Reasons for shrinkage
During the processing of foaming materials, shrinkage may occur due to various reasons. The main reasons are as follows:
1. Formula problems. There are many factors in the formula, and they need to be eliminated one by one if necessary. From the selected foaming agent, catalytic system, polyol, material temperature, material ratio, mold temperature, various materials, etc., all need to be calculated. Any problem can lead to problems. At the same time, the quality of the foaming agent and stabilizer is unstable, the amount of addition exceeds the standard or is insufficient, or the order of addition is improper, which will also cause shrinkage.
2. Improper control of the processing process: such as insufficient fusion time, too high or too low foaming temperature, too fast or too slow stretching speed, etc.
3. Problems with the mold or process: such as rough and uneven mold surface, improper mold temperature control, uneven mold pressure or stretching force, etc.
4. If the machine is not stable enough, deviations will also occur, including whether various parameters are normal. It is best to calibrate the flow and pressure of the equipment before production, and replace the sealing ring regularly.
5. Check whether there are vents at the location of the cavitation. If there are no vents, add more vents.
6. Dissect the newly foamed refrigerator to determine the filling density at each location. Generally, the core density of cyclopentane foam material (without skin) is preferably 34kg/m^3 (141b is above 32kg/m^3). If the density is insufficient, add material.
7. Check whether there are structural abnormalities at the location where the refrigerator shrinks. The back injection of the box body is prone to shrinkage at the trident position of the foaming liquid flow direction. You can consider adding a block.
Treatment methods
For the shrinkage problem, the following measures can be taken to deal with it:
1. Control the foaming process
The foaming process is one of the main reasons for the shrinkage of foaming materials, so the processing process should be reasonably controlled. The processing conditions should be controlled according to the properties and requirements of the foaming materials to reduce the possibility of shrinkage. For example, control the fusion time, pressure, temperature, etc. so that the foaming agent and stabilizer can fully play their role.
2. Optimize material selection
Select foaming agents, stabilizers and other additives with stable quality to ensure the uniformity and consistency of the materials. Appropriate materials should be selected according to specific process requirements to avoid problems such as material mismatch or excessive or insufficient addition.
3. Maintain molds and equipment
The mold surface should be kept flat and smooth to avoid defects such as roughness or cracks. At the same time, the control accuracy of the mold temperature should be ensured to avoid overheating or overcooling. Ensure the normal operation and timely maintenance of the equipment to ensure the accuracy of process parameters.
4. Optimize processing conditions
Including controlling parameters such as processing temperature, speed, pressure, and tensile force. The processing conditions should be optimized according to the characteristics of the material and the specific requirements of the process to reduce the possibility of shrinkage.
In summary, the reasons for the shrinkage of foaming materials are relatively complex and need to be comprehensively treated from multiple aspects. It is recommended that enterprises in related fields strengthen quality management, technical training, and equipment maintenance in the production and manufacturing process to better solve the problem of shrinkage of foaming materials and improve the quality and market competitiveness of products.