Defective products refer to those that fail to meet specifications after being cut by the slitting machine.

Formula definition: Loss area = (trimming width × number of cuts) × cutting length × number of defective-product cutters.

Causes: improper operator handling, poor base paper quality, and inadequate lamination, among others.

Loss area = (trimmed width × number of cuts) × cut length × number of defective-product cutting blades.

Causes: improper operator handling, poor base paper quality, and inadequate lamination, among others.

Improvement measures: Strengthen operator management and control the quality of the base paper.

Overproduced items refer to conforming products that exceed the predetermined paper feed quantity. For example, if the planned paper feed is 100 sheets but 105 sheets are produced as conforming items, then the additional 5 sheets are considered overproduced items.

Formula definition: Excess product loss area = (trimmed width × number of cuts) × cutting length × (number of defective cuts – scheduled cuts).

Causes: excessive paper feed on the corrugator, inaccurate paper splicing on the corrugator, etc.

Improvement measures: Implementing a corrugator production management system can resolve issues such as inaccurate paper feed on single-facer machines and imprecise paper splicing.

Edge trimming refers to the portion removed during edge-trimming and creasing operations performed by an edge-trimming and creasing machine.

Formula definition: Edge-trimming loss area = (web width – trimming width × number of cuts) × cutting length × (number of good-product cuts + number of defective-product knife cuts).

Causes: Normal waste is expected, but if the waste is unusually high, the underlying reasons should be investigated. For example, suppose an order calls for a trimmed web width of 981 mm, while the corrugator requires a minimum trim width of 20 mm. In this case, 981 mm + 20 mm = 1,001 mm, which exceeds the standard 1,000-mm web width. To accommodate this, a 1,050-mm web must be used, resulting in a trim width of 1,050 mm − 981 mm = 69 mm—significantly larger than the normal trim width—and consequently increasing the area of trim waste.

Remedial measures: If the issue stems from the aforementioned reasons, one option is to leave the trim untrimmed for such orders and feed 1,000 mm-wide paper through the press; the excess 50 mm can then be trimmed off during the subsequent printing-and-box-making stage, thereby saving 50 mm of paper width. However, this approach will to some extent reduce printing efficiency. Another measure is for the sales department to take this factor into account when accepting orders, optimizing the order mix to achieve overall operational efficiency.

● Jumping loss

A “skip” refers to the portion of a web that results when, due to a shortage of base paper in the required width, it becomes necessary to run the machine on a wider web. For example, an order may call for 1000 mm-wide paper, but if 1000 mm base paper is unavailable or for other reasons the machine must operate at 1050 mm, the extra 50 mm constitutes a skip.

Formula definition: Skip-plate loss area = (post-skip web width – scheduled web width) × cut length × (number of cuts for good products + number of cuts for defective products).

Causes: unreasonable stock preparation of base paper or untimely procurement of base paper by the sales department.

Improvement measures: The company’s procurement function should review whether the procurement and inventory management of base paper align with customer needs, striving to coordinate with customers in maintaining appropriate paper stock levels and thereby implementing a “T-mode” operational approach. Meanwhile, the sales department must submit material requisition orders well in advance to provide the procurement department with sufficient lead time, ensuring that base paper is delivered accurately and on schedule. In addition, losses due to defective products and overproduction should be classified as performance-related losses for the corrugated board production department and used as key performance indicators to drive continuous improvement.

Due to factors such as trial runs of the printing press and unforeseen incidents during carton production, a certain amount of waste is inevitable; therefore, a buffer quantity is included in the order scheduling.

Formula definition: Additional production loss area = Scheduled additional production quantity × Unit area of the carton.

The root causes are significant equipment wear and tear on the printing presses, insufficient operator skill levels, and substantial packaging losses in the downstream stage. In addition, the sales department lacks effective controls over order quantities and overrun allowances. In fact, there is no need to set such high overrun allowances; excessive overruns lead to unnecessary overproduction, which, if unsold, becomes “dead inventory”—that is, expired stock—and represents yet another form of avoidable waste.

Improvement measures: This issue should be regarded as a performance loss attributable to the printing and box-making department and can be incorporated as a departmental performance metric to drive improvements in staff competence and operational proficiency. The sales department should tighten its order-approval process for additional production volumes, differentiating between complex and simple jobs in terms of allowable overage. It is recommended to include additional quantities in the first-article inspection to control deviations at the source, thereby preventing unnecessary overproduction or underproduction.

During carton production, the excess cardboard trimmed off by the die-cutting machine is referred to as trim loss.

Formula definition: Edge-rolling loss area = (paper stock area – rolled area) × inbound quantity.

Causes: Normal material loss; however, when the amount exceeds acceptable levels, the underlying causes should be investigated. In addition, fully automatic, manual, and semi-automatic die-cutting machines each have different edge-rolling requirements.

Improvement measures: Different die-cutting machines must be pre-equipped with the corresponding edge-rolling settings to minimize edge-rolling waste as much as possible.

Some carton manufacturers require that there be no white edges at the seams. To ensure quality, an additional margin of a specified width—such as 20 mm—is added around the perimeter of the original carton to prevent white edges from appearing after the carton is die-cut and folded. This extra 20-mm margin represents the full-coverage trim allowance.

Formula definition: Full-coverage trimming waste area = (paper stock area – actual carton area) × inbound quantity.

Cause: Normal wear and tear; however, when the quantity is excessive, the underlying causes should be analyzed and corrective measures implemented.