Plate register

Hi everyone.
I've just printed a school year book on a komori 528 which consisted of 38 sets of plates to change. Not much fun after a while as it only has semi automated plate changing which means squeezing inbetween the units nearly 150 times to change them. The problem I had was that for some reason I only had a couple of sets of plates which went on square. The rest of the time I had to skew one or two colours slightly to get a fit. I'm not sure how they can go on the machine out of square when all they do is drop onto the pins in the cylinder. Does anyone else have to skew plates that often or does every job generally fit straight away?

 

dude i do the same type of work on a 2004 5/28 as well, I will always get register differences between sections if one has full solids on one of the pages and the next section has bugger all on it, i just put it down printing (work conditions, ink tack etc). I know most owners think because they have ctp it's just a case of plating up and hit the production, button but most of us still believe there is still room for a craftsman.
jet screamer

 

Hi ding, we have Lithrone626 with semi APC as well as AGFA Palladio CTP.

Just before the Xmas break we did some calendar overprints, a variety of spot colours and cmyk totalling over 90 plate changes. Checking with the pressmen they hardly had anything more than minor tweaks (say the thickness of a register mark) to attain registration.

If this is a constant issue you need to analyse in order to correct it.

Did you check the plates affected for correct image positioning as well as correct seating on the press register pins?

Is the issue confined to one particular unit? If so, is the deviation constant? If so then the pins may need repositioning. Checked packings and blanket tension?

Do you punch the plates manually or is it built in to the CTP?

A good CTP system shouldn't deviate more than .01mm.

 

We had this problem with our L540 and after months of guesing we determined to have our tech come in and take apart our plate clamps and reset them all to zero. that solved the problems. What happens is that the gum and solvent build up and causes problems. Dont try to take it apart yourself there are lots of springs in side. Its a pricey project for a tech but well worth it if you have to hang alot of plates.

 

Thanks to everyone for replying. We do have to punch the plates manually after they come out of the CTP. We tried checking whether all the register marks were spot on before the plates went on the press, by laying a piece of film over them with register marks on it. Everything seemed to be ok according to the staff upstairs , but I suppose it's very dififficult to be sure as it's really only the width of a register mark out each time. I think maybe we're all expecting too much, and just presumed every job would sit bang on and we'd never have to move anything. All my mates think I just have to push one button and the press does everything else anyway. Thanks again guys, it's much appreciated.

 

I manually punch my pates before they go into the CTP, then they are punched again with the KPS before they go on the Press. Perfect 99% of the time. Once my bosses son came in to make plates as i had 150 to do. pretty soon i realised they were all over the place, and it was down to the way he punched them before platemaking. the plate was moving in the punch.

 

If it's only that amount out then you'd be hard pushed to point the finger at any one area. Punching plates manually after CTP imaging and variations in physical position of the cylinder register pins or even whether the plate is sitting snugly on the pins..all will have a bearing on your issue.

If it was just one unit and one 'direction' of misregister then you could have the pin position altered to compensate.

If it's any consolation we do get a hairline out on occasions too. I've put that down to fluctuations in the plate tensioning mechanisms or even ambient conditions.

 

I have noticed that on a couple of the units the clamps don't do up very tightly thus causing the plate to pull away from the pins when you tension it. This could be something worth looking at? I don't seem to be able to tension the plate very much at all without it slipping.

 

What amount of coverage were you printing and what kind of stock?

 

we had it with our ctp plates We found out that some of the transport rollers in side the imagesetter where dirty and when cleaned the problem stopped

 

Hey Dingabell, there is no such thing as a flawless make ready. Our bosses have a hard time dealing with that fact but that's just it, it's a fact. If you have semi-auto hangers and sometimes they're perfect and sometimes they're not, it could be one of about ten different things. My first question, do you notice the problem on your first pull or does it seem to creep up as you are running? Like mentioned before, if the plate is off and you can visibly tell that it's on the pins than your pin system might need re-shimming or the grippers between that unit and the preceding might need cleaning or re-adjustment or if you have a heavy solid and your tack hasn't released then it might just need to run for a few minutes. How far is it off? Can you feel any slack in the lead edge or the tail of the problematic plate. If so, it could be a neumatic problem. I ran a 1999 6/40" that had auto hangers. Second unit always slipped during the run. Had to chase it everytime. Finally, got fed-up with the problem and dropped the plate clamp.
Their were adjustment screws on the tail tensioner that needed a slight adjustment, fixed the problem. The hard part was re-installing the plate clamp. Wasn't the funnest thing I've had to do in my printing career but got er' done!!