사이즈 프레스 오렌지 필 현상: 닙 출구에서의 필름 분리
Orange peel after film sizing appears as a fine, irregular texture on the paper surface, sometimes accompanied by uneven gloss. It can develop when the wet sizing film separates unevenly as the sheet leaves the press nip.
The film stretches between the paper and applicator roll before splitting. If the separation disturbs the coating or leaves liquid patches that fail to level, the texture remains visible.
Start with the last acceptable production run. Changes in paper absorption, sizing-liquid condition, or operating speed may explain the defect. If these conditions remain comparable and orange peel appears after roll replacement or surface deterioration, the rubber cover deserves closer inspection. Its hardness alone cannot identify the cause.
What Does Orange Peel Look Like After Sizing?
Orange peel usually appears as small, irregular patches across the treated surface. The texture may be difficult to see under direct light but becomes clearer when the sheet is viewed at an angle.
More pronounced patterns can develop into branching marks known as turkey track coating. These are a visible form of orange peel associated with uneven film separation.
Compare the base paper with the treated sheet. If the pattern first appears after the size press, the nip-exit film split is a useful starting point.
The position of the defect also matters. A pattern covering the full sheet calls for a different comparison from one concentrated near an edge. If the texture becomes visible only after drying, retain an earlier sample wherever safe sampling arrangements allow.
A close-up photograph taken under consistent lighting helps establish whether the appearance changed between production runs.
What Changed Before Orange Peel Appeared?
When a previously stable line starts producing orange peel, compare the first defective run with the last acceptable one.
Look for changes in the paper, sizing liquid, or applicator roll. The most useful evidence comes from a change that coincides with the defect while other conditions remain comparable.
Where Should You Look First?
| Possible source | What changed? | What to compare |
|---|---|---|
| Base paper | Paper grade, batch, incoming moisture, or absorption behavior. | If the defect follows a paper change, compare the new and previous sheets under the same liquid and roll conditions. |
| Sizing liquid | Liquid batch, solids content, temperature, or flow behavior. | If the pattern follows the liquid change, compare its preparation and condition with the previous acceptable run. |
| 도포기 롤 | Replacement, grinding, wear, or surface contamination. | If paper and liquid conditions remain comparable, inspect the old and current covers and check for changes in nip contact. |
Line speed and the amount of liquid applied also affect film separation. Include them in the comparison, particularly if production settings changed at the same time as the paper grade or roll.
For example, orange peel may appear immediately after a paper-grade change while the sizing liquid and applicator roll remain unchanged. The new sheet's absorption behavior is the more useful starting point in that situation.
A defect appearing immediately after roll replacement, with the paper, liquid, and operating settings unchanged, gives stronger reason to examine the replacement cover.
Why Does the Film Split Unevenly at the Nip Exit?
In a film metering sizer, the applicator roll carries a pre-metered liquid film into contact with the paper. Where a metering rod is fitted, it controls the film before the nip.
During contact, the paper absorbs water. In pigmented film coating, part of the coating next to the sheet becomes immobilized as water leaves it. A thin layer above it remains mobile.
When the paper separates from the applicator roll, this mobile layer stretches and splits. A small amount of wet coating remains with the roll, while the rest transfers to the sheet.
The thickness and behavior of the mobile layer determine how cleanly the film separates.
When the Coating Loses Water Too Quickly
Rapid dewatering can leave too little mobile coating at the nip exit.
The film may then separate through coating that has already become partly immobilized. Instead of splitting cleanly through a thin liquid layer, separation can disturb the coating surface. Coating deposits may also develop on the applicator roll.
This condition deserves attention when a new paper grade absorbs water more rapidly or when the coating’s water-retention behavior has changed.
When Too Much Mobile Coating Remains
A thick mobile layer can stretch into liquid filaments as the paper leaves the roll.
These filaments break and retract. If they leave uneven patches on the sheet that cannot level sufficiently, orange peel becomes visible.
At higher running speeds, the remaining mobile layer and its ability to separate cleanly become particularly important. Changes in the applied film amount or liquid behavior can make the pattern more pronounced.
Starch sizing behaves somewhat differently from pigmented coating. Starch size is generally more fluid and can transfer almost completely to the sheet. Its film can still form irregular filaments at the exit, leaving orange-peel-like marks when they break and retract.
The actual sizing liquid therefore matters. A defect that begins after changing from one formulation or application condition to another needs to be understood in that specific context.
When Should You Check the Applicator Roll Cover?
The applicator roll cover becomes a meaningful investigation point when orange peel changes after roll replacement, grinding, or visible surface deterioration.
The strongest supporting evidence is a defect that follows the roll under comparable paper, sizing-liquid, and operating conditions.
Cover Thickness and Hardness
Cover thickness and hardness affect how the rubber deforms under nip loading. This deformation influences the contact area and pressure distribution experienced by the wet film.
A replacement cover with different thickness or hardness may change the contact even when the nominal nip setting remains unchanged.
For example, if the original roll produced an acceptable surface and a replacement develops orange peel under the same production conditions, compare the two cover specifications.
Check whether the cover thickness, hardness, or nip loading changed. The original specification gives a practical reference for identifying the difference.
Changing to a softer cover without that comparison may create another contact mismatch.
Surface Finish and Wear
The wet film also interacts directly with the rubber surface.
Glazing, contamination, uneven wear, or a different grinding finish can change how the liquid contacts and releases from the cover.
If orange peel is concentrated near one side of the sheet, inspect the corresponding area of the roll face. Visible deposits or uneven surface condition in that location provide a useful clue.
The defect’s timing adds further evidence. A pattern that gradually worsens as deposits accumulate suggests a different surface condition from one that appears immediately after installing a newly ground roll.
Compare photographs or maintenance records where available. Confirm whether nip settings changed during the same work before attributing the defect to the cover.
When the evidence points toward rubber-cover contact, Wolorin’s 압력 롤러 page provides a relevant reference for custom rubber-covered nip applications.
What to Confirm Before Replacing the Roll
A previously successful applicator roll provides a useful starting point for replacement.
If its operating conditions remain unchanged and the original drawings, dimensions, and cover specification are available, a straightforward replacement can proceed using those documents.
When orange peel repeatedly appears after replacement, compare the old and new cover specifications alongside the observed surface condition. Differences in thickness, hardness, or finish may help narrow the manufacturing requirements.
Wolorin can manufacture custom rubber-covered rollers based on confirmed drawings and specifications. Where the defect points toward the cover but the information is incomplete, existing roll details and the observed problem are enough to begin discussing the replacement requirements.
Share a defect sample and any known paper or sizing-liquid changes. If the evidence points to the roll, send Wolorin its drawings or dimensions, old-roll photos, position, contact liquid, and current cover problem for manufacturing confirmation or quotation.