Plate Scratches – What Causes Them?

 

Scratches on printing plates happen in our pressroom on a somewhat rare, but consistent basis.  We start up the press sometimes and voila!  There it is.  Other times, they don’t show up until three or four hundred thousand copies.  Most of the time, just looking at the scratch can tell us where it came from.  Let’s take a look at some of the causes and a few preventative measures that we use.

Cause #1:  Handling

Carts to prevent plates scratches.

This is our most common problem.  Plates are sensitive and require careful handling by the pressmen and plate room personnel.  Most of our presses run four color and so just in bringing a set of eight plates from the prepress department to the press can cause abrasion.  We designed carts to transport them and place the non-abrasive sheet that is between the plates back between them for transport afterwards.

Additionally, we’ve set a system up whereby after each plate is burned, the prepress person must visually inspect each plate.  When he catches something, the procedure pays off.

Cause #2:  Particles in Roller Train

Scratches can come from debris in roller train.

This one plagued us once for about six months.  We could not figure out the source of them.  After printing from 100,000 to 500,000 vertical scratches would show up.  They ran right through the image and non-image area.  When inspecting the plate, we could see that they wore down to the metal.

Only after time did we discover very small metal pieces in our roller train.  Extremely minute but enough to cause damage.  Our plate hanging process would sometimes cause a few metal flakes to break off on the edges and then make their way to the ink train. Form rollers that were set heavy exacerbated the problem.  Whatever the source, you have to find it.

Cause #3:  Poor Plate Quality

Good printing plates require a decent anodic layer.  Consult your plate manufacturer about how you can get better quality plates that will last longer and not wear so fast..  The plate should also be durable enough to avoid cracking over time.

We have found that this is something we constantly have to stay on top of.  It plagues our pressroom if we don’t diligently follow up on the cause.  I welcome your comments.