Three Common Problems in Box Forming Processes: Delamination / Deformation / Misalignment — Real-World Data

In July, a customer who sells zongzi gift boxes contacted me. They produced 120,000 gift-box sets for this year’s Dragon Boat Festival, with 4,800 sets returned, a return rate of 4%. There were three reasons for the returns: ①delamination (the box body and lid came apart); ②deformation (the box body was warped or uneven); and ③misalignment (the lid and box body did not line up properly).

The customer told me: “The printing plant said this is normal industry loss, but last year we used a different printing plant, and the return rate was only 1.5%.” I accompanied the customer in reviewing the entire process for an order of 120,000 sets. In the end, we found that: the actual root causes of the three problems were completely different. This was not a matter of the printing plant’s “capability,” but rather how the printing plant handled specific process steps.

This is actually the most counterintuitive aspect of the box-forming process—many customers assume that forming simply means “putting something in a box,” whereas it involves four process variables: adhesive selection, storage conditions, die-cutting tolerances, and gluing speed.

Category 1 issue: Delamination—incorrect adhesive selection accounts for 65%

Delamination is the most common problem in package forming, occurring at a rate of 8-12%. Of these causes, incorrect adhesive selection accounts for 65% of delamination cases, the storage environment accounts for 25%, and gluing speed accounts for 10%.

What adhesive is used for the customer's 120,000 gift boxes? I took a sample for testing—it is EVA adhesive. EVA adhesive has a melting point of 80-85℃ and provides good adhesion at room temperature, but it will "soften" in environments above 50℃ (such as warehouses or truck compartments in summer). This is the greatest drawback of EVA adhesive.

This batch of gift boxes was shipped in early June, coinciding with the rainy season in Jiangsu, Zhejiang, and Shanghai. The warehouse temperature was 28℃ and the relative humidity was 75%, while the temperature inside some transport compartments reached 55℃ upon delivery to the South China market. EVA adhesive softened under high-temperature and high-humidity conditions. In addition, the gift boxes used film-laminated paper surfaces, to which EVA has 30% lower adhesion than to uncoated paper, causing the delamination rate to soar to 8%.

Solution: Replace EVA adhesive with PUR adhesive. PUR (moisture-curing polyurethane hot-melt adhesive) has a melting point of 110-120℃ and a temperature resistance of -40℃ to 120℃ after curing. Its bonding strength to laminated surfaces is 40% higher than that of EVA. However, PUR adhesive costs 2.5-3 times as much as EVA (approximately 0.10-0.15 yuan per box vs. 0.04-0.06 yuan for EVA).

Second type of problem: deformation—storage humidity accounts for 60%

Deformation is the second major issue in package forming, with an incidence of 5-8%. Among these factors, storage humidity accounts for 60% of deformation causes, paper moisture content accounts for 25%, and transport stacking accounts for 15%.

The cardboard used for this batch of gift boxes is 350 g grey-base white board paper with a moisture content of 8.5% (factory standard). However, 120,000 sets of gift boxes were stacked in the printing factory warehouse for 18 days, awaiting consolidated shipment during the Dragon Boat Festival peak season. The warehouse has no dehumidifier, and the relative humidity during the plum rain season is 75-85%, causing the cardboard moisture content to rise from 8.5% to 12-13%.

When the moisture content of the cardboard exceeds 10%, two problems occur: ① the cardboard fibers absorb water and swell, causing the carton body to warp and deform; ② the mounting layer (the adhesive layer bonding the greyboard of the carton body to the facing paper) absorbs water and delaminates.

Solution: ① Install dehumidifiers in the printing plant’s warehouse (investment of 3000-8000 yuan per unit, sufficient to cover a 200 m² warehouse); ② Inspect the moisture content of incoming cardboard and return it if it exceeds 9%; ③ Immediately seal the finished gift box with heat-shrink film to prevent moisture penetration; ④ Use moisture-proof bags + desiccants during transportation.

Category 3: Misalignment—Die-Cutting Tolerance Accounts for 70%

Misregistration is the third most common issue in carton forming, with an incidence rate of 3-5%. Of all causes of misregistration, die-cutting tolerance accounts for 70%, gluing machine precision for 20%, and manual carton placement for 10%.

The die-cutting for the customer’s gift boxes uses woodboard dies (standard precision), with a die-cutting tolerance of ±0.3 mm. The theoretical clearance between the lid and box body is 0.1-0.2 mm, but with a die-cutting tolerance of ±0.3 mm, the actual clearance fluctuates between 0-0.5 mm.

When the clearance is 0-0.1 mm, the lid becomes "jammed" and is difficult to open and close; when the clearance is 0.4-0.5 mm, the lid "wobbles" and the seal is not tight. Customers will consider both situations defective due to "misalignment" and return the products.

Solution: ① Replace the wooden die-cut tooling with laser cutting tooling (accuracy ±0.05 mm) or steel rule tooling (accuracy ±0.08 mm); ② Upgrade the carton-gluing machine with servo drive (accuracy ±0.05 mm); ③ Perform secondary positioning inspection on the glued and laminated blanks.

The Real Yield Difference Between PUR Adhesive and EVA Adhesive

This is the largest variable in the current box forming process. The yield difference between PUR adhesive and EVA adhesive is 8-15%, while the cost difference is 2.5-3 times.

What types of orders are worth using PUR adhesive for? ① Gift boxes with a unit price ≥ 50 yuan per set (where the cost share is acceptable); ② Orders involving transportation or storage environments with temperatures ≥ 40℃ or humidity ≥ 70%; ③ Orders with strict delivery deadlines (such as seasonal products for the Dragon Boat, Mid-Autumn, and Spring Festivals, where missing the sales window would result in substantial losses); ④ Orders from brands that have zero tolerance for bond failure (such as luxury goods, cosmetics, and high-end food products).

What types of orders are suitable for EVA adhesive alone? ① Gift boxes with a unit price ≤ 30 yuan/set (cost-sensitive); ② Ambient-temperature and normal-humidity environments (dry northern regions, winter); ③ Standard e-commerce logistics (with a controlled transportation environment); ④ Brands that can accept occasional delamination (e.g., low-cost fast-moving consumer goods).

3 Practical Recommendations for the Molding Process

First, the customer explicitly specifies the transportation and storage environment when placing the order. The printing plant selects the adhesive based on the environment rather than defaulting to EVA.

Second, the printing plant’s warehouse must be equipped with a dehumidifier. A dehumidifier costs 3000-8000 yuan per unit and can keep the moisture content of cardboard stable at 8-9%. One dehumidifier can cover a 200 m² warehouse, with annual electricity costs of approximately 2000-3000 yuan.

Third, the forming process inspection should be conducted on a daily basis. Randomly inspect 50-100 finished boxes each day, testing for three indicators: delamination, deformation, and misalignment. A full inspection is recommended for every 10,000 finished boxes.

3 Details You Can’t See in a Printing Factory’s Quotation

First, the glue brand and model. Many printing factories quote only “EVA glue” without specifying the model, leaving customers unaware of its temperature resistance. It is recommended that the contract specify the “glue brand + model” (e.g., “Henkel EVA 3525”).

Second, die-cutting method. Wooden dies have an accuracy of ±0.3 mm, laser dies ±0.05 mm, and steel dies ±0.08 mm. The three methods vary significantly in cost, but even more so in precision. It is recommended that the contract specify the "die-cutting tolerance" requirements.

Third, Finished Product Inspection Standards and Return Terms. In the industry, finished product inspection is usually conducted on a "5% sampling basis," but customers with stringent requirements should request "10% sampling" or "100% inspection." The return terms should clearly state that "any order with a delamination rate of > 3% will be fully refunded."

Further Reading