1.) What problems can rollers cause?
A worn out roller, a roller with damaged bearings, rollers set with too much pressure or, a roller that has not been properly cleaned, can cause:
- color inconsistency
- poor solids, or mottling
- dirty print
- excessive dot gain
Besides the obvious costs of poor print quality, including wasted paper and ink, bad or poorly maintained rollers can cause excessive press downtime, increased running costs, and shorter roller life.
Many times the problems caused by bad rollers are blamed on other factors. Or worse, pressmen accept them as inevitable and “learn to live with it” by making frequent adjustments, using extra ink or fountain solution, or throwing out a lot of spoiled paper. The good news is that using the proper rollers, and using them correctly, can eliminate many of these problems. When a press is fitted with high-quality rollers, and the rollers are properly set, cleaned and maintained, they can give months, even years of trouble-free printing and superior print results. You will notice, too, that you use less ink and fountain solution, less energy to run the presses, and waste less paper. And, the rollers may last two or three times longer.
What is roller glaze?
If the rollers look shiny and have a glassy feel to them, they are glazed. When rollers are glazed, the “fingers” in the rubber surface do not transfer ink effectively, which means you will need to run more ink and more water on the press to achieve the required ink densities. Higher levels of ink and water will result in dot gain, mottled solids, hickies, ink drying problems, reduced quality, and most likely, increases in your spoilage or unplanned waste.
Glaze is caused by the buildup of particles in the nap of the roller surface. See the Anatomy of a Roller for a detailed explanation and some great microscopic close-ups of roller nap.
One step in fighting glaze is proper cleaning. See Roller Cleaning for advice on the best technique.
But the first step is to use TCR glaze-free rollers. These rollers run much longer than conventional rollers without developing glaze, and they’re easier to clean.
What’s the best way to clean a roller?
Use a three-step system.
1) Use a water miscible wash to remove the top layer of solvent-soluble and water-soluble particles from the nap of the roller.
2) Use a non-grit roller paste to remove the insoluble particles.
3) Finally, wash a second time with a water-miscible wash to remove the remaining soluble particles.
For a full tutorial on roller cleaning.
Can I leave FEBO Clean on overnight?
Yes. In fact, we recommend it. You can leave FEBO Clean on the rollers as long as a few days—for example, over the weekend.
How much can I trust durometer readings?
Durometers are commonly misunderstood and misused. If they are misused, they give unreliable readings that can’t be trusted.
To work, a one kilogram weight must be secured in the top of the durometer guage. This gives an even downward pressure and consistent readings.
Durometer readings must be taken on a flat surface, which means the roller has to be out of the press and on a table. Getting an accurate reading requires following a certain technique. The technique, and details about durometers, can be seen.
How much pressure should I use when I set my rollers?
As little as possible! Also, never tighten the rollers beyond the press manufacturer’s specifications. See our guide to setting rollers for more information.
Setting rollers with too much pressure is a common mistake, and an expensive one. Pressmen sometimes think that the pressure is what moves the ink and water. It’s not. It’s the shearing forces generated by the different speeds of rollers with different diameters. More pressure does not help, and it can actually impair the quality of the printing and lead to unnecessary downtime and operating costs.
Always back rollers off before inserting new ones because new rollers may be slightly fatter than the old rollers. Set the new ones by coming forward until making contact with any surface, never by backing off.
Can I reuse bearings?
No. Never reuse bearings! Why risk damaging your expensive press?
Turning a bearing on your finger is not a reliable way to check if it is true, because the bearing has no load on it. An imperfection too small to feel could be enough to cause serious problems.
The bearing is ruined just by pulling it off the journal because the seals are forced against the rows, causing them to be permanently indented and obstruct the free turning of the bearing balls. This can cause the journal to grab, leading to indexing, stripe-width changes around the roller, and inconsistent ink transfer and color variations.
What’s the best way to install bearings?
Bearings must be mounted using an arbor press. This is the only way to get perfect alignment and not damage the bearings or the journal in the process.
Never, never use a hammer!
Never, never tap the journal end on the floor!
No hammer can deliver the balanced force that is necessary to mount bearings correctly. Tapping on the floor is a crude technique that almost guarantees the pressure will be uneven and the bearings damaged.
If you aren’t equipped to install your own bearings, then order your rollers “press ready,” with the bearings factory installed. Almost all TCR rollers come press ready, including re-covered rollers.
How do I know if I’m using the right chemicals?
Using the wrong chemicals on your rollers can contribute to the deterioration of the rubber. Others are perfectly safe because they were formulated and tested to be kind to the rubber. How do you know which is the best?
If you are using chemicals recommended by the manufacturer, including any TCR-brand chemicals, you will be safe. For any other chemical, ask you He has a list of TCR-approved chemicals, including mixing instructions for some of them.
If you are contemplating using a wash-up solvent, ink, or fountain solution that is not in the TCR database, your TCR representative can arrange to have it tested in TCR laboratories. Don’t test new chemicals on your rollers; let us do it for you.
What’s the best way to store backups rollers?
New rollers held in your inventory can be damaged if not stored correctly.
To avoid creating flat spots in the rubber, do not lean them against the wall or store them flat on a shelf or the floor. Instead, suspend them from the journals, keeping the rubber surface free of any pressure or load.
Heat and light can cause the rubber compounds to break down prematurely. Keep the paper cover on the rollers and store them in a cool place away from heat sources and sunlight. The UV light in sunlight, or emanating from fluorescent lights, can also damage the rubber.
And, be careful not to store rubber rollers near electric motors unless the area is well ventilated. This is because the ozone generated by motors can also break down the rubber compound.
Why do rollers shrink?
Sooner or later all rollers change size, but poor shop practices and poor rollers speed up the process, requiring frequent stopping of the presses to make adjustments. In fact, shrinkage is the leading cause of roller resetting. Running with shrunk rollers leads to ink/water balance problems, color variation, and excessive downtime.
Shrinkage can be caused by excess heat, usually from the settings being too high from insufficient lubrication, or bad bearings. The heat causes a chemical reaction in the rubber that breaks the long molecule chains (specifically the plasticizers) which give the rubber compound its flexibility and ability to hold its shape. This breakdown occurs naturally as a result of the constant flexing of the rubber during normal operation, which is why even the best rollers won’t last forever. But excessive heat speeds up the deterioration process.
It can also be caused by the plasticizers leaching out of the rubber over time. TCR scientists have found a way to “lock in” the plasticizer so rollers won’t shrink.
The molecular integrity of the rubber can also be broken down prematurely by chemical reactions. Harsh chemicals or inks shorten the life of a roller. So can using the wrong solvents—rubber rejuvenators, liquid glaze removers, or the wrong washes. So will leaving the solvent on the rollers too long after wash up, or worn wash-up blades that leave a residue of solvent on the rollers. And beware of fountain solutions with too low pH, alcohol sub formulation, or injurious additives like NPA.
TCR labs have tested all of the common chemicals for suitability with Toso Corp rollers. See the discussion of Chemicals above.
Sometimes using the wrong roller for the wrong function will cause shrinkage. The rubber compounds on rollers are specialized for specific conditions such as the speed at which they will be running (higher speeds generate more heat) and the types of chemicals they will be exposed to. Mixing them up will almost always cause problems.
What is the Toso Corp Rollers exchange program?
The roller exchange program is a way to get rollers shipped to you quickly.
The program works like this:
1) You call us and we ship your new rollers immediately—by Federal Express if you need them the next day.
2) We invoice you for the full cost of the rollers. You are, in effect, paying a deposit on the core that TCR is “lending” you, similar to the bottle deposit required in some states on beverage bottles.
3) You ship us your old rollers, the ones being replaced. It’s a good idea to use the same box the new (re-covered) roller came in.
4) When we receive your old rollers, we credit you with the cost of the cores, in effect returning your deposit.
Our Roller Exchange Program, unequaled in the industry, means that you do not have to wait with your presses idle when you need a roller. And you don’t have to keep a full inventory of rollers on hand.
Almost all of the rollers in our exchange program are shipped press ready. This means they are fitted in our factory with new bearings and spacers so you are assured properly aligned rollers. You can take them right out of the box and put them on your press.
How do I evaluate the real cost of a roller?
The price you pay for a new or re-covered roller is only one factor in the “true cost” of the roller. The life of the roller measured in the total number of impressions is another factor—a roller that lasts longer is obviously cheaper in the long run. And, the performance and collateral operating costs are another very important factor.
Think of all of the costs of owning a car. The cost of operating it (gas, oil, and repairs) is as important as the sticker price. If you buy a car that wastes gas or, is always in the shop for expensive repairs, the total cost of owning that car is higher to keep running reliably and efficiently. And, a car that will go 200,000 miles will be cheaper over the long run than one that has to be junked at 100,000 miles.
You evaluate rollers the same way. To compare costs you need to consider how long the roller will last—how many impressions you will get from it during its life. Then you should consider if the roller will shrink and glaze easily, forcing expensive down time to reset and clean. And if the roller will not hold its shape, or changes properties by running too hot, you need to consider the cost of wasted ink, paper, and time tweaking the press to force it to print to your customers’ standards.
You can compare the total cost of TCR rollers to the rollers you are using now by going to our Value Comparison page.