Cutting Parent size stock for press

[RGPW17100]

Before we were acquired by another printing firm we used to cut our flolio sheets as follows. 25x38 would be 12.25x18.75 and 28x40 would be 13.75x19.75. Doing this would be a four sided trim to each press sheet. The new place does 25x38 to 12.48x18.98 only trimming off the wild dirty side from the cut. We felt the way we originally cut was helping reduce hickeys by trimming all four sides. The new establishment disagrees with this practice. Just curious how others cut there parent size stocks?

 

[ondemandbindery]

A nice debate you brew on this topic. At the end of the day try to not take stock to the cutter prior to Printing. There are always reason why some substrates have to be precut (size and grain direction are the easy hitters on the list) but it definitely creates potential hickeys on press. And people can talk about back trimming a sheet to use the clean side of the blade only but the fact is you have layed the stock all around paper dust on the cutter bed. I sat right out of the box when possible and it makes it easier on the press and frees up finishing scheduling.


John Weaver

 

[Al Ferrari]

" the fact is you have layed the stock all around paper dust on the cutter bed."

Why does this not apply equally well to stock purchased in cut sizes? Or do you buy into the mill claims that they use vacuum cleaners to prevent this problem, in today's price sensitive market?

Al

 

[RGPW17100]

I believe digital quality is cleaner. If particles from the paper damage the drum or other intricate parts of copiers and other digital printers there can be real serious problems. I have noticed this when running stocks like Hammermill color copy with solids. Our press operator feels most of his hickeys come from the way stock is currently being cut. I know we have always fought hickeys especially when we buy the cheapest paper we can there is probably just as much problems from picking as there is from dirty edges.

 

[ondemandbindery]

A good response about the dust on a cutter bed. You could kind of look at it as double trouble I suppose. I would like to think a paper mill is no more dust free than a Print shop but that I could not tell you. As for the vacuum systems they have on sheetfeds, I only have minimal experience with those devices. And it wasn't good from what I remember. Some stock has to be precut. Are you sure they are properly trimming the stock? As simple a process as it sounds I have seen it done wrong more than right. You really have to pay attention since there is no print to keep your cutting sequence correct. The best fighting chance to give it is wipe the material with glycerine but that is additional work. Could there be reasons other than this for the Hickeys? It can turn it into a blame game for sure. I base my opinion on working in so many shops and having seen this debate. Now reading the original post it sounds like it was getting cut right. I call it T4S. The easiest way to explain the procedure is every side of a stack must have a final cut edge from only the inside of the blade. There is no other way to do it properly. Leave a cut edge from the front side of a blade and you will generate a ton of paper dust.

John

 

[RGPW17100]

. I call it T4S. The easiest way to explain the procedure is every side of a stack must have a final cut edge from only the inside of the blade. There is no other way to do it properly. Leave a cut edge from the front side of a blade and you will generate a ton of paper dust.

John

This is how we used to do it. Trying to convince the new management is the problem. Our old program to cut 25x38 for our SM52 was
18.95
24.90
18.75
24.80
12.25
12.25
This would cut half the sheet Their program is
18.98
12.48
12.48
This would cut half the sheet. Bindery supervisor says it is too much cutting and not worth the extra effort. Our old program not only reduced dirty edges but also makes the sheet square in case we are doing flops or work and tumbles.

 

[ondemandbindery]

The short version of the cutting will create additional paper trash. There is no getting around it. Now, the supervisor makes a valid point. It is very time consuming to properly pre cut stock for the press room. But his theory of it not making a difference will not hold much real estate in my head either. This is where a company has to make decisions based on their throughput as to what the protocol needs to be. My theory is if the stock is not cut properly, a train wreck will not be far behind. It is very disruptive to the Finishing Department cutting prestock as the cutter is typically feeding the beast all day. Most stock cutting that I have been involved with that worked from a production standpoint is done on a 2nd or 3rd shift but your Plant may not have that option. But to give an opinion on the original question, absolutely this method is creating additional trash for Printing Department.


John Weaver

 

[Rikkie]

I might be pedantic about this, but I like my paper to be cut on all 4 sides. That way, I know it is a) square b) cut clean on all edges. Given a sharp blade, I don't have difficulty with hickeys. In theory, they should be pretty much eliminated by properly fanning / knocking up of the paper.

I believe the extra guillotine time is well spent. My 2c

 

[graficworx]

I will quite often trim even cut stock before it goes to press, as more often than not cut stock will have ragged edges, or not be entirely the right size. Also, it helps it feed better after cutting and re-jogging, and makes work and turn come out better.

 

[otherthoughts]

Perhaps a compromise solution can be found?

Perhaps a compromise solution can be found?

In my experience, cover-weight stocks produced more debris on the bevel edge side of the blade than did book weight stocks. C1S cover-weight stocks were worse than C2S.

Perhaps you could take photos of the bevel-edge side of the cut and the behind the knife side of the cut for the range of stocks that you typically use? This would help to demonstrate and clarify the differences between the bevel side of the cut and the behind the knife side of the cut in general. It would also help to document which stocks would benefit the most from being trimmed on all four sides behind the knife.

Another consideration would be "How prone is the job to show hickeys". Jobs with large solids and significant total coverage vs. jobs with minimal coverage.

A further test might be to trim half the stock for a hickey prone job on all four sides behind the knife and then trim the second half of the stock without regard to the bevel edge. Be sure to run the trimmed four sides stock firstly, being that it should be the cleanest and therefore should not pollute the ink train with paper debris. Running the dirtier stock first could pollute the ink train with debris and therefore hide any benefits of trimming on all four sides. Ideally, this test should be run after a press wash-up. Running the test on a press that hasn't been washed up for one or more shifts, may reveal more about the current state of the ink train than it does about the differences in trimming methodology.

After running the test job, ask the pressman if they noticed a difference in the amount of hickeys they encountered or any other differences they may have noted.

The quantity of stock to be cut should figure into the equation somewhere. A few extra cuts for a lift or two is negligible. A few extra cuts for a skid or two is not.

One final delineation might be price/quality expectations for a job. In other words, you might trim 4 sides for high quality jobs, but not for quick-and-dirty jobs.

In the end, you should be able to document when 4 side trimming is justified and cost effective, and when it is not.

Best Regards

OT

 

[RGPW17100]

It is hard to explain but the dirty side is being cut off. The edge put into the cutter never gets trimmed. the stock with the dirty bevel side is spun 180 degrees and a couple thousands of the dirty side is being trimmed.