Finding Distortion factor for coating blankets

[Anthony Hyatali]

Hello all!
I work for a vendor in canada (not here to sell product i promise!just here to ask for some advice and guidance.)
We recently purchased a CAD table to convert printing blankets, however I have been approached by a couple of customers and asked if we could cut spot coating blankets for them. I have run several test samples just to figure out what we could do in terms of detail and it turned out very well. Unfortunately I have not cut Spot AQ/UV blankets to go on press as of yet.
My question is...
How do I figure out the distortion factor? Also, does using a Mylar backed blanket eliminate the distortion factor?
Thanks in advance for your help, and please do not mistake this post as a way to sell products/services...

 

[rich apollo]

Mylar backed blankets won't necessarily eliminate the distortion. The value you're looking for is what percentage the coating blanket increases the circumference of the coating cylinder. Maybe something as simple as:

a = length of the blanket
b = blanket thickness
C = circumference of cylinder with blanket
D = diameter of the cylinder
D2 = diameter of the cylinder and blanket

a ÷ pi = D

D + (2b) = D2

D2 x pi = C

a ÷ C = distortion factor

 

[Anthony Hyatali]

Hello Rich,
Thanks for the info, I will give that a shot and let you know how it worked!

Thanks again!

 

[Mike Herndon]

Mylar backed blankets won't necessarily eliminate the distortion. The value you're looking for is what percentage the coating blanket increases the circumference of the coating cylinder. Maybe something as simple as:

a = length of the blanket
b = blanket thickness
C = circumference of cylinder with blanket
D = diameter of the cylinder
D2 = diameter of the cylinder and blanket

a ÷ pi = D

D + (2b) = D2

D2 x pi = C

a ÷ C = distortion factor

This is great info, we were looking for this as well!

Looking at this formula theoretically you could change the values a little bit and use it to find distortion percentage when perfing on press. We do some fairly intricate perfs and usually it takes a few tries to get the perf rules to line up.

Mike

 

[peter61]

Hello Rich,
Thanks for the info, I will give that a shot and let you know how it worked!

Thanks again!

It's very hard to do a spot coat on a coater blanket while it's off the cylinder(actually that part is easy,it's when you remount the blanket,that's where the trouble begins).You can do ok with glue flaps,large areas but if you want to get really fancy(knockouts ect) you have to cut the blanket or plate while it's mounted on the cylinder and even then you have to be very careful.

 

[Anthony Hyatali]

Hi,
I tried it out using this distortion factor and it worked out rather well! I can't really see a problem with it if i'm using coating plates or mylar backed coating blankets.
Rich, thanks for the information, it was extremely helpful!

 

[couriergraphics]

Very well done Rich!

 

[rich apollo]

Thanks for the feedback, Anthony. I was kinda' guessing.

 

[CD102]

It's very hard to do a spot coat on a coater blanket while it's off the cylinder(actually that part is easy,it's when you remount the blanket,that's where the trouble begins).You can do ok with glue flaps,large areas but if you want to get really fancy(knockouts ect) you have to cut the blanket or plate while it's mounted on the cylinder and even then you have to be very careful.

My old shop used cyrel polymer coating blankets and they were great as long as some muscle-bound operator didn't over-tighten them. My new shop cuts 4-ply blankets on a special machine and they never fit right. And the misregistration from bearer to bearer is worse than from gripper to tail.

 

[Anthony Hyatali]

is it possible that they have not found the proper distortion factor? Or perhaps there is just way too much stretch in the 4 ply blanket?
There are macinhes on the market that will cut coating plates, i figure it's the same idea right? the only difference is that I will be cutting on a falt bed table instead of a cylinder with tractor feed (gerber sector)

 

[mazengh]

Mylar backed blankets won't necessarily eliminate the distortion. The value you're looking for is what percentage the coating blanket increases the circumference of the coating cylinder. Maybe something as simple as:

a = length of the blanket
b = blanket thickness
C = circumference of cylinder with blanket
D = diameter of the cylinder
D2 = diameter of the cylinder and blanket

a ÷ pi = D

D + (2b) = D2

D2 x pi = C

a ÷ C = distortion factor

how would this formula work for a cyrel flexo plate? would the length of the blanket include the bars which means the plate length includes the area that goes under the clamps? also for the b variable, do you add the mylar thickness, that goes under the flexo plate, to the plate thickness? and finally the diameter of the cylinder can't be considered as a true diameter since the plate doesn't extend from one end all the way to the other like in flexo, as in offset you have the clamps... can someone please explain how this is done?

 

[Anthony Hyatali]

Hi,

Check out this article posted by Folex, it helped me understand the process. The information regarding distortion is on page 19.
hope this helps!

http://www.folex.com/data/docs/download/1792/en/Folacoat-Folacomp-EN-.pdf

Anthony