Roller coverings in the graphic industry should not be a daily topic of conversation because the fulfillment of the customer requirements is the responsibility of the Supplier. Compromises in print quality, increased waste and machine down times are unacceptable in todays competitive world and can not be afforded by printers.

Thus the innovative concepts and continuous developments of roller coverings - compounds for the various printing fields such as and Newspaper Web Offset Illustration Web Offset for both the Inking Units and Dampening Units that have been developed throughout the years through active partnerships with worldwide leading machine manufacturers.

Roller coverings for the graphic industry should not be a printers daily concern, as the fulfillment of all product requirements is the responsibility of the roller manufacturer.

In today's competitive field, no cost conscious printer can afford to make compromises in print quality, allow excessive paper waste or avoidable machine downtimes.

The innovative concepts and developments of our product line have continuously evolved through many decades of active partnerships with the worlds leading printing machine manufacturers.

Al Dobowi research team has developed new compounds designed especially for the extreme demands of newspaper web presses. These compounds resist the shrinking caused by soy-based inks, which means they can run longer at the same settings. The frequent resetting of rollers in newspaper pressrooms is a thing of the past.

As more and more newspapers venture into color printing, they require more precision from their presses than they have in the past. Al Dobowi rollers deliver the precision needed for color printing because they are engineered to the optimum specifications of the press manufacturers. CONCENTRICITY What does this mean? According to the dictionary, concentric means having the same center. A very simple definition.

What this should mean to a printer is also very simple: If the rollers you are using are not concentric, they are defective.

For a roller to be concentric, all parts of that roller must be made and kept true to the center hole. The original center hole of the journal is machined into the core when it is manufactured. The rubber covering is applied and is built to that same center hole, ensuring the concentricity of the journal to the core to the rubber.

The importance of concentricity in press performance If you have a roller recovered just once, there is a 20% chance that it is no longer concentric. The odds multiply each time you have that roller recovered. During the recover process, your core is handled and turned on a lathe several times. Each time this is done, there is one more opportunity for the center hole to be wallowed out. Each time a bearing puller is used there is a chance of nicking or damaging the uniformity of the center hole.

Defective (non-concentric) rollers are the underlying cause of many of the problems that create so much frustration for a printer. If you have ever spent the afternoon chasing dry-ups you will know exactly what we are talking about. The lack of concentricity in a printing roller causes uneven pressure, which in turn causes vibration, which creates heat. These heated spots then dry up the fluids near them; thus disrupting your ink and water balance. Premature wear and end- pitting on a roller may also be attributed to the fact that the roller lacked concentricity. Also, you cannot hope to set this defective roller correctly if with each quarter turn of the roller, the stripe size varies anywhere from 1/16th of an inch to 1/8th of an inch.

When you consider that it only requires approximately .006 inch movement to create a correct stripe, if you set a roller on the low side and it was out of concentricity by as little as .003 inch you would be squeezing the high side .009 inch. If you set the roller on the high side and it is out enough, this will result in winking. Being out by .003 inch is common on used roller cores; we have seen them out as much as .008 inch.

Of course, if your running your press at only 5,000 impressions per hour, you really don't have anything to worry about. However, if you are a high-speed printer, concentricity is essential to you.