I’ve just begun to teach at shop with a 320 that has a deadline that as of right now is a solid 2 inches past the original scribe line. I know that its not unheard of to have up to 3 picas off the original, but this seems excessive! Previous instructors and students have told me that this has drifted since they bought the press last year, but i’m not aware of the previous history of this press.
Any help as to how I might be able to get that deadline back up to its original home would be great.
I agree with DGM. I just retimed the cylinder of a 320 at Wayne State University. We used a Big Joe forklift and turned the cylinder in place and then pushed the carriage back onto the cylinder racks,
The cylinder is incorrectly keyed to the tracks on the bed. If press is printing forward of the dead line you will have to roll it past the rack and rotate the handle a couple of teeth, re-engage to the rack and test. It may take a few tries to get it just right, but you will get there. On some of the press models there is not enough rail to support the cylinder beyond the rack to allow this to happen. If that is the case on your press, you are going to need a gantry to support it or a seriously strong team of trustworthy helpers.
Could it be that the cylinder packing is slipping?
What are you using for a head guide bar? My 325 originally had a pin bar for a register device, but without that piece I had to add furniture to move the head bar back to the dead line.
In addition to the scribe line on the bed, my press also has plates with arrows making clear where the image area begins and ends. Never had the slightest shift (with proper lockup). However, I do often have change in image length when there are blank areas in the form and the sheet sags into them. But that can be solved by putting sheets of binders board into those blank areas to support the sheet as it passes over, or locking in strip material that is just below type height.
Thanks for your quick responses! From what I understand, when the press was moved to its current location one year ago, the head dead line matched the scribe line on the bed (not the bed plate). Over the course of the year, the headline has “drifted” south- a bit ago, it was only 6 picas off, and now, the printing begins 12 picas below the scribe line, making the non-printable top margin 2.25 inches. I don’t believe the tail dead line has shifted.
I don’t believe the cylinder was removed for the move, but I’m unsure. I’m nearly positive it hasn’t been moved since- if it was out of time, wouldn’t the grippers be out of place (forward or backward)?
I will take a video and post tomorrow.
The relative position of the cylinder moving along the bed is a fixed thing and is a function of the gears. I don’t see how any drift is possible with intact gears (and normal trip/print lift, and bumpers in place). This position can be changed when the cylinder is removed and then replaced at a different position (out of time). Correct position at rest at the feed table is with the line between cylinder and clamp at 12 o’clock high.
There is a head dead line and a tail dead line. You might have a different drop off in image at the tail if you are not using full-length packing. I’d also note that the tail dead line falls in between the form rollers, and the rear roller can actually stop on a form extending to the tail dead line.
I also wonder if you are referring to the scribe line on the BED, or one on the BED PLATE, which can shift but would have no effect.
Drift is a curious description, but we need more information. A video of the back side of the carriage as it travels down the bed, in print mode, may be helpful.