Step-by-step Analysis of Rotary Die Cutting Process

The primary function of a rotary die is to achieve continuous rolling and die cutting through gear transmission. It typically consists of a driven wheel with gears that vertically drives a steel roller with gears, which then drives the rotary die vertically. The material passes between the rotary die and the steel roller and is die-cut into the desired shape. The process of rotary die cutting can be divided into the following major steps:

【1】Material Feeding

This step involves placing the material onto the machine. Proper and accurate material feeding is crucial as it directly affects the setup process and production efficiency. During material feeding, the position should be aligned correctly, and the material should have a certain tension to ensure proper alignment. When changing materials, the joints should be well connected to ensure smooth passage. Overlapping joints for adhesive materials and aligning joints for base papers are recommended.

【2】Waste Discharge

This step is about removing the waste generated during die cutting. Waste discharge is a key and challenging aspect of the rotary die cutting process. Various methods have been developed over time to address different situations.

Common waste discharge techniques in rotary die cutting include:

- Material Strip Waste Discharge: This technique involves designing the die to semi-cut the material, leaving the waste on the base film strip to be directly removed. This is mainly used for products with internal frames that require waste removal.

- Pin Extraction Waste Discharge: This technique is suitable for products with larger waste. It avoids the need to replace the base paper and involves removing the waste after composite materials are die-cut, leaving behind the desired product.

- Needle Push Waste Discharge: This technique uses a needle push die, commonly known as a needle push cleaning die or needle push waste discharge die. It is the most commonly used waste discharge tool in the industry, especially for small hole waste discharge in the die-cutting process. It helps to protect the cutting edge, eliminates waste buildup, and ensures smooth waste discharge. The needle push die is convenient to use, does not require an air source, produces no noise, and offers efficient waste discharge.

- Air Blow/Suction Mold Waste Discharge: This technique utilizes high-pressure air to blow waste material away from the die-cutting material and cavity, preventing waste from sticking. It typically involves installing an air guide ring on the side of the die body to direct high-pressure air to the corresponding waste discharge holes to blow the waste out. This technique is often used in conjunction with waste collection boxes to effectively collect the die-cut waste.

- Drop-off Waste Discharge: This technique involves creating a cavity in the middle of the die body that allows waste to be trapped and automatically expelled through waste discharge openings. It offers easy waste discharge, minimal noise, but requires regular-shaped waste, such as circular or square cut waste. The best waste discharge results are typically achieved with circular waste of diameters ranging from 3-10mm.

【3】Alignment

For products processed by multiple rotary dies, alignment of the dies is necessary. Alignment includes both horizontal and vertical dimensions. The vertical dimension is controlled by adjusting the knobs on the die holders, which are locked after adjustment. The horizontal dimension may be subject to larger variations. Each rotary die usually has alignment marks, often designed as two perpendicular "┍" and "┙" marks that form a cross shape when aligned. The alignment marks may vary depending on the number of rotary dies and the design preferences of the engineers.

【4】Stability during Production

The stability during the production process directly impacts both efficiency and product quality. Factors affecting stability include process-related factors and the skill level of the operator. Changing the die after it has been made increases the cost, so it is essential to improve stability through operational knowledge. Some key factors to consider include:

- Appropriate overall tension: Proper tension of the entire material during the rotating process is essential. Too tight tension can lead to shrinkage, deformation, or displacement, while too loose tension can result in unstable dimensions and large variations. Properly adjusting the tension of each feed and take-up wheel is critical.

- Use constant tension during material feeding: For materials prone to slippage, using a baffle to prevent horizontal movement is recommended. Avoid exposing adhesive materials during feeding to prevent adhesion issues.

- Add auxiliary rollers: In areas where the material is prone to wrinkling or instability, adding auxiliary rollers at appropriate angles can help improve stability.