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problems cutting paper with heavy impression - pulling

Let me first say that our blades are sharpened once a week so it’s not a sharpness issue.

Anytime we print business cards with a large impression area, a flood of color, diagonal lines on the page, or anything else with lots of coverage, we have a hard time cutting straight. This applies to business cards that we run 2-up and it’s typically on the very last 2 inch cut!!

Our cut stacks are usually about 2-2.5 inches so I tried reducing the stacks to 1 inch….same problem.

I know I can avoid this all together and die cut them, but I’d really like to find a work around to keep these jobs on the paper cutter.

I’ve tried more clamp pressure, less clamp pressure, smaller stacks…you name it. Just can’t cut these jobs straight. The right side pulls off the backgauge (the direction the blade is going) to give me an off square cut.

ideas?

btw…the paper is crane lettra 220.

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One has to be a bit smarter than the machine. Not a lot, but some.
You speak of having the problem with stock printed with lots of coverage. That should not be the source of the problem, but it might.
First investigate any mechanical problem. Cut a stack of unprinted stock. My bet is that it will cut the same way, but I may be rong.
The typical guess solution from those who are not there to see your cutter would be a dull knife and/or insufficient clamp pressure. Also potentially too tall a stack. You have
investigated these variables and assure us that your blade is sharp. You can rule these out for the moment (but may have to go back to investigate further).
You have not said wherher it is a hand lever cutter or a power cutter. It should not make a difference except that with the hand lever cutter you can bring the blade down slowly and see if it is level at the cutting stick.
Maybe it does have something to do with the printed stock, but you must examine all the mechanical aspects first. It would be nice to be able to cut a printed stack on another cutter. That would tell you something.
Please keep us informed of your progress and solution.

I cut a ton of business cards. The problem is ONLY on the cards with the large impression area.

Other cards cut perfectly straight. it’s a power cutter with manual clamp.

I always have the same problem, no matter if the card is printed or not. It doesn’t happen when the blade is fresh, but starts when its done 30-40 cuts, and get gradually worse. Heard plenty of people with the same problem.

I’ve even set the blade height so it doesn’t touch the cutting stick incase that was wearing the blade out quickly, this didn’t help.

So just costs a fortune in blade sharpening.

Let us know if you find a solution to your problem, not that it’s the same.

How do you manage sharpening the blade every week? It seems this is quite extravagant, and should not be necessary. Mine is not a high production shop, but my cutter blade gets sharpend when it needs it, and that is generally only a couple times per year. Are you cutting very abrasive materials that cuses the blade to dull so quickly?

It does seem, if the image and variance in thickness that brings, is causing the stock to pull, you probably do not have enough clamp pressure to hold the stock in place.

John H.

we drop-off/pickup blades every week.

Too much clamp pressure gives you an uneven stack.

Lettra is a filled paper, think a Lunchbag (paper) with a nice surface and the bag filled with whatever to give it thickness. Dampen a piece of Lettra and see it bubble up.

Than you have a deep impression on Lettra, the material compresses but also throws up a slight edge. Stack up a 1 inch stack of your cards and precisely mike the thickness of the stack on all 4 sides. If there is a slight difference, your pressure bar will add uneven pressure, hence the knife will pull out (sharp) or undercut (dull).

Can you use a heavy duty card slitter instead?

Just from first impression, re: the frequency of your sharpening, Seems like the blade might possibly be knocking into the cutting stick too hard, causing it to dull more quickly?
What are your cutting sticks made out of? How often do you rotate them?

But that is another issue. Maybe you just do a LOT of cutting and have softer material blades? Back to your REAL question.

~~~~~

You might want to try and orient the cards so they are perfectly parallel to each other long way, and therefore you can make the two 2” cuts at the same time across an object which is wider than 2” (double plus waste, about 5”), then split the cards up and make the 3” cuts. Perhaps this would help a bit with the pressure problem you’re having, which could be caused by slightly warped stock that has been put upon with a lot of impression. Or so I suspect.
One wouldn’t THINK this would create a huge issue, but if you have a lot of impression in one area or all over with some knockout, the cards may be a bit thinner in that area/thicker in others, or even have a bit of a concave warp to them- causing an uneven amount of pressure from the paper clamp, no matter how tight it is.

Is this the case?

If you’re having difficulty with what I mean-

Consider a bunch of paper plates stacked up. These things have a concave/convex property to them, albeit much more exaggerated than what I’m describing above.
If there are 10 paper plates stacked up and you look at them from the side, you’ll notice there is a center point which- if they are flexible- you could push down on and make the plates ‘flatten’. While it would seem the plates might flatten to the same point, the more plates you add- the more distortion will be created.

Now, make the plates into a long rectangle, and clamp down on only half; you can see how this could potentially create a lot of skewing.

So if you are cutting with the longer side of the cards running into the cutter, to nick off a bit of the short edge, you may find this to contribute to their being slightly ‘off’.

I hope you find the solution to your confounding problem- I hate when this sort of thing muddles up what would otherwise be a simple/clean process, but when you find the fix, it makes it worthwhile to pass it on. Orienting cards so that I could make the narrow cuts all at once was mine, so I hope it helps!

Probably a stupid idea, BUT as I have been told many times by self styled experts, paper (except for rubbish photocopy paper maybe) and possibly card as well, has a grain and presumably,* is normally fed in the appropriate direction, at least on the first pass, and as logic would imply, effects the stock on a large print area, which would also imply a curling effect, turning the stock upside down and cutting from the back, to put the clamp at a far more favourable attitude to the acquired curl/bow. Just once as an experiment wouldnt be rocket science???????? **It would appear, that if you are putting that much ink onto/into that percentage of the paper as a whole you must inevitably by absorption and expansion and contraction, effect the curvature and/or the flatness of the paper (or card) is this not the very reason that,I see the expert printers fanning apart and putting an adverse curve into the stock when loading it into the feeder units, presumably so that the sucker feet hit the stock, in the correct approach/sequence as MAYBE the clamp on the cutter needs to.??????

Probably a stupid idea, BUT as I have been told many times by self styled experts, paper (except for rubbish photocopy paper maybe) and possibly card as well, has a grain and presumably,* is normally fed in the appropriate direction, at least on the first pass, and as logic would imply, effects the stock on a large print area, which would also imply a curling effect, turning the stock upside down and cutting from the back, to put the clamp at a far more favourable attitude to the acquired curl/bow. Just once as an experiment wouldnt be rocket science???????? **It would appear, that if you are putting that much ink onto/into that percentage of the paper as a whole you must inevitably by absorption and expansion and contraction, effect the curvature and/or the flatness of the paper (or card) is this not the very reason that,I see the expert printers fanning apart and putting an adverse curve into the stock when loading it into the feeder units, presumably so that the sucker feet hit the stock, in the correct approach/sequence as MAYBE the clamp on the cutter needs to.??????

I think that Mick raises some really good points too.

I think a couple of you have stated the problem. The heavy impression causes the stock to lay uneven on the cutter.

Front is higher than the back and the clamp can’t apply even pressure. Lets say my sheets are usually about 9x5 to start.

The cut from 9x5 to 9x3ish no problems. (Larger sheet helps maybe)
9x3ish to 8x3ish no problems
8x3ish to 7.25x3ish no problems.
Then when I clamp the 7.25x3ish you can see it’s under the clamp a little off. I can see pressure isn’t applied evenly.

That cut from 7.25x3ish to 7.25x2 is always the problem!

And my blades will last longer than a week, but with our volume, I notice a difference after a couple of weeks.

Maybe do this as havenpress stated? See attached image.

image: image.jpg

image.jpg

Yes. That is what I am saying. Try it and see if it helps. But remember- cut the left and right sides (As that diagram is oriented) FIRST.

H.P. Thanks, for your comment, its nice to see that somebody works out where I am coming from, although I would stress that in this case they were offered as ideas and not facts, but here is a little follow up that was factual, some time back I did one or two repairs to a small cutter, for a friend. I found and fitted a replacement motor, and elongated the slots in 2 blades (they were both ground down too far), and he was in the realms of cash flow I believe, how can a non commercial printer (cash only) be there??? However some little while later I gave him a vulcanised rubber plate, as used on flatbed and/or on rotary machines in wrap round form, which he spent some time on with a razor blade, tapering a length down about 3/4 of an inch wide to about maybe 3-3 1/2 inchs long which he then stuck under his clamp, at point of contact with his cards. I didnt understand what or why, I got my gallon of diesel and was long gone, But with hindsight could this have been a solution to the problem in question.

Have you ever tried putting an equal amount of waste stock under the far end of the clamp? That would balance clamp pressure.

Thats an idea. Never tried rotating some waste stock underneath to balance pressure.

I’m thinking die cutting them is the real solution. Even though I don’t like it.

Try turning the stack upside down

Parallel has a good point and micks flipping the sheet over has benefits in some cases especially when the stock has tight edged (gone saucer shaped) .
because your clamp is “pressed” at the centre you should have an equal wad of stock at either end when using the ends of the blade ,the nature of the clamp action and pressure points on small guillotines require you balance out the pressure or things just go wrong .
having said that you also want to make sure you note the swing of the blade in action and place dodgy jobs so that the drive of the cut pushes the cut sheet into the side plate of the guillotine not away from it .