Rounding the Clamp Edge to reduce colour bruising

[DeletedMemberx0938140]

We're trying to eliminate colour bruising that occurs when cutting with the guilotine.
See Picture below for example. Notice the dark line at the edge.

!http://printplanet.com/discuss/servlet/JiveServlet/download/7-2209-12460-749/colourbruising.jpg!

My theory is that this is caused by edge of the blade where there is an increase in pressure.
Perhaps it's caused by the motion of the blade so close?

So what about if we rounded the edge closest to the blade?
A gentle slope. Maybe over 5-6mm (quarter of an inch)

Would that cause other problems with cutting? More draw out or in?
Any better ideas to reduce or eliminate the bruising effect?

Thanks for any advice or tips!

 

[PeterA]

Re: Rounding the Clamp Edge to reduce colour bruising

Dwane

By the look of it you are trying to dead split sheets - and if that is the case you will always get this problem - The rule I have is that you must always have a least 3mm between cuts. and that the "job" is under the clamp.

Peter

 

[DeletedMemberx0938140]

Re: Rounding the Clamp Edge to reduce colour bruising

Peter,
> By the look of it you are trying to dead split sheets - and if that is the case you will always get this problem - The rule I have is that you must always have a least 3mm between cuts. and that the "job" is under the clamp.Yeah, we still run a 3mm gutter between products, but we get the "lines/halo" effect on the product that is under the clamp.

In fact it is the part that is NOT under the clamp that comes out better off. (less marking)

I'm thinking it's because the pressure increases at the edge of the clamp.

It's an old guilotine...:8}

 

[PeterA]

Re: Rounding the Clamp Edge to reduce colour bruising

U do sharpen the blade

 

[DeletedMemberx0938140]

Re: Rounding the Clamp Edge to reduce colour bruising

Oh, so it could be a blunt blade then? Never thought of that.

Yeah they get it sharpened fairly regularily.

However there's a bit of a crisis in our city getting blades sharpened correctly.

Some printers are sending them 3,000 km to get sharpened, since they're not getting the life out of them that they used to.
(blades aren't polished when they finish? Something like that)

 

[maddskill]

Re: Rounding the Clamp Edge to reduce colour bruising

Sharp blade hard drying inks will help you a lot. And the sharpening is a big deal we send ours our of state via UPS ground so they get done properly. Also if your using high pigment inks like Toyo you will need to coat them or add "hardner." for drying. We use this ink and it runs great but it dries soft and is a constant problem for marking and feathering in the cutter and folders. So if its large solids or critical work we usually coat it and everything seems to be fine.

Edited by: maddskill on May 12, 2008 7:37 AM