Was wondering if anyone could help, I have a small print business and recently decided CTP was definitely worth the expense in the time it should save. I bought a used DPM but am getting a quite a bit of inconsistency and I'm wondering if the plates are the root cause. I gather this forum is maybe more for pre-press but figured some may have print experience.

Admittedly, my problems could be due to my press's configuration not being fine tuned for poly plates, but on some jobs makeready is 2 minutes, others will just repeatedly ink up (or fail to ink properly). I don't understand why I could be getting such inconsistency.

A Presstek engineer said if a plate has not developed properly the image will be bronze as opposed to silver but I'd have assumed that when your chemistry goes bad, then all plates from that point on will be poor - not some good some bad. I should also note it is new chemistry I'm running!

Could anyone comment on running these types of plates and what my problems may be?

Hello chrig,

Welcome to the group. There are many accomplished former pressmen in the group. I have ran all kinds of presses with silvermaster & poly type plates. Logic tells me it is not your developer or plate processing. If you are having a good plate after a bad plate it is most likely variation at the press (I think). If you are used to running metal, poly is way less forgiving, harder to get to clean up, harder to get to tone up. Ink water balance is more critical to hit, especially as you are starting up.

I would say for starters, review your fountain solution. Try to find someone else doing exactly what you are doing, compare notes on fountain chemistry mixture etc. This forum won't be the right place, ask your CTP suppliers and graphic arts suppliers to network you to some folks with same equipment, dampening system and plates. Are you saying you are running new FOUNTAIN chemistry? If so, this is all critical. Another great place to check is your press repair technician. Pre-mix your fountain in large batches of several gallons and pour from there. Mixing every time in the bottle as some will do leads to inconsistant chemistry. This stuff has to be dialed in to work real well.

OK, on the press. Some of this will sound really basic and fundamental, but I'm going down to a really simple level, maybe will help, maybe you are way ahead of me? Now working with poly plates is like kicking field goals. Before you ink/kick you have an exact timing and method that is consistant every time. What press are you running and what dampener? I will assume small offset but is this a duplicator or a real press? You can have success or failure just in how quickly you drop the rollers to the plate. Also, I never would run a dry plate. Just before you start the press, always take a cotton pad with fountain solution and wipe the lead edge of your plate, right at bend, so it's edge is not dry when you drop your rollers. Then, timing, always get two or three revolutions of water roller only, drops first, then ink rollers. Find your timing, be robotic of that procedure. It's important that the plate is not dry, so won't ink up, but not too wet, so will take ink. If you are using a single lever, never go all the way to ink rollers in one motion, go in stages. First drop one click, water rollers go down, couple of revolutions, now drop ink rollers.

I think you are right on plates. If the plate chemistry goes bad, it's worn out, it doesnt go good plate bad plate. Nor does the plate material itself. What does go up and down is the operator maybe. You and or your pressman probably know all that I'm saying in here. But I'm just saying that if your chemistry is verified to be a good mixture, one plate should ink up like the next. Usually the reason they don't is the operator isn't really timing and controlling that part with the right care and consistancy.

The bronze like image? Well, I don't know about that because I printed many plates with bronze like image fine. This does bring up another thing to look at. How long are plates sitting around drying out before use? This too can be a variable that will affect one vs another. You may look at that as a possible variable to control. Fresh plate is better plate but really if you wet the lead edge, drop your rollers with good timing, really that should not matter. Let me know if any of that helped. Still interested in what press, chemistry, and dampener.
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JoePostscript -- support administrator

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Hi Joe,

Thanks very much for the detailed reply, very generous of you to share the time and knowledge!

I am still a newbie printer (must have given myself away!) - well, been at it on-off for 3 years now but am self-taught so there's still likely huge gaps in my knowledge (some of it no doubt, very basic stuff). I run 2 machines, first is an old Ryobi 3200 (Crestline dampening system has always given me major problems on this but just had an engineer give it a tune-up) and the other is a Heidelberg QM46-2.

I had been running an alco free fount and rubber-based ink but on the engineer's recommendations, switched to a blue fount (tried 2%, not sure if that's suitable for the soft water in my location?) and oil based inks - I've only had a chance to give one run a try on this set-up but it was still a mess, entire plate just kept inking up (a nightmare cleaning the blanket on the QM by hand!).

I do give the plate pre-fount for a few revolutions on each press - you're right about timing though, sometimes I can be almost ready to go but have to stop for the odd mark, at which point it almost always inks up the plate. I used a poly plate prep for the plates, which I apply before mounting but hadn't tried foun solution for the leading edge, so will try that if you think it would be any better than the prep.

Just to follow up on this, I switched from my poly plate prep to using fount and all my problems have more or less stopped, I can't believe how well it's running now! The plates really don't like stopping once they've started though, almost certainly ink up when stopped.

Which DPM dio you have ?

We a going to change over to a metal proceless system with all the bell
and whisles as soon as I can work out which one

Angelo

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Originally posted by chrig:
Was wondering if anyone could help, I have a small print business and recently decided CTP was definitely worth the expense in the time it should save. I bought a used DPM but am getting a quite a bit of inconsistency and I'm wondering if the plates are the root cause. I gather this forum is maybe more for pre-press but figured some may have print experience.

Admittedly, my problems could be due to my press's configuration not being fine tuned for poly plates, but on some jobs makeready is 2 minutes, others will just repeatedly ink up (or fail to ink properly). I don't understand why I could be getting such inconsistency.

A Presstek engineer said if a plate has not developed properly the image will be bronze as opposed to silver but I'd have assumed that when your chemistry goes bad, then all plates from that point on will be poor - not some good some bad. I should also note it is new chemistry I'm running!

Could anyone comment on running these types of plates and what my problems may be?

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