Hoping there is a simple solution to my impression problem. I’ve had my Vandercook No. 4 for several years now and this problem just started happening on my last job. It seems to me that the impression cylinder is dropping into impression mode later than it ought to be. Rather than the typical 3 1/2 pica area lost to the grippers, I don’t get a full, clean impression until 1 1/2 inches onto my paper.
On an SP-20 I have used, sometimes if type is set right against the dead bar, I’ll have slight issues right where the impression starts, but this seems unusual being so far out. The type is 3 picas away from the dead bar and no matter how far I move it, the bad impression line remains in the same location. Tried several different forms to make sure it was the impression cylinder, not the type. I have fairly fresh tympan and no slipping of the packing which could also cause the consistent line of bad impression across the sheet.
Please let me know your thoughts, your expertise and advice is greatly appreciated!
Erin Beckloff // Inky Winke Letterpress & Design
It looks to me like one of the sheets of tympan isn’t all the way to the gripper bar. Open up the press packing and look for any irregularities. Shuffle the sheets all the way to wear the gripper bar, re-tighten, and try it again.
DGM
Hi Erin,
Did you also try and handbrayer the type?
This way you could easily find out if it is a inking or an impression problem.
Good luck.
I have limited experience on these presses, but could the form rollers be hitting the front edge of wood type assuming it is .918 evenly all over-and bouncing upwards, have you run through a piece of paper to check there is even impression on it the full length of type-but you say you have checked the type….hhhmmm
Are you certain it is an impression issue and not a possible inking issue?
I’ve had marks like this appear on a #4 when the front ink-bearers (the metal rollers that support the form-roller carriage) were hitting a stuck glob of something (it was either old ink or crushed tape or ??? – it was sticky, and the rollers were riding directly over it).
It took a while to find because those rollers ride the rails in advance of the form rollers, and the bump wasn’t aligned with the under-inked spot. It was easy to diagnose as an inking issue in my case because it was further down the bed. Had mine been immediately at the start of the sheet, I might have thought it was an impression/trip issue too.
If it is an impression issue, the trip lever on a 4 is in a very fixed position and shouldn’t move or shift under any circumstances.
The Trip Rack (located on the non-operator side of the carriage — it shifts up and down with each Print/Trip cycle) could have a bad or worn tooth. This is accessible behind a brass cover panel on the back of the press. There’s a manual for the #3 available on letterpresscommons.com, and the parts are identical. I don’t recall how user-servicible that part is, so I wouldn’t start removing screws until you’re certain it won’t all fall apart on you. A worn tooth, either on the rack or the gear it rides on could cause issues like this
It’s also conceivable that some debris on the top or underside of the rails could be causing impression issues as the cylinder or the bearings roll over it.
Check your rails first, top and bottom, and make certain they’re clean and smooth, then start digging deeper. Good luck!