This article provides solutions to common presswork problems encountered on a Vandercook and similar brands of flatbed cylinder proof presses. Experience adjusting a Vandercook press is assumed. Most makeready can be eliminated by standardizing materials. One element out of specification may lead to problems that cannot otherwise be corrected.
Much press repair can be avoided by routine cleaning, lubrication and checking of fasteners. However, be prepared for potential repairs by acquiring model specific replacement parts. For example, all models should have a spare worm crescent (CS-23) for the oscillator and a few extra copper paper guides (LB-7). SP series presses should have spare Delrin trip rollers (X-21119) and cylinder eccentric trip springs (X-23790 for the SP15 and X-23780 for the SP20 or SP25). These proprietary parts can only be purchased from NA Graphics, who also sell operators manuals. Other useful information can be found at Vandercookpress.info and the book Vandercook Presses: Maintenance, History and Resources by Paul Moxon.
Keep the cylinder bearers, bed bearers, under rails and carriage bearings clean by wiping them with a slightly oiled rag before each work day with SAE 20 wt. or 3-in-One oil. These surfaces are not meant to be wet, the oil merely removes dust and grime before it accumulates.
Vandercook operators should know the amount undercut of the cylinder face and the thickness of the paper to be printed in order to determine how much packing to include. The undercut, stamped in the channel between the cylinder bearer and the impression surface, can be seen when the carriage is at the feed board. Paper to be printed and non standard packing material should be measured with a micrometer. Generally, cylinder packing consists of tympan (.006 or .010”) in combination with other materials each of which must be of uniform thickness. It should be free of indention, the grain parallel to the grippers, and tightly secured under the drawsheet.
A proper drawsheet, whether made of tympan or Mylar, should have a sharp 90 degree score and fold at the hem, which is clamped behind the gripper bar. The reel rod around which the tapered tail of the drawsheet is wound can be shifted laterally to eliminate bagginess that may cause slurs. The cylinder should not be over-packed, requiring tremendous effort to move the carriage over the printing form, as this will stress the carriage bearings and may cause wear to the under rails.
Impression balance across the bed can be tested by taking a blind proof on heavy paper. To do this, lock up two lengths of type high rule, slightly shorter than the length of the bed, placed parallel to and one inch in from to the bed bearers and take a blind proof on heavy paper. The resulting deep bite impression in the paper should appear even on each side, if not then the cylinder is out of balance and the carriage bearings can be adjusted. In print mode, roll the carriage to the middle of the bed, onto .003” feeler gauges to reset eccentrics. Do not undertake without prior mechanical experience.
The condition of form rollers is the most significant factor in producing quality printing. The rubber may swell, shrink or become pitted and hardens over time. The diameter of the rubber should be either 2.5” or 3 inches, depending on the model. Significantly undersized rollers will not make contact with type high forms. The durometer, or hardness, should read 20 as measured on the Shore “A” scale by a gauge also called a durometer. A reading above 30 means that the rubber is too hard to properly transfer ink onto a printing form.
The roller height bearing assemblies must be in good condition. There should be no play between them and the journal ends of the roller cores. Reamed out blocks can be replaced and most models require bushings, called nyliners, for a close fit. Roller height adjustment screws and lock screws must have threads and heads in good condition or be replaced. Use a .918 roller setting gauge to confirm that rollers are set for a type-high form. If height adjustment cannot improve inking—and ink, plate, paper or packing are not to blame, then the rubber on the form rollers needs to be replaced.
For best results printing forms locked in the press bed should be type high (.918”). When in doubt, use a plate gauge or calipers to measure the height of wood type, woodcuts, wood engravings, old wood-mounted photoengravings, linoleum, blocks and especially collotypes or other homemade relief plates. Add underlay (paper of known thickness) to build up low elements. Adding Kimlon, a latex impregnated paper to the packing may help achieve even impression of mixed forms. Elements above type high should be milled. Place the face of a plate or block higher than .918” on its side away from the saw so that the bottom can be trimmed.
Good registration is dependent upon a well maintained press with a balanced impression cylinder that is properly packed and a smooth functioning paper gripper assembly. The operator must consistently feed paper to the grippers. Close registration requires a pedal, hand lever or power grippers to open the grippers when the carriage is at the feed board.