problem on three knife trimmer

[mazengh]

we are having a problem on our three knife trimmers (we have two, one is modern, the other is old). we are getting chipped edges. we tried installing new knives, it didn't help, we tried different settings, we even tried different films of side and spine glues... but still can't find the issue, can someone give a hint what it could be? I have attached images that show the problem.

 

[Al Ferrari]

Both of those images show the same end of the spines. Is the same thing happening at the other end?

Al

 

[mazengh]

yeah it happens on both sides.

 

[Al Ferrari]

Have you not always had this problem? Maybe the glue brand has to do with it. Anyway, the glue film looks heavy to me, but I am no expert.

Al

 

[mazengh]

we tried different glues... the side isn't an issue as it doesn't get to the edges... just the spine. we also tried less glue, didn't solve it.

 

[lmercer]

At the previous company I worked at, we encountered the same issue. Sorry, but we were never able to resolve it. Obviously the more the nailhead, the worse it would be. Making the book block on the bottom of the clamp the exact same size, gave us the best results.

 

[TJ77]

You don't give many details on the type of equipment, but I'll assume this is a hotmelt binder. Here's a suggestion:

Set a handful of books aside for a few extra minutes, then trim them as normal. If this helps, you may look into slowing down your cooling conveyors to allow the hotmelt to cool a bit more before trimming.

Also, if you're running a Zenith trimmer, I do recall some kind of attachment that could be installed near the side knives that would pre-cut the cover before the main knives came down.

 

[mazengh]

we have a 2006 kolbus HD trimmer, it's got those side knives. I had the technician check if they are installed correctly. question... what type of material is used for the book block that the books down? we use some kind of thick gray cardboard.. we also tried waiting for the glue to fully dry, but it didn't help

 

[richardtheroadie]

If this problem just popped up out of nowhere check the angle of the knives. Our old sharpener changed it on us once and it drove us crazy. Good luck!

 

[Buntpapier]

I would try different height compensations and first in a normal cutter. Maybe a wedge made of grey board will tell how many clamp pressure you need for the spine. If the clamping area is not nicely holding the spine (to far inside the book), the spine is moved by the knife. Cutter operators often use 1/4 up to 1/2 thick industrial felt if they cut books day in day out.

Buntpapier

 

[mazengh]

Thanks for the tips guys... still struggling with this issue. Today we noticed that we only get this issue when we are cutting more than one book. If we cut one at a time, it doesn't show. On a side note, to improve our cutting, I designed special wooden clamping areas for each book size I cut, so I don't think this is an issue for me, but i have to add that the felt grey board we are using is made of layers of thick cardboard that we are gluing together, it's not one piece. Does this have an effect on the cutting?

 

[Buntpapier]

The clamping area has to be as close as possible to the knife. The distance from the clamp to the knife in a normal paper cutter is 0.3mm (12/1000”) up to 0.5mm (20/1000”). The wood should not touch the knife, but the grey board or felt is not a problem.
The height compensation is really important. If you have just one book, you don’t so much compensation. This sounds logic. I know normal cutters well and where is the differents?

Buntpapier

 

[mazengh]

can you better describe height compensation? is it the the gap set between the clamp and the number of books stacked?

 

[Buntpapier]

I made a picture for you. You can see how the industrial felt compensates the not even paper. With felt or with grey board you get everywhere clamp pressure.
Buntpapier