Magnus 800
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PACH
Well-known member
Joe is correct regarding the trial of plates. But if you change to another supplier, Kodak technician will have to calibrate the THead to that plate and also there is the issue of the processor.I know it is a crazy question, but have you tried using Staccato?
True, and not a test at all, let alone a fair one. We are now concerned with a new platesetter. And we don't know the laser is good...or at least I don't although being reassured by Kodak it is.
Typically, banding is a known obstacle remedied by laser adjustments (focus, curves, slopes, power, etc.). Same lasers are known (by Kodak) to vary and are therefor slated for press shops that best fit the characteristics of the manufactured/tested laser. Our 3rd laser represents what Kodak believes to be a laser that has excelled during testing. Example: a lesser laser may get sent to a shop printing newspapers, for instance.
Joe, I appreciate your response, but as you know, testing takes lots of time. And we actually "test" a lot of things around here. No excuses not to test, but we believe Kodak needs to step up to solve this.
Typically, banding is a known obstacle remedied by laser adjustments (focus, curves, slopes, power, etc.). Same lasers are known (by Kodak) to vary and are therefor slated for press shops that best fit the characteristics of the manufactured/tested laser. Our 3rd laser represents what Kodak believes to be a laser that has excelled during testing. Example: a lesser laser may get sent to a shop printing newspapers, for instance.
Joe, I appreciate your response, but as you know, testing takes lots of time. And we actually "test" a lot of things around here. No excuses not to test, but we believe Kodak needs to step up to solve this.
Thead calibrations...processor changes...yikes. Been there done that.
We tried staccato awhile back, and we were not pleased with what we perceived as "graininess" in certain areas, so we decided it is not for us. However, Kodak believes staccato is even more susceptible to banding, and I agree.
I did consider this...240 ls at 2400 dpi...halftone cell is 10x10 (only 101 shades of gray!, so thank somebody for modern algorithms that make that not a factor)...essentially our 1% dot = 10 microns...P45s can only do ~25 microns (yet 1's and 2's do show on plate and press)...interesting...but our ls looks better than staccato in too many areas.
We tried staccato awhile back, and we were not pleased with what we perceived as "graininess" in certain areas, so we decided it is not for us. However, Kodak believes staccato is even more susceptible to banding, and I agree.
I did consider this...240 ls at 2400 dpi...halftone cell is 10x10 (only 101 shades of gray!, so thank somebody for modern algorithms that make that not a factor)...essentially our 1% dot = 10 microns...P45s can only do ~25 microns (yet 1's and 2's do show on plate and press)...interesting...but our ls looks better than staccato in too many areas.
PACH
Well-known member
REgarding the calibration of the Head. In your case Focus, Slope and Curve are VERY important that it is done correctly. Did the guy who calibrated the Head put the Curve than the Slope plates on the press or just took the values from looking at the plate?
Interesting. The latter...just took the values visually from the processed plates. And on several occasions, it was by committee (technicians). Only went to press after all adjustments were made.
Very interesting. Never heard of this approach. But keep in mind that our banding is intermittent, and independent of plate lot #s. I've heard that technically, laser adjustments can or should be done every time a new lot of plates is imaged.
Very interesting. Never heard of this approach. But keep in mind that our banding is intermittent, and independent of plate lot #s. I've heard that technically, laser adjustments can or should be done every time a new lot of plates is imaged.
gordo
Well-known member
Small difference in power between channels of the swath are sometimes amplified so that banding becomes visible on paper. The finer the screen (AM or FM) the greater the potential that small variations in the process can result in amplifying banding so that it appears visible in presswork. Media quality, processing and press conditions can all contribute to banding.
Have you tried rotating the plate? Plate grain can make it difficult to see the true imaging quality from the head required for fine-tuning. Rotating the plate can help isolate the plate grain from the actual imaging ability of the head. Sometimes imaging perpendicular to the grain during setup will make setup more effective.
You can check for processor-related artifacts by skewing the plate so that it is processed at a slight angle. If the marks follow the angle the plate was processed at, they
were likely caused by the processor. Note: also that gum lines can be the same width as the swath.
There is a phenomenon in the pressroom known as 'Grind-lines' which will take on the appearance of what is called 'banding' and will completely have all the visual attributes of 'banding'. Plates can certainly appear band-free before going to press so it's worth checking for banding on the used, inked up plate.
Depending on the compounds used in conjuction with the solvents in the inks, washes and dampening solutions the surface anomalies in the form of line/streaking from manufacturing will begin to show in screen and solids. This streaking can also show up in dead-rollers, these are rollers that may still have the required durometer but the compond under the surface has lost its ability to rebound. In the dampening systems the chrome rollers will take on these lines and transfer the lines to the work (really shows up on older presses).
Blankets, will often have the same wear attributes of rollers. However, paper, packing, torque requirements and back cylinder pressures may accentuate the problem.
High lpi screens like 240 lpi AM/XM and FM makes these issues more visible to the eye.
best, gordo
(I'm not affiliated with Kodak in any way. I do not do Kodak customer support. Banding can appear on any external drum CtP system therefore my post is generic.)
PS tBirk1 wrote: "I did consider this...240 ls at 2400 dpi...halftone cell is 10x10 (only 101 shades of gray!, so thank somebody for modern algorithms that make that not a factor)" To avoid confusion, the more appropriate term for the artifact seen when not enough grey levels are available is "shade stepping." Shade stepping is not limited to the imaging direction and does not usually have anywhere the frequency of banding.
Have you tried rotating the plate? Plate grain can make it difficult to see the true imaging quality from the head required for fine-tuning. Rotating the plate can help isolate the plate grain from the actual imaging ability of the head. Sometimes imaging perpendicular to the grain during setup will make setup more effective.
You can check for processor-related artifacts by skewing the plate so that it is processed at a slight angle. If the marks follow the angle the plate was processed at, they
were likely caused by the processor. Note: also that gum lines can be the same width as the swath.
There is a phenomenon in the pressroom known as 'Grind-lines' which will take on the appearance of what is called 'banding' and will completely have all the visual attributes of 'banding'. Plates can certainly appear band-free before going to press so it's worth checking for banding on the used, inked up plate.
Depending on the compounds used in conjuction with the solvents in the inks, washes and dampening solutions the surface anomalies in the form of line/streaking from manufacturing will begin to show in screen and solids. This streaking can also show up in dead-rollers, these are rollers that may still have the required durometer but the compond under the surface has lost its ability to rebound. In the dampening systems the chrome rollers will take on these lines and transfer the lines to the work (really shows up on older presses).
Blankets, will often have the same wear attributes of rollers. However, paper, packing, torque requirements and back cylinder pressures may accentuate the problem.
High lpi screens like 240 lpi AM/XM and FM makes these issues more visible to the eye.
best, gordo
(I'm not affiliated with Kodak in any way. I do not do Kodak customer support. Banding can appear on any external drum CtP system therefore my post is generic.)
PS tBirk1 wrote: "I did consider this...240 ls at 2400 dpi...halftone cell is 10x10 (only 101 shades of gray!, so thank somebody for modern algorithms that make that not a factor)" To avoid confusion, the more appropriate term for the artifact seen when not enough grey levels are available is "shade stepping." Shade stepping is not limited to the imaging direction and does not usually have anywhere the frequency of banding.
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Gordo, thanks for your input.
cannot rotate plate in Magnus...1030x800mm, but have rotated in processor...same results.
'Grind-lines' have been observed and eliminated at press, as well as wash-up issues. Press' are maintained well. Pressmen here will claim it's overkill. Of course, I like it that way.
cannot rotate plate in Magnus...1030x800mm, but have rotated in processor...same results.
'Grind-lines' have been observed and eliminated at press, as well as wash-up issues. Press' are maintained well. Pressmen here will claim it's overkill. Of course, I like it that way.
gordo
Well-known member
Just a small correction. I said "You can check for processor-related artifacts by skewing the plate so that it is processed at a slight angle." not "rotated in processor" which might imply a 90° rotation.
I'm surprised that your issue hasn't been escalated to a higher engineering/professional services level than "technicians" at Kodak (perhaps it has?). Usually, when vendors see discussions like this on public forums they engage more aggressive resources at resolving the customer's problem.
best, gordo
PACH
Well-known member
Good luck and hope for a quick resolution. Do not forget the previously mentioned hardware issues.
Please let us know the outcome.
It's the laser adjustment, not the power or anything else.
We had exactly the same problem for half a year. Less then a year old Magnus800.
Lines were mostly visible in midtone areas. And not on plates, but after we printed it.
Seems that not every technician from Kodak are capable of fixing this.
We had several technicians from Finland, Lithuania, Bulgaria - no help.
Finaly they sent us one from Germany and he managed to fix the problem.
patience, PACH, please...still not resolved.
we too had "another" technician take a look. he hailed from Israel. better results, but not permanent. we ordered and finally just received a power conditioner today. in time we will know if it is the cure or not. i figure 1-4 weeks to be sure. i will post the results.
we too had "another" technician take a look. he hailed from Israel. better results, but not permanent. we ordered and finally just received a power conditioner today. in time we will know if it is the cure or not. i figure 1-4 weeks to be sure. i will post the results.
PACH
Well-known member
No problem. Good luck.
Alas....power conditioner installed, but banding persists. More Kodak experts...this time they think it's press related. Explored that avenue further (and again, I should say), and more opinions share this idea, most importantly, a technician from Komori and a few of our pressmen! Yes, we did indeed have had laser related banding. And Kodak did rid us of that (as I now believe more strongly). Frustrated. At least we're working toward a solution now.
If anyone has information that could help, the following area is where we have turned our collective attentions:
blanket wash bar (no rubber bladder)
blanket wash material (fabric is ribbed in direction of paper travel)
blankets receptivity to banding from blanket wash system (newer versus older blankets)
blanket wash bar replacement (to rubber bladder type and maybe low VOC wash too)
Thanks to all for your help. Onward!
If anyone has information that could help, the following area is where we have turned our collective attentions:
blanket wash bar (no rubber bladder)
blanket wash material (fabric is ribbed in direction of paper travel)
blankets receptivity to banding from blanket wash system (newer versus older blankets)
blanket wash bar replacement (to rubber bladder type and maybe low VOC wash too)
Thanks to all for your help. Onward!
QualityPrint
Well-known member
I have a Tech coming up today to work on the same problem. Our banding you can see on the plate itself, how did Kodak fix the laser related issue?
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PACH
Well-known member
I bet they fine tuned the head with more care, like making sure that the Focus is spot on, and also the Slope and Curve. As I mentioned before the best way to see the correct value for the Slope and Curve is to put the plate on the press and take the values from the printed paper.
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