Blankets on press

[pacificiam]

Hi,

We are very confuse while choosing blankets from different manufacutrer. Every1 saying their blanket is best. But we couldnt find best. Many blankets are getting puncture after 3 lac impression.

Many manufacutrer giving their technical specification but we cant figure out which is best for sheetfed and web presse.

Kindly help us to find good blankets with justification and their techincal specification.
We are using Valcun , Day , Cow , Nurania blankets for sheetfed and web presse.

What should be

• hardness of blankets?
• Tensile strengh?
• Elongation?
• Hardness?
• Compressiblity?
• Surface roughness?

I hope you fill help us to figure out good blan

 

[Cornishpastythighs]

I think only a printing blanket manufacturer could answer most of your questions, as a printer I would have no idea of the 'elongation' or tensile strength of a blanket. I do know that you must follow some simple basic steps when packing your press for quality print and maximum blanket life.
1. Use recommended torque when tightening the blanket. Ask your press manufacturer or blanket supplier what is the correct torque required. Remember to re torque a new blanket after running a few thousand sheets.
2. Get into the habit of using a packing guage to verify correct printing pressures.
3. Make sure your press chemistry is compatible with the rubber blanket surface.
4. Use name brand blankets and verify the thickness/caliper of the blanket to what is stamped on the back.
5. Always make sure your cylinders are clean before installing a new blanket.
6. Verify with your press manufacturer the correct packing requirements for your press to give you the required printing squeeze. Use good quality packing sheets and use the minimum amount of sheets to achieve the required height.
7. Do not use harsh chemicals like rubber rejuvinator to clean your blankets as these can damage the thin printing layer of the blanket.
8.Select either 3 or 4 ply compressible blankets as recommended by your printing press manufacturer.
9. Make sure your web tension or feeder is set up correctly to avoid wrinkles that will cause premature blanket failure.
10. Blankets that are treated correctly will usually die from old age
Good luck

 

[BeauchampT]

While as pressmen we are not experts on blankets, we are experts on the results. We know what works well, and what didn't. But where we often fail is in taking the time to document the problem so that our suppliers can actually help us out. They need to view us as partners, not just a user.

Here are a few things that may help you:
1) Do you actually know the exact blanket-to-plate squeeze you need for a good impression? Figure that out and you can start to evaluate the effective life of your blanket (by tracking the overbear height and printing pressures)
2) What is causing the blanket punctures/smashes? Ink piling? Wrap arounds? jams? Explain to the supplier your exact issues and they may be able to find a blanket in their supply that is more suited to your application
3) Give the supplier lots of details - sort of stock you run, level of quality you expect, etc.
4) Temperatures!!!! Most of the time we don't think about it, but when rubber compresses and rebounds it builds and then releases heat. A cooler running blanket tends to be rebounding better. This means two things: first, cool blankets mean less piling, second, a blanket the rebounds well smashes less.

Find the things you need to track, and track them. Use measurements that are real not "I think" or "I feel". That way, you will get the best product for your needs.

T

 

[REYES1377]

Look into products from Conti-Tech

 

[Tomtech]

I am a believer in the adage "If at first you don't succeed, try reading the directions" if you have them. If not get them and find out the manufactures recommendations. It is a good place to start. If the operator's manual is not available from the manufacturer, try on line
I found that good hard blankets provide a better image but compressible blankets resist dents from miss feeds or envelopes. Hard blankets are usually plies of rubber over canvas material. Compressible ones have a foam layer somewhere between to absorb dent pressures. .
Presses with bearers need to be packed to a specified height over bearers to provide proper plate to blanket and impression cyl. to blanket. Packing sheets come in various thicknesses; the fewest sheets needed to achieve the desired results, the better.

You may already know what I have outlined. It is offered to perhaps clear the air and direct your thinking. Good luck.

 

[JL.]

I think only a printing blanket manufacturer could answer most of your questions, as a printer I would have no idea of the 'elongation' or tensile strength of a blanket. I do know that you must follow some simple basic steps when packing your press for quality print and maximum blanket life.
1. Use recommended torque when tightening the blanket. Ask your press manufacturer or blanket supplier what is the correct torque required. Remember to re torque a new blanket after running a few thousand sheets.
2. Get into the habit of using a packing guage to verify correct printing pressures.
3. Make sure your press chemistry is compatible with the rubber blanket surface.
4. Use name brand blankets and verify the thickness/caliper of the blanket to what is stamped on the back.
5. Always make sure your cylinders are clean before installing a new blanket.
6. Verify with your press manufacturer the correct packing requirements for your press to give you the required printing squeeze. Use good quality packing sheets and use the minimum amount of sheets to achieve the required height.
7. Do not use harsh chemicals like rubber rejuvinator to clean your blankets as these can damage the thin printing layer of the blanket.
8.Select either 3 or 4 ply compressible blankets as recommended by your printing press manufacturer.
9. Make sure your web tension or feeder is set up correctly to avoid wrinkles that will cause premature blanket failure.
10. Blankets that are treated correctly will usually die from old age
Good luck

Hello, Cornishpastythinghs
Could I ask a technical question?
Why do we need to re torque after running a few thousand sheets?
I always have doubt about this working process and I have never known the answer.
Thank you.

 

[Cornishpastythighs]

Hello, Cornishpastythinghs
Could I ask a technical question?
Why do we need to re torque after running a few thousand sheets?
I always have doubt about this working process and I have never known the answer.
Thank you.

Blankets are made from stretchable materials, after being put under the high rolling printing pressures both from the plate and impression cylinders they will lose some of their tightness to the cylinder. Correct re-torqueing helps maintain the smooth transfer of ink from one surface to another. A loose blanket may result in a slurring of doubling problem, Overtightening will result in loss of blanket thickness and blanket failure. Very similar to the practice of re torgueing the wheel nuts after driving 100kms after a wheel or tire change good luck

 

[turbotom1052]

My recommendation would be to purchase blankets unmounted. Im not very fond of the blankets that come pre mounted on extruded aluminum blanket bars. Ive found that the extruded bars do not distribute the tension on blanket evenly around the cylinder at the point where the blanket just enters the gap. Also I recommend that when you mount a new blanket on the cylinder, you should begin with the blanket being longer at the tail reel to start. This allows you to periodically pull more blanket into the gripper reel as the lead edge begins to get weak.