We’re completing the rebuild of an SP15 that was begun by someone else (who is now deceased, so we can’t ask them questions) and we are running into some challenges with the inking system.
We were trying to set the rollers to the lightest stripe possible for photopolymer printing, which we did with the press in print mode. But when we tried to ink up the plate in trip mode, parts of the plate were not inking up at all. So we re-checked the stripes, and we discovered that the stripes were different on trip and print, not a good sign. And especially confounding, after shifting from print to trip, the front (press bed side) roller kept basically the same stripe, but the rear (geared) roller’s stripe disappeared, first on the non-op side, and by the end of the press bed, all the way across. Also at the end of the bed, the stripe on the non-geared roller had disappeared as well, but only on the non-op side.
So then we tested the stripes all over the press bed. We noticed the stripe fluctuated at different points on the press bed on both rollers, on both operator and non-operator sides of each roller, and changing in an unpredictable way between both rollers. Enough to drive you crazy.
The form rollers we started with were slightly worn, but we tested for flat spots by lightly rolling the rollers on the press bed while shining a light behind, and saw no gaps. We also tried manually rotating the rollers while mounted on the press, with a light aimed at the top edge to see if we could detect any fluctuation in the projected shadow. We didn’t see any variation there, so it seems like the rollers are adequately concentric. And to add to the confusion, we had a second, fresh out of the box set of rollers (old, but unused), which we installed, and those displayed similar issues, overly heavy stripes on both sides of the geared form near the gripper, becoming much more acceptable over the rest of the bed. And similar to the first set of rollers, heavier stripes in print than in trip.
So, we tried adjusting the top carriage bearings per Fritz Klinke’s instructions in Moxon’s Vandercook book (putting a 0.003 mylar strip between bearings and rails, tightening, then rolling carriage off the mylar). We did nothing to the lower (underrail) bearings. This adjustment resulted in a slightly more even impression (nonop side was ever so slightly lighter to begin with) and the carriage seems tighter to the rails in general, but most importantly, the form roller stripes are as erratic as they were before.
Any insight you might offer will be MUCH appreciated!