Process control without colour density bars

[Benk]

Good morning everyone,

I am returning with the problem I face regarding printing off-set roll-to-roll where we have no online method to control ink density. Since we no longer have room on the plate for colour density bars our only solution in to "eyeball" the printed result alongside a target proof. Correct me if I am wrong, this would require a good quality inkjet printer controlled by a rip. "Eyeballing" would be done under controlled lighting conditions - D50. Does this sound like a good solution to you? I do know that it is not ideal by any means, but this is the situation I find myself in.

All responses will be gratefully received.

Thanks

Ben

 

[curiosity]

Looks like no one wants to touch this one. No color bar. The 'ole "Eyeballing" method. A target proof...inkjet; hmmmm, different ink, paper, double hmmm. Obviously a very tough and undesirable position you are in. A color bar is so necessary. Please find a way to include one. We use up every inch of available space on our paper and yet very tightly fit a color bar along the lead edge. So to answer your question...Does this sound like a good solution to you?...I'd say no...not at all.

 

[michaelejahn]

Eyeballing is never a good solution. What happens when someone notices things are too warm ? Do they adjust ink keys, and do they know which ones ?

 

[gordo]

Use ink preset software and heavy GCR separations (a.k.a. Ink optimization). FM screening will also help.

The heavy GCR will result in more stable color or color that more closely aligns to the proof even when SIDs aren't quite right or out of balance.

You can also identify color areas within the live image areas and use them. Or, if you have control over the graphics, design the images so that they can act as measurable targets (like USA Today does with their section headers).

Best gordo

 

[danremaley]

no color bars

no color bars

Good morning everyone,

I am returning with the problem I face regarding printing off-set roll-to-roll where we have no online method to control ink density. Since we no longer have room on the plate for colour density bars our only solution in to "eyeball" the printed result alongside a target proof. Correct me if I am wrong, this would require a good quality inkjet printer controlled by a rip. "Eyeballing" would be done under controlled lighting conditions - D50. Does this sound like a good solution to you? I do know that it is not ideal by any means, but this is the situation I find myself in.

All responses will be gratefully received.

Thanks

Ben

I would print a test form that I could measure, collect the "data" Density, dot gain, gray balance, etc. Make adjustments to the plate curves to print "standard" numbers. Now if you get 'close' on density the color will be more accurate. It would be nice if you could place a solid Y-M-C-K 1/4" patch that could be "honed" off before the production run. A midtone gray patch would even be better, made of 50C-40M-40Y. A gray patch will show 'casts' and saturation. Hope this helps.
Dan Remaley 412.889.7643

 

[Cornishpastythighs]

With roll to roll printing any form of process control is very difficult. In my experience of running roll to roll I spent a lot of time and effort reducing the number of things that could cause colour variation during the run. These included having a good roller maintenance and setting program, RO Water fed fountain solutions, ink spec to correct colour using DeltaE, always running minimum ink/water and correctly zero set ink fountains.Our ink and water speed curve was verified at least twice a year and we did not make fast speed changes. I still had to eyeball it and could only get to measure a sample at a splice change but if you remove many of the reasons that the colour would vary then you at least have half a chance. Before anyone reminds me you should also have all these things in place on any type of process not just roll to roll.
Cheers

 

[Benk]

Thank you all for your input.

I don't see the way forward. Our graphics change on a monthly basis so including so measurable area within the graphics is out of the question. The idea of printing a test image sounds good although we also use the presses for spot colour work where we change ink densities all the time. It is possible to run a test print before every print run to bring the press into line but the setup time and plate cost would never get approval.

I guess none of you see the target proof solution as a good solution. Am I right ?

I feel that there are too many variable in the mix. All I need is some blue sky thinking here. The work we do is not colour critical but it does need to be within reasonable limits. This is why target proofs to me sound acceptable. I would consider proofing on the same media used in the actual print run and simulating the offset profile via the rip. The printer has a lighting booth - D50. In our case a visual assessment is better than nothing.

Please say this idea IS better than nothing.

Awaiting your wisdom PrintPlanet.

Ben

 

[CKP]

Hi Ben,

as inline measurement system developer and producer we often meet the request you mentioned regarding colorbarless measurement. We handle it as follows:
Color Key Pro has a brand new development, which ensures colour measurements with a ISO 13655 compliancing INLINE spectrodensitometer and a closed loop process control.
For fulfilling ISO standard's requirements we normally apply 3 mm aperture size, where a patch size of W=3mm x H=4mm is needed.
In case of customer's special need we can provide also smaller aperture sizes, on request.
Of course smaller apertures under a certain sizes can not fulfill ISO 13655 requirements measured with the spectrodensitometer, but the TVI% (dot gain) should be measured with a camera on proprietary way.
For jobs where is absolutely no place for colorbars we provide an option for an additional high quality image sensor (camera) - all this in one unit with the inline spectro.
The highlight of the solution is, that the image sensor is continuosly and automatically (during the production) calibrated by the high resolution spectrodensitometer ensuring the exact colour values.
That way you don't have to give up printing according ISO standards (13655 and 12647-2), but you have possibility for printing without colorbars in emergency case.
While other manufacturers requires calibration days wasting many tons of paper, Color Key Pro's process calibration is based on measurements during the production, so no extra time and paper is required for calibration (including calibration of the ink key opening curves) at all: the jobs with colorbar supply measurement data for the self-learning process calibration.
Based on my best knowledge no one else provides at this moment inline measurement system with ISO-13655 compliance for web offset presses, although this standard is since 2009 alive. As all the spectrophotometers used widely for quality control (like X-Rite i1PRO-II, eXact, Techkon SpectroJet, Barbieri) have been released with ISO-13655 compliance in the past years, the minimum requirement should be, the such an inline measurement device is applied on the web offset press as well. In other case EVEN SPECTRAL MEASUREMENTS CAN RESULT DIFFERENT VALUES ON THE SAME SAMPLE and valid comparisons are impossible. That was the reason for creating the standard ISO-13655...
For more informations don't hesitate to contact me ([email protected]).

Peter

Thank you all for your input.

I don't see the way forward. Our graphics change on a monthly basis so including so measurable area within the graphics is out of the question. The idea of printing a test image sounds good although we also use the presses for spot colour work where we change ink densities all the time. It is possible to run a test print before every print run to bring the press into line but the setup time and plate cost would never get approval.

I guess none of you see the target proof solution as a good solution. Am I right ?

I feel that there are too many variable in the mix. All I need is some blue sky thinking here. The work we do is not colour critical but it does need to be within reasonable limits. This is why target proofs to me sound acceptable. I would consider proofing on the same media used in the actual print run and simulating the offset profile via the rip. The printer has a lighting booth - D50. In our case a visual assessment is better than nothing.

Please say this idea IS better than nothing.

Awaiting your wisdom PrintPlanet.

Ben

 

[Benk]

Hi Peter,

Thanks for the info. Your solution is not new to me although it is by far the best way forward for offset press colour management.

I will be in touch.

Ben

 

[rich apollo]

Benk, I've been in a similar situation. What are you doing for proofs, now? Also, how would the press operator view the printed product against the proof if he's running roll to roll?

It's not tough to set up a good proofing system. With a decent proofing system you can imitate printing on all kinds of stock.

As to process control during the run, an inline tool is the best solution. "Eyeballing" is not a good solution, but it's better than not looking. Sometimes a crappy solution is all you've got.

PM me if you want some help outlining a proofing system.

 

[Deleted member 16349]

Good morning everyone,

I am returning with the problem I face regarding printing off-set roll-to-roll where we have no online method to control ink density. Since we no longer have room on the plate for colour density bars our only solution in to "eyeball" the printed result alongside a target proof. Correct me if I am wrong, this would require a good quality inkjet printer controlled by a rip. "Eyeballing" would be done under controlled lighting conditions - D50. Does this sound like a good solution to you? I do know that it is not ideal by any means, but this is the situation I find myself in.

All responses will be gratefully received.

Thanks

Ben

Just curious. Is your web press printing on both sides or just one side? A picture on your company web site seemed to show a press with the web path that was quite low.

 

[D Ink Man]

Here's a great question.

What inks are you running?

Process or spot?

The ink film thicknesses and resulting densities have a great deal of variation, factually. Particularly spots. Refer to Pantone 123..... post, for a full flavor into that one.

An IGT ink fim thickness guage would actully help you, but you need help from an ink technician who understands formulation as well as what is going on during printing. Good Luck! It tis achievable.

D Ink Man

 

[Benk]

I am looking into setting up an Epson Inkjet with Fiery XF rip in order to print simulated proofs. I would use actual stock for the proof which would be viewed under a D50 lighting booth.

Anything "inline" as far as continuous colour measurement goes is not an option for now.

I thank you for your response

Ben

 

[rich apollo]

Using the actual printing stock on an inkjet device usually doesn't work well. Give it a shot, but I'd guess you're gonna need some inkjet paper.

 

[marialewis520]

Eyeballing might be good solution but rather than that there are some other solutions through which you can easily solve this of your problem the another solution you must for another printer which has an ability to solve this problem of your's secondly you must try to make authentic or proper plan to print off set roll.