The uneven thickness of the vegetable net cover produced by the vegetable net cover machine can be adjusted based on the following key parameters:
Raw material supply parameters
Adjustment of raw material extrusion volume:
Reason: If the extrusion amount of raw materials is unstable and varies over time, it can cause fluctuations in the thickness of the mesh cover. In areas with excessive extrusion, the mesh cover becomes thick; In areas with low extrusion volume, the mesh cover is thin. This is usually caused by unstable screw speed or uneven feeding of the hopper.
Adjustment method: Check and stabilize the screw speed, and precisely control the screw speed through the motor's frequency converter to keep it constant. For the problem of feeding from the hopper, a mixing device can be installed to prevent the raw materials from bridging or blocking in the hopper, ensuring that the raw materials enter the extruder evenly. At the same time, check if the size of the discharge port is appropriate and adjust it if necessary to ensure that the raw materials enter the extrusion system at a stable flow rate.
Raw material temperature control:
Reason: The temperature of the raw material has a significant impact on its fluidity, which in turn affects the thickness of the mesh sleeve. Excessive temperature and flowability of raw materials may lead to difficulty in controlling extrusion volume and thinning of mesh thickness; Low temperature, poor flowability of raw materials, difficulty in extrusion, may cause local accumulation and make the mesh thicker.
Adjustment method: Accurately control the temperature of each heating zone of the extruder, feedback the temperature signal through the thermocouple installed on the extruder barrel, and use the temperature controller for precise adjustment. According to the characteristics of the raw materials, set an appropriate temperature range. Generally speaking, for common polyethylene raw materials, the extrusion temperature can be controlled between 160200 ℃. At the same time, attention should be paid to the uniformity of temperature to avoid local overheating or overcooling.
Foaming parameters
Adjustment of injection amount of foaming agent:
Reason: The injection amount of foaming agent directly affects the degree of foaming of the mesh cover, thereby affecting the thickness. Excessive injection, excessive foaming of the mesh cover, and increased thickness; Insufficient injection volume, insufficient foaming, and thinning of thickness.
Adjustment method: Use a high-precision metering pump to control the injection amount of foaming agent, and accurately adjust the flow rate of the metering pump according to the target thickness of the mesh and the performance of the foaming agent. At the same time, attention should be paid to the uniformity of the mixing of foaming agent and raw materials. Special mixing sections can be set on the extruder screw, such as barrier type screws or pin type screws, to strengthen the mixing of foaming agent and raw materials and ensure uniform foaming effect.
Foam temperature and pressure control:
Reason: The foaming process requires appropriate temperature and pressure conditions. Inappropriate temperature and pressure can lead to uneven foaming, resulting in uneven thickness of the mesh cover. Excessive temperature or pressure, and fast foaming speed, may result in local large bubbles, causing uneven thickness of the mesh cover; If the temperature is too low or the pressure is too low, incomplete foaming will occur, and the thickness of the mesh cover will also be affected.
Adjustment method: Install temperature and pressure sensors in the foaming mold or foaming area to monitor temperature and pressure in real-time. Control the foaming temperature and pressure by adjusting the heating device and pressure regulating device (such as valves, compressors, etc.). Generally speaking, the foaming temperature can be adjusted between 120 and 180 ℃ according to the type of foaming agent and the characteristics of the raw materials, and the foaming pressure can be controlled between 0.31.0MPa.
Mold and traction parameters
Optimization of mold aperture and structure:
Reason: The aperture size and structure of the mold can affect the extrusion shape and thickness of the mesh sleeve. Uneven aperture or defects in the internal structure of the mold can lead to inconsistent thickness of the mesh sleeve during extrusion.
Adjustment method: Check whether the aperture of the mold is uniform and measure it using tools such as calipers. If there is a deviation in the aperture, the mold needs to be repaired or replaced. At the same time, optimize the internal structure of the mold, such as using special diversion cones or flow channel designs, to evenly distribute the raw materials inside the mold, thereby ensuring uniform thickness of the mesh after extrusion.
Stable traction speed:
Reason: Unstable traction speed can cause uneven stretching of the mesh sleeve, thereby affecting its thickness. If the traction speed is fast and slow, the thickness of the mesh sleeve will change during the stretching process, with the fast part becoming thinner and the slow part becoming thicker.
Adjustment method: Use high-precision traction equipment, such as servo motor-driven traction rollers, to accurately control the traction speed through encoder feedback signals. At the same time, set up a suitable tension control system to ensure that the mesh sleeve has appropriate tension during the traction process, avoiding thickness changes caused by excessive or insufficient tension. Tension can be monitored through tension sensors and the traction speed can be automatically adjusted based on feedback signals.