I’ve owned a Vandercook SP-20 since April of this year, and it’s been, to this point a beautiful machine. About a week ago, I started getting a strange issue that I have not been able to decipher, and is not covered in any of the books I have looked at. Here is what’s happening:
1. When the machine is ON impression, the form rollers seem to lift up when they are at about 10″ into the printing cycle (so about 10″ from the feedboard end of the bed). If I’m printing something where the form is longer than 10″, there is a distinct line where the rollers stop applying ink. I have verified this with my roller height adjustment tool. At the beginning of the print bed they are adjusted perfectly. At 10″ and beyond they don’t touch the tool.
2. This problem is confounded by the fact that when the machine is OFF impression, on Trip, the rollers maintain their proper height for the entire length of the print cycle, and ink the form correctly. The cylinder still makes an adequate impression, so it’s not moving… just the rollers.
So, the only think I can surmise is that there is something going on with the trip/print mechanism that causes the whole carriage to somehow shift part way into the print cycle. I haven’t been able to find an exploded diagram of the internal cylinder mechanism to even try to start deciphering the issue. I would be grateful for anyone with more service experience with the machine that can possibly point me in the right direction for tackling this issue.