How to Improve Paper Machine Trim Edge

How to Improve Paper Edge Trimming Process

Edge Trimming and Tail Cutter Nozzles

The edge trimming nozzles is mainly used for trimming the paper edge and cutting the tail. The purpose of trimming on a paper machine is to separate the formed edges, which is to separate the irregular and loose wet or dry edges of the paper after forming, thereby forming a clean and precise edge. This not only ensures that the paper can be cut according to the size of the produced product, but also reduces the occurrence of paper breakage during subsequent processes.

In order to achieve the desired effect of edge trimming nozzles, it is necessary to comprehensively consider and optimize from the following aspects:

1. Maintenance of Trim Nozzles for trimming

The trimming nozzle is the "heart" of the trimming system, and its state directly determines the cutting quality. Ensure that the trimming nozzle is in good condition. Wear of the trimming nozzle will weaken the water flow, resulting in a significant decrease in cutting efficiency.

Wear and tear cause the water column to break and scatter before reaching the paper sheet. When the shape of the water column breaks, it begins to atomize and lose its "glass rod" shape. The small particles that fall off from the water flow can also weaken the impact force of the water flow, leading to irregular cutting, burrs, fiber drawing, and paper breakage. Regularly replacing the nozzle helps prevent these issues from occurring due to wear and tear. High quality materials such as ruby nozzles can extend the replacement cycle.

2. Suitable water pressure for cleaner edge cutting

Water pressure is a key parameter that determines cutting quality. If the pressure is too low, the nozzle water flow will not be able to effectively cut the paper. If the pressure is too high, it may cause splashing problems and damage the forming fabric where the paper is located.

The setting of water pressure needs to take into account various factors such as the weight of the paper, the speed of the production line, and the aperture of the nozzle. When the water pressure is high, the impact force of the water flow is greater, and the cutting is cleaner. The following table provides suggestions for adjusting nozzle aperture and quantity based on factors such as operating line speed, water pressure used, and the basis weight of the produced paper.

3. Use double hole trim nozzles or use two trim nozzles

In paper production, the trimming process is crucial for the quality and operational stability of the finished product. The use of double hole nozzles or two nozzles is a recommended approach. In paper mills, fresh and clean water is a valuable resource. Although trimming nozzles consume less water compared to other processes, it is still important to pay attention to water conservation. Using a double hole nozzle allows for the simultaneous use of multiple smaller diameter water streams. This can not only achieve cleaner cutting, but also reduce the amount of water required for this operation.

One of the reasons for using double hole nozzles is for redundancy. If there are bubbles in the water pipe or other interruptions in the main water flow, the second set of nozzle flow will provide cutting redundancy. This helps ensure that the paper can achieve seamless and clean edge cutting at all times. A clean cutting effect can greatly reduce the possibility of paper breakage on the production line.

4. Nozzle arrangement and spray angle

• Tilt the trim nozzle at a 10-20 degree angle to the direction of machine operation, facing towards the drying end.

Adjusting the angle of the trimming nozzle is mainly to avoid water mist splashing back onto the mesh or fabric. Even if splashing occurs, water droplets will fall back onto the paper instead of accumulating outside the nozzle. If the water mist splashes back onto the nozzle, debris is likely to adhere to the outside of the nozzle. Once the debris accumulates too much and falls onto the paper, there is a risk of paper breakage in the machine.

The design of the trimming nozzle is also a key point. The trim nozzle with an angled outlet edge can be installed in a directional manner to allow debris or droplets to fall onto the damaged part of the paper, thereby avoiding contamination of the effective paper.

• Tilt the trim nozzle horizontally towards the edge of the machine by 5-15 degrees

When the trimming nozzle is tilted towards the edge of the machine, it helps to separate the broken paper edge from the main paper web. Ensure that the broken paper edge does not accidentally reattach after the edge cutting operation is completed. When the nozzle and pipeline are also tilted towards the edge of the machine, any droplets or debris can be concentrated on the broken edge of the paper, preventing them from falling onto the paper web.

• Place the trimming nozzle 50-150mm above the forming fabric

Choosing the appropriate trimming spray distance is crucial. If the trimming nozzle is too close to the paper web, it will cause a large amount of sprayed material to splash back onto the nozzle, damaging the fabric. On the contrary, if the nozzle is too far away from the paper web, the sprayed water column will start to break, resulting in a decrease in impact force and inability to achieve a clean cutting effect.

Due to the different operating modes of each machine, we generally recommend a spraying distance between 50mm and 150mm, with specific values adjusted according to the actual production situation of each device. It is also necessary to consider various factors such as the grade of paper produced, the pressure of the trimming nozzle, and the speed of the machine.

• Place the water needle nozzle behind the vacuum suction tank of the high-speed paper machine

On high-speed paper machines, water generated by trimming processes or suction rollers may re wet the paper web, causing its edges to close again. This situation can cause paper breakage and increase energy consumption in the press and dryer sections. If the trimming process is carried out afterwards, it can reduce the possibility of re stitching the edges of the paper web to the paper web.