Showing posts with label Offset Problem. Show all posts
Showing posts with label Offset Problem. Show all posts

Friday, March 12, 2010

Multi Color Info

Important information for Multi-Unit presses from Pm2:
Does this sound familiar?

At one time your press was brand new and printed with the consistent performance and dot value of a new press . . . over the years you observed problems with inconsistent dot value and experienced increased adjustments to achieve consistent dot value.

How does this happen?

Over time a roller becomes hard, pitted and worn creating hickeys. Eventually the durometer is too high, causing the rubber to shrink unevenly. Consequently, glazing occurs, as a result of excessive leaching of extractable oils. The result is a roller that is about 40 durometer and that will require 10X the amount of mechanical pressure as a 26 durometer to achieve the same stripe setting. With additional MECHANICAL PRESSURE - you get additional UNWANTED heat. Additional ENERGY creates additional HEAT - the law of science.

Consider this . . .

The roller train can only be as good as its weakest link. Consistency in rollers from unit to unit will deliver consistent water and ink balance, as well as, consistent dot value from unit to unit. Unfortunately, the accepted practice when time to change rollers has been to use “exchange” or used cores. Used cores lack concentricity to the detriment of press performance. Regrettably, the objective of replacing rollers in the press has never been to maintain consistency throughout the ink train. Therefore, the range of effectiveness of the individual printing units can go from excellent to very poor. When starting out with all new rollers in each of the units - meaning new core, cover and bearings - you have TOTAL CONCENTRICITY.

Why is consistency in rollers from unit to unit important?

The function of a roller is to transfer and split ink, as well as to work in cooperation with the vibrating roller to fold-blend ink and water together as to maintain water and ink balance. Therefore, the performance of the actual press is in the ink train: Water and ink balance.

How do you obtain and maintain water and ink balance?

Consistent pressure and new rubber.
When you buy a new printing press then look at the press performance 3 to 4 years later, the only thing that has changed is the performance of the rollers and blankets. Rollers and blankets in poor condition lack the ability to provide optimum performance and this significantly affects print quality. The press still picks up and delivers sheets the same. The main difference is the - HEART OF THE PRESS - the printing unit: the INK TRAIN.
What can be done to establish consistency from inking unit to inking unit?
Pacesetter presents: A BETTER WAY TO DRESS YOUR PRESS A plan to RESTORE consistent press performance and maintain:

  • Consistent dot value
  • Less downtime
  • Reduced make-ready time

A program to install NEW ROLLERS in each of the inking units at one time:
  • Brand new steel core and rubber covering guaranteed for concentricity
  • A quality product supported by the manufacturers guarantee
  • Developed exclusively for the printing industry
  • The largest inventory of finished rollers in the U.S. to guarantee on time delivery

What could one year of TROUBLE-FREE printing do for you?
With Pacesetter’s “A Better Way to Dress Your Press” Program YOUR DOWNTIME WILL DIMINISH AND SAVE YOU THOUSANDS OF DOLLARS WITHIN THE NEXT FISCAL YEAR. In a year you could spend $25,000 - $30,000 in down time. When we put all new cores, cover and bearings in ever unit of the press we are taking it back to the day you bought it. With the traditional method of changing rollers - one here - a few there - the downtime adds up. After a couple hours of downtime: for each change.

By changing all inking units at once the press is RESTORED to:

  • Consistent print quality in ALL the inking units
  • Consistent mechanical pressure
  • Same heat or temperature
  • Consistent water and ink balance

If you want your press to print like the day you bought it “BRAND NEW” try dressing it with ALL NEW CONCENTRIC ROLLERS - new cores, new cover and bearings.

Doesn’t it make sense to install Brand New CONCENTRIC Rollers in each Inking Unit IT’S LIKE BUYING A NEW PRESS.

Saturday, May 10, 2008

Common problems encountered in Offset printing

Here is a list of problems that need to be paid attention to during the process of offset printing:

Uneven colour: Always make sure that the colour is the same on both sides of the sheet by rolling the sheet up so that you can look at opposite edges of the sheet side by side.

Ghosts: These are either
  • Images formed in areas where they should not appear, or
  • Formation of lighter areas where there should be even inking.
Hickies (aka Fish-Eyes): These arenon-inked circles created by lint on the plate or blanket. They are generally something that can be cleaned up when appearing on several sheets in a row. However, chances are you will never be able to eliminate every single hickie, especially if you have large solids in your printing piece and have to print thousands of sheets.

Picking: These are the non-inked areas that look like snow created in areas where the ink and some of the paper has been lifted off the sheet when the ink is too tacky.

Note : Picking can occur due to a paper related problem.

Muddy or Uneven Screens: These occur as a result of dot gain (see SCREENS.) In the worst case scenario caused by a muddy or uneven screen, you may need to remake a plate using a coarser screen. However, some dot gain can be alleviated by
  • Running the ink a little lighter and
  • By ensuring that the gradients on your piece, if any, look even. (Refer to GRADIENTS to see how to avoid banding in the design and prepress stages of the job.)
Offsetting: This is the appearance created on the back of a sheet by an image present on the sheet touching it. Offsetting happens as a result of
  • Too much ink
  • Insufficient driers in the ink or
  • Irimming of the job done when the ink is too wet