Gear Lines or Gear Streaks or similar lines in print

[Deleted member 16349]

I am guessing that there are a lot of causes for unwanted lines or streakes that go across the print.

These happens occasionally in Dry Offset printing and maybe more so than it does in conventional offset.

Dry Offset tends to have form rollers that have higher Durometer values than conventional offset. Soft form rollers do not work well. We run with rollers that are about 60 durometer (Shore A I believe).

So here is the question that I would like to ask.

In conventional offset, does the hardeness of the form rollers have an affect on the tendency of having Gear Streaks or similar unwanted lines in the print?

Thanks for any comments.

Erik

 

[RGPW17100]

One of the main causes for ghosting on conventional offset is the stripe to the plate is larger then the stripe to the oscillator. Form to oscillator should be around 1 mm wider then the form to plate stripe. Conventional printing transfers and forms are typically the same durameter. Water rollers play a more important part in roller hardness.

 

[bspillai78]

hallo erik,

i do agree with rgp's statement, reg roller setting. i am not much familiar with dry offset. but in conventional offset, mostly it accqires because of dampening system.

regards,

balaji.

 

[BillJ]

Gear mark issues also differ depending on the press and type of gearing. Helical gears are less prone to marks. Also motorized dampening can cause gear marks

 

[Deleted member 16349]

Thanks for all the comments.

Does anyone see any relationship to the hardness of form roller to gear marks?

Do harder form rollers make the problem worse or have no affect?

That is really the question I am looking for. Maybe there is no relationship.

 

[JOHNYPRINT]

Hi Eric
Most inking rollers are of a similar durometer and would not have the effect you are encountering, you should be able to contact your roller supplier,they can be very helpful . if this was happening whilst printing conventional, i would first check all damper settings plus damper and pan roller bearings. what sort of condition has the press been kept in. regards johnyprint

 

[bspillai78]

no

no

dear eric,

i don't see any important relationship with roller hardness & streaks problem.

 

[Alois Senefelder]

Salient Points !

Salient Points !

Hello Mr. E. Nikkanen and fellow Lithographers,

Having trawled through the archives, I can find no relationship between " Shore Hardness of Compliant Rollers and Gear Streaks"

1) Compliant Rollers (Plate Inkers) in roller trains are made from ink-receptive compounds of "Buna-N" rubber, layered onto a metal core.

2) Roller Train compliant rollers are "Friction Driven"

3) Rotational surface speeds of compliant rollers "Vary" as it passes through the roller nips.

PDFs - "I hope you will find of interest and value"


Regards, Alois

"Traume nicht dein leben, sondern lebe deinen Traum !! "

 

[Deleted member 16349]

Hello Mr. E. Nikkanen and fellow Lithographers,

Having trawled through the archives, I can find no relationship between " Shore Hardness of Compliant Rollers and Gear Streaks"

1) Compliant Rollers (Plate Inkers) in roller trains are made from ink-receptive compounds of "Buna-N" rubber, layered onto a metal core.

2) Roller Train compliant rollers are "Friction Driven"

3) Rotational surface speeds of compliant rollers "Vary" as it passes through the roller nips.

PDFs - "I hope you will find of interest and value"


Regards, Alois

"Traume nicht dein leben, sondern lebe deinen Traum !! "

As your first PDF stated, vibration in the system seems to cause these lines. My problem now is to find a way to reduce that vibration input. This is not so simple since there are several sources on these Dry Offset presses.

Thanks for all the comments.