Even the best printing machines in the world require small margins for error. Occasionally, as incredibly sharp cutting blades fall and trim paper to size, there can be a minute shift in the placement of the hundreds or thousands of sheets of paper that are layered for the print run. This can result in incredibly small changes (typically under 1mm) from piece to piece.
This is the reason projects need ‘bleed’, where you print beyond your trim line. This means that if there is a small cutting variance, there will be no unprinted edges exposed. Always add bleed to your print files and also take into consideration our recommended quiet area to keep any important design elements away from the page edge.
Similarly, when printing 4 colour CMYK ink from metal plates in very high volume litho print runs, it’s possible for colours to move very slightly. To help prevent this, we strategically print lighter colours first, followed by the darker colours, to ensure you don’t see white lines between two blocks of colour if any manufacturing variance occurs.