Web printing press with delivery stream length determination

1. A printing press comprising:

at least one print unit printing a first job on a web;

a folder splitting the web into a plurality of ribbons, combining the ribbons, and cutting the ribbons into signatures, the folder having a folder delivery for delivery of the signatures;

a marking device marking every ribbon;

a sensor sensing the marks on every ribbon; and

a controller connected to the marking device and the sensor and determining a shortest ribbon value and a longest ribbon value, the shortest ribbon value being a function of a shortest path length of a first ribbon through the folder and the longest ribbon value being a function of a longest path length of a further ribbon through the folder.

2. The printing press as recited in claim 1 wherein the mark has magnetic properties.

3. The printing press as recited in claim 1 wherein the mark is ferromagnetic ink.

4. The printing press as recited in claim 1 wherein the sensor is a magnetic sensor.

5. The printing press as recited in claim 1 wherein the controller determines the number of impressions of the longest ribbon and shortest ribbon printed with the first job.

6. The printing press as recited in claim 1 further comprising a waste gate after the folder, the controller controlling the waste gate.

7. The printing press as recited in claim 6 wherein the waste gate is controlled as a function of the shortest ribbon value and the longest ribbon value.

8. The printing press as recited in claim 1 further comprising at least one second print unit printing a second print job on the web when the first print unit is not printing.

9. A method for determining printed ribbon lengths comprising the steps of:

printing a web of material with at least one printing unit;

splitting the web into ribbons;

marking each ribbon of the ribbons with a mark; and

detecting the mark on each ribbon;

determining a longest ribbon value as a function of the detecting, the longest ribbon value being a function of a longest distance a longest ribbon of the ribbons travels through a folder; and

determining a shortest ribbon value as a function of the detecting, the shortest ribbon value being a function of a shortest distance a shortest ribbon of the ribbons travels through the folder.

10. The method as recited in claim 9 further comprising operating a waste gate as a function of the shortest and longest ribbon values.

11. The method as recited in claim 9 wherein the printing occurs for a first print job, and further comprising switching over to a second print job using a same folder configuration.

12. The method as recited in claim 11 further comprising determining when good products for the first print job are no longer formed as a function of the shortest ribbon value.

13. The method as recited in claim 12 further comprising determining when further good products for the second print job begin to be formed as a function of the longest ribbon value.

14. The method as recited in claim 12 further comprising operating a waste gate to discard bad products after the good products for the first print job are no longer formed.

15. The method as recited in claim 11 further comprising determining when further good products for the second print job begin to be formed as a function of the longest ribbon value.

16. The method as recited in claim 9 wherein the determining of the shortest ribbon value includes determining when the mark for the shortest ribbon passes a last printing unit and when the mark for the shortest ribbon passes a sensor downstream of the last printing unit.

17. The method as recited in claim 9 wherein the mark is separate from any registration mark.

18. The method as recited in claim 9 wherein the mark is not provided to every image.