Inking and Registration
Hi,
I have a few questions and was wondering if anyone can help me or has any advice?
1. I have a GT Platen and have been doing some business cards up (2 plate design) - when i print my first plate everything is all good but when i change the plates over (placing them in the exact position on my base) they don’t seem to line/match up once printed?? Is this a problem with my base and plate or is this just a matter of where the paper is dropped? How can I make sure they both align perfectly?
2. How do you prevent the ink from transferring onto the bed of the press and hence onto the back of the sheets when printing?
Any advice or tips will be much appreciated!
Thanks
1) Are you certain you’re running with guides? I’d check that first. If you are, make sure the paper is set to the far left on the feedboard (and set for the right kind of guides you’re using – nickel or brass).
2) You need to watch the press and disengage the impression lever when the grippers miss a feed, otherwise you’ll print onto your tympan.
I disagree about disengaging the impression levers. Unless GTs are differently designed than the standard T-Platen, Heidelberg has intentionally not installed a feeler mechanism that will trip the press off impression in case of misfeed. I have never seen a GT in person, but the impression is engaged with a larger, crescent shaped handle, not a ball like on the T, and I have a feeling tripping impression on-the-fly is harder on that press.
Instead of a feeler/trip mechanism, there is an auto-stop mechanism on the press. It will need adjustment depending on the stock and size you are printing, but make sure it is properly adjusted so that the clutch disengages when sheets are missed.
Danak, where are you? The auto-stop function, as well as getting a print into register, are two of the most fundamental processes related to printing on an Original Heidelberg and it’s a bit worriesome that you have no handle of them yet. In most major centres you will be able to meet up with someone familiar with the press who can instruct you. If you do not do this, at best you will be wasting a lot of time and materials troubleshooting the press by trial and error. At worst, you will do some very serious (or at least expensive) damage to your press, or yourself.
Paul
Sorry about the misinformation. I just assumed the GTs were built like the 10x15, just larger. Regardless, he’s still got to figure a way to either stop the press or throw impression off when it misfeeds, or he’ll continue to print on the tympan.
Yep, and there is a way the press is designed to do it and it doesn’t involve turning the machine off impression (well, you will need to turn it off impression, but only once the auto-stop has engaged.)
I am sure one of you knows there is an adjuster for the trip on the platen its immediately below the paper feed push knob if the machine wont stop when you miss a sheet you undo the outer ring and screw in the inner bar take a hit and if it picks up and then stop you gradually reverse the bar out again a small bit only a tenth of a turn at a time, repeat a feed and keep going turn try and so on till it stops. It is funny that it wont stop as usually the problem is the opposite and other than operator who isnt so light fingered its wear but not stopping is purely the screw too far in .
I have never worked on a heidelberg without a trip and my colleague tells me that in his 60 years nor has he .seen one
Sorry the screw too far in will cause the press not to continuously run and too far out it wont stop. Yes that made me look stupid.!!!
I’m not familiar with this press or the other similar ones mentioned…with our C&P we register by taping the plate in place on the paper, then place the paper on the platen, then close the press and the plate’s adhesive will grab the base and will be exactly where it needs to be for that run.
Would something like that be possible?
Thanks for all the helpful advice.
The trip function is working fine on my press - I think I just need to get a better handle on turning the impression on and off at the right time. Have spoken to a local pressman and he has given me some handy tips to prevent inking of my tympan.
In regards to the alignment/registration issue, I am running with guides and have my paper set in the correct position. Still not sure why it wont align when I run the second plate? I would expect the alignment to be off either top or bottom or left and right, but it seems to be on an angle? Could this be a problem with the suction on the gripper bars as it takes the paper through? Any suggestions?
On an angle suggests to me that maybe the paper is slipping behind the guides or bouncing as it comes down to rest. Check your guides to see if there is any space between them and the platen. I had to glue some little pieces of paper onto the back of mine so the sheet wouldn’t slip behind the guide. It was very frustrating to figure out.
I’d also look at where your left guide is positioned. I try to have mine at the far end of the sheet.