Didde Web Press and Plate Blinding

[DeluxeBD]

We are experiencing issues with one of our Diddes and plate blinding. We run Mitsubishi SilverMaster Poly plates with a Mitsubishi SLM-OD50 Fountain Solution. We checked our bearer pressure and blanket squeeze to ensure that it wasn't related to pressure wearing the plates and all is good. It is not limited to a specific tower or ink color. We run four other Diddes with the same plates, same ink and same fountain solution with out issue. The only difference with this Didde in comparison, is that it requires a sticky back blanket. This press uses a Trelleborg Rollin blanket, whereas our other Diddes use a clamp to clamp Day blanket. The theory here is that this blanket is carrying more calcium from our paper to the plate, ink rollers, and fountain solution. The fountain solution pH on this press does drift significantly more than our others. So, I guess some questions...

1. Can anyone recommend a calcium fighting additive to add to our current fountain solution mixture that will work with the poly plates?

2. Or maybe recommend a better stick back blanket that may not carry as much of the paper fibers, etc.?

3. Any one have similar experiences or have any other suggestions or theories?

Thanks in advance.

 

[Bill Borcicky]

Sounds like you already answered your question, if everything is the same on all your presses except the blanket more than likely it is your answer. Is the blanket harder/softer than your other machines ?

 

[DeluxeBD]

Thanks for the reply Bill. I'm feel like I'm in agreement with you on the blankets, however we did try a different blanket, that was closer in surface texture to what we're using in the other presses in the last couple of weeks with not much of a difference in outcome. One of our operators thought we should be using a thinner blanket, but we've checked to ensure we're in the squeeze range. We're using the thinnest blanket we've been able to find anyway. I've studied the plates carefully and it is wear and not chemical blinding. We did a good calcium wash 2 weeks ago with our chiller clean, etc. and that seemed to have helped reign in the pH drift we were experiencing. We're kind of at a loss... it's hard to imagine it being something mechanical since it can occur on any of the towers with any color, but we're looking into that as well.

 

[Bill Borcicky]

Calcium is hard to control when it is from the paper/stock especially from canary 24/60 #. I have noticed some on white 50# and even on newsprint stocks. I had to look at the plate and actually see the outer edges of wear on the plate. On a few machines I had matched the wear marks to the blanket and other machines I had found the wear marks match the form rollers. I had reset stripes to minimum and underpacked where possible by a few thousandths.(note : expect a change in printing quality if you do this) This only made my plates last a while longer. The best solution is to buy higher quality paper, I however had chose just to wash blankets often and save money on paper cost. There are some additives which you can try in your fountain solution but I had never tried them myself. I had heard good and bad both from people who claim to use them.

 

[DeluxeBD]

Yep, if only we didn't buy the cheapest paper known to man. They aren't going to let us do anything with that, unfortunately. That's the thing I don't like about having to use a sticky back blanket...there is no play in how you can pack it, and there are subtle changes or tolerances to the blankets that come from the vendor.

Setting our forms to a minimum stripe may be a good test anyway. Hate to lose any quality, but maybe we can find a better setting that won't wear our plates as fast.

Thanks Bill.