Register drift after blanket replacement.

[LoSeR1695]

Dear all, I'm currently facing a problem which I don't have enough experience to solve.

We are using Goss Community SSC, which is only 18 months old, printing on CMYK order. When we replace 2 new blankets on black, which is the highest level of a 4 HI tower, the register of K will drift during production in the range of 10mm even we keep the press at constant speed. We did something before production and during production, and it's not improving. We had to put the used blankets back on, and everything running smooth and steady after that.

What I did after replacing the blankets are:
1, Put the impression on, and run for about 1000 copies, stop and re-tighten.
2, Repeat the step above for 2500 copies, and 4500 copies.

During production,
1, Maintain constant speed and adjust the register back in range.
2, Increasing the web tension step by step, until it was almost double than what they usually had.
3, Check the blanket height, tighten the blankets.

None of the job done above made things improve. Our machine is only 18 months old, impression setting was done by installer, blankets and packing are recommended and supplied by manufacturer.

Need opinions and suggestions from the experienced senior here, Thanks a lot.

 

[Cornishpastythighs]

So everything is fine when you put the old beaten down blankets back on? Is the register moving the same way all the time or is it random.
Just some suggestions/questions.
Maybe your blankets are not being supplied with a constant caliper(thickness) Have you checked your plate/blanket squeeze using a packing guage. Do you 'mike' the blankets prior to installation. Are you putting the correct packing under the blanket? Do you torque the blankets or just rely on the strongest guy on the crew to tighten them up? Are you mixing different manufactures blankets. Have you checked/calibrated the infeed nip.

 

[Alois Senefelder]

Register !

Register !

Hello LoSe


Questions - 1) Is the unit to unit C+M+Y register(lateral/circumferential) OK ? 2) Is the Web - tight/slack before entering

the Black(K) unit? 3) Is the Web following the yellow unit blanket after impression? 4) Is the Web slack/tight travelling

forwards to the folder after leaving the Black(K) unit? 5) Is the Infeed PIV driven ?


Regards, Alois

 

[LoSeR1695]

So everything is fine when you put the old beaten down blankets back on? Is the register moving the same way all the time or is it random.
Just some suggestions/questions.
Maybe your blankets are not being supplied with a constant caliper(thickness) Have you checked your plate/blanket squeeze using a packing guage. Do you 'mike' the blankets prior to installation. Are you putting the correct packing under the blanket? Do you torque the blankets or just rely on the strongest guy on the crew to tighten them up? Are you mixing different manufactures blankets. Have you checked/calibrated the infeed nip.

To answer your questions, Everything back to normal after I put the used blanket back on. Black just getting advance and advance, it's moving the same way all the time.

1. I did not measure the thickness as I assume it is the same 1.71mm supplied by the same supplier.
2. Sorry can't understand what is 'mike' the blanket, if you mean fold it, yes I did.
3. Packing had not been change, and it was supplied by Goss. I did inspect the packing, and I'm sure they are in good condition.
4. We keep tighten the blankets using torque wrench from the beginning, until we get fed up and just over tighten it, nothing was improve.
5. Nope, Vulcan 1.71mm, we are using only one brand from one supplier.
6. Sorry, what is infeed nip?

 

[LoSeR1695]

Hello LoSe


Questions - 1) Is the unit to unit C+M+Y register(lateral/circumferential) OK ? 2) Is the Web - tight/slack before entering

the Black(K) unit? 3) Is the Web following the yellow unit blanket after impression? 4) Is the Web slack/tight travelling

forwards to the folder after leaving the Black(K) unit? 5) Is the Infeed PIV driven ?


Regards, Alois

Dear Alois,

1) C+M+Y is ok.
2) Web is tight before entering black.
3) No, the web is going up straight to the black blankets.
4) The web was tight at the beginning, then it slowly become slack at same speed without lowering down the web tension.
5) Sorry, not understand about this questions.

 

[Cornishpastythighs]

So nothing has changed 'except' you install a brand new blanket and problems arise and the problem goes away when you put back the old blanket. If this was me I would most certainly look at the caliper or type of blanket you are using. Does it do this everytime you install a new blanket, then I guess it gets better as the blanket gets older and is ok until the next blanket change.

 

[Deleted member 16349]

Dear Alois,

1) C+M+Y is ok.
2) Web is tight before entering black.
3) No, the web is going up straight to the black blankets.
4) The web was tight at the beginning, then it slowly become slack at same speed without lowering down the web tension.
5) Sorry, not understand about this questions.

Different batches of blankets can have different pulling rates. Basically they can result in different effective diameters on press. A supplier might say the blanket is made the same as before but it can be that something was changed in their manufacturing operation.

I remember one time we got the same type of blanket and it performed very different from earlier similar types. It turned out their manufacturing process was changed. We were insetting and the difference was very noticeable in the level of infeed tension required.

Mixing new with old blankets can do the same thing. And if you mix new and old blankets and there is a difference in manufacture of the new blanket, in normal production (not insetting) it is hard to see the result, except by looking at the tension levels between units. Also the tension out of the unit will affect how the blanket feeds paper.

It is an interesting subject. I wrote a TAGA paper in 1997 on this topic.

 

[BeauchampT]

We have a very good blanket supply, but we have noticed, much like Eriks comments, that changing only a few blankets at a time can cause serious register issues.

I would recommend changing all your blankets at the same time, and see if taht helps.

Also if you are running a vertical tower, have you confirmed that the blankets you are running are neutral feed? If they gave you a postiive feeding blanket and your original are neutral feed (or vice versa)...well, besides getting another blanket supplier, you need to change to right combo of blankets.

Regards, T

 

[LoSeR1695]

We have a very good blanket supply, but we have noticed, much like Eriks comments, that changing only a few blankets at a time can cause serious register issues.

I would recommend changing all your blankets at the same time, and see if taht helps.

Also if you are running a vertical tower, have you confirmed that the blankets you are running are neutral feed? If they gave you a postiive feeding blanket and your original are neutral feed (or vice versa)...well, besides getting another blanket supplier, you need to change to right combo of blankets.

Regards, T

Thanks Sir, I'll get some information about positive feeding and neutral feeding blanket first as I'm not really understand about it. Replacing whole 8 pcs blankets are the only things I can do now.

 

[jbeniston]

On the back of your Blankets there are usually some thin lines of coloured thread. They should form a right angle with the blanket edge.
If not it will mean that there will be uneven tension in the blanket when the tensioning reels pull it tight. The lines will not be at right angles to the cylinder axis.
You can check by getting a sheet if paper that is cut square. Put one edge of the paper along one of the lines preferably one close to the blanket edge.
Check at the point where the corner of the paper/line meets at that part of the blanket and see if the paper follows the blanket edge across.
I have seen this more than 1cm out by the time I was three quarters of the way across the width of the blanket.
Cut the excess off so that the lines will be at a right angle to the edge. When you install the blanket the lines will be at right angles to the cylinder axis. Give it a shot it worked for me.