Plate curves survey

[gordo]

I'm trying to get a reality check on a few issues. It's not about right or wrong just about what is common practice. The more responses to this survey the more reliable the results.
The first survey question is about using dot gain plate curves:

 

[maxon]

Gordo you may get false results. People using several offset machines will respond with second option, they will use different plate curves for coldset, heatset and sheetfed machines because dpi and screening is (usually) not the same.

 

[gordo]

Gordo you may get false results. People using several offset machines will respond with second option, they will use different plate curves for coldset, heatset and sheetfed machines because dpi and screening is (usually) not the same.

Thanks, I should have qualified the question to mean presses of the same kind within the shop i.e. 4 Heidelberg sheetfed presses in the shop, or 3 Komoris.
My experience is that one averaged curve would be used.

 

[ponnapati123]

We use one average dot gain curve to all our sheet fed presses. One curve for coated and one for un coated

 

[gordo]

We use one average dot gain curve to all our sheet fed presses. One curve for coated and one for un coated

Thanks - my experience is that what you're doing is typical. That's good info.

 

[vaugh6288]

We have been using different curves for 2 different Hberg presses. Both are the same configuration, just different sizes: one SM74 and one SM102.

Do you think we should be trying to keep one set of curves for both presses to share?

Thanks everyone

 

[gordo]

We have been using different curves for 2 different Hberg presses. Both are the same configuration, just different sizes: one SM74 and one SM102.

Do you think we should be trying to keep one set of curves for both presses to share?

Thanks everyone

That depends on how different the curves are. If you create a curve based on the median between the two - is that new value within the "noise" i.e. not enough of a difference on press to see the difference?
If that's the case you could simplify production with one curve for both presses.

 

[toronar]

Hi gordo,

we did use one curve for our 2 sheetfed presses (SM102 and CD102 from Heidelberg), which were within 1-2% of each other.
We then exchanged the CD102 for a CX102 and the difference between the 2 presses is much greater so that we now use one curve per press. Dot gain difference of 10% (51% on SM102 vs 62% on CX102 with the same linear plate and paper) is too great to average out.

Of course there are different curves for coated and uncoated stock, and for AM/FM screening ... and for wannabe-paper that totally screws up dot gain.

A print shop near us has 4 Heidelberg SM102 and they all run with one curve and minimum differences (1-2%) that can as easily be explained by tolerance of measuring equipment / phase of moon / ...

 

[gordo]

[SNIP]Dot gain difference of 10% (51% on SM102 vs 62% on CX102 with the same linear plate and paper) is too great to average out.

I find that a dot gain of 1% from a linear plate hard to believe (on any press). Are you sure there's no error in your measurements?

 

[toronar]

I find that a dot gain of 1% from a linear plate hard to believe (on any press). Are you sure there's no error in your measurements?

Whoops. Forgot to mention that this is 40% on plate.

 

[gordo]

Whoops. Forgot to mention that this is 40% on plate.

Even if it's 40% a 1% dot gain from a linear plate makes no sense. I think there's a boo boo somewhere.

 

[toronar]

Even if it's 40% a 1% dot gain from a linear plate makes no sense. I think there's a boo boo somewhere.

You got that wrong gordo: 40% on plate turn to 51% (62%) on press.

 

[Ferran]

Hi Gordo, nice survey

I have voted the second option, however this is not really true and I would like to clarify. - I prefer to use the term "set of curves", each curve attached to an ink because not every unit (same press) print exactly the same way. And then, we use a "set of curves" for each combination of press and substrate. This is a typical example: if we had two different presses (A and B), we will end up with 10 different "set of curves".

- Heatset Web Offset Press A - Gloss Coated
- Heatset Web Offset Press A - Matte Coated
- Heatset Web Offset Press A - Improved/Standard Gloss Coated (LWC)
- Heatset Web Offset Press A - Machine finished coated (MFC)
- Heatset Web Offset Press A - Uncoated White Offset
- Heatset Web Offset Press A - Super calandered (SC)
- Heatset Web Offset Press A - Standard Newsprint (SNP)


- Sheetfed Offset Press B - Gloss Coated
- Sheetfed Offset Press B - Matte Coated
- Sheetfed Offset Press B - Uncoated White Offset


regards,
ferran