How to prevent cavitation in polyurethane foaming machine
1. Strictly control the ratio and injection volume of the original solution
Control the ratio of black material, combined polyether and cyclopentane. Under the condition that the total injection volume remains unchanged, if the proportion of black material is too large, cavitation will appear, if the proportion of white material is too large, soft bubbles will appear, if the proportion of cyclopentane is too large, bubbles will appear, and if the proportion is too small, cavitation will appear. If the proportion of black and white materials is out of balance, there will be uneven mixing and shrinkage of foam.

The amount of injection should be based on process requirements. When the injection amount is lower than the process requirement, the foam molding density will be low, the strength will be low, and even the phenomenon of filling incompact vacuoles will occur. When the injection volume is higher than the process requirements, there will be bubble expansion and leakage, and the box (door) will be deformed.
2. Temperature control of polyurethane foaming machine is a key to solving cavitation
When the temperature is too high, the reaction is violent and difficult to control. It is easy to appear that the performance of the bubble liquid injected into the larger box is not uniform. The bubble liquid injected at the beginning has undergone a chemical reaction, and the viscosity increases rapidly, and the bubble liquid injected later has not yet reacted. As a result, the bubble liquid injected later cannot push the bubble liquid injected first to the front end of the foaming process of the box, resulting in local cavitation in the box.
Black and white materials should be treated at a constant temperature before foaming, and the foaming temperature should be controlled at 18~25℃. The temperature of the preheating furnace of the foaming equipment should be controlled at 30~50℃, and the temperature of the foaming mold should be controlled between 35~45℃
When the temperature of the foaming mold is too low, the fluidity of the foam-liquid system is poor, the curing time is long, the reaction is not complete, and cavitation occurs; when the temperature of the foaming mold is too high, the plastic liner is deformed by heat, and the foam-liquid system reacts violently. Therefore, the temperature of the foaming mold and the ambient temperature of the foaming furnace must be strictly controlled.
Especially in winter, the foaming mold, preheating furnace, foaming furnace, box and door must be preheated for more than 30 minutes every morning when the line is opened. After foaming for a period of time in summer, the foaming system must be cooled down.

Pressure Control of Polyurethane Foaming Machine
The pressure of the foaming machine is too low. The black, white material and cyclopentane are not mixed uniformly, which is manifested as uneven density of polyurethane foam, local large bubbles, foam cracking, and local soft foam: white, yellow or black streaks appear on the foam , the foam collapsed. The injection pressure of the foaming machine is 13~16MPa