Tinting on Hamada H234C

[BrGoody]

We had been running polyester plates for about 20 years on our Shinohara, Hamada H234C, and Ryobi presses. Last week we switched to metal plates and we are now getting some tintng (or scumming in the background, see pictures) on the Hamada. Not getting it at all on the Ryobi with same fountain solution. Doesn't seem to show up on the plate but you can see it on the blanket. Have tried a couple different fountain solutions, tried adjusting the fountain/water mixture, checked all roller & blanket pressures and are still seeing it. Shows up pretty quickly, after only a couple hundred sheets in some cases. Has anybody seen this before? Never got it with the Polyester plates. It's worse with some colors than it is with others.

 

[printerdan]

Are you adding control bars on your plates?. Our tech included them in the plate bend area only after we asked about such. I wasn't real impressed with their initial setup of our ctp so I leaned on them quite a bit.
Two weeks or so in your developer should be fresh but you might want to address the imaging or development time. We start increasing development and even double through the processor after perhaps three weeks of a flush. Control bars on the plate make visible inspection simple.
As I recall we even sent back the initial processor and changed plates 30 days after install.
What ctp, processor and plate make?
And I for one have fond memories of poly plates. Never an old plate. Never had to worry if it was an outdated file. No plate files. No plate cleaning.

 

[turbotom1052]

Is the tinting making onto the sheet? If not I wouldn't worry about unless it builds up really thick and makes for a real mess outside of the sheet perimeter. You could try using a deletion pen on the plate in a non image area and see if the area you used the pen on stays clean on the blanket. If after the plate deletion your blanket stays clear in that area I would begin by looking in prepress to the plate processor. Make sure that the processor maintenance is followed, and also that all chemistry is changed on schedule. Let us know it that helps?

 

[Adil]

the amount of ink on the rollers is more than the amount to be consumed. suddenly it gives a fontome image as an extension of the GAT tile. it is necessary to reduce the load of ink in the group until the good minimum. also put bands in the unprinted areas to consume a little ink. and then properly adjust the inking rollers in relation to the distributor according to the standards

 

[BrGoody]

Thanks for the replies but let me add a little more info... We had been running polyester plates made on an AGFA Phoenix Platesetter for the last 20 years but since that machine has pretty much gone by the wayside, we made the decision to switch to metal plates. We just purchased a new Glunz & Jensen Platewriter Infuse to now make the metal plates. There is no chemistry, just dryer & gum and then they are press ready. The plate itself looks perfectly clean when running on press but the tinting does build up on the blanket and then transfers to the sheet leaving a background tint, or haze on the sheet. The odd thing is that it is in a striped pattern that runs from the leading edge of the blanket all the way to the tail edge. (see pictures in original post) Our Hamada H234C press that we are running the plates on has a Crestline dampening system and never really gave us much trouble with the polyester plates so I don't really know why we are having this problem just because we switched to metal plates on the same press?? Not having the problem on our Ryobi or Shinohara presses.

 

[turbotom1052]

The fact that your not having the problem on your other presses should NOT carry all that much weight when it comes to troubleshooting this problem on the Hamada. There's a long list of differences between the various presses that could be causing this issue on just one of the presses to include fountain solution requirements, mechanics of the dampening systems, roller durometers, variations in stocks being run... this list goes on! Considering that these plates get developed on press by the presses dampening system, Im assuming that you just drop the dampener down on the clean plate for a bunch of revolutions, and then drop your inking rollers down to roll up the plate before printing. Have you tried to hand develop the plates before rolling them up? I would suggest doing that as your next step if you haven't allready tried.

 

[Adil]

the amount of ink on the rollers is more than the amount to be consumed. suddenly it gives a fontome image as an extension of the GAT tile. it is necessary to reduce the load of ink in the group until the good minimum. also put bands in the unprinted areas to consume a little ink. and then properly adjust the inking rollers in relation to the distributor according to the standards

Plzase sir do what i yold you yo do to be sure that this not a fantome image .
Good luck