Missregistration between fist and second printing station.

[Irida]

We are expiriansing missregistration between the first and the second printing station. The first station image seams to increase verticlay ass the image progresses from bottom to the top. And it gets worse the thiner the paper we use. We tried many things but we can find the solution. Offset machine is a 1997 Speedmasted 52-2p. Any sudgestions?

 

[CKL]

Are you saying the that unit 4 is printing longer than unit 1 ?
Is this a new problem ? or reoccurring daily problem ?
If you can't measure the cyl. bearer height? Start with cylinder packing and torque.

 

[old guy]

i would start with fresh blankets and fresh packing

 

[Magnus59]

Are you using metal or polymer plate material?
If polymer, you need to eliminate any stretch in the plate material first.
If metal plates, you need to ensure all packings are correct to give you accurate print length

 

[Irida]

Are you saying the that unit 4 is printing longer than unit 1 ?
Is this a new problem ? or reoccurring daily problem ?
If you can't measure the cyl. bearer height? Start with cylinder packing and torque.

This is a new problem. The unit that has the problem is the one that is right after the feeder. We already checked bearer height , blancket and under packing and they are ok. Could you please tell me what do you mean with torgue? Is there a chance that the Zero point presure wise of that Printing unit is not the same as the other unit and more presure is applied on the fist unit?

 

[Cornishpastythighs]

http://premo-concept.biz/en/documents/Print-Media/Europe/Blanket_Tensioning.pdf

Some reading material

 

[SteveSuffRIT]

Is your paper flat?
Are there any indications of the paper being wavy or tight edge due to moisture content or relative humidity (HR)?
Also, is the paper grain long and not short?
Steve Suffoletto

 

[Irida]

Is your paper flat?
Are there any indications of the paper being wavy or tight edge due to moisture content or relative humidity (HR)?
Also, is the paper grain long and not short?
Steve Suffoletto

Paper is flat (no waves due to humitity ) . Relative humitity is maximum at 54%. Paper grain is short.

 

[SteveSuffRIT]

Irida,
It is strongly recommended you run the paper with the grain parallerl to the cylinders, so grain LONG.
Steve Suffoletto

 

[Irida]

Irida,
It is strongly recommended you run the paper with the grain parallerl to the cylinders, so grain LONG.
Steve Suffoletto

I know this. But why do i have this problem only on the fist unit?. if i remove the first unit and print all color on the second unit i dont have a problem

 

[CKL]

Before you spend too much time on it. I would recommend you have a tech put a dial indicator on each unit and see if anything is worn or moving around. If the units are stable try to adjust your print length with packing adjustments, then adjust your plate cyl squeeze to be uniformed.

 

[Alois Senefelder]

Hello Irida,

You have received lots of excellent advice - BUT what are you doing wrong?

Take us through your step by step Make-ready sequence

1) How many Units does your press have ? 1 / 2 or more

2) Are you sure all the Blkt/ Plate Heights are correct and Torqured down correctly?

3) Are all the Cylinder Bearers nice - clean and bright looking?

4) On all presses, #1 Unit is the first beginning at the Feeder, 2 3 4 and so on!

A quick press check - CLEAN all the bearers the 1) Dab a spot ink (make sure you thin this down) - about 25mm in from the Plate leading
edge, then place 1more halfway around the circumference, place the last one about 25mm in from the leave edge of the cylinder.

DO THIS ON BOTH THE - GEAR SIDE/ WORK SIDE OF THE PLATE CYLINDER BEARERS.

Put the Press Impression and rotate the press 2/3 times, Off impression, these "Dabs should have transferred onto the Blanket Cylinder

neatly!

Next, post a picture of what you are seeing on the sheet


Regards, Alois

 

[turbotom1052]

Breakaway solids, and a full evaluation of everything printing pressure related, would be the starting point in troubleshooting this problem. I would add.... do NOT trust what is stamped on press plaques or on the back of blankets and packings. Measure everything. When arriving at correct printing heights for your plates and blankets, use a packing gauge. Be certain that your running long grain paper as mentioned earlier, and have it be of a known good quality.

 

[wyagow]

Just a thought. Check the squeeze (gap) between your transfer jacket(s) and the back impression cylinder. When you said it gets worse with thinner paper it makes me wonder if there is to much play between cylinders. If there is to much gap the sheet will tend to wiggle more and cause registration problems. I may or may not be wrong but worth checking into.

 

[DeckledAgain]

If the sheet is "Growing" wider at the tail of the press as compared to the second unit tail (but the lead edge registers the same) the issue is with sheet growth. This issue is common with grain short paper as the sheet absorbs moisture it will swell in width and this is the main reason most paper is printed grain long, so the swelling is around the circumference of the cylinder . The only way that I know of controlling this is to reduce the amount of squeeze (impression cylinder pressure) and more importantly reduce the amount of water on the plate. If it is consistent you maybe able to spread the tail of the plate a little to compensate and find a happy medium.

If you are getting doubling of the images then it sounds mechanical: As you are stating that the press is a 1997 SpeedMaster 52-2p (assuming ZP) meaning there is a perfecting unit between the first and second unit of a two color press. I would suspect there is a sticky grippers in the transfer units (clean them all) or a Thrust Bearing is going out which will produce a doubling from grip to tail of the press speeds up or shuts down.

 

[kev_24]

Measure the accurate print length if using metal plates

 

[Irida]

So funny not so funny story. After a while we started having problems with the print in perfecting mode. We found out in the end that the misregistration between the two printing units was due to a damadge on the perfecting transfer unit. In the end after spending enough money and time changing the hole thing we solved our problem. Btw just for information the damadge was caused because the suction from the refrigerator was blocked and there was bad circulation. Water was slowly leaking and was corroding the perfecting transfer unit. thank you all for your answers. i hope this helps someone in the future.

 

[Irida]

If the sheet is "Growing" wider at the tail of the press as compared to the second unit tail (but the lead edge registers the same) the issue is with sheet growth. This issue is common with grain short paper as the sheet absorbs moisture it will swell in width and this is the main reason most paper is printed grain long, so the swelling is around the circumference of the cylinder . The only way that I know of controlling this is to reduce the amount of squeeze (impression cylinder pressure) and more importantly reduce the amount of water on the plate. If it is consistent you maybe able to spread the tail of the plate a little to compensate and find a happy medium.

If you are getting doubling of the images then it sounds mechanical: As you are stating that the press is a 1997 SpeedMaster 52-2p (assuming ZP) meaning there is a perfecting unit between the first and second unit of a two color press. I would suspect there is a sticky grippers in the transfer units (clean them all) or a Thrust Bearing is going out which will produce a doubling from grip to tail of the press speeds up or shuts down.

No ZP is a GTO model if Im not mistaking around 94-95. this is the fist SM52p model with fully automatic perfecting mode. I posted above what was the problem in the end. thank you for replying