By R.O. Vandercook. From a speech at the Second Conference of the Technical Experts in the Printing Industry, March 16-17, 1931, Washington, D.C. Published as “Vandercook Proof Presses” in Photo-Engravers Bulletin, June 1931. Present title by moderator.
The “rule of thumb” is becoming obsolete. In its place are used deﬁnite and planned systems developed by laboratory tests. When many of us were ﬁrst drawn to printing, 0.001 inch was nothing in our young lives. The growing appreciation of the value of micrometer measurements, which has been brought into the industry by mechanical engineers, is a great factor in the modern development in the graphic arts. Accuracy and rigidity of construction of presses for printing from relief surfaces are just as beneficial as in building presses for the other processes, and it is a question whether the other processes would have come into such general use had engineers first considered the benefits of extreme accuracy and rigidity in regular printing-press construction. Great improvements have recently been made in the printing quality of plates and the elimination of make-ready time. But how can this good work be further carried on? Some make-ready time is now needed to make corrections for the high and low spots in the metal on which the etching is made. Research may find a way to roll the metal in sheets so that the surfaces will not vary much as they now do. The more accurate the printing surface and the more accurate and rigid the press the less resiliency is needed in the tympan.
We once built a press to test foundry type on which no tympan was used. The cylinder and bed were ground to the closest possible limits. Test proofs made on paper 0.002 inch thick showed some slight errors in the best of foundry type. On test sheets of 0.004 inch thick the type looked absolutely perfect. It may be possible in the future to build and use high-speed rotary presses using no tympan, the only resiliency needed being that of the stock on which the edition is printed. It may be necessary to grind the cylinder to suit different thicknesses and quality of stock; but when great editions are run on standard stock the paper mills now seem able to furnish, this may not be a too great detriment.
It is now possible to treat plates so that the high lights are relieved in the plates. More expeditious and less expensive ways may yet be found to put all the make-ready into the plate. Even if the plates are absolutely accurate on the surface, is thought, it is still necessary to make less trouble on the more resilient tympan on the producing presses.
On forms that will go to the smaller automatic presses it has been found good economy to test each form after it has been locked up. The greatest of guides are made the same on the test press as on the automatic press. With the aid of the test press the composing room can shift the form to register so that there will be no need to shift the guides on the automatic press. Spot-out sheets can also made on the proofs from the test press while the automatic is producing on other work.
Interesting experiments have been made on presses using only one sheet of manila, or about 0.006 in of tympan, Plates that were too high could be felt by the pull on the handle of the cylinder. Cuts that were below 0.918 inch high could be measured very accurately by laying on the top of the test sheet sufficient tympan paper of 0.001 inch thick to bring the low spots up. It was found that much of the make-ready on the 11-point-lead plate could be put in between the plate and metal base. Because of the hard, unyielding tympan, the effect of the tissue back of the plate showed up sharply through the 11-point-lead backplate.
It is believed that wood is destined to be of less and less use in mounting cuts. Printers who have typecasting machines will increase the use of their machines by casting their own sectional base. It may be possible to design a more efficient hook to hold the plates on the homemade bases. We once made some light and inexpensive bases by casting metal around well-seasoned wood, The plates, when properly shaved, held their accuracy because the wood was protected from the air by a thin coating of metal. Plates could be tacked to the metal-coated wood as well as to the all-wood base.