Casting is a very optical process, and the quality requirements for the products after casting are very strict. The following points can be used for reference:
1. Surface smoothness of scraper
The casting scraper is usually made of tool steel, which has good wear resistance and short service life. However, it needs to be maintained and cleaned after each use to prevent hard objects from scratching the surface and keep the scraper smooth and flat. A smooth and flat scraper is the key to obtaining a uniformly thick and smooth surface film strip.
2. The highest point of the liquid level in the slurry tank
The highest point of the liquid level in the slurry tank increases, and the pressure inside the slurry tank increases, which increases the inflow velocity of the slurry through the gap of the scraper and increases the thickness of the casting film. Therefore, maintaining the balance of the highest point of the liquid level is crucial for controlling the uniformity of the thickness of the casting film. Large scale casting equipment generally requires a liquid level sensor to control the slurry supply valve and ensure that the highest point of the liquid level changes to the maximum extent.
3. Uniformity of the slurry
The slurry used for casting must be fully dispersed and evenly distributed. If there are hard lumps or aggregates that have not been well dispersed and cannot be filtered out, scar like defects may occur on the film strip, or depressions may occur due to different shrinkage caused by wet burning. So it is necessary to pay attention to the preparation of the slurry, and after use, it must be sieved to remove these hard blocks and aggregates. If there are bubbles in the slurry, defoaming treatment must be carried out after casting.
4. Casting thickness
The thickness of the scraper gap and the actual drying thickness will never be the same. It should be due to the evaporation of solvents during the drying process, the stability of the slurry, and other conditions such as flow rate and humidity temperature during casting. Generally, there will be a stable ratio. Accurate parameters can usually be obtained through casting tests.
5. Develop and implement the best wet process
The slurry film produced by casting can peel off from the substrate after being exposed to moisture. Therefore, developing appropriate wet processes is a key factor in obtaining low-quality film strips. If the wet process is not properly formulated, the cast film often exhibits defects such as bubbles, pinholes, wrinkles, dry cracks, and is prone to detachment from the substrate. The principle of developing a wet process is to ensure that the solvent is slowly released, so that the diffusion rate of the solvent in the film layer and the surface evaporation rate tend to be the same, and to prevent defects such as cracking, foaming, wrinkles, etc. caused by premature hardening of the surface.
