Start With the Shape Before You Change the Setting
A single average width can hide the most useful part of the reading. A stripe measuring 3 mm on the left, 4 mm in the center, and 5 mm on the right is very different from a straight 4 mm stripe across the roller, even though the average is almost the same.
| What the Stripe Looks Like | First Place to Look |
|---|---|
| Too wide across most of the roller | Working temperature, the correct target for that roller pair, current setting, effective diameter, and cover condition. |
| Too narrow across most of the roller | Setting, cover wear, finished diameter, hardening, and roller seating. |
| Wide at one end and narrow at the other | Left-right setting, journal seating, mounting, bearings, taper, and uneven wear. |
| Wider in the center than at the edges | Intended crown, roller profile, center/edge diameter, previous grinding, and the mating roller. |
| Broken or missing in local areas | Ink build-up, glazing, contamination, dents, local wear, hardened areas, or surface damage. |
If the Whole Stripe Is Too Wide
When the left, center, and right are all wider than the specified range, the change is affecting most of the nip rather than one isolated area. Check the measurement condition first. A cold press and a fully warmed press can give different stripe widths even when the adjustment has not been touched.
Once temperature has been ruled out, look at the setting and the roller itself. A larger effective diameter puts the two surfaces farther into contact at the same mechanical position. A cover that has softened or swollen also deforms more easily and can produce a wider stripe.
A wide stripe by itself does not tell you that ink transfer is better. If the machine manual calls for a narrower contact at that position, increasing the stripe simply moves the roller farther away from its intended setting.
If the Whole Stripe Is Too Narrow
A stripe that gradually becomes narrower over months of service is worth comparing with roller diameter and cover condition. Normal wear removes rubber from the surface. Aging, heat, ink, and wash chemistry can also change the way the cover deforms under contact.
The timing helps narrow the check. If a roller that used to run correctly becomes narrower little by little, wear or cover aging moves higher on the list. If the stripe becomes narrow immediately after grinding or replacement, measure the finished roller before adding more adjustment.
The same narrow stripe can come from different combinations of diameter, hardness, and setting. Measure the variables that can be measured instead of trying to judge hardness or roller condition from stripe width alone.
If One Side Is Wider Than the Other
A wedge-shaped stripe is a strong left-to-right contact signal. Make the normal adjustment allowed by the press and watch how both ends respond.
If both sides return to the specified range and remain stable, the setting was part of the problem. If the wedge quickly returns, one end already needs much more adjustment than the other, or the pattern appeared after bearing or roller work, check the mechanical condition before adjusting farther.
Confirm that both journals are seated correctly. Look for bearing play or mounting differences, and measure both ends of the roller when taper or uneven wear is suspected. Do not rely on a single diameter taken at the center when the stripe already shows a clear cross-width difference.
Similar cross-face contact issues also matter on Rodillos de presión, where stable pressure distribution depends on the roller profile, mounting, cover condition, and actual nip.
If the Center Is Wider Than the Edges
A center-heavy stripe calls for a profile check. Find out whether the roller is supposed to be cylindrical or whether a crown is built into the design.
Crown is intentional on some printing rollers. Heidelberg SM/CD 102 documentation, for example, identifies its water pan roller as a crowned rubber roller. A center-wide contact on a roller like this has to be compared with the specified geometry before anyone decides that the surface should be ground flatter.
If an old roller worked normally for a long time and the center stripe has slowly become heavier, compare the center diameter with both edges. Look at the wear pattern, swelling, previous grinding history, and the mating roller.
If the pattern appeared immediately after grinding, check the finished profile against the drawing. Grinding until the stripe simply looks equal across the width can remove a crown that was supposed to remain on the roller.
If the Stripe Breaks in the Same Area
Start with the surface before treating a broken stripe as a geometry problem. Clean the roller and the mating surface, then repeat the test under the same condition.
Dried ink, polished glaze, hardened deposits, a small dent, or damaged rubber can interrupt the visible stripe. If cleaning removes the gap and it stays gone, keep monitoring the surface rather than sending the roller straight to grinding.
If the same section keeps returning at the same axial position, inspect that area more closely. Check local diameter, surface hardness if practical, glazing, indentation, wear, and visible damage.
On an ink-transfer position, a polished or damaged band may also change wetting, pickup, and release before there is a large measurable loss in diameter. Related contact requirements are covered on Transfer Rollers.
Compare the Stripe at the Right Temperature
The target should come from the manual for the exact press and roller position. There is no single stripe width that can be used as a general setting for every offset press.
A Heidelberg SM/CD 102 manual shows why. Its table uses different values and tolerances for different contacts, including 4 ± 0.5 mm, 5 ± 1 mm, 4 ± 1 mm, and position-specific one-sided tolerances. The values belong to those roller relationships on that machine; they are useful as an example of how position-specific the setting can be, not as a general offset standard.
The same manual states that its listed stripe settings refer to inking and dampening rollers at working temperature. For a contact specified at 4 ± 0.5 mm, it gives 3.5 mm as the cold-setting example because the contact area grows as the rollers warm up.
This makes temperature part of the measurement record. A 4 mm stripe taken just after startup and a 4 mm stripe measured after a long production run were not obtained under the same condition. When checking an adjustment or a replacement roller, compare readings taken at similar temperatures whenever possible.