3 Real Causes of Digital Printing „Curling“ — Paper Edge Curling / Skewed Web Feeding / Excessive Drying: The Cause Print Shops Most Often Misdiagnose by Adjusting Only One Parameter

In early October 2026, a printer specializing in premium cards and invitation cards received an order for 5,000 foil-stamped cards. On the day the digital printing was completed, the paper surface looked smooth and clean; the next day, the client came to inspect the samples and said, “The paper looks wrinkled, like a shirt that hasn’t been ironed.” The technician retrieved the printing conditions for that batch and found that the drying temperature, line speed, and paper-feed direction had not been changed. However, the “wrinkling” described by the client was not present at the time of printing.

The difficulty in diagnosing this type of problem lies in the fact that wrinkling often does not appear until one or two days after the machine has stopped, or even after the printed material has left the printing plant, while printers habitually focus only on “the moment immediately after printing.” In addition, it may be caused by three entirely different factors, so focusing solely on the one you know best and adjusting accordingly can lead to a cycle of “adjusted today, but it reappears tomorrow.”

Cause 1: Paper curling due to environmental factors—the issue most easily mistaken for a equipment problem

Paper, especially neutral paper and matte-coated paper that have not been moisture-proofed, expands and contracts according to the relative humidity of its environment. If one side of the paper is exposed to an open area of the workshop while the other rests against a wall, uneven moisture absorption on the two sides can cause slight curling or waviness. The high-temperature drying process in digital printing can “set” this curl, making it more apparent when the paper comes off the press.

Determination method: Turn off the dryer and gently run your fingers over the paper surface to feel the direction of the undulation. If the direction of the wave matches the orientation of the paper on the delivery table (usually transverse), it is most likely environmental curl in the paper itself rather than web misalignment.

Handling: This issue cannot really be solved by the equipment. What needs to be done is to let the paper “temper and acclimatize” in the workshop—paper taken from the warehouse should be laid flat in the workshop environment for a period of time before being fed into the machine, avoiding the need to proceed directly to drying after coming out of a temperature-controlled environment. At the same time, check whether there are any heat or cold sources around the paper-loading table (such as air-conditioning outlets, heaters, or densely populated areas).

Cause 2: Web Skew — A Fixed Wave Pattern Caused by Uneven Heating on Both Sides

If the web path is skewed, or the paper is slightly twisted on the feed rollers, the distance and travel time from each side of the paper to the drying zone will differ, causing one side to receive more heat than the other. This type of wrinkling has a characteristic feature: the wave pattern is fixed and directional, usually parallel to the web direction or appearing as regular diagonal lines.

How to identify it: Hold the finished product up to the light. If the wrinkles form regular straight lines parallel to the web direction, web skew is the likely cause. If they are random, irregular, fine undulations, the issue is more likely caused by Cause 1 or 3.

Corrective action: Adjust the sheet-feed registration, remove paper debris and adhesive residue from the feed rollers, and check whether the paper was curled by a preceding process. This issue is often unrelated to die cutting or forming and may instead result from a misalignment already present when the paper entered the press for printing.

Cause 3: Excessive Drying Energy — The Cause Most Prone to Misdiagnosis

If the energy supplied during drying in digital printing (hot air or infrared) is excessive, the temperature is too high, or the web speed is too slow (i.e., the heating time per unit area is too long), moisture migration within the paper will become uneven. The paper may appear flat when it comes off the machine, but the internal stress has not been relieved; after a few days, the paper will “spring back” and wrinkle.

The point of distinction between this item and the preceding two is that after adjusting the drying parameters, the severity of wrinkling should visibly change. If lowering the temperature by 5-10℃ or increasing the line speed by 10-20% reduces the wrinkling, cause 3 is the primary cause. If the parameters are adjusted but there is no change, the problem lies in the paper or web handling, not in drying.

Adjustment: While ensuring that the ink layer is dry and properly adheres, set the drying to a level that is “dry enough but not excessively dry.” Digital ink layers are thin and often do not require high temperatures. However, the thicker the paper and the greater the ink coverage area—for example, in solid-color backgrounds—the more drying energy is required. This balance must be determined through testing, not guesswork.

Three Causes: How to Troubleshoot Systematically

Because the three causes require entirely different adjustment approaches (some involve equipment, while others involve paper management), blindly adjusting only one parameter at a time is highly inefficient. A more effective troubleshooting sequence is:

After completing these four steps, the primary cause can usually be identified. If the printing plant standardizes this troubleshooting sequence as a small SOP, there will be no need to start the investigation from scratch each time wrinkling occurs.

How the printing plant and the customer view this matter

If wrinkling is caused by the printing plant—for example, clearly improper drying parameters—the printing plant must accept responsibility. If it is caused by the paper environment or customer storage, the cause must also be clearly explained. The key is to maintain records: the paper grade, time of entry into the workshop, drying parameters, line speed, and front-and-back orientation for each batch of printed products. Only by combining these records can the conditions at the time be reconstructed.

Additionally, premium thin-paper products such as cards and invitation cards have an extremely low tolerance for wrinkling, and customers often reject even a single defective piece. When accepting orders of this type, printers can place the finished samples in the workshop and under simulated customer conditions for 24-48 hours during the proofing stage before reviewing them, thereby identifying wrinkling risks in advance rather than delivering the order immediately after printing.

Further Reading