Heidelberg SBBK Cylinder question

[Stinger]

Hi all. We have a heidelberg cylinder die cutter and I was hoping someone on here knows a little about this machine. When we score jobs with score rule and matrix, seems to work just fine but will cut the paper near the gripper. When we die cut jobs like pocket folders, does not work as well. It cuts better at the lead edge and not so good as you get closer to the tail edge. Also, does not even start to diecut fully until about 7 sheets into production. I don't know if it is a packing issue or possibly a mechanical issue. Also, is it normal that the die-cutting jacket is indented severely where the pocket folder die hits it. We have a heidelberg windmill platen that I die cut b/c's etc and it doesn't show any wear on the jacket. Thanks in advance, Richard.

 

[Magnus59]

It sounds like either your packing is thicker at the grip edge or your jacket is sitting up at that edge, you should get an even cut both around and across the cylinder, if the scoring rule is cutting through the paper at the grip, it is too heavy at that point, same with the indent on the jacket. Check that the jacket + packing is pressed hard down on the cylinder, also ensure the packing hasn't bunched up at the grip. If neither of these are the problem, you may need to adjust your packing so there is less where you are getting too much impression.

 

[pdan]

You're noticing the characteristics of how a cylinder press operates vs a platen. A platen has to develop enough force for the total area being impressed all at one moment whereas the cylinder accomplishes the task throughout its revolution cycle. A score on a platen requires force equal to the length of the score. On the cylinder a score horizontal on the cylinder requires the same but a score in the direction of travel only contacts the sheet 2 points wide (or the width of the rule). Additionally, unfortunately, and dependent on the condition of the machine as the cylinder meets the rule it lifts slightly so that a consistent score around the cylinder becomes a challenge. (Try a double score, two scores within an inch of each other. Notice that the second score is not a deep as the cylinder was lifted by the first.)

You should consider a new cutting jacket given that yours is showing severe wear. We like to use a "good" jacket for perfs, especially microperf. Use the older jacket for die cutting. Try to layout the jobs and run rules across the cylinder, not around it. We try to lay out the job with several inches a cutoff at the front of a score around the cylinder when necessary.

Pocket folders - I've committed some sins to a jacket. You may even have worn into the bed of the press at the V. Check it closely. Having worn deeply into the jacket you're likely adding packing to get a cut and have severally dulled the cutting rule. Bad combination. Have the die re-ruled or cannobolize old dies yourself and replace as you can. Consider spinning the die and job 180°.

 

[ColorMonkey]

So a couple things comes to mind (keep in mind I ran several cylinder presses but it was a couple decades ago so hopefully I recall correctly).

One is inserting the packing and the method you use to roll up the jacket onto the cylinder. What I mean is, the way I did it was I would hang the jacket on the pins and then push firmly on the edge of the jacket as I tighten the clamp. I would then rotate the cylinder until the bar just came into sight with room to rotate the skirt on it by hand. I would get my packing which was 3 shts I believe .017 not 100% sure but I would echelon or fan a tiny bit the packing and slide it in the jacket to gripper edge. The echelon is important if using multiple sheets of packing.

Then I would wrap my skirt under and over bar and then this is the part that is really important that is one hand on bar and one hand starting at gripper edge of jacket pushing the jacket against the cylinder as you wrap the skirt and slowly working your hand up the jacket. Reason for this is it is important you don't get any sag in your packing as you tighten the jacket against the cylinder.

Either you are way over packed or under packed which is forcing someone to build up the backside of the die. That jacket 100% needs to be replaced. That will create all sorts of problems.

Also a trick with the lead edge a lot of operators will do is on the matrix at the gripper edge of the jacket is, the rule the runs against the cylinder all the way to the edge is to cut a tiny "V" into the matrix starting at the edge and about 1/4" in length. Then take your razor blade and shave it down a little bit.

I have to get back to work but if I think of anything else I will add to.

Apologize for the TLDR if this is all stuff you know.

Also if running .918 cut, score rule generally will be .895 against the cylinder and .900 with the cylinder. Generally. .900 score rule going against the cylinder can cause issues if run to the the lead edge of the chase.

 

[Stinger]

Thank's everyone for your reply. First of all, I just would like to say that I am not the operator of the cylinder, I am a journeyman pressman by trade transformed into shop foreman. We have had about 4 different operators run this cylinder and what I noticed is that they all had their opinions of how to run it. (packing wise, where to put the packing, how to put the packing and building up die's etc.) Our current operator is a folder operator by trade and know's nothing about bearers, packing etc. Without even taking off the jacket, I measured the height of the jacket above the bearers to be .060" above bearer height which I know is way overpacked just as colormonkey noted. I also wondered about the condition of the dies as well with the amount of pressure these guys are using to get them to cut through and have suggested we get a new die for our most common p/f and start with one to see if it is any better. We are getting a new jacket this week so I am going to be working with our operator to get the packing on the cylinder correct and then build up under the plate on the type bed.

Pdan, we have a steel plate under the die's on the type bed so I will check that very closely to see if it is damaged, esspecially where the v's are like you suggested.

So our cylinder undercut is 0.47" and the jacket is 0.315. so adding 0.017 brings us to around bearer height. Just making sure this is where it should be and then you pack under the plate until you are cutting? There's not a lot of information out there about this, therefore that is why I am asking so we don't wreck the new jacket instantly.

I've added a couple of pictures of old jackets that will surely make you cringe. What I have noticed even in the printing side is if something doesn't work, some people just keep adding more and more pressure until they can get the job off (fake it until you make it) where I would rather get down to the root cause and make it right.

Thank you very much again guy's, I really appreciate it. Richard

Sorry, say's the picture files are to large to upload.

 

[ColorMonkey]

Hi Stinger,

So this is what I personally would do. Use however much packing to get the jacket to bearer height.

The bottom of the bed (regardless if there is packing under the plate or not) to the bearer height should be type high, .918

Now with brand new cut rule build your chase so you have three pieces of rule evenly spaced across your chase, running against the cylinder, or, vertically. Don't put the outside rule all the way to the edge of the chase come in about 4" or so. Remember when you tighten the rule down you use a piece of furniture or something to make sure the rule is resting on the bed.

Then run a sheet of paper. So this should prevent you from initially carving into you jacket. the adj from here to get it to cut is a matter of thousandths.

The problem your going to run into is some of the existing cut/perf rule and dies are most likely smashed meaning the cut edge. This is where ppl panic and start building the back side of dies. This you need to watch for.

This is what I was taught. The cut rule never is supposed to touch the jacket or platen. Essentially the knife via pressure finishes the cut at the end by blowing the paper apart. So really the cut edge never touches the counter or jacket, platen, etc. However, if tolerances aren't scrutinize and maintained this is not possible to sustain.

Alright I really do hope this helps Stinger and if anything I said was incorrect I'm sure someone will post.

Good luck buddy

 

[Stinger]

Thank's guys.

So we got the new jacket and we have it packed to bearer height. We then put in a very good (nearly new die that an outsourced bindery shop used maybe twice so very good condition). Then we only added 2-3 thou packing at a time. Eventually, you could start to see the cut lines all the way from top to bottom nice and even. So then we kept adding packing until it would cut through. This is where we start to struggle. The top cuts nice all the way down to where the pockets start and then it doesn't cut the last 3 inches and the bottom of the pocket.

We then turned the die 180 degrees and now it cuts the pockets and down the sides to the last 3 inches.

We turned the die back around and slightly tapered the packing to the back (bottom where folds go) and got it to cut through the whole pocket folder. So then we put on the matrix and the score rule (yes, the score rule) cut right through the paper at the top of the folder, scored nice on the pockets and the pockets don't cut anymore.

This according to our operator is exactly where we were before the new jacket. What he has been doing is putting 4 sheets of 5 thou paper on the back of the die over all the cut rules and then puts tape on top of the score rule to soften it up so that it doesn't cut through the stock.

I know that we shouldn't have to be doing that and not sure what we need to do to correct this.

Do you think it is possible that the cylinder is losing impression as it goes towards the back of the bed?

Any thoughts, thank's again. Richard

P.S. Colormonkey, we has already started to do this before your post. Also, we don't have any cut rules that we could to that test with.

 

[pdan]

I use old film under any cutting rule that is not getting through; it has less chance to fail before the end of a run. The best way would be to spot make ready under the jacket but rolling the jacket off and on is a chore and more guesswork than one platen. I suppose to do it correctly you would jog a semi cut sheet into the grippers and MR where needed.

I run the V and the pockets to the front. My predecessors ran it spun 180. Our dies are not set to cut below the V; we do that cut at the cutter (for round corner folders. For square corner we removed the cut rule and trim top and bottom at the cutter). We run centered on a 17.5" sheet. Our tabs for the pockets are above the pocket. I've seen them with the tab extending from the pocket.

Do what it takes but check the jacket. You'll know every hundred sheets if you're ruining a good jacket.

 

[ColorMonkey]

So Stinger if you don't mind me asking when was the last time this press has had a once over by someone. I suspect their is something else going on however it sounds like you have found a better way or at least be a bit more cautious as far as packing and what to shoot for.

So has the bed been shaved or refinished/refurbished? Or more, what state was this when you got it and was there mention at that time of this being an issue?

So you say there was a plate on the bed correct? That can be removed? If so, this may help you in this particular situation. I'll explain after you respond.

 

[Stinger]

Hi Colormonkey.

First off, I started this post being told that this cylinder was a SBBK model but after getting further into this project, I now know that this is a SBG model. So, if it was ever a model that printed, that part of the cylinder has all been removed and it is strictly used for diecutting and creasing.

We got the press about 10 years ago from an auction so don't really know the history but I can tell you that one of the gears on the cylinder has been hit so hard (smashed apparently before we got it) that it broke off about 1/4 to 1/3 of the tooth. Not to sure what can fall in there to break off part of a tooth.

We have not had anyone in to look at it (I'm trying to get our production manager to get someone to look at it but so far to no avail) as I do believe there is definately a mechanical issue going on here.

The bed is shaved and we have 2 steel plates, one for .918 rule and a thinner one for .937 rule.

So this is why I also believe there is a mechanical issue. When we get the die to where it would start to cut the pockets (at the tail edge of the sheet) it would start to cut the pocket on the non operator side first. Then we put in 4 score rules spaced out equally (no matrix) running vertical to the cylinder, the score rule on the non operator side cut through the paper and barely touched the paper on the operator side. Then we put 4 score rules spaced out horizontal the the cylinder and the first score was very prominent and decreased each rule after and was almost non existant on the last rule. Also, we set up with impression on heavy paper and when it barely would cut the pockets on the pocket folder, we went to light paper and then it would cut stronger. From what I was reading on another thread, when the lever in on heavy, there is more pressure on the impression cylinder for die cutting, creasing and heavy forms so moving it to light form should be less pressure but in our case, it gives more pressure.

One more thing, there is an electric switch on the operator side under the counter and to the left a bit that has two positions, 1 and 2 and our operator was told to only use number 2. Do you have any idea what this switch is for?

Thank's again

 

[ColorMonkey]

Okay is there any way you can post a picture of the box under the counter as well as the lever you say is for heavy and light pressure?

I think if it is the knob I am thinking of it is actually the position of the brush which you can change the pressure of. Changing the pressure of the cylinder is not something I am familiar with.

So one last question. Is the side that is hitting light(er) the same side with the damaged tooth on the cylinder?

I am work right now so I am unable to offer my suggestion but to let you know ahead of time this will help to balance out your pressure but you really need to have a technician in there. Are you in the states by any chance?

I will try to post over the weekend the method/technique to balance pressure but please try to post those two pics for me in the meantime.

Thanks Stinger