banana roller , it would be preferable to use a grooved roller , just before infeed into the drum nip . ( Grooved outwards.. )
Before rewind you could do the same , or otherwise use gum tape around the idler roller .. also wound outwards . This may help to keep the web central in the press .
Just for info , ensure that the paper is placed centrally on the unwind , rewind and place cores where required , and then only drop the nips .
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Re: slitting on press

Postby gricey » Tue Mar 05, 2019 4:31 pm

guy de cafmeyer wrote:The fact that you mention slack edges is already a major issue if it is paper .. or any non-extensible substrate , as these cannot be pulled out with tension .
Rather than using a banana roller , it would be preferable to use a grooved roller , just before infeed into the drum nip . ( Grooved outwards.. )
Before rewind you could do the same , or otherwise use gum tape around the idler roller .. also wound outwards . This may help to keep the web central in the press .
Just for info , ensure that the paper is placed centrally on the unwind , rewind and place cores where required , and then only drop the nips .


Hello Guy.Thanks for the reply, Yes the web runs through the center of the press, Can you explain a little more about the grooved roller not sure what you mean by this.
gricey
 
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Re: slitting on press

Postby gricey » Tue Mar 05, 2019 4:44 pm

Hello longtime fan Thanks for the reply.(Sorry for the cap letter reply it was easier to cut and paste your reply)
Have you tried to run guides in center and see if still an issue? This would verify if from Fife or not...YES THE WEB IS RUN THROUGH THE CENTER OF THE PRESS.

Taper tension set right?...YES THE TENSIONS ARE SET CORRECTLY, HOWEVER THEY ARE BEING MONITORED AT ALL TIMES.

You just may have to turn up tensions at rewind.... I WILL TRY THIS A LITTLE MORE.

Cores enough air?... YES CORES ARE FINE

If there is a bow roller or banana roller, is it set right?... YES THERE IS A BANANA ROLLER. BECAUSE WE SLIT INTO 4 LANES WE USE IT TO SEPARATE THE WEB JUST BEFORE WE SPLICE. CAN YOU GIVE ME ANY TIPS ON THE CORRECT SETTINGS FOR THE BANANA ROLLER.

Rider roller, or lay on roller out of adjustment?.... NOT CHECKED THIS, DO YOU MEAN THE ROLLER THAT RUNS ON THE REWINDING REEL?

Cores under cut to eliminate any issues there?....WE CAN TRY THIS.
Thanks once again.
Gricey
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Re: slitting on press

Postby longtimefan » Wed Mar 06, 2019 10:03 am

Bow roller..

Should be some sort of lock down on it.. Loosen it and then should be able to turn it clock wise or counter cw.

Play with it to see if it works.. Normally they are only to seperate the slit edges.

I ran thick paper.. And could go up to 190 pounds on rewind.

Try going up on rewind tensionif you can
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Re: slitting on press

Postby RedsInABox » Thu Apr 18, 2019 2:16 am

I don't have much experience with printing and slitting in line on paper but I do with other substrates such as HD/LD PE and PET. In particular, when we ran into this issue on our PE films it would almost always be caused two factors. For one, if the rider rolls and idler rolls on the rewind or leading up to it were not square this would cause the very same issue you're having. Usually minor level adjustments and increased rider pressure would alleviate the issue. The lesser seen issue is gauge variation in the film from one side of the web to the other. If one side is hit with the micrometer at say... 1.5 mil and the other end is reading +/- .10 to .25 after the film is slit that single lay on and rider rolls can't account for the film variation as the roll diameter increases. It might be worth checking your paper and making sure the gauge is consistent from one side to the other. If you're diameters are not increasing at a consistent rate, one side will eventually be lacking enough tension to allow for the rolls to slide.
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Re: slitting on press

Postby Gorilla Printer » Fri Apr 19, 2019 6:38 am

I don't know if it will help any but we have fife web guides and what I've learnt over time (through experimentation and watching the maintenance guys lol) is the guides can be set to sort of react to the material faster or slower by adjusting them in settings.We can usually run PE tubing on the same settings as film.But there is one particular film that is waxy and wants to slide all over the place causing stepping in the profile of the roll on the rewind.Yet the roll's edge profile on the unwind is flush all the way up the side.After experimenting in settings and increasing the sensosr speed to react I found we could replicate the out rolls profile to the in rolls .The sensors reaction time was near set to the max.The camber roller was constantly fast twitching/vibrating .
It's quick to do on the run and I do it regularly.
I 'm guessing the science or jargon behind web guides and hope I have explained this OK

Two tips:
Always know where the original setting was set before experimenting.

You'll know when you have set them to the sweet spot.Your rolls will wind up with a good edge profile and the web guides will not throw the camber roller out when a splice goes through.

Cheers
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Re: slitting on press

Postby colbyc36 » Mon Sep 09, 2019 6:45 am

Is the web shifting before or after the slitting?
If it is happening after the slitting process, do all the lanes shift in proportion to one another, meaning...do they do it all together in the same direction? Are you experiencing overlap that prevents roll separation?
A floppy edge will cause the lanes (after slit) to track differently.

8mm is a lot of shift.
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Re: slitting on press

Postby Jonathanburbank » Sun Oct 20, 2019 12:06 am

Are we talking about a walk at rewind, or is the substrate moving before the print unit?

What kind of bow roller setup? If it is a ZPos, then I deal with this all the time.
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