Ink Estimation During Prepress

[BlacknTan]

I work in a corrugate printing plant, and a large number of our cartons are diecuts. I've been tasked with estimating ink coverage on print jobs, to enable our ink department to purchase enough inks to run a given job. However, the challenge comes with screened jobs and die cuts.

With a diecut, I can't just use the artboard in Adobe Illustrator to estimate the ink coverage, as there is a lot of negative space that is not part of the carton. I've tried using InkQuest from Astute Graphics, however the ink coverage is not always accurate, especially with screens and diecuts.

I've reached out to our ink vendor, and he recommend we estimate coverage of the carton. I should also note that we print with spot colors, rarely CMYK.

Is there a better software solution that the community is using?

 

[Stephen Marsh]

Do you have a sample file from a past run where you do know the approx. square unit of coverage and or total ink % coverage for each colour? Working backwards from a known figure helps.

Many ink calculating solutions also include the white space around or between elements in a file, which can skew the result.


Stephen Marsh

 

[BlacknTan]

Thanks Stephen... Your suggestion is what my ink vendor recommended, weigh what you start with, then weigh what you end with, and that gives you the ideal percentage. My task is to be proactive, and estimate exactly how much ink is needed for the job, not including setup, and ink to fill the system. I've reached out to Esko to see if they have a possible solution, since they also focus strongly on CAD layouts.

 

[Stephen Marsh]

Thanks Stephen... Your suggestion is what my ink vendor recommended, weigh what you start with, then weigh what you end with, and that gives you the ideal percentage. My task is to be proactive, and estimate exactly how much ink is needed for the job, not including setup, and ink to fill the system. I've reached out to Esko to see if they have a possible solution, since they also focus strongly on CAD layouts.

That is part of what I was recommending… You will need to evaluate different tools/methods against a known job/result.

Take for example the attached PDF files and reports from Enfocus PitStop Pro, which does have an ink report (including spot inks)…

File 1 has a 100x100mm coverage of 100c100m100y50k, 350% total ink. The document size is 100x100mm, no white space. This is correctly reported as expected (apart from minor rounding errors).

File 2 has the same 100x100mm coverage of 100c100m100y50k, 350% total ink – however the document size is 100x200mm, it has the same area blank as covered by ink. Although the printed surface square mm area coverage is the same/correct, the reported & value of ink is misreported at half the value of the actual content at 175%.

Unless I am misunderstanding something, my expectation is that both files still consist of 350% total ink, independent of the amount of blank space in the file.


Stephen Marsh

 

[BlacknTan]

Thanks Stephen...this looks promising. I'm going to dig into the program and see if this will work. Much thanks!!!

 

[Stephen Marsh]

Thanks Stephen...this looks promising. I'm going to dig into the program and see if this will work. Much thanks!!!

I also have a bit of a hack Photoshop method/workflow, however purpose built methods such as PitStop Pro are of course preferred if you can make them work for you.

I imagine that if you are in a postprint setting, then you probably have more of the carton blank than covered in ink, which I would imagine would skew the results somewhat and would probably need to be taken into account.



Stephen Marsh

 

[[email protected]]

There may be some functionality in your prepress workflow. Prinergy for example has a softproofing element called VPS in which marquee selections can be made (so white space outside the work area can be excluded) and % coverage of inks given. This can be done for a single piece or an imposed form. I was aware that PitStop can do this also but wonder Stephen, can the reading of ink be constrained to trim box or bleed box? In that case, you'd have a much closer readout than including everything out to the media box.
-dan

 

[Stephen Marsh]

Good points Dan!

In the case of say a shipping carton layout, there would still be a lot of unprinted space even if the trim or bleed box “made sense” for an irregular dieshape trimmed file.

PitStop can now check irregular shaped contours… ABC – are you out there?


Stephen Marsh

 

[abc]

Interesting idea stephen, I'll take a look.

 

[avpsoft]

Take for example the attached PDF files and reports from Enfocus PitStop Pro, which does have an ink report (including spot inks)
.....

Stephen Marsh

I’ve tested these files with our APFill Ink Coverage Calculator software. I’ve got the same coverage results as soon as APFill calculates ink coverage as a percent value of the page area. APFill outputs CMYK + pantone coverage results and also the PDF pages size for each page so you can convert all coverage results to one standard page area you need, for instance A4. In general, if you need to calculate the X% coverage of a page with an area of S1 and you know the Y% coverage of a page with an area of S2, you can use the following formula:

X% = Y%*(S2/S1)​

In your example K=50% for the first file. The area of the page S1 = 100X100 = 10 000 mm[SUP]2[/SUP].
For the second file K= 25% and area S2 = 100x200 = 20 000 mm[SUP]2[/SUP].

So if you need to know the coverage of the second file equivalent for the 100mm x 100mm page:

K = 25%*(20 000 / 10 000) = 25% * 2 = 50%.​

We’ve got the same 50 % coverage for 100x100 page as for the first file. So you can easily convert coverage results into any page size you need.

APFill allows to output coverage results (with pages sizes) into the Excel using a template file with formulas so you can convert results into your company standard page size. All you need to know is your standard page area in square inches. As an example, the default CMYK template in the APFill distributive contains formulas that adapt coverage data for A4 sheet coverage (the “Equivalent A4 coverage” sheet).

Also the latest APFill 5.9 version allows to select the part of the page (PDF Page Box: Crop,Media,Trim,Art) that will be used when displaying and calculating coverage of PDF files.

 

[Stephen Marsh]

avpsoft, thank you for your input.

This “page area” is what I see as a problem for some market sectors such as in carton printing – averaging the result based on the page area skews the results.

350% total ink coverage is 350% total ink coverage – should it really matter how much unprinted area is around the objects? Or is this a naive way of viewing things?

For an A4 page full of black text with an inch margin, the averaged page area of black in is approx. around 7% (ballpark figure). This factors in well with traditional ink calculation methods. However for other work that does not consume the majority “full page” should the value be averaged on the blank areas, or only on the live printed areas?

As long as the reported % or area is logical and consistent one can base calculations off the reported values and attribute costings to these values, so in practice it may not matter if the total ink used is less than reality, as long as this can be factored in and costed.



Stephen Marsh

I’ve tested these files with our APFill Ink Coverage Calculator software. I’ve got the same coverage results as soon as APFill calculates ink coverage as a percent value of the page area. APFill outputs CMYK + pantone coverage results and also the PDF pages size for each page so you can convert all coverage results to one standard page area you need, for instance A4. In general, if you need to calculate the X% coverage of a page with an area of S1 and you know the Y% coverage of a page with an area of S2, you can use the following formula:

X% = Y%*(S2/S1)​

In your example K=50% for the first file. The area of the page S1 = 100X100 = 10 000 mm[SUP]2[/SUP].
For the second file K= 25% and area S2 = 100x200 = 20 000 mm[SUP]2[/SUP].

So if you need to know the coverage of the second file equivalent for the 100mm x 100mm page:

K = 25%*(20 000 / 10 000) = 25% * 2 = 50%.​

We’ve got the same 50 % coverage for 100x100 page as for the first file. So you can easily convert coverage results into any page size you need.

APFill allows to output coverage results (with pages sizes) into the Excel using a template file with formulas so you can convert results into your company standard page size. All you need to know is your standard page area in square inches. As an example, the default CMYK template in the APFill distributive contains formulas that adapt coverage data for A4 sheet coverage (the “Equivalent A4 coverage” sheet).

Also the latest APFill 5.9 version allows to select the part of the page (PDF Page Box: Crop,Media,Trim,Art) that will be used when displaying and calculating coverage of PDF files.

 

[avpsoft]

What if we base ink coverage results only on the printing local area where toner/ink is placed?

Let’s take your example – the first file K = 50% and the page area is 100x100. Suppose we say that the second file K coverage has to be 50 % based on only local area where ink placed not on whole page area. Then what if we fill the whole page area in the second file with 50% black. Then according to the coverage based on local area - coverage will be the same 50%. But in this case the real ink consumption will be 50% of the 100x200 area what is two times greater than 50 % of 100x100 in the first file.

So I think if we need to be able to compare coverage of two files we should base our calculation not on a local area covered with ink/toner but on one the same page area. You can use any size, shape area as a base. All we need to know is area in square mm/inches and then you should convert all coverage results to this area terms (as described in the previous post) then all coverage results are comparable.

That is when you print on a traditional CMYK printer there is the base area already in the cartridge yield specification - say 10000 A4 pages with 5% coverage.

This “page area” is what I see as a problem for some market sectors such as in carton printing – averaging the result based on the page area skews the results.

350% total ink coverage is 350% total ink coverage – should it really matter how much unprinted area is around the objects? Or is this a naive way of viewing things?

...
Stephen Marsh