The Offset Pressman

An infrared temperature sensor is a tool I would like to add as another essential tool to your press room.  They cost only about $100 which is very little in comparison to the payback they offer.  I would like to share why we find them so useful and then I'll show where you you can get them.  So let's talk first about why this little device is so useful. How We Use Infrared Sensors In Our Press Room 1. Measuring unit temperature.  As I discussed in a previous entry, the knowing the temperature of your ink as it flows through the ink train is critical to prevent piling as well as controlling your ink and water balance window.  You can measure the plate and blanket as well to ensure optimum temperatures for ink flow and proper control. 2. Finding poor settings while running.  A good way to tell if you have any roller settings out of tolerance is to measure each roller while running.  A hot roller will indicate a setting is too hard.  Additionally, a plate that is hot, e

Take a look at the graph above.  It reveals countless hours of testing to find the optimum press temperature for minimizing blanket piling.  Yes, the temperature of your press can and does effect how quickly your blanket piling happens.  I've written before about how to prevent blanket piling , but this time I want to hone in on one particular variable that contributes to blanket piling - temperature. What The Graph Reveals About Piling The above graph reveals two things.  First, an ink and water balance window that shrinks as temperature increases.  You can get the formula for calculating this here .  The yellow line represents the lowest point you can set your water without scumming at a particular temperature as measured at the oscillating or vibrator roller in the printing unit.  The pink line represents the highest water setting possible at the limit of emulsifying your ink. As you can see, the gap between the two naturally narrows as temperature (as indicated at the b

Our printing group has done some detailed testing regarding dot gain recently.  It is driven by the ever present goal of reaching the ISO standard.  But that's another story I'll get into one day.  Today though, I would like to explain the chart above.  It is a guideline we go by to chase dot gain issues on our presses and it helps us to troubleshoot possible causes of dot gain, or sometimes called tonal value increase (TVI).  It shows the factors that affect dot gain in relation to how much of an influence they have. Dot Gain Causes in the Offset Printing Process 1.  Ink.  The ink itself plays the single most influential role in controlling dot gain.  Properties such as viscosity and tack are a good start.  These properties we look at first when chasing dot gain problems. 2. Temperature.  The best place to start with this is the temperature of your oscillating rollers.  Use a infrared sensor to measure the temperature across each side of the transfer rollers,

I've written before about controlling web tension on an offset press , but wanted to share exactly what the tension settings are on our press.  Above is a screen shot of the tension settings on our 4 unit heat-set press.  To give you a better idea of what our web press looks like, I include here a picture below to imagine what it looks like.   We've recently done much tweaking to get just the right tension between all nip points on our press and I just wanted to share our conclusions.  Likely it will resemble what you may already have.  If not, it may give you an idea where to start.  First of all, I realize the screenshot above does not have enough detail to reveal the tension settings, so I will spell them out here: Our tension settings: After infeed nip: 70 daN Between last print unit and chill nip: 73 daN  Right after chill nip: 67 daN (+1%) After first nip on superstructure: (+1%) The ribbons split the web and after each ribbon nip: 20-24 daN (+.8%) RTF ab