Blanket Packing

[Davis.zhou]

Would like to ask anyone having the experience of over squeeze of blanket and plate.
The press is Heidelberg CD-102, with semi-auto plate feature.
The thickness of plate is 0,28mm, using the pack gauge to check that the height higher than the plate cylinder bear is 0,13mm
The blanket is thickness is 1.95mm, used 2 sheets of blanket pack at 0.20mm. The measurement of pack gauge is 0,03mm higher than the blanket cylinder bear. From calculation, this should be 0,05mm, but the actual measurement is 0,03mm.
This makes the squeeze 0,16mm in total. The new operator insist to use blanket pack at 0,40mm. The previous blanket pack is 0,30mm.
Whether this will affect anything besides of the dot gain. After used this new setting, the got gain is around 4% higher than before.

Thanks.

 

[The Heidelberg Guy]

Would like to ask anyone having the experience of over squeeze of blanket and plate.
The press is Heidelberg CD-102, with semi-auto plate feature.
The thickness of plate is 0,28mm, using the pack gauge to check that the height higher than the plate cylinder bear is 0,13mm
The blanket is thickness is 1.95mm, used 2 sheets of blanket pack at 0.20mm. The measurement of pack gauge is 0,03mm higher than the blanket cylinder bear. From calculation, this should be 0,05mm, but the actual measurement is 0,03mm.
This makes the squeeze 0,16mm in total. The new operator insist to use blanket pack at 0,40mm. The previous blanket pack is 0,30mm.
Whether this will affect anything besides of the dot gain. After used this new setting, the got gain is around 4% higher than before.

Thanks.

The best packing thickness on the blanket cylinder is EVEN with bearer. Period.

With at .012" Plate (0.30mm) you should be .006" (0.15mm) over bearer on the plate cylynder (This goes for ALL Heidelberg machines).

Optimum printing pressure between the plate and blanket should be between .004" and .006" (0.10mm and 0.15mm)

 

[Davis.zhou]

The best packing thickness on the blanket cylinder is EVEN with bearer. Period.

With at .012" Plate (0.30mm) you should be .006" (0.15mm) over bearer on the plate cylynder (This goes for ALL Heidelberg machines).

Optimum printing pressure between the plate and blanket should be between .004" and .006" (0.10mm and 0.15mm)

Unfortunately, the plate thickness is 0,28mm not 0,30mm. We cannot get 0,30mm plate in here.

Thanks.

 

[The Heidelberg Guy]

Unfortunately, the plate thickness is 0,28mm not 0,30mm. We cannot get 0,30mm plate in here.

Thanks.

As long as this statement stays true "Optimum printing pressure between the plate and blanket should be between .004" and .006" (0.10mm and 0.15mm)", you should be fine!

Edited to add that 0.28mm is acceptable, and not to think that you could run with a thinner plate and raise the heigth of the blanket TO the plate.

 

[Davis.zhou]

As long as this statement stays true "Optimum printing pressure between the plate and blanket should be between .004" and .006" (0.10mm and 0.15mm)", you should be fine!

Edited to add that 0.28mm is acceptable, and not to think that you could run with a thinner plate and raise the heigth of the blanket TO the plate.

Thanks, would make sure that the blanket would be the same eight as the bear.

 

[vik la luna]

great theory but in the real world of print production this not always work except maybe when your blankets are new (and bearers)
these days we print on more recyled substrates than before and keeping this in mind with the inevitable bearer compaction and blanket sinkage you wil have a poor print job if you followed this rule rigidlyanket
blanket packing even with bearers does not always work in the real world
it does not matter what press you are running especially the much vaunted heidelberg

 

[inkinveins]

great theory but in the real world of print production this not always work except maybe when your blankets are new (and bearers)
these days we print on more recyled substrates than before and keeping this in mind with the inevitable bearer compaction and blanket sinkage you wil have a poor print job if you followed this rule rigidlyanket
blanket packing even with bearers does not always work in the real world
it does not matter what press you are running especially the much vaunted heidelberg

I completely agree, everyone gets wrapped up in factory specs. (Which, I frimly believe in). But when It comes to blanket to bearer heighth, its not where you start, its where you end up. Start .002" to .003" over bearer and fall down to 0 - .001" over bearer. Otherwise it is very difficult to get into those ultra lightweight uncoated papers.

 

[Jim Claxton]

president - Claxton Printing Co.

president - Claxton Printing Co.

We have been running a sm-74 4p and now have 2002 sm-74-8p + L so we're no stranger to printing. However for years we have been fight a bump streak on the 74 it is exactly 10.25 inches from the lead edge of the press sheet, which is exactly 1/2 of the max press sheet. It seems to be worst on the cyan unit.

We have all new rollers, using 12 mil plates with packing to the bears on the blanket.
quick release blankets. The heidi does not have a setting to change the pressure between
the plates and the blanket. so we though of going to a 8mil plate might help
We understand .004 and .006 of pressure for printing.

Sometimes we can hide it, other times we can't. I just had a job pulled from a customer because of the streak.

We have tried changing fountain solution, tack on ink, different blankets. New rollers.
It gets better for awhile then comes right back.

I could use some help with suggestions or ideas.

 

[printerpete]

12 mill plates? i assume you mean 12 thou?

 

[madjock]

Hey Jim, regarding your bump streak, have you tried feathering your packing, i.e cutting each sheet 5 millimetres shorter, this helps soften the bump when the blanket falls of the edge of the cylinder gap and usually works, although for some reason it does not work on card stock, on older presses you can see a wear mark on the bearer which coincides with the bump streak, hope this helps, it has worked for me on many ocaasions.

 

[JOHNYPRINT]

vik la luna and ink in viens.
you talk about getting a better print on recycled and un-coated stock but this has nothing to do with the original question and reply from the hiedelberg guy. to get better transfer from blanket to stock you increase the back pressure from the impression cylinder you do not change the plate to blanket settings???

 

[Jim Claxton]

President

President

Yes 12 thous. plate thinkness..

I will try cutting the packing , do you cut all three sheets the same... it we use 2 thous. packing sheets, do I cut all of them the same 5 mill. short?

 

[The Heidelberg Guy]

Yes 12 thous. plate thinkness..

I will try cutting the packing , do you cut all three sheets the same... it we use 2 thous. packing sheets, do I cut all of them the same 5 mill. short?

How much total packing do you use?

 

[vik la luna]

vik la luna and ink in viens.
you talk about getting a better print on recycled and un-coated stock but this has nothing to do with the original question and reply from the hiedelberg guy. to get better transfer from blanket to stock you increase the back pressure from the impression cylinder you do not change the plate to blanket settings???

you dont have to change the settings between plate and blanket
the reason being , when the unit goes on impression its the blanket cylinder that moves into contact (eccentrically) with plate and impression cyinders.
the setting between plate and blanket should never be adjusted once you have done your dry cyl breakaways and found your zero settings.

 

[The Heidelberg Guy]

you dont have to change the settings between plate and blanket
the reason being , when the unit goes on impression its the blanket cylinder that moves into contact (eccentrically) with plate and impression cyinders.
the setting between plate and blanket should never be adjusted once you have done your dry cyl breakaways and found your zero settings.

100% accurate!

 

[JOHNYPRINT]

We have been running a sm-74 4p and now have 2002 sm-74-8p + L so we're no stranger to printing. However for years we have been fight a bump streak on the 74 it is exactly 10.25 inches from the lead edge of the press sheet, which is exactly 1/2 of the max press sheet. It seems to be worst on the cyan unit.

We have all new rollers, using 12 mil plates with packing to the bears on the blanket.
quick release blankets. The heidi does not have a setting to change the pressure between
the plates and the blanket. so we though of going to a 8mil plate might help
We understand .004 and .006 of pressure for printing.

Sometimes we can hide it, other times we can't. I just had a job pulled from a customer because of the streak.

We have tried changing fountain solution, tack on ink, different blankets. New rollers.
It gets better for awhile then comes right back.

I could use some help with suggestions or ideas.

jim
regarding your bump streak problem, i have seen this kind of thing before and it can be traced back to a bad setting in your damp system rollers, more often the intermediate roller (AKA, Z roller, link roller) setting. check the relevant settings are not too hard, also check that the oscillating motion of intermediate roller is functioning ok , the bearings inside should be greased and well looked after.
A simple test would be to remove the intermediate roller from the offending unit and switch it with a unit that does not have a problem, if the problem occurs on the previously good unit, then you have found the cause of the problem. Your pressman should understand the details in this message. hope this helps , regards john h

 

[madjock]

A quicker and easier way to determine if the streak is damp related is to pull a dry solid, if the bump is still there then it is most likely the infamous Heidelberg bump that is a feature of most presses I have operated, the only way round this is to either cut your packing short or feather it, ie each packing sheet cut 5 millimetres shorter than the last.

 

[Alois Senefelder]

Gear Streaks

Gear Streaks

Gentlemen,

Please read the PDF, Thread - H/berg GTO Gear Marks, posted on 06-23-2010 at 09-52 AM



Regards, Alois