Troubleshooting a damaged core concerns mostly web offset printing presses.  It is considered a serious defect only if it prevents the paper roll being loaded onto the press.  Some damage is so bad that the entire roll is unusable.  A damaged core can have several causes: 1. The shaft was improperly inserted into the roll, causing it to slip.  If there is not enough grip from the shaft, it will slip and grind up the shaft (see below).  This is generally the fault of the offset printer. Core is ground up inside because of shaft. 2. The poor design of the shaft causes damaged to the edges (see below). Some roll stands clasp onto the ends of the roll and do damage to the core.  If a roll is reloaded several times, it can get damaged to the point that there is nothing left to grip.  Once again, this is the fault of the equipment and not the paper mill. Damage caused by poorly designed shaft. 3. Poor mechanical strength of the core . This is an issue at the paper mill.  At times the core c

What is it a protruding or slipped core? A protruding or slipped core is when the core of the wound paper sticks out beyond the width of the paper roll.  This defect concerns web offset printers or any other printing application that uses rolls. What causes a slipped core? If a core is sticking out the side, it is probably caused by a slack start when the paper is made at the paper mill.  Fore more detail on how paper is made,  go here . When a new reel is started, tension must be absolutely tight.  This can be a challenge when getting the reel started.  Below shows a picture of the result if the tension is not tight. Occasionally this will cause the core to slide.  It can occur at the paper mill or later when the roll is loaded onto the press. Other causes of a protruding core Sometimes this is not due to a slack start, but to the fact that the roll was made at the end of a reel at the paper mill.  The core was simply a little too long for the entire reel. In this case, the roll shoul

Crushed cores on paper rolls can happen at the mill, in transportation to the press room, or at the press itself. This paper defect concerns web press offset printers.  There are two main causes: 1. The roll was dropped. 2. The clamps were too tight at some point during transportation. 3. The inserted roll shaft at the press was done improperly.   How to fix crushed cores. There are several companies that specialize in repairing this problem such as this one .  Or the core can be fixed right in the press room. It really depends on the extent of the damage.   There are different tools to accomplish this yourself. The first one every web offset printer should have.  It's simply called a 'paper core restorer'. Here is what it looks like: Paper core restorer. Of course this type can only restore the ends of the roll.  Deeper core damage requires better equipment.  Notice the video below.  This is the approach take with better machinery. Below is a core repair done by a company

This paper defect mostly concerns web printers.  At the paper mill, splices have to be made from time to time.  When making these splices, the splice tape will sometimes go beyond the edges of the paper.   When the rolls are finally cut to size according to the orders from offset printers, the slitter should make a nice cut.  But if it doesn't cut properly, or tension causes the web of paper to shift slightly, this will protrude the edge of the roll. It could end up as a wrap in a printing unit or nip point. Splice tape should stop just before the edge. Such defects should be visible from the side of the roll before loading it on the press.  What you can do about protruding splices? When we see this paper defect on the side of our rolls, we usually dab a little bit of grease on the protruding splice.  When the edge of the splice passes through the web offset press nip points, it will be less likely to stick.  The splices must also pass through the nip points of the printing unit, s

Even when producing paper rolls for web offset printers, a paper mill must make splices to their rolls.  This is most often referred to as a "mill splice" since this designation specifies that it happens at the paper mill. Troubleshooting this issue requires understanding how it happens. How a stuck splice happens Since mill splices are only necessary on rare occasions, most rolls do not contain them. Paper mills are obligated to show the location of the splice in the roll so that the press operator can watch to see if it comes through. Mill splice is indicated on the side of the roll. What is a stuck Splice? Exposed splice tape from mill. The exposed part of splice tape will stick to the layer of paper that is tightly wound above it.  On a web offset press, the paper will break when released at high speed. On a sheet fed offset press, the sheets will feed double and jam. What to do? The best defense is awareness.  Watch for indications of these splices.  When we see these ma

Both offset printing and inkjet printing are completely different processes to accomplish the same purpose. Offset printing uses aluminum printing plates to transfer ink from a rubber surface (known as a blanket) to paper.  Inkjet, or digital printing, is much like a desktop printer.  Much like it's name suggests, it sprays like a jet onto paper for form pictures or text. There are differences to each process and each have their advantages.   What is Inkjet Printing? The most common type of inkjet printing is probably on your desktop - an inkjet printer.  It is the simplest form of digital printing.  By definition it is a computer that sends a digital image and puts it on paper by sending a stream of ink.  Desktop inkjet printer. Today, very sophisticated inkjet printers have been made to make posters, books and brochures.  Here is an example of a commercial inkjet printers that can print in a much wider format for posters. Inkjet printer for making posters. Inkjet printers have no

Offset printing plates are what transfers an image from the ink supply to the paper.  They are usually made from paper, rubber, plastic or metal depending on the printing process.  Printing plates have an image that is burned onto them.  This image will transfer the ink to the paper. Most offset printing plates are made from aluminum.  The reason is that the metal is long-lasting and has special properties that attract water.  An aluminum printing plate can be considered an offset printing plate when it completes three steps.  For a more detailed explanation as to how the actual aluminum plate is made, see this article. Blue coating on offset printing plate. Step 1. A blue coating shown above is applied to the aluminum sheet about  1μm thick.   Here are some of the coatings that are applied. Silver Halide (printing runs 0-3000 copies).  This is a photosensitive material, similar to that which used to be used in photographic film.   Diazo (printing runs 0-250,000 copies)  This is an org

The difference between doubling and slurring in offset printing is the the cause.  The result looks almost exactly the same.  Here is what both slurring and doubling generally look like. Slurring and doubling are an elongation of a printed dot.  The difference lies in the cause.  For example, slur happens in the direction of the paper travel while it goes through the press.  Doubling can happen in any direction. Here is a list of what can cause slur or doubling: blankets packed improperly loose blanket(s) bad cylinder bearings poorly timed grippers (sheetfed) worn gripper pads (sheetfed) poor infeed setup lateral movement (web) bad side guides (sheetfed) smashed blanket or cylinder surface drive gears misaligned registration adjustment distortions in paper blankets not torqued properly Correcting any one of those issues are another article all unto themselves. Let's cover a few of them: Doubling caused by distortions in paper In sheet fed printing, doubling can occur as a result of

There are several advantages and disadvantages of UV printing inks.  I would like to discuss some of them here from the perspective of an offset printing company.  But they could apply just as well to any printer.   First, let's make sure we are all on the same page and understand what UV printing is. What is UV printing? This is becoming very popular lately among newspaper printers.  The newspaper that used to stink now have a beautiful gloss look, odor free and nothing rubbing off on your hands.  This is all thanks to UV cured inks.   It is gaining popularity as there were many concerns about the environment and health of the press operators.  Because of advancements in the formula and process, these concerns have all but disappeared. How do UV inks work? UV inks work by utilizing ultraviolet radiation to dry printing ink.  UV light is a product of our sun, and in very small amounts is harmless.  However this spectrum is magnified to dry printing inks between the light wavelength

Yes. It is possible with offset printing. It is done by many unscrupulous people throughout the world. I worked in a sheet fed shop for a number of years with a man from Fiji.  He said that when he was young he worked in an offset sheetfed printing shop there. They printed commercial jobs during the day and printed Canadian $20 notes at night. This would have been in the 1970's.   Today, people try do copy money with a scanner and a printer.  They even try using offset printing presses.  But real money is still difficult to duplicate.  Why? Offset printing makes it look more real, but not enough. Offset printing is part of the process to print real money.  A Simultan sheetfed press is used by the US government to print money.  The difference is that this is only the first pass.  Money has to look and feel real, and offset printing isn't enough to give it that real look/feel.  Here are the actual steps to print money as done by the US government. Offset sheet fed printing press.

To maintain rubber rollers on your offset printing press, you need to have a good system for checking and storing them.  Here I will outline the maintenance system we have in place, the tools you need, and how we deal with problems that happen.   First of all, here are the reasons why maintenance is needed. Bad settings on the press.  I have covered this before in another article .  Settings must be done right.  Too hard and the roller will wear out prematurely.  There will be more heat leading to other problems.   Improper storage. For example, not being covered or suspended. When the rollers come from the supplier, they should have a certain hardness and be of the proper diameter.  To maintain this they cannot be sitting on their side. They must be suspended on a rack in order to not get flat spots. They should also have a wrapping that prevents them from being exposed to light.  If not, it will cause them to become hard prematurely. Age. Rollers will lose their properties over ti

If you have worked with solvents in the printing industry, there are a few things you should know. I've been reading about people who have worked in the industry for many years and develop cancer later in life.  They wonder about the ink and solvents they have used and wonder if they are the reason for their illnesses.   I have written before about diseases from the offset printing industry before , but I want to write about what you should know about these solvents and what a couple of recent studies have found. Some of the most carcinogenic chemicals used in the printing industry are Benzene and Toluene.  I will talk about some of their effects here. But first I want to share with you the results of a more recent study about the contents of some of the chemicals used in the press room.  Independent testing was done and it was found. It turned out that not all of these chemicals were declared on the safety data sheets.   This is the report in it's entirety. The study was done