scratches on plate.

During printing I get litlle scraches on my plate.
I am using Saphira quikplate from Heidelberg.
Ink is new/fresh
most scraches are on the first unit, black.
I think it has to do with the paper.
I am using offset pro 80 GSM
Is there somebody with the same problem.

Thanks.
André

 

First thing to check is to make sure you are getting proper fluid to the plate cleaning device. If it is not moist enough, that will certainly cause some scratching. The tube that goes across the cleaning device that has holes about every 1.5" can sometimes get clogged up and you need to clean it free of foreign particles.

Another cause could be a lost sheet that is caught up in the unit, sometimes around the plate cleaning or blanket wash devices or even around the laser unit.

Also check the black roller on the inside of the red plate cylinder guard to ensure it is clean and free of any dried ink.

Last I can think of is make sure your paper is free of paper dust, use a sharp blade to trim, as small paper particles that stick to the blanket could possibly cause this too.

Cheers,

Tracy

 

There are many things that can cause plate scratches, the most common being dirt. First, lets explain the mechanical items that could cause a scratch.

On the classic machines the vacuum unit in the first unit which is responsible for removing excess silicone is a culprit. This unit is difficult to remove at best, as a result it gets dinged up due to the fact it is made of aluminum. This unit will scratch the plate during the loading process if there are burrs or dried ink on it. When the plate loads it must release first, when this happens the plate material actually comes off of the plate cylinder 2 or 3 mm very briefly. At this moment it touches the vacuum unit and scratches the tail end 4 inches of the plate. This is an easy one to identify for 3 reasons:

1. The scratches are about 4 inches long on the tail.
2. They are always on the first unit.
3. They are always in the same place.

This problem does not happen on the Plus or the Pro machine as the vacuum units were redesigned, for easier removal and to move closer to the plate mechanically during the cleaning process.

The next mechanical issue is the plate wash cloths themselves. The early material Heidelberg originally used had short grain, it ran from side to side. Because of this it would stretch during the clean up process causing wrinkles in it. This wrinkles would come up high enough to drag on the plate while the press was running. This would scratch the plate during the press run. Also this plate wash cloth was notorious for having fibers come loose and drag on the plate causing the same problem. Once again this problem is easy to identify. Any time you have a plate scratch that is not apparent during make-ready and appears during the run it is due to something dragging on the plate. The location of the scratch will be random. We have not used this style of cloth since 1997, although it is still available through aftermarket companies and is used by quite a few QMDI shops. They may be a bit less expensive than the ones we sell, but that savings is offset by the plate re-burns they are responsible for. The way to tell the difference between the aftermarket ones and ours is that ours have dimples in them to reduce loose fibers and the grain runs long to stop stretching.

If the air pressure is too high for the plate cleaning pistons (these actually press the plate wash cloth against the plate). You will get scratches consistently on all units in random places. The adjustment for this next to the console by the delivery on the operator side (You will have to move the console). It should be set between 3 and 4.5 bars.

If the plate scratches look like Morse code (Dots and dashes) , you more than like have a problem with the black rubber covered shaft not spinning freely on the plate gap guard.

The last mechanical issue is the foam rubber strip on the plate wash mechanism itself. This strip gets damaged due to the pressman trying to save a buck. The plate wash material will run out, instead of changing it right away the pressman will reset the count knowing that there are about 4 more cleanings left. He forgets he did this and runs the unit free of cloth. Now instead of the cloth hitting the, plate the foam hits it and gets ripped off of the device. (I have seen the tail end of the cloth wrap around a plate cylinder by a pressman doing this and pull the whole mechanism out of the brackets. 25K repair tag on this mistake, all in the name of saving 2 dollars and some change.) When the press operator orders the new foam to install he needs to glue it to the bar. We recommend using Loctite 406 for this, as it is a type of superglue which dries sort of rubbery. Typically the operator uses superglue instead, some of it gets on the outside of the foam and hardens. This hardened glue now scratches the plate during wash up. These scratches are identified as being in the same place, going from gripper to tail and noticeable at make-ready. Usually they are very dark.

The main reason for plate scratches is the this… Dirt. All it takes is a piece of dried ink, powder, or dust to scratch a plate. The first unit is where 90% of the scratches happen. This is because there is typically powder and paper dust everywhere as the feeder is rarely ever vacuumed or cleaned on any regular basis. Take a look at the guard on this unit, when you open it you will see powder on it. If you accidentally drop the guard, all of that powder and dust comes free and settles on the plate wash cloth which is exposed. (The other cleaning units are in the press under the cylinders so they do not collect the amount of dust the first unit does.) This causes random light scratches at startup. If you keep the guard and feeder area clean it will reduce scratches dramatically.

Another thing most people notice, is that after the press sits for the weekend and the first job is burned on Monday, plate scratches are apparent on the first unit. This is because dust settled on the cloth over the weekend and the lines which supply the wash-up solution are dry. I recommend to prime the lines in special function 12 on each unit a couple of times and to advance the plate clothes by manually starting the plate cleaning mode and hitting the stop button as soon as it starts. You will hear the clothes advance three times after you hit the stop button. By doing this you will have a new cloth ready to go and solution in the lines.

I have been working on this machine since 1996. I have done countless shows with new and used machines, not too mention how many I have worked on in the field. Plate scratches are rarely an issue, if I had to place a number on them I would say 1 in every 20 plates will get scratched, as we cannot control every piece of dirt there is in a print shop. I have used the plate washers in every situation. The only time I suggest to turn them off is to hand wipe a large solid, then I start the wash up program to finish up (this prevents silicone from getting in the rollers causing hickeys.). I never use them to clean hickeys from the plate during a run, more than likely whatever is on the plate causing the hickey is something that will scratch the plate if you use the hickey cleaning mode (I affectionately call this the " Plate scratcher mode".). Just wipe it off by hand, it only takes a minute which is much less than having to re-burn a plate.

Hopefully this long winded explanation will help you get a handle on your scratches.

 

Thanks Paul - the best article to date I've seen on plate scratches.

Our DI Plus came from Prestek with the air pressure set double recommended, we fought with the issue for a year or more before getting the answer from a forum from the DI expert from England!

I think a Infrared drier also helps as one can use a smaller amount of spray powder. For those without a drier I would suggest buying a $20.00 500 watt halogen light and shining it in to view the amount of spray powder. It helps one see the haze indicating the spray is working without actually seeing the spray powder which is an indicator your using too much.

Another item is running a blanket wash possibly every couple thousand on the 2nd side to remove powder before it builds enough to scratch.

Regards priming SF12, we do it more like 15 times. (a side note - anyone thinking the bottom cylinder cleaner doesn't do the job - prime 5 or 6 times with SF13 - this also needs extra solution to do the job.)

Ken

 

Ken,

You are correct about the IR drier helping, obviously anything you can do to keep powder down to a minimum is in your best interest.

You have to watch out you do not prime too much. A couple of things used to happen when the washup cloths were overprimed. One, was the plate wash up devices would over flow. In the past I had shops who had primed before every plate wash. When I pulled out the plate washer soap solution would drain out of them. The other problem is if you prime too much the soap soultion starts to get the entire roll of wash up material damp/ wet. What you will notice is that the plates seem to get harder and harder to clean up properly. This is because the whole wash up roll is wet and slides across the plate without removing any silicone. During the cleaning process the material is actually supposed to be dry in some portions of the process to help pull out the silicone in the finer screen areas. Trial and error will help you determine how much you should prime the wash up cloths. If you run everyday you should not have to prime at all. Just on Mondays when you come back from the weekend.

When Heidelberg was selling this machine all of our field technicians were stressing to the owners and operators how important it was to keep the machine as clean as you possibly could. Any down time you had should be spent cleaning excess powder, paper dust or dried ink out of it. If you did this it would pay off in the long run with less plate scratches and fewer hickies.

It is a pleasure posting anything that will help DI owners become successful with their machines. Hopefully, you will grow with it and get an XL105... ; )

 

Hi Tracy

I have had a similiar problem with the Saphira quikplate from Heidelberg.
When i called the Heidelberg Tech i was told that a couple of customers have complained about these plates scratching easier than the Presstek Plates. I believe it has something to do with the silicone layer being too thin on the Saphira plate. I heard that Heidelberg in SA have had a conference call with the manufacturers about the complaints of scratching and are looking into it. I have gone back to the Presstek plates and have not had a scratched plate for a while "Touch Wood".

Hope this info helps a bit

Quinton

 

The Heidelberg and Presstek plate materials are one and the same coming from the same production line then having a Heidelberg or Presstek label put on. The difference you are seeing is probably the manufacture date and a possable difference in how a roll was produced on a certain date that's why all the rolls have batch and roll numbers on the removable label.

 

Hi Paul.. well again... here in the forum... Is there any way to fix the plates when they are scratched ...? there must be some kind of chemical or some form of repair ... is too very expensive the plate if it seems that every time you scratch, i having to burn a new ... If you know of some method or some chemical help me with some name ... would be good to know .. And part of me thank you very much for everything ... One day this way for me, i going to travel to brazil for do greeting ... Sincerely, Augusto

 

Augusto,

The only item I know that will fix the scratches is liquid silicone. Unfortunately even this is not a cure all. On light scratches it will work, but not on the heavy ones.

The best thing to do is try and isolate whatever is causing the scratches to begin with.

Someone in this forum may know where you can aquire silicone to fix the plates.

And yes, someday I would like to come to Brazil to meet with you. I do need a vacation soon...

 

Paul
I sell the stop out solution for the waterless plates. These work great on scratches. They are a much better version of the one that heidelberg came out with years ago.

Paul
I have to disagree with a couple of things you mentioned about scratching. The vacuums are just as easy to remove on a classic as plus or a pro. Maybe except the first unit. I will give you that one. As far as them getting burs and being dirty. Take care of them and keep them clean and you will avoid that problem. Yes the plus and pro vacuums are closer to the plate but I have never notice any difference of one working better that the other. I ran both presses side by side for many years. The Heidelberg brand plate cleaner in my humble opinion is no better than presstek or the brand that I sell. 9 out 10 times when you get scratching it because of one or more of the things that you mentioned.

Paul keep up the good work you are the man!

By the way did I mention that I have the largest inventory of preowned Heidelberg QMDI presses and parts
in North America or anywhere else for that matter.

Anthony Tatulli
QMDIPRESS@aol.com
www.QMDIPRESS.COM
Parts, DI Plates and service
201-264-1553

 

Anthony,

One thing you have to keep in mind between the Classic vacuum set up when compared to the Plus and Pro is that it is always two millimeters from the plate. The Plus and Pro are only that close during the cleaning process. This prevents the plate from hitting them during the plate loading process. Therefore if there are any burrs on them from an operator being careless they are less likely to cause plate scratches than on the Classic machine.

The article I posted was originally written in 2003. Back then there was still alot of the old plate wash material floating around being sold by aftermarket companies. I find it highly unlikely any of that is left. As I said it was easy to identify, there were no dimples in it.

Way to keep the DI flame going! I still think the machine has a market for the right people.

Take care.