Egg Carton Production Line Introduction

Main Components

The Egg Carton Production Line mainly consists of a drum molding machine, multi-layer drying line, finished product conveying line, hot pressing conveying line and an automatic hot pressing stacking machine.

Egg carton production line Drum Molding Machine

Working Principle

The working principle of the drum molding machine is to pump the well-prepared pulp into the pulp trough of the molding machine through a pulp pump. When the drum machine is started, the molding molds rotate with the drum. When the pulp level is reached, the vacuum pulp suction valve is opened to draw pulp. As the molding mold rotates out of the pulp, the pulp is adsorbed onto the mold net through vacuum filtration to form a wet paper mold blank. The wet paper mold blank continues to dehydrate as the drum rotates and hot air is sent in from the upper hood for preheating. When the wet paper mold blank rotates to the transfer position, the transfer mold and the molding mold close.Then the wet paper mold blank is transferred by blowing compressed air into the molding mold and creating a vacuum in the transfer mold. Then, the transfer mold rotates 90° to a horizontal position to blow the product onto the receiving tray, completing one working cycle.

The duration of suction, dehydration, and transfer, as well as all actions, are controlled by a reducer + converter + precision divider.

Vacuum System Configuration

Each paper mold forming vacuum system is equipped with a gas-water separator, which is connected to the drum machine vacuum interface through a vacuum pipe. When the molding mold of the forming machine draws pulp, the water and air passing through the filter net enter the mold cavity, then pass through the vacuum pipe, and flow into the gas-water separator. In the gas-water separator, water and air are separated, with air being sucked away by the vacuum pump and water being pumped into the white water pool by the filter liquid pump for recycling.

Other Features

The intermittent rotation of the drum realizes pulp drawing, dehydration, and transfer of the wet paper mold blank, placing it on the multi-layer drying line connected to the machine. The multi-layer drying line shares a power source with the drum machine, making adjustments simple and convenient.

After the wet paper mold blank is formed by the drum machine, it is automatically shaped and corrected by an adjustable automatic mold washing, burr washing, and buckle position washing device to ensure the quality of the appearance of the wet paper mold blank. The top of the drum is equipped with a preheating system, which uses the tail gas of the drying line to preheat the formed wet paper mold blank. This can greatly save drying costs and make the formed wet paper mold blank better shaped, resulting in a flatter and more beautiful product after drying.

The series of drum-type forming machines can be equipped with two-sided, four-sided, or eight-sided forming drums. The main parameters of the four-sided drum machine are shown in Table 4-4.

Multi-layer Drying Line

Working Principle

The working principle of the multi-layer drying line is that the high-temperature air produced by gas combustion is sprayed from the main combustion chamber into the secondary combustion chamber and mixed with the low-temperature wet air sucked in by the circulation fan from the lower air duct. The wet air is heated, the temperature rises, the relative humidity decreases, and it is sent back into the upper air duct. It enters the first layer of the drying room through the perforated partition at the lower part of the upper air duct. In the drying room, the temperature of the first layer is the highest. Here, the hot air contacts the wet paper mold blank with the highest water content just out of the forming machine. The hot air passes through two layers of feeding trays and enters the second layer of the drying room through the perforated plate at the lower part of the first layer drying room. It then passes through two layers of feeding trays and enters the third layer drying room through the perforated partition at the lower part of the drying room. In the third layer, the hot air passes through two layers of materials and enters the return air duct through the perforated partition at the lower part of the third layer drying room. Through the circulation fan, part of the hot air enters the combustion chamber again, and part is sent to the forming machine’s hot air hood to preheat the wet paper mold blank and then discharged. As the hot air flows from top to bottom, the temperature gradually decreases and the water content increases. The wet paper mold blank is flipped and runs from top to bottom, and the water content gradually decreases. By the sixth layer, it is basically dried and sent out of the drying line.

Structure and Heating Method

This drying system adopts a six-layer feeding tray structure from top to bottom, making full use of space and saving floor area. The heating method uses direct combustion of natural gas or liquefied petroleum gas. The drying process temperature is automatically controlled by the PLC through setting the relevant parameters of the control system. The drying temperature is usually set at 220 – 250℃. Relying on the circulation fan, the hot air in the drying box circulates from top to bottom, saving energy consumption in the drying process.

Finished Product Conveying Line

The finished product conveying line is used to transport the paper mold blank from the multi-layer drying line to the hot pressing conveying line through a belt conveying device.

Hot Pressing Conveying Line

Working Process

The hot pressing conveying line is used in the fully automatic paper pulp molding egg carton/egg box production system to connect the drying line and the hot pressing shaping machine. The dried paper mold blank slides from the high position to the receiving hopper of the flipping mechanism through the unloading channel of the drying line. The paper mold blank falls onto the push plate conveying machine with the flipping of the receiving hopper. The paper mold blank, originally arranged in 6 or 8 rows, rotates 90° along the conveying direction and becomes one row pushed forward by the push plate. The receiving hopper returns to its original position to repeat the receiving process. The paper mold blank on the push plate conveying machine is pushed forward. When passing through the turning mechanism, the paper mold blank is sent out of the push plate conveying machine by the grabber of the turning mechanism at a rhythm of 3 or 4 pieces per group to the wetting part flat belt. The wetting device wets the product from both top and bottom. The wetting water is mist-like and can be adjusted arbitrarily to ensure the smoothness of the paper mold surface in the next hot pressing process. After the wetting adjustment, the paper mold blank rotates 90° along the conveying direction, becomes 3 or 4 rows, and moves forward with the flat belt. On the flat belt, the paper mold blank is guided and sent into the push plate conveying part through the round belt. The push plate pushes the paper mold blank forward at a rhythm of 4 pieces per group. The paper mold blank, whose water content has been adjusted by the wetting part, is sent to the feeding end of the hot pressing machine and dragged into the hot pressing feeding device by the upper and lower brush rollers installed at the feeding end of the hot pressing machine.

Drive and Synchronization Features

The entire conveying line is driven by three servo motors. The speed of conveying products automatically adjusts according to the speed of the hot pressing machine, and the rhythm of conveying products is synchronized with the hot pressing rhythm. The mechanical synchronization structure is used, with fewer electrical induction points, making adjustments simple and convenient.

Automatic Hot Pressing Stacking Machine

Working Process

The feeding mechanism sends the paper mold blank from the conveying line to the hot pressing feeding mechanism. The hot pressing feeding mechanism moves the paper mold blank into the hot pressing mold cavity. The hot pressing mechanism drives the motor to rotate the main shaft, and the convex wheel pressure mechanism generates enough pressure to shape the dried paper mold blank. During the above process, the pressure limiting mechanism acts as a pressure protection switch to prevent overpressure damage to the equipment. The shaped product automatically slides out of the hot pressing mechanism into the stacking feeding mechanism. The拨rod of the stacking feeding mechanism rotates a certain angle to send the product onto the stacking belt, where the products are automatically stacked one by one. This cycle is repeated to complete the hot pressing shaping and stacking of each product.

Water Content Control and Action Features

The suitable water content for product shaping is 15% – 10%. Too dry or too wet will affect the quality after shaping, and the water content of the product entering the hot pressing mechanism must be well controlled.

All actions of the automatic hot pressing stacking machine, including hot pressing, feeding, knife board lifting, and stacking, use one power source, making adjustments simple and convenient. The hot pressing and pressure holding time are completed through the cam, ensuring stable motor load during the pressure holding time, and the speed is nearly twice as fast as other methods such as screw connecting rod pressurization.

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