3.4. F4 CREEP REDUCTION panel

3.4. F4 CREEP REDUCTION panel

In every signature, there is a phenomenon known as page creep. The closer to the center of the publication, the greater the creep. This is caused by the fact that the wire staple touches only the cover page (the first page), while the subsequent pages are pushed away from the staple by the thickness of the preceding pages.

This phenomenon causes undesirable effects in some publications. One of them is the shifting of page numbers, for example. The printing craftsmanship requires that the pagination be at the same distance from the edge of the page, i.e. that the printed page numbers on successive leaves be at the same distance from the edge of the page.

The Impozycjoner software can reduce creep by shifting the image of the mounted page by a step calculated for each page. The figure shows a 16-page booklet. After enabling reduction, we should ultimately achieve the effect shown in the figure. For comparison, here is the version with creep reduction and the version without reduction, before and after cropping the edges.

The easiest way to determine the creep size is to make a mock-up of the booklet using the target paper and measure the distance between the edge of the cover and the edge of the center pages.

This value should be entered after selecting the maximum creep value as “Measured”. The program will automatically calculate the creep value for each page.

The distance by which the pages will be moved is calculated according to the following formula:

where 4-Page is the consecutive sheet number (the printing 4-page), and Number_of_4-Pages is the total number of 4-pages in the signature.

The second way to calculate creep based on paper thickness is to use the following formula:

The "stitching" quality factor is an empirically selected correction (usually 1.2 to 1.4) indicating the degree of compression by staples – the ideal value is 1.

Reduction methods: Cropping and Scaling

Cropping method: the width of each imposed page will be cropped by the calculated value appropriate for the page, and the cropped page will be moved to the center of the spread. The disadvantage is that a fragment of an illustration crossing from one page to another may be cut off.

Scaling method: the width of each imposed page will be scaled (reduced) by a calculated value appropriate for the page. The disadvantage is that the shape of objects on the PDF page will change.

Additionally, the program allows you to change the number of the 4-page cover, i.e. pages without creep reduction. A value of 0 (zero) for the 4-page number means that reduction will occur on the first card. If the 4-page number is greater than 1, selecting the Start correction below base 4-page option will reverse the correction on pages below the base 4-page. This means that instead of pushing pages inwards, they will be pushed out, and instead of reducing them when scaling, they will be enlarged.

Creep reduction usually refers to saddle stitch binding, but the program allows you to enable this mechanism for sewn binding (for signatures) and perfect binding (for sheets, e.g. 32 page ones).