Consiistent-excessive dot gain/TVI on all units.

[CClyde]

I think we agree, but I've included the extra step of RIPing between artist's file and file imaged to plate, whereas I think you are referring to linear plates of requested tone in artist's file and the resulting values on the sheet.


Now that I've figured out how to remove the lens cap…..

Does this look like a normal dot?

It looks pretty ragged and possibly ghosting to me.

 

[Cornishpastythighs]

How are your solids printing, that will give you a better indication of how the ink is laying down. Dots are just but little islands of solids

 

[CClyde]

The black next to the 25 shown above is OK. It's relative density (i.e. to sheet white) is 1.60.

 

[cementary]

Can I ask what ink you are describing as your "acceptable" ink as that would be very helpful.
Thanks, Ian

Yes, you can. But i'll ask you the same - what's your ink?
Acceptable were Huber (hostmann steinberg) quick fast 250 and one shipment of quick fast 260.
Unacceptable were Huber (hostmann steinberg): Reflecta rl250, Resista rs250, alpha intense 363
Partly acceptable was premium print from Epple (partly 'cause they dry too long and medium setting range, the dot was ok)

 

[cementary]

I think we agree, but I've included the extra step of RIPing between artist's file and file imaged to plate, whereas I think you are referring to linear plates of requested tone in artist's file and the resulting values on the sheet.


Now that I've figured out how to remove the lens cap…..

Does this look like a normal dot?

It looks pretty ragged and possibly ghosting to me.

I see a little bit doubling here. And bad dot. If your press is mechanically ok, grippers cleaned and revised maybe you should try positive rollin' blankets? They won't heal the dot but will help with doubling/slurring issue

 

[gordo]

I see a little bit doubling here. And bad dot. If your press is mechanically ok, grippers cleaned and revised maybe you should try positive rollin' blankets? They won't heal the dot but will help with doubling/slurring issue

I would agree about the doubling. (it took me a while to realize there was a clear protective cap over the lens too, LOL. But I hope you (and others) can see the value of this kind of scope.)
The doubling could be a loose blanket or incorrect packing. You K SID is on the low side (but within range) There appears to be some mottle in the solid K. This is what that looks like when ink density (ink film thickness) is projected in 3D:

The ragged edge of the dots (because it's not apparent on the other colors) could be:
Poor squeeze (impression cylinder pressure
Unit chiller temperature incorrect causing the ink to change its tack/viscosity
Fountain solution issues (ph, conductivity)
Low ink film thickness (low SID) enabling the fountain solution to attack the ink.

 

[aqazi81]

I see a little bit doubling here. And bad dot. If your press is mechanically ok, grippers cleaned and revised maybe you should try positive rollin' blankets? They won't heal the dot but will help with doubling/slurring issue

Can you please explain what are positive rolling blankets?

 

[cementary]

No Title

Can you please explain what are positive rolling blankets?

Nope, i can't, contiair can – i think it's their term

 

[aqazi81]

Nope, i can't, contiair can – i think it's their term

This looks to me more of a marketing term or may be it is used for web fed presses.

 

[cementary]

This looks to me more of a marketing term or may be it is used for web fed presses.

Maybe so. But their "positive feed" blanket worked fine for us. Better than "neutral feed".

 

[ianmcc]

Yes, you can. But i'll ask you the same - what's your ink?
Acceptable were Huber (hostmann steinberg) quick fast 250 and one shipment of quick fast 260.
Unacceptable were Huber (hostmann steinberg): Reflecta rl250, Resista rs250, alpha intense 363
Partly acceptable was premium print from Epple (partly 'cause they dry too long and medium setting range, the dot was ok)

Thanks for that. We are in the UK and are using Heidelberg's own product - Saphira Extreme Bio.

 

[cementary]

Thanks for that. We are in the UK and are using Heidelberg's own product - Saphira Extreme Bio.

Interesting. I thought that hiedelberg printing materials are just like manroland's printcom series – where printcom is just a label and who is producer nobody knows.

 

[cementary]

There appears to be some mottle in the solid K. This is what that looks like when ink density (ink film thickness) is projected in 3D

Gordo, can you describe how do you create such 3D projections?

 

[Deleted member 16349]

Can you please explain what are positive rolling blankets?

I wrote a 1997 TAGA paper related to this subject so I will make some comments that might help.

It has been known for a very long time that the rolling length of a soft roller does not usually equal the calculated length based on the diameter of that soft roller. For a rubber roller, the tested length usually is longer than the calculated length based on the diameter. So this lead to the concept of the "effective diameter" of the roller, which is usually larger than the actual diameter of the roller.

A rubber roller, when squeezed, deforms the rubber. This stretches the rubber surface at the nip and this stretching of the surface of the roller gives it the extra length.

Blankets are a little different because they are not made of a solid flexible material such as the robber roller, which does not lose volume when distorted. Blankets due to their construction, will deform and lose volume and this makes mathematical analysis difficult but it is relative easy to just test the blanket to determine its "effective diameter".

My TAGA paper was based on studies I did back in the mid 1980s on a web press to support our use of "insetting", which is the process of registering the print to a preprinted repeat length in the substrate. Insetting is very critical when one is running stiffer board than if one would run more normal substrates.

In those studies, the blankets we used showed an effective diameter that was slightly larger than the calculated diameter of the blanket cylinder. Also the effective diameter could be changed by changing the impression squeeze and also by changing the tension before and after the impression nip.

My view is that the difference in feed rate would not directly affect the dots. The differences in feed length are on the order of a fraction of 1% and this should not cause visible slur. Less than 1% distortion of a dot, that does not print sharp in the first place is not an issue. But different feed rates might affect the mechanical linkages in the press, gear etc. which might indirectly cause issues.

I could see that blanket manufacturers could design blankets with both positive and negative effective diameters. This might be more helpful on sheetfed presses than on web presses since on a sheet fed press the sheet is only held in place by the grippers and the sheet can distort under different printing conditions. In a web press, the web itself tends to help stabilize the substrate.

In general it is more important to have matching blankets in a press. Is is not as critical for a web press with respect to fit as it would be for a sheetfed press.

Hope this helps.

 

[Deleted member 16349]

Gordo, can you describe how do you create such 3D projections?

Snap shot of the Canadian Rockies

 

[gordo]

Gordo, can you describe how do you create such 3D projections?

You can do it in the 3d module in PShop CC or, because that's difficult, you can use a bit of software called imageJ. ImageJ is used for a variety of image analysis purposes in the science/engineering realm. In this case I used it to map tone to height. Darker tones map to higher levels than lighter tones. This helps visualize relative ink film thickness as well as how the substrate affects ink laydown.

 

[cementary]

You can do it in the 3d module in PShop CC or, because that's difficult, you can use a bit of software called imageJ. ImageJ is used for a variety of image analysis purposes in the science/engineering realm. In this case I used it to map tone to height. Darker tones map to higher levels than lighter tones. This helps visualize relative ink film thickness as well as how the substrate affects ink laydown.

Thanks for response. Do you make any image adjustments before feeding to ImageJ? White balance maybe? sRGB?

 

[CClyde]

Thanks gordo.

The scope images are very helpful. Possibly too helpful

Now I'm questioning a lot of what I could never see before.

For example…..



At first I thought this was over-emulsification, but looking at the ink in the plate bend, I now think it's just too much water?

 

[cementary]

Thanks gordo.

The scope images are very helpful. Possibly too helpful

Now I'm questioning a lot of what I could never see before.

For example…..



At first I thought this was over-emulsification, but looking at the ink in the plate bend, I now think it's just too much water?

Ink water pick up rate? Maybe too low yeild value of the binder?

 

[gordo]

Thanks for response. Do you make any image adjustments before feeding to ImageJ? White balance maybe? sRGB?

In this case I posterized it first 'cause I thought that would be clearer. Here's the projection just using the source image:

With imageJ you can rotate the 3D projection as well as adjust height and granularity - so you see what's happening more clearly than just a single image shows.